Troubleshooting a JAP Special

[Rockburner]

I guess I should also state that I don't want to be grinding material off the crank itself; I could grind down that nut and the crank-pin shaft end to get more clearance; because I don't want to mess with the crank's balance: I've no idea how well balanced it is.... but I don't want to mess with it!

[cardan]

"I fitted the 0.060 thrust washers on the timing side, and a 0.023 on the output side..."

I guess this is part of the mis-matched engine thing. It would be nice if there were no shims between the face of the crank and the bearing inner. Usually this is accomplished by shimming the bearing outer in the crankcase. As it stands, your shims are pretty large and heavy, and there could be quite a "hula hoop" effect as they spin around the main shafts (or the shafts spin inside them), which could cause damage to the shafts and/or the shims. In reality, if you're not going racing, it will probably be ok. But it would worry me. Maybe check with your JAP man?

You mention there is not much end thrust when the engine is vertical: true provided the piston is square and centred. You might be amazed to see the inside of an engine that has been running with a bent con rod!

Leon

[Rockburner]

"I fitted the 0.060 thrust washers on the timing side, and a 0.023 on the output side..."

I guess this is part of the mis-matched engine thing. It would be nice if there were no shims between the face of the crank and the bearing inner. Usually this is accomplished by shimming the bearing outer in the crankcase. As it stands, your shims are pretty large and heavy, and there could be quite a "hula hoop" effect as they spin around the main shafts (or the shafts spin inside them), which could cause damage to the shafts and/or the shims. In reality, if you're not going racing, it will probably be ok. But it would worry me. Maybe check with your JAP man?

You mention there is not much end thrust when the engine is vertical: true provided the piston is square and centred. You might be amazed to see the inside of an engine that has been running with a bent con rod!

Leon

I took a 0.050 and a 0.040 thrust washers out of the engine when I stripped it, and the internals seemed ok. The engine is pretty unstressed and won't be used for racing or anything.

The thrust washers are part of the design on the engine, it's not possible to adjust the main bearing liners, they're pressed into the cases, and the thrust washers/shims allow for the end first to be adjusted. This IS a 1930's design....

But you're right that a call to the expert is in order.

[Rockburner]

In regards to the issue of the crank-pin nut contacting the bearing liner screw......




I've had a word with the JAP Guru... and his advice was to simply take an angle-grinder to the crank-nut and make clearance!

Apparantly it's a common thing, the cases are "not" exactly precision made, and there's a lot that were cast by jobbing engineering firms after JAP stopped production, so exact fitting is not always going to happen. His advice was to figure out the desired shims on the crank (to get the piston and con-rod as central as possible), then see if the nut is striking the liner screw (and the casing), and then get the grinder out! 

He also suggested that if I wanted to confirm the clearance I've created, I can fit slightly narrower shims (eg ten-thou thinner), and see if there's contact.  If not, then I should be good for the lifetime of the engine.  Sounds like a plan to me.

He also pointed out; when I mentioned my concern about affecting the overall balance of the crank; that shaving a 1/16th off 1/3rd of the crank nut would be akin to taking a piss before a weigh-in... totally irrelevant! Which was reassuring.

So - that'll be the next thing on the list!  GRINDING!

[Rockburner]

So, last night I started out by making up the new base gasket :


I have made myself a set of templates out of some thicker carboard and used that.  I've trimmed the inner circle to be slightly larger, so hopefully there won't be a capillary path from the cylinder base straight out under the gasket this time.

I also made up a quick Mag-pinion cover gasket from the excess paper to avoid wasting it.


I then tidied all that away and got down to the main job of the evening.  I finished stripping down the crankcases again and experimented a bit with the shims just to confirm the crank-touching-the-cases issue.

I'm sure I took more photos over the course of the evening, but it looks like the phone camera didn't actually save them, which is odd....

Anyway: here's a few shots of the same modification that was done to the Output side of the assembly at some time before:



This is, essentially, what I need to emulate on the other side.
Interestingly.... the output side is the nut that was removed when we replaced the big-end bearings: in this photo you can see that the nut has been done up slightly tighter this time than it had been before: you can just see the threads on the crank-pin becuase the nut has been rotated on the pin about 5 degrees more this time.


I decided that the grinding would have to be done.
So I cleaned up the wheels as best I could, wrapped a tea-towel around the bigend to prevent too much grit getting to it:


Protected the timing-shaft oilway:


Experimenting with the best way to clamp up the wheels so they don't wander about.


Then remembered I have a little B&Q trestle that would make life a bit easier, clamped it to that and did some taping to protect other gaps and holes:


I also marked up the approximate area that needed work:


In addition I wrapped some duct tape around the shaft just in case the grinder got away from me!

Work in progress:






I did the majority of the grinding outside (to avoid any conflagrations...!) with a 115mm Ryobi, and it worked very well - nice and controllable.  The light was just enough that I could see what I was doing, but more would have been preferable.




And for some reason, that's where I stopped taking photos. (soz!)

