41
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rex on January 30, 2026, 04:38:58 PM »Got any spare enthusiasm going spare? I could really use some this time of year...
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42
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:07:33 AM »I'm starting to think that I really need to get in the workshop a bit more often - there's still a lot to do, and I'm definitely taking my time with things.
So - last night I went in and made gaskets. ... I know, it's soooo exciting!
Some of the parts that need gaskets, with existing old ones:
I started with the output side shaft seal plate gasket - this is a "non-standard" fitment anyway to slow down the loss of oil around the output shaft.
The outer and the fitment holes were relatively simple - but I need to break out the school-boy drawing tools for the inner circumference.
Note to self... for f*cks sake draw on the OTHER side....
But a reasonable finished product.
Next - the oil-drain chest cover.
Should be functional:
Funnily enough - the oil-collection chest gaskets can be bought, but this is an older one that's been used, and I can use it as a "master" template: it's a bit out of shape, but not enough to be a problem:
Much easier to work on the non-printed side of the paper!
With the old one that I pulled off: I'm going to leave this one as is, and not bother to trim out the internal "web" - it's not necessary.
The last gasket is the base gasket, but first I wanted to get the surfaces a tad smoother, so I dug out the fine grinding paste....
It's an improvement (I hope).
The initial circles I drew out with a compass, then tested for fit on the barrel
I then put the barrel onto the cases and marked the cut-outs for the bolts that tie the head & barrel down, then trimmed them out and checked the fit
I also trimmed out a smalle cutout on the inner of the gasket to match the slight cutouts which allow the con-rod to not-hit the cases.
I've put them in "storage" for now, (under a couple of books as well), and will very likely make up another complete set, using these as templates.
I then decided to make another fix:
The timing chain cover has another little cover over the mag-cog to allow you to adjust the timing without taking the entire cover off: you can lock the mag-shaft, then loosen the pinion nut and tweak it through a hole in the timing chain cover.
BUT - the threads on the tiny holes were tired - so I found some new set-screws with wide heads in the box of bits: figured out what thread they were M6 as it happened, ideally it would be nice to use Imperial all over, but there's other Metric threads on the bike so I'm kinda beyond caring at this point; re-cut the threads in the timing chain cover and hey presto!
I cut the set-screws down to ensure they don't interfere with the timing chain
And there'll be another paper gasket going under that cover to reduce any oil weep (the timing chain isn't lubed much, I don't think..., so it shouldn't be an issue really).
Actually quite pleased with the evening's progress.
Like I say - I'm going to make up another complete set of gaskets and will use that 2nd set for the build, and keep the first ones (the ones made directly from the mating faces) as the "master-templates". I may well find there's other places where a gasket might be useful, but we'll cross those bridges when we get to them.
So - last night I went in and made gaskets. ... I know, it's soooo exciting!
Some of the parts that need gaskets, with existing old ones:
I started with the output side shaft seal plate gasket - this is a "non-standard" fitment anyway to slow down the loss of oil around the output shaft.
The outer and the fitment holes were relatively simple - but I need to break out the school-boy drawing tools for the inner circumference.
Note to self... for f*cks sake draw on the OTHER side....
But a reasonable finished product.
Next - the oil-drain chest cover.
Should be functional:
Funnily enough - the oil-collection chest gaskets can be bought, but this is an older one that's been used, and I can use it as a "master" template: it's a bit out of shape, but not enough to be a problem:
Much easier to work on the non-printed side of the paper!
With the old one that I pulled off: I'm going to leave this one as is, and not bother to trim out the internal "web" - it's not necessary.
The last gasket is the base gasket, but first I wanted to get the surfaces a tad smoother, so I dug out the fine grinding paste....
It's an improvement (I hope).
The initial circles I drew out with a compass, then tested for fit on the barrel
I then put the barrel onto the cases and marked the cut-outs for the bolts that tie the head & barrel down, then trimmed them out and checked the fit
I also trimmed out a smalle cutout on the inner of the gasket to match the slight cutouts which allow the con-rod to not-hit the cases.
