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British Bikes / Re: Troubleshooting a JAP Special
« on: May 05, 2024, 11:43:03 PM »
I'd say that's more than tired.
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I'd say that's more than tired.
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British Bikes / Re: Troubleshooting a JAP Special
« on: May 02, 2024, 05:45:45 PM »Might be time to file the slot on the kickstarter a little wider enabling the bolt to clamp more.
I've done that already - the slot physically can't close up.
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British Bikes / Re: Troubleshooting a JAP Special
« on: May 02, 2024, 01:40:56 PM »
To carry on the Saga....
I've been tinkering with the bike recently and reduced the size of the main jet down 1 size. This seems to have helped when WOT. I've a feeling that giving the carb a good sitz clean has affected some of the fuel pathways and they're now more open than they were - thus messing up the ratios.
I'm going to reduce the size of the needle jet next - to see if that helps the lower-throttle openings - obviously after seeing what the needle is doing.
However I may also be having electrical issues: I took the bike round the block and it ran fine at WOT, roughly at lower throttle, but after about 2 miles it just died a death and I couldn't get it to fire at all. The plug seemed nice and dry (and not sooted) when I pulled it out on the side of the road, so I don't know yet why it wasn't re-starting.
I also have the issue that the kickstarter splines seem to be going - no matter how tight I bolt up the kickstart lever I seem to able to twist the lever on the shaft after about 10 or so kicks.
Fingers crossed it's just the splines on the lever, and not the shaft....
I'm also going to take a good look at the coil - see if it's still measuring the correct resistance.
I've been tinkering with the bike recently and reduced the size of the main jet down 1 size. This seems to have helped when WOT. I've a feeling that giving the carb a good sitz clean has affected some of the fuel pathways and they're now more open than they were - thus messing up the ratios.
I'm going to reduce the size of the needle jet next - to see if that helps the lower-throttle openings - obviously after seeing what the needle is doing.
However I may also be having electrical issues: I took the bike round the block and it ran fine at WOT, roughly at lower throttle, but after about 2 miles it just died a death and I couldn't get it to fire at all. The plug seemed nice and dry (and not sooted) when I pulled it out on the side of the road, so I don't know yet why it wasn't re-starting.
I also have the issue that the kickstarter splines seem to be going - no matter how tight I bolt up the kickstart lever I seem to able to twist the lever on the shaft after about 10 or so kicks.
Fingers crossed it's just the splines on the lever, and not the shaft....I'm also going to take a good look at the coil - see if it's still measuring the correct resistance.
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 28, 2023, 08:48:49 PM »There is some chat about viton tipped fuel needles, or not, in monoblocs.
Yep, some claim that the Viton needles are prone to sticking "up" and shutting the supply of juice off.
Re the pit bike Choagy carbs, an old boy I know paid £14 for one off Ebay, and stuck it on his reluctant Tiger Cub. Apparently it started second kick and even ticks over fresh out the box.
I've heard this myself which is why I'm considering it. Ebay also has sets of main & idle jets for a couple of quid or so. I've never had the experience if viton needles sticking despite using them for decades.
Got any links for the jets?
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 28, 2023, 03:26:33 PM »The obvious answer is to fit another carb that is known to work OK.
Its certainty a thought.
Do you have one to lend?
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 27, 2023, 02:19:18 PM »
Well, I've still not figured out what's wrong with the JAPton. Did some checks last week and fuel flow is good ( more than half a litre per minute, which ought to be fine).
Raised the needle by one because i thought it might be a bit weak, and tried starting it up and although it started easily enough, its still spitting back and backfiring.
I'm beginning to think the ignition timing has slipped, so i took a cover over the magneto drive sprocket to check it.
Seemed fine so went to put the little cover back on, and bugger me if the sodding thread didn't strip.
GAH!
So I'm going to put the JAPton aside for a bit and concentrate on the other projects i need to get done before winter, and will very likely spend the winter stripping the thing down and learning more of its foibles.
Raised the needle by one because i thought it might be a bit weak, and tried starting it up and although it started easily enough, its still spitting back and backfiring.
I'm beginning to think the ignition timing has slipped, so i took a cover over the magneto drive sprocket to check it.
Seemed fine so went to put the little cover back on, and bugger me if the sodding thread didn't strip.
GAH!
So I'm going to put the JAPton aside for a bit and concentrate on the other projects i need to get done before winter, and will very likely spend the winter stripping the thing down and learning more of its foibles.
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 21, 2023, 09:22:59 AM »JAPs traditionally breathe only through the oilbox ......if you put breathers anywhere else ,you upset the lubrication system,and may even cut off the big end feed
That's pretty much my understanding too.