I got to a point where all the marker had been eradicated, then, as the light was fading, I took the trestle back into the workshop and get the Dremel out to tidy up and polish.  I used the Dremel grinding wheel to make the ground-away area slightly concave and to take off the rough edges, then wire-brushed and polished it a bit.

I then cleaned it all up, using meths and paper to try to get rid of as much grit as possible, before removing all the protective stuff and unclamping the wheels.

I tried the wheel in the cases with a 0.023 shim (which is the minimal it would need I think.. I stil need to figure out exactly the best shims to use - more on that later*.

The $%^&&er is still scraping. GAH!

So - I need to take a bit more off - I suspect I just need to "round-off" the ground area so that it clears the head of the bearing-line-fixing-screw.

It's sooooo close!! 


* Something from the conversation I had with the Guru:  Although the recommended end-float in the Greenway book (which is the Speedway "Bible") is 0.012" - 0.015" : The Guru recommends letting it be a little looser : 0.015"-0.020"... and the engine will rev more freely.  Given that my engine is "square" (bore = stroke) and will be wanting to rev more easily due to that: I am taking that advice and giving it strong consideration.  The flip-side is that the Guru tends to be building up engines for actual racing... ie, they'll get stripped down again after a season, and a season is not really that many miles.   So: my thinking is to compromise on this and aim for an end float that takes into account the hopefully longer mileage that the engine will do before it's next strip down:  I'm going to aim for around 0.015", or slightly higher, end float: ie the looser end of the Greenway figures, and the tighter end of the Guru's advice.  The aim is to have the engine in good fettle for a few years of riding around on the road with the occasional classic "parade" track-day.  It's unlikely to get utterly thrashed, but I would rather not be rebuilding it every winter!

[Rockburner]

More grinding...



(forgot to block off the timing shaft oil feed... oops )

Progress:


Checking with a 1/2" wide rule


Checking with a 1" wide rule


The cleared area needs to be around 4/5" from the shaft - approximately.

Almost done....



After all that I stuffed the wheels back into the timing side case... and it's STILL "just" touching that odd ovoid shape in the cases with no shim in place - and it's just the outer parts of the ground area (there's a distinct double touch I can feel).

However - there WILL be a shim in there and when there's a shim, there's no touching. So that's gone relatively well I think.

I buttoned up the cases dry again and without any shims to check the end float, and conrod centrality, with the intention of fitting shims not just for good end-float, but also to get the conrod as central as possible.

Overall end float with no shims :


Using the case joining line as the "centre-line" for adjusting the conrod centering. There's nothing else on the cases that is machined in any way so that it could be used for an accurate measurement for centre-ing the conrod: ie, there's no matching face or point on either side that I can use to measure the offset to the conrod and get a balanced measurement with any accurary.
This is with the wheels as far "left" as they will go:


This is with the wheels as far "right" as they will go (the rule hasn't moved).


So - need to play with this a bit more, figure out the shims and tinker, then rebuild again.

Over night I also had a nasty though that I may have put the output side case on without the main bearing pins and carrier... D'OH!  So I'll be checking that end-float again!

I think I'm getting a little pressured and starting to make stupid mistakes - so need to try to slow down a bit and be thorough.

[cardan]

More grinding...

I think I'm getting a little pressured and starting to make stupid mistakes - so need to try to slow down a bit and be thorough.

Yes. What you're doing is not OK; I'm not sure why. Better get some help.

Leon

[Rockburner]

More grinding...

I think I'm getting a little pressured and starting to make stupid mistakes - so need to try to slow down a bit and be thorough.

Yes. What you're doing is not OK; I'm not sure why. Better get some help.

Leon

Care to be a tad more specific?  I did in fact forget the output bearing liner so I know I made that mistake - but have I made any more? This is still my first time doing this sort of work, and part of the reason for describing every step is to make sure that I'm not missing things, even if I have to go backwards again.

[Rockburner]

So - yesterday I got the opportunity to dive into the workshop...

4 hours of facking about later....

In imperial...


and metric units:


9.3 kilos.... yeah - that's pretty hefty.

I pushed some oil through the big end to clear it out before proceeding:



Then left it to drain for a few minutes


Before starting the iterative process of finding the best mix of shims for an acceptable end-float and conrod centering:

Each trio of photos will be: the measured overall end-float, then conrod vs case centre-line with crank to LEFT, then crank to RIGHT.
one:




two:




three:




four:




six, no five! :

(fecking guage)




That's acceptable and seemed to be as close as I was going to get with the shims I have.  Between 0.015 and 0.020 overall end float, and the conrod (allowing for the big-end float as well) is as centred as I can get it.

A sure sign of a troubled mind.....


I've ended up with a very thin shim on one side, and quite a thick combo on the other.

I believe the main reason for this is that the main bearing liners are of different vintages, and protrude into the cases by different amounts (which is the main reason for the adjustable shimming).  The old liner in the Timing side case is only slightly proud of the case it fits into (which is the side of the crank-wheel I had to grind down).  The new liner I fitted into the output side is much more proud of the case: ie, it has a thicker "brim" (think of it shaped like a top hat); so, to center the conrod, there is less "room" on the output side between the liner and the wheel.