I've put them in "storage" for now, (under a couple of books as well), and will very likely make up another complete set, using these as templates.
I then decided to make another fix:
The timing chain cover has another little cover over the mag-cog to allow you to adjust the timing without taking the entire cover off: you can lock the mag-shaft, then loosen the pinion nut and tweak it through a hole in the timing chain cover.
BUT - the threads on the tiny holes were tired - so I found some new set-screws with wide heads in the box of bits: figured out what thread they were M6 as it happened, ideally it would be nice to use Imperial all over, but there's other Metric threads on the bike so I'm kinda beyond caring at this point; re-cut the threads in the timing chain cover and hey presto!
I cut the set-screws down to ensure they don't interfere with the timing chain
And there'll be another paper gasket going under that cover to reduce any oil weep (the timing chain isn't lubed much, I don't think..., so it shouldn't be an issue really).
Actually quite pleased with the evening's progress.
Like I say - I'm going to make up another complete set of gaskets and will use that 2nd set for the build, and keep the first ones (the ones made directly from the mating faces) as the "master-templates". I may well find there's other places where a gasket might be useful, but we'll cross those bridges when we get to them.
43
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:07:14 AM »Had a fun afternoon yesterday fiddling with the flywheel (dem tings are heavy)
Parts assemble!
First assembly:
Yes - I did you a little video!
(yes, the music was too loud... my bad!)
https://youtu.be/C0fcM7KXcNU
(I initially wanted to do a time-lapse video... but I ended up just posting it as is)
This is how the dial guage ended up being mounted - seemed to work well and enabled a consistent (mostly!) location:
It took a bit of fiddling to get the dial to zero properly (with the crank pulled all the way to the left).
Finding the initial float:
https://youtu.be/E4PKg67gMYo
Correction: the end float should be 0.012" - 0.015" (I made the same misread last time - because it's written in the booklet as .012" (the initial 0 is missing so I keep misreading it!)
Maths.
I initially chucked in 2 0.023" shims, one each side to see where that got me - theoretically, that should have been very nearly there....
The results:
https://youtube.com/shorts/MKNfHrS-ffc
I was also trying to get the conrod as central as possible - using the crank-case split line as the centre-line (an assumption - but I think a relatively safe one.... I hope!)
The polished crank means it's "relatively" easy to see where the conrod is
Crank pushed to left
Crank pushed to right.
I then added a 0.020 shim to the Timing side (right side) of the crank, and still had too much float (0.02xx something IIRC)
So I added a 0.010 shim to the left side as well
Too much??
Or just right?
While I pondered that...
I pulled out the compression plates that I have (which would sit under the barrel), which I was going to use as templates for the base gasket, and luckily had the thought to try them on the cases while I had the cases together.
They're not JAP.
Well - they might be JAP.... but they're not THIS Jap!
GAH!
I suspect they're from one of the other bikes... the Matchless maybe?
So - I also checked the spare head gaskets I found... and THEY'RE not right either! I could possibly use them... because while the inner diameter of the gaskets is larger than the bore, the outer diameter is considerably smaller than the outer diameter of the depression the gasket sits in! GAH!
I also have a box full of piston rings that I know are wrong (I think they're pre-war JAP)
So - I did a bit of tidying up...
TBH, I think the float is now acceptable, so I dry assembled the piston and barrel (no rings or gudgeon pins)
On a full 500cc engine with 15:1 compression... the piston should come right to the top of that barrel....
https://youtu.be/jHgrizea2ik
There's a fair bit of play in the small end - so I figured I could see roughly how central the conrod/piston is by gently lifting the barrel and observing the small end :
It looks ok to me!
Happy Bunny! Didn't need to buy more shims this time around.