This bike "has" run well in the past, but was parked up for a few years (my Dad's health deteriorated and he died in '21, it took me a year or two to be ready for looking after the bike).
Last Friday I Took the JAPton out for a spin round the block:
It might run ok at less than 1/4 throttle, but any more than that and it starts bogging down, won't fire at all, then after 2 or 3 deafening explosions from the exhaust it'll pick up and run well for about 10 seconds or so before it starts bogging down again.
Rinse and repeat again and again if I try to ride it anything more than 1/4 throttle (ish).
I've been pouring over the literature I've got (the JAP books, and the AMAL tuning leaflet) and I still can't get my head around whether these symptoms are the carb set too rich, too weak, or something else completely.
The Amal booklet seems to suggest that issues with firing in the exhaust are ignition related.... But that doesn't balance with the fact that the engine WILL run properly for a few seconds before it bogs again, so I'm somewhat confused.
As I say, it'll run ok for a bit, then it seems as if something "builds up" and it stops firing, until the fuel in the exhaust detonates, and it clears up and runs again.... Until the "blockage" builds up again. That's what makes me think it's not ignition or timing - because presumably it wouldn't run at all at lower throttle openings etc if the timing had shifted?
Next thing I'm going to do is go over the inlet manifold and exhaust joins and check there's not gaps or holes in the system.
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 18, 2023, 11:58:26 PM »
last week I "fixed" the hole in the JAPtons crank cases (timing chest actually).
I did stick an endoscope down it, but there wasn't a lot to see!
I cut down the new bolt so that it was roughly the length required to fill the cases, with a crush washer on top:
Then fitted it in with a good amount of Soudall Fix-All smeared into the threads and around the crushwasher and head. With any luck that will act as a seal and thread-lock even though the bolt isn't done up that tight. I tried very hard NOT to strip the threads so only did it up as tight as I dared....
Obviously will be keeping an eye on it, but I can't move it with my fingers... so it's an improvement
I had an idea that the issue with the carb tickler might have been the paper gasket between the jet block and the main body (the surfaces this gasket mates to are not the smoothest....). So I stripped the carb down and put a small amount of blue-hylomar on each face of the gasket and reassembled it.
No difference. Whatever is preventing the tickler working correctly is still evading me. Next attempt will mean going into the float bowl itself and seeing there's something odd about the interface between the tickler and the float. I've been doing some reading up and it seems that the new nylon floats sometimes cause minor problems so it's worth taking a look.
Took the JAPton out for a spin round the block this evening.
It might run ok at less than 1/4 throttle, but any more than that and it starts bogging down, won't fire at all, then after 2 or 3 deafening explosions from the exhaust it'll pick up and run well for about 10 seconds before it starts bogging down again.
Rinse and repeat again and again if I try to ride it anything more than 1/4 throttle (ish).
And obviously it's still pissing oil....
So... Back to to the tuning leaflets....
I did stick an endoscope down it, but there wasn't a lot to see!
I cut down the new bolt so that it was roughly the length required to fill the cases, with a crush washer on top:
Then fitted it in with a good amount of Soudall Fix-All smeared into the threads and around the crushwasher and head. With any luck that will act as a seal and thread-lock even though the bolt isn't done up that tight. I tried very hard NOT to strip the threads so only did it up as tight as I dared....
Obviously will be keeping an eye on it, but I can't move it with my fingers... so it's an improvement
I had an idea that the issue with the carb tickler might have been the paper gasket between the jet block and the main body (the surfaces this gasket mates to are not the smoothest....). So I stripped the carb down and put a small amount of blue-hylomar on each face of the gasket and reassembled it.
No difference. Whatever is preventing the tickler working correctly is still evading me. Next attempt will mean going into the float bowl itself and seeing there's something odd about the interface between the tickler and the float. I've been doing some reading up and it seems that the new nylon floats sometimes cause minor problems so it's worth taking a look.
Took the JAPton out for a spin round the block this evening.
It might run ok at less than 1/4 throttle, but any more than that and it starts bogging down, won't fire at all, then after 2 or 3 deafening explosions from the exhaust it'll pick up and run well for about 10 seconds before it starts bogging down again.
Rinse and repeat again and again if I try to ride it anything more than 1/4 throttle (ish).
And obviously it's still pissing oil....
So... Back to to the tuning leaflets....
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 09, 2023, 02:10:01 PM »Ive sort of wanted a copy of "The JAP Engine " by Fenner for years ,but never going to pay a silly price .........then I just happened to see an as new copy with the red dust cover intact for $10 at a flea market .........anyhoo,this book includes a section by Wal Phillips on the speedway engines .........and thats where the photo of the timing gear comes from .