I think I spent about 3 hours on that: each measurement above represents unbolting the cases, pulling out the wheels, pondering the next combo, then reassembling (making sure not to fling bearing pins everywhere), bolting up and resetting the guage.  The guage was a bugger to zero each time.

I then restarted the assembly process:
First get the mating faces clean:

Can you get high on meths fumes??


Stick the wheels in with the bearings and shims, then fetch the sealant.


Oh FFS!


Even with having squooged the stuff up and down the tube to try to get it mixed a bit better.. (metal tube - hence the leak above) it still came out very runny. In fact, it literally poured out of the tube (which is why I ended up with slightly more on there than I had planned.  )




I cleaned it all up as best I could before it got too sticky




It does make quite a mess....


I can only hope that there isn't too much dribble inside the cases themselves.

Just for shits and giggles I checked the end-float again:

(fecking guage)


Satisfied with that, the end-float is still as I hoped and with luck, the 3Bond will go off properly.

I decided to carry on and fitted the piston again: naturally I scratched hell out of the piston getting the sodding gudgeon pin circlips in:




Then fitted the barrel rods:



To get a good "heft" on the barrel rod nuts I put the whole thing into the vice briefly:


So - we're back on track, if behind schedule slightly...


I left it there for the evening to let the 3Bond go off, and to ponder the next move:
Specifically: do I try the 3Bond on the base gasket again... or use something else: the immediately available options are Hylomar Blue, or silicon RTV.  I'm tempted to try the RTV to be frank, mainly because (from memory of last time I used it), it's much, much less runny than the 3Bond, and so easier to be exacting about where it's applied.  I don't really want too much of it dribbling into the cases.

So, I went back in and fed the cat:

[murdo]

Liking your work so far. My preference is for the Hylomar blue as have seen too much RTV stuck in oil galleries.

[Rockburner]

Liking your work so far. My preference is for the Hylomar blue as have seen too much RTV stuck in oil galleries.

Yes, that's one of my concerns, not that there's many oil galleries in this thing!

[Rex]

If you ever have to (God forbid) centre the conrod in this way again, stick a piece of masking tape on the face of the rod and measure and mark the centre line using vernier calipers.

[Rockburner]

If you ever have to (God forbid) centre the conrod in this way again, stick a piece of masking tape on the face of the rod and measure and mark the centre line using vernier calipers.

I was trying to do exactly that with the rule laid against the conrod sides but it was quite difficult to find a point on the cases that the caliper point would hook into reliably and consistently. Which is why I ended up simply using my Mk. 0.9 eyeball.

But making a centerline on the conrod to facilitate that would be an excellent idea, thank you.

[Rockburner]

So - I got into the workshop for a lengthy session on Saturday... lots of photos!

First I turned the piston around... :roll:  The gudgeon pins are getting a little easier, but they're still gits to get into place properly.

Then confirmed that the ring gaps were in the right places:




Fitted the ring clamp


Then I fed some oil into the output side main bearing, to make sure it has some. Mainly because I still don't really see how oil gets into that tiny hole... just from splashing up??


I'd decided to use the RTV for the base gasket this time. (Once I'd cleared the dried out stuff in the nozzle.)


It's a lot more controllable than the 3Bond.


I put a layer on the top of the gasket too, once I'd got it in place over the piston.  I managed to not get too much goo in places it shouldn't be!


Cylinder back on. Wasn't too hard this time.


Prepped the head gasket again - both sides this time. Note to self... that mat is NOT fully heatproof... (I'm sure I took a picture of the somewhat heated newspaper the mat was sitting on...)


Before dunking it.


I wanted to redo the head gasket mainly because I'd only heated it up on one side previously and I didn't think it had "taken" properly.

Head gasket in place.



Once I'd spun the head rods up into the head I put the whole thing into the vice again to get things tight.


Fitted the timing wheel - mainly because it give me a decent grip for rotating the thing. (and marked a reminder....)


Stuck the tell-tale into the plug hole:


Fitted the lower valve covers.


Fitted the push rod guide fittings. (Only using the adjustable because they're rather large...)


Valve caps.


Fitted the rocker box


These two oil feed nuts are an absolute !"£%^% to get tight because you can't get a spanner on them.
I eventually (more later) managed to get them as tight as possible, but they need to be loose AS you fit the box in order to get the pipes into the feed holes in the head that feed the valve guides. I may need to find a split spanner or something to get them done up properly. (I'm also tempted to replace them because they're completly knackered).  I had the box on and off about 3 times trying to figure out how to fit the thing properly.


This is the point where I realised that the thread in the rocker box for the hole that holds the valve cover was $%^&&ed.


So the rocker box came off again!


I then spent quite a while trying to find larger screws that would be appropriate. I initially had the plan to drill out the hole to a larger diameter, then thread for a bigger screw.
After I'd started finding screws and had dug out some taps...
I realised that I should figure out what the original thread was...
It's a 1/4 BSF. 
And I've got a thread repair kit for that!

So I dug it out, drilled the hole out and tapped it for the repair:




All good!


Still got plenty of inserts left, but hopefully I won't need many more!


I also shortened the bolt