Next job is to do some light grinding paste action with the barrel and the cases - the faces of the cases where the barrel mounts are a little lumpy, so I'm going to use some light grinding paste just to get the barrel and crank meeting faces "flat" which will a) help the paper gasket seal better and b) maybe possibly increase the compression by a gnat's chuff?? hey - every little helps!
After that - make up the barrel gasket and the oil-chest gasket (the volume under the timing chest where the oil collects for dispersal post use), and the gasket for the fitting under the oil-chest. I'm thinking I'll probably make up 2 or 3 of each: so I have spares for the future, and in case I have any accidents in assembly....
Then it's <gulp> time to start final assembly....
Although - I do still need to assemble the head and check the valves are sealing: using meths or paraffin this time!
I hope it gets a bit warmer soon.... at the end of every evening like this the ends of my fingers are freezing.
Parts assemble!
First assembly:
Yes - I did you a little video!
(yes, the music was too loud... my bad!)
https://youtu.be/C0fcM7KXcNU
(I initially wanted to do a time-lapse video... but I ended up just posting it as is)
This is how the dial guage ended up being mounted - seemed to work well and enabled a consistent (mostly!) location:
It took a bit of fiddling to get the dial to zero properly (with the crank pulled all the way to the left).
Finding the initial float:
https://youtu.be/E4PKg67gMYo
Correction: the end float should be 0.012" - 0.015" (I made the same misread last time - because it's written in the booklet as .012" (the initial 0 is missing so I keep misreading it!)
Maths.
I initially chucked in 2 0.023" shims, one each side to see where that got me - theoretically, that should have been very nearly there....
The results:
https://youtube.com/shorts/MKNfHrS-ffc
I was also trying to get the conrod as central as possible - using the crank-case split line as the centre-line (an assumption - but I think a relatively safe one.... I hope!)
The polished crank means it's "relatively" easy to see where the conrod is
Crank pushed to left
Crank pushed to right.
I then added a 0.020 shim to the Timing side (right side) of the crank, and still had too much float (0.02xx something IIRC)
So I added a 0.010 shim to the left side as well
Too much??
Or just right?
While I pondered that...
I pulled out the compression plates that I have (which would sit under the barrel), which I was going to use as templates for the base gasket, and luckily had the thought to try them on the cases while I had the cases together.
They're not JAP.
Well - they might be JAP.... but they're not THIS Jap!
GAH!
I suspect they're from one of the other bikes... the Matchless maybe?
So - I also checked the spare head gaskets I found... and THEY'RE not right either! I could possibly use them... because while the inner diameter of the gaskets is larger than the bore, the outer diameter is considerably smaller than the outer diameter of the depression the gasket sits in! GAH!
I also have a box full of piston rings that I know are wrong (I think they're pre-war JAP)
So - I did a bit of tidying up...
TBH, I think the float is now acceptable, so I dry assembled the piston and barrel (no rings or gudgeon pins)
On a full 500cc engine with 15:1 compression... the piston should come right to the top of that barrel....
https://youtu.be/jHgrizea2ik
There's a fair bit of play in the small end - so I figured I could see roughly how central the conrod/piston is by gently lifting the barrel and observing the small end :
It looks ok to me!
Happy Bunny! Didn't need to buy more shims this time around.
Next job is to do some light grinding paste action with the barrel and the cases - the faces of the cases where the barrel mounts are a little lumpy, so I'm going to use some light grinding paste just to get the barrel and crank meeting faces "flat" which will a) help the paper gasket seal better and b) maybe possibly increase the compression by a gnat's chuff?? hey - every little helps!
After that - make up the barrel gasket and the oil-chest gasket (the volume under the timing chest where the oil collects for dispersal post use), and the gasket for the fitting under the oil-chest. I'm thinking I'll probably make up 2 or 3 of each: so I have spares for the future, and in case I have any accidents in assembly....
Then it's <gulp> time to start final assembly....