Wow! That's an excellent find!
I have both the Fenner, and 2 copies of the Pitman "The Book of the J.A.P. Engine" (2nd and 3rd editions). My Dad always like to check the definitive sources as much as he could. The problem is that I think a lot of his notations were for his other J.A.P engined bike... a 1930 HRD Vincent, which had an earlier J.A.P. engine in it, than the one in the special I've got.
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 08, 2023, 08:24:49 PM »
Managed to unscrew the bolt this evening.
The threads on both the bolt and the case are "tired". But i found a bolt in my grab bag of Imperial bolts that actually screws in and will go "tight".
https://flic.kr/p/2oUxRsd
https://flic.kr/p/2oUwLGC
Old bolt on left....
So I'm going to cut it a bit shorter (both bolts are twice as long as they need to be), and smother the top end of the threads with silicon and put it in with an ally crush washer (unless i can find a suitable fibre, but i detest fibre washers).
Before that though, I'm going to stuff an endoscope into the hole!
The threads on both the bolt and the case are "tired". But i found a bolt in my grab bag of Imperial bolts that actually screws in and will go "tight".
https://flic.kr/p/2oUxRsd
https://flic.kr/p/2oUwLGC
Old bolt on left....
So I'm going to cut it a bit shorter (both bolts are twice as long as they need to be), and smother the top end of the threads with silicon and put it in with an ally crush washer (unless i can find a suitable fibre, but i detest fibre washers).
Before that though, I'm going to stuff an endoscope into the hole!
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 08, 2023, 11:22:26 AM »
oh yeah - there's one other weird thing...happening:
On the Monobloc carb, although I've cleaned it all up, when I use the tickler to push the float down, it "works" - but the fuel doesn't overflow through the ticker - it eventually overflows out of the bellmouth! (or possibly a tiny hole in the inlet manifold).
The tickler is imply a metal tube, closed at the top end, but with a small hole on the side about a mm down from the top. The bottom of the tube is squared off, but not closed up, and it's completely clean - it's not blocked in anyway.
The top of the float - which the tickler pushes down on, is rounded, so there's no "flat plane" on which the end of the tickler could possibly "seal".
So I'm highly confused as to why the fuel isn't exiting out of the tickler!
On the Monobloc carb, although I've cleaned it all up, when I use the tickler to push the float down, it "works" - but the fuel doesn't overflow through the ticker - it eventually overflows out of the bellmouth! (or possibly a tiny hole in the inlet manifold).
The tickler is imply a metal tube, closed at the top end, but with a small hole on the side about a mm down from the top. The bottom of the tube is squared off, but not closed up, and it's completely clean - it's not blocked in anyway.
The top of the float - which the tickler pushes down on, is rounded, so there's no "flat plane" on which the end of the tickler could possibly "seal".
So I'm highly confused as to why the fuel isn't exiting out of the tickler!
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 08, 2023, 11:07:10 AM »
Yeah - that's the first thing I'm going to try when I'm next in the workshop. The engine was very hot when I first observed the issue so I was struggling to get at the thing!
I seriously hope that there isn't a nut underneath it... but knowing my Dad..... there's a possibility....
I seriously hope that there isn't a nut underneath it... but knowing my Dad..... there's a possibility....
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 07, 2023, 12:45:44 PM »Most likely the thread in the crankcase is stripped. I think it unlikely there's a nut underneath. Getting the head & barrel off will only take half an hour or so.
Re the spitting back - I had a similar problem with my ES2 fitted with a monobloc and found that a richer slide cutaway (lower number) sorted it out, as the cutaway controls the mixture on transition between idle and the point that the needle jet takes over. The slide was kindly donated by someone on here but sadly I can't remember who.
I "believe" that I need to get into the timing chest, rather than the crank case volume itself - so need to get the timing apparatus off the rhs, rather than the head and barrel off, but need to find some internal schematics first to check that.
It looks to me like the pushrods are actuated by the cam-followers in a side-chest.
Would be seriously useful to have a 2nd engine to play with and see where everything goes!
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British Bikes / Re: Troubleshooting a JAP Special
« on: August 07, 2023, 09:46:21 AM »
I tinkered with the JAPton last night. (Life is busy at the moment, so I don't often get into the workshop).
It's all back together but wasn't running properly - lots of spitting back and backfiring in the exhaust.
Got it running, and spent about an hour going back and forth between the ancient Monobloc "Notes" leaflet (Dad had some photocopies so at least I wasn't getting the original filthy!)* Eventually got my head around it and realised that the damn thing was running "weak" in the mid-range and so pulled the needle up a notch (the first thing I'd done was lower it a notch to the "top" notch, it refused to run on that setting). Now it's in the middle of the needle's range its actually running pretty well (once it's hot). The occasional spit back or backfire, but I think I can live with that for now.
Happy bunny!
During the course of the session I'd spotted a couple of nuts that had fallen on the floor - one was an engine bolt that (in hindsight) I know was loose - the primary chase mounting lug is held in place by it and I'd simply forgotten it was loose.
The other was the nut off the forward connection for the gear linkage.... it's a nyloc, but I discovered that Dad had cut the bolt for it down so short that the threads aren't actually engaging the nylon locking collar! ( ffs). Couldn't be arsed at that point to root around for a better bolt so I just pushed the nut on upside down. Hardly ideal but it'll do to hold it all together while I figure out another issue.
I was wiping some oil off the top of the crankcase when I discovered something that terrifies me...
That bolt, the one between the push-rod tubes, is loose, and it won't go tight.
It just revolves.
Now - I may be wrong.... but, to me, that indicates that there's a friggin NUT on the other side of the case, that is loose, and is hanging on the threads of the bolt.
I may be wrong, and the loose bolt is caused by the threads on either the bolt or the casing being thoroughly knackered.
But - either way, the mininum work needed before I can do anything with the bike is to strip the entire right side of the engine away to check what's going on in the timing box. :roll:
I can't take a chance on the probability of a nut dropping into the timing box.
So - The JAPton is unlikely to see tarmac again this side of Easter, simply because I know that I've never done any of this stuff before and I'll be taking things very slow and thoroughly checking it all, and researching how it all works. Oddly, for all the tinkering I've done over the years, this is the first time I've ever had to actually do the timing on anything.
I also seem to have been thrown off / barred from the JAP Engine Facebook group I was on - so also need to find a J.A.P. specialist source of further information.
Dagnabbit.
* I must get a copy of that leaflet blown up and laminated. I did the same with the exploded diagram for the carb and it's an invaluable reference sheet).
It's all back together but wasn't running properly - lots of spitting back and backfiring in the exhaust.
Got it running, and spent about an hour going back and forth between the ancient Monobloc "Notes" leaflet (Dad had some photocopies so at least I wasn't getting the original filthy!)* Eventually got my head around it and realised that the damn thing was running "weak" in the mid-range and so pulled the needle up a notch (the first thing I'd done was lower it a notch to the "top" notch, it refused to run on that setting). Now it's in the middle of the needle's range its actually running pretty well (once it's hot). The occasional spit back or backfire, but I think I can live with that for now.
Happy bunny!
During the course of the session I'd spotted a couple of nuts that had fallen on the floor - one was an engine bolt that (in hindsight) I know was loose - the primary chase mounting lug is held in place by it and I'd simply forgotten it was loose.
The other was the nut off the forward connection for the gear linkage.... it's a nyloc, but I discovered that Dad had cut the bolt for it down so short that the threads aren't actually engaging the nylon locking collar! ( ffs). Couldn't be arsed at that point to root around for a better bolt so I just pushed the nut on upside down. Hardly ideal but it'll do to hold it all together while I figure out another issue.
I was wiping some oil off the top of the crankcase when I discovered something that terrifies me...
That bolt, the one between the push-rod tubes, is loose, and it won't go tight.
It just revolves.
Now - I may be wrong.... but, to me, that indicates that there's a friggin NUT on the other side of the case, that is loose, and is hanging on the threads of the bolt.
I may be wrong, and the loose bolt is caused by the threads on either the bolt or the casing being thoroughly knackered.
But - either way, the mininum work needed before I can do anything with the bike is to strip the entire right side of the engine away to check what's going on in the timing box. :roll:
I can't take a chance on the probability of a nut dropping into the timing box.
So - The JAPton is unlikely to see tarmac again this side of Easter, simply because I know that I've never done any of this stuff before and I'll be taking things very slow and thoroughly checking it all, and researching how it all works. Oddly, for all the tinkering I've done over the years, this is the first time I've ever had to actually do the timing on anything.
I also seem to have been thrown off / barred from the JAP Engine Facebook group I was on - so also need to find a J.A.P. specialist source of further information.
Dagnabbit.
* I must get a copy of that leaflet blown up and laminated. I did the same with the exploded diagram for the carb and it's an invaluable reference sheet).
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British Bikes / Re: Troubleshooting a JAP Special
« on: July 25, 2023, 01:33:14 PM »What carb is it ......the pic seems to indicate a Type 27 speedway carb ,or maybe a 10TT
Amal Monobloc 389.