Although - I do still need to assemble the head and check the valves are sealing: using meths or paraffin this time!
I hope it gets a bit warmer soon.... at the end of every evening like this the ends of my fingers are freezing.
44
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:06:51 AM »err, not been in the shop much over the hoidays... but managed to get in last week for an afternoon of shivering.
It's been preying on my mind somewhat that the measurements I took for the crank play weren't very accurate... so I decided that I really ought to do it properly with a dial guage. It was with this in mind that I entered the shop....
.. and pulled out the toolbag support bracket to finish off that job first. :roll:
So - first the next hole up needed a little file so that I could get a small bolt through it inline with the hole in the frame
Top view of the assembly in situ:
Internal view: Washer and lock washer in place
Just a view of the main shock support bolt in place.
And this is the tie-clip just stopping the toolbag falling forward or backward during riding (it can't fall off)
SO - with that done.... I remembered the dial guages...
I currently have 3: an imperial one and 2 metric ones - all bought randomly from jumble shows ( why I haven't just bought a new one from wherever.com is a mystery.... it had just never occurred to me.)
The imperial one seems to move and work ok, the Draper one seems to have a sticky movement, and the other metric one is ...well... just iffy.
So - in the best bulldog spirit of pressing forwards with the most important jobs....
I prevaricated again and started dismantling the sticky dial guage to figure out what the problem is....
Looked ok at first glance...
However..... the eyeglass reveals all... (this thing is turning out to be really useful! )
(open the photo in Flickr and you can zoom in.)
The teeth on the main shaft are $%^&&ed. :roll:
So - instead of hurling the thing across the workshop in a fit of pique (it was tempting.... )
I calmly placed it to one side to see what was wrong with the other metric guage.
Hmm - something missing from here... I'm sure of it!
...
...
Can you see where this is going??
Can you?
I bet you can.
Yup !
FIXED IT!
In addition... the knackered guage had a mounting lug on the back, and the newly fixed one didn't... so I figured that while one lug may not be as good as two lugs, it's still better than no lugs if lugs are to be needed.... (ahem) so I decided to fit the back from the dead guage onto the fixed one.....
which has 3 equally spaced threaded holes to secure the backplate.
The backplate with the lug... has 4 .... equally spaced ... holes.
<sigh>
FINE!
Get the drill out, carefully layer the 2 backplates so the old one can be used as a template..
And bingo!
A fully functioning, belugged, metric dial guage! (sorry, no photo.
)
I also dug out a nice bit of ally hanging bracket (or something) to use as the "stand" for the guage - I can screw it to a bolt-hole on the cases easily enough.
I just need to reassemble the crank in the cases and figure out the arrangement of the guage....
Which will probably happen this week at some point... hopefully.
in the meantime... I'd be a lying little toerag if I claimed I wasn't strongly pondering the purchase of one of these...
(or similar)
It's been preying on my mind somewhat that the measurements I took for the crank play weren't very accurate... so I decided that I really ought to do it properly with a dial guage. It was with this in mind that I entered the shop....
.. and pulled out the toolbag support bracket to finish off that job first.
:roll:So - first the next hole up needed a little file so that I could get a small bolt through it inline with the hole in the frame
Top view of the assembly in situ:
Internal view: Washer and lock washer in place
Just a view of the main shock support bolt in place.
And this is the tie-clip just stopping the toolbag falling forward or backward during riding (it can't fall off)
SO - with that done.... I remembered the dial guages...
I currently have 3: an imperial one and 2 metric ones - all bought randomly from jumble shows ( why I haven't just bought a new one from wherever.com is a mystery.... it had just never occurred to me.)
The imperial one seems to move and work ok, the Draper one seems to have a sticky movement, and the other metric one is ...well... just iffy.
So - in the best bulldog spirit of pressing forwards with the most important jobs....
I prevaricated again and started dismantling the sticky dial guage to figure out what the problem is....
Looked ok at first glance...
However..... the eyeglass reveals all... (this thing is turning out to be really useful! )
(open the photo in Flickr and you can zoom in.)
The teeth on the main shaft are $%^&&ed. :roll:
So - instead of hurling the thing across the workshop in a fit of pique (it was tempting.... )
I calmly placed it to one side to see what was wrong with the other metric guage.
Hmm - something missing from here... I'm sure of it!
...
...
Can you see where this is going??
Can you?
I bet you can.
Yup !
FIXED IT!
In addition... the knackered guage had a mounting lug on the back, and the newly fixed one didn't... so I figured that while one lug may not be as good as two lugs, it's still better than no lugs if lugs are to be needed.... (ahem) so I decided to fit the back from the dead guage onto the fixed one.....
which has 3 equally spaced threaded holes to secure the backplate.
The backplate with the lug... has 4 .... equally spaced ... holes.
<sigh>
FINE!
Get the drill out, carefully layer the 2 backplates so the old one can be used as a template..
And bingo!
A fully functioning, belugged, metric dial guage! (sorry, no photo.
)I also dug out a nice bit of ally hanging bracket (or something) to use as the "stand" for the guage - I can screw it to a bolt-hole on the cases easily enough.
I just need to reassemble the crank in the cases and figure out the arrangement of the guage....
Which will probably happen this week at some point... hopefully.
in the meantime... I'd be a lying little toerag if I claimed I wasn't strongly pondering the purchase of one of these...
(or similar)
45
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:06:34 AM »The new rear-shock mount bolts turned up.
Exactly as specced:
The left side:
With the pannier-mount in place, the shank does reach through to the outside of the mounting plate - exactly as measured.
Did the nuts up loose, just to hold things together for now.
On the right side I can either spin the die down one of the bolts to make the shank the right length - or simply pack out the nut like this, with a couple of extra spacers.
This is how the pannier will sit, but it will have a secondary nut and bolt to hold it straight as well.
Should be much better, out of the way, and won't interfere with anything that moves. :thumbup:
I'll probably use tie-clips or something similar to prevent the bag moving along the axis of the bike (currently it can do that - but it won't fall off the mounting bar, the bar is too long). I'll get it all mounted tight and see what the best solution for that is later on.
Exactly as specced:
The left side:
With the pannier-mount in place, the shank does reach through to the outside of the mounting plate - exactly as measured.
Did the nuts up loose, just to hold things together for now.
On the right side I can either spin the die down one of the bolts to make the shank the right length - or simply pack out the nut like this, with a couple of extra spacers.
This is how the pannier will sit, but it will have a secondary nut and bolt to hold it straight as well.
Should be much better, out of the way, and won't interfere with anything that moves. :thumbup:
I'll probably use tie-clips or something similar to prevent the bag moving along the axis of the bike (currently it can do that - but it won't fall off the mounting bar, the bar is too long). I'll get it all mounted tight and see what the best solution for that is later on.
46
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:06:13 AM »A few more steps in the journey on Friday night last:
I ordered up some bolts for the rear-shock mounts, but there was a communications failure and they turned up with the wrong specs:
The shank length should be 1"5/8s, (1.675"): hey ho... more on the way... I'm sure these will be useful somewhere else.
I want the shank that length specifically so that the threads are not bearing on the inner mount plate, but the shank is.
New spacers for the rear-shock mounts: these are perfect (and a right git to fit).
I inadvertently undid the nut & bolt I put into the valve-lifter pivot hole, so replaced it, and used a felt washer to attempt to make it a touch less prone to weeping.
Thinking about it now... I may add a lock washer or a nyloc to that....
I also realised that I hadn't offered up the cases with the mag-platform bracket into the frame and engine plates. So after a bit of swearing and cajoling I put the empty cases back in the mounts (I'm really not looking forward to that job when the engine is fully assembled!)
The bracket clears the plates nicely.
I also took the opportunity to drill a little hole in the flange that protrudes from the output side engine case:
The reason for that hole is that the engine oil drain bolt has a lockwire hole in it, and it was lockwired before (for good reason...), but Dad had the lockwire attached to a cut down penny washer that was under the bolt on one of the engine case screws. It just always seemed untidy, so - this way, the drain plug can be lockwired to the engine case itself and it's a neater job.
I've no idea what the flange is for - there are some numbers on there, but they're not the usual place for engine numbers, and I've not seen that flange on any of the engine diagrams or drawings I've seen - I think it "might" be an extra flange used on the stationary engines, eg ditch pumps, lawnmowers, generators etc (which are pretty much the same engine cases) to indicate... something!
I've also seen a few more engines in photos recently and they do often seem to have mag-platform brackets that aren't hugely chunky, so I'm going to go with the one I've made for now, and try to make some more progress.
Next job is make a few more paper gaskets for various covers and things that mount to the engine: the oil drain chest and vent chest covers both need one, and the cylinder base.
I was considering whether or not to try to "lap-in" the cylinder base to the engine cases, but I think I'll just go for a .4mm paper gasket. I've got some compression plates which should serve as templates for that gasket (they're normally used for reducing the compression so I won't be using them!).
Also need to heat-treat the copper cylinder head gasket, and I've got a few more spares too, so I may well just do them all at once, so the spares are ready to go. Trying to remember if they need to be quenched, or just left to cool down after I heat them to pink...
I ordered up some bolts for the rear-shock mounts, but there was a communications failure and they turned up with the wrong specs:
The shank length should be 1"5/8s, (1.675"): hey ho... more on the way... I'm sure these will be useful somewhere else.
I want the shank that length specifically so that the threads are not bearing on the inner mount plate, but the shank is.
New spacers for the rear-shock mounts: these are perfect (and a right git to fit).
I inadvertently undid the nut & bolt I put into the valve-lifter pivot hole, so replaced it, and used a felt washer to attempt to make it a touch less prone to weeping.
Thinking about it now... I may add a lock washer or a nyloc to that....
I also realised that I hadn't offered up the cases with the mag-platform bracket into the frame and engine plates. So after a bit of swearing and cajoling I put the empty cases back in the mounts (I'm really not looking forward to that job when the engine is fully assembled!)
The bracket clears the plates nicely.
I also took the opportunity to drill a little hole in the flange that protrudes from the output side engine case:
The reason for that hole is that the engine oil drain bolt has a lockwire hole in it, and it was lockwired before (for good reason...), but Dad had the lockwire attached to a cut down penny washer that was under the bolt on one of the engine case screws. It just always seemed untidy, so - this way, the drain plug can be lockwired to the engine case itself and it's a neater job.
I've no idea what the flange is for - there are some numbers on there, but they're not the usual place for engine numbers, and I've not seen that flange on any of the engine diagrams or drawings I've seen - I think it "might" be an extra flange used on the stationary engines, eg ditch pumps, lawnmowers, generators etc (which are pretty much the same engine cases) to indicate... something!
I've also seen a few more engines in photos recently and they do often seem to have mag-platform brackets that aren't hugely chunky, so I'm going to go with the one I've made for now, and try to make some more progress.
Next job is make a few more paper gaskets for various covers and things that mount to the engine: the oil drain chest and vent chest covers both need one, and the cylinder base.
I was considering whether or not to try to "lap-in" the cylinder base to the engine cases, but I think I'll just go for a .4mm paper gasket. I've got some compression plates which should serve as templates for that gasket (they're normally used for reducing the compression so I won't be using them!).
Also need to heat-treat the copper cylinder head gasket, and I've got a few more spares too, so I may well just do them all at once, so the spares are ready to go. Trying to remember if they need to be quenched, or just left to cool down after I heat them to pink...
47
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:05:54 AM »Mag-Platform bracket mk2:
In progress:
In place:
To be honest.... I'm not convinced. I bent that bit of steel cold, with just a hammer and then twisted it with mole grips. I think it's just a bit of mild and may not provide the support that I would get with the thicker stuff.
But - it'll do initially and I can have another go if I decide I want to. At least now I have a "pattern" piece for reference when making another one.
I made this one by doing the bend first: after figuring out roughly where it should be with the bracket bolted to the cases; then I put the twist in to bring the upper hole (the mag-platform end) into alignment with the underside of the mag platform. However - that meant that the twisted part of the bracket works against getting the bracket flat against the mag-platform.
If I try again, I'll probably start at the other end - the mag-platform end, and work out what the bend needs to be from that end. I thinkt it could be done with a single bend, but at a funny angle across the bracket, it's not quite 45 degrees - maybe about 30 or so.
In progress:
In place:
To be honest.... I'm not convinced. I bent that bit of steel cold, with just a hammer and then twisted it with mole grips. I think it's just a bit of mild and may not provide the support that I would get with the thicker stuff.
But - it'll do initially and I can have another go if I decide I want to. At least now I have a "pattern" piece for reference when making another one.
I made this one by doing the bend first: after figuring out roughly where it should be with the bracket bolted to the cases; then I put the twist in to bring the upper hole (the mag-platform end) into alignment with the underside of the mag platform. However - that meant that the twisted part of the bracket works against getting the bracket flat against the mag-platform.
If I try again, I'll probably start at the other end - the mag-platform end, and work out what the bend needs to be from that end. I thinkt it could be done with a single bend, but at a funny angle across the bracket, it's not quite 45 degrees - maybe about 30 or so.
48
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:05:36 AM »Managed a couple of hours yesterday in the workshop:
Polished up what I could get to on the conrod :
And the sides of the fly-wheels:
Probably won't make a gnat's chuff of a difference but it felt like the right thing to do. Someone's had a go at the flywheels with an angle-grinder by the looks of it, so a mirror finish ain't gonna happen, but they're a lot shinier now
Then turned my attention back to the mag-platform bracket. I want to get this sorted before I assemble the crank in the cases because dealing with the cases and how they fit in the bike is a lot, lot easier when they're empty!
I spent about an hour repeatedly heating and belting the hell out of the bracket I'd previously made to try to get it to reach the smaller case-bolt where it's "supposed" to mount to.
This is as close as I could get it:
To be honest, I think that bit of steel has had enough of me hammering at it.
So, I dug out another couple of potential victims:
Will assess these for suitability and have another go next time.
Polished up what I could get to on the conrod :
And the sides of the fly-wheels:
Probably won't make a gnat's chuff of a difference but it felt like the right thing to do. Someone's had a go at the flywheels with an angle-grinder by the looks of it, so a mirror finish ain't gonna happen, but they're a lot shinier now
Then turned my attention back to the mag-platform bracket. I want to get this sorted before I assemble the crank in the cases because dealing with the cases and how they fit in the bike is a lot, lot easier when they're empty!
I spent about an hour repeatedly heating and belting the hell out of the bracket I'd previously made to try to get it to reach the smaller case-bolt where it's "supposed" to mount to.
This is as close as I could get it:
To be honest, I think that bit of steel has had enough of me hammering at it.
So, I dug out another couple of potential victims:
Will assess these for suitability and have another go next time.
49
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:05:20 AM »Remembered I had some loom tape yesterday, so completed the job:
I also took some remediating action concerning the battery flopping about on it's single screw....
Will help for now - but a better solution will be engineered eventually.
I also took some remediating action concerning the battery flopping about on it's single screw....
Will help for now - but a better solution will be engineered eventually.
50
British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on January 30, 2026, 11:04:56 AM »I've had another project on the workbench for the past week, but managed to find myself at a loose end on Saturday morning.... always dangerous...
I found myself looking at the wiring "loom" on the JAPton and thinking how messy it looked....
Especially things like this connector block near the battery :
The connector block cable-tied to the cross-beam visible in this photo: (left of photo, lower part of cross-beam)
And especially this mess:
In regards to this - I really dislike the way the horn (black button) wire just dangles down to the headstock.
So - I perused, and pondered, and tinkered and eventually...
Yes the horn IS wired in.
No new holes were drilled - all these holes were pre-existing (for one reason or other...)
A make-do 'grommet' at each end
At the other end - the feed wire to the brake light has always bothered me because it was pulled quite taut, so I soldered on an extension to the yellow wire (which is the wire between the brake light switch and the bulb), and gathered up the few wires that actually needed to be all together with a Wago instead of a shitty plastic screw block. The Wago is glued to the battery.
Much neater.
The entire wiring circuit is simple 2 loops - one for the brake light:
Battery -- switch --- bulb --- battery.
And one for the horn:
Battery --- horn --- switch --- battery.
It's currently setup as a "positive earth" with the frame as earth - so both the horn and brake-light simply earth to their nearest bit of metal, and the battery has a wire from the + terminal to the frame. Nice and simple.
The 3rd "out" connection at the Wago is for a battery charger connection that I wired in so I could charge the battery directly without removing the seat.
I may try to do a bit more tidying up - the horn wires are just loose and could probably do with "looming" together at some point, and similarly the group at the Wago could be tidied, but generally I'm happy with the end result.
There is also the Kill-switch to be replaced - but that will be moving to the right handlebar and is part of the Mag/coil/plug wiring circuitry which are totally separate from the "ancilleries" wiring. Yes - there's no way to charge the battery, so it has to be charged up before a ride... but it's "only" powering the horn and brake light (the brake light will be replaced with an LED at some point) so it's just a case of making sure it's charged before use.
Nasty looking little home-made implement for hooking wires through holes.... may well come in handy. (made from a dentist pick that had lost it's end.)
I found myself looking at the wiring "loom" on the JAPton and thinking how messy it looked....
Especially things like this connector block near the battery :
The connector block cable-tied to the cross-beam visible in this photo: (left of photo, lower part of cross-beam)
And especially this mess:
In regards to this - I really dislike the way the horn (black button) wire just dangles down to the headstock.
So - I perused, and pondered, and tinkered and eventually...
Yes the horn IS wired in.
No new holes were drilled - all these holes were pre-existing (for one reason or other...)
A make-do 'grommet' at each end
At the other end - the feed wire to the brake light has always bothered me because it was pulled quite taut, so I soldered on an extension to the yellow wire (which is the wire between the brake light switch and the bulb), and gathered up the few wires that actually needed to be all together with a Wago instead of a shitty plastic screw block. The Wago is glued to the battery.
Much neater.
The entire wiring circuit is simple 2 loops - one for the brake light:
Battery -- switch --- bulb --- battery.
And one for the horn:
Battery --- horn --- switch --- battery.
It's currently setup as a "positive earth" with the frame as earth - so both the horn and brake-light simply earth to their nearest bit of metal, and the battery has a wire from the + terminal to the frame. Nice and simple.
The 3rd "out" connection at the Wago is for a battery charger connection that I wired in so I could charge the battery directly without removing the seat.
I may try to do a bit more tidying up - the horn wires are just loose and could probably do with "looming" together at some point, and similarly the group at the Wago could be tidied, but generally I'm happy with the end result.
There is also the Kill-switch to be replaced - but that will be moving to the right handlebar and is part of the Mag/coil/plug wiring circuitry which are totally separate from the "ancilleries" wiring. Yes - there's no way to charge the battery, so it has to be charged up before a ride... but it's "only" powering the horn and brake light (the brake light will be replaced with an LED at some point) so it's just a case of making sure it's charged before use.
Nasty looking little home-made implement for hooking wires through holes.... may well come in handy. (made from a dentist pick that had lost it's end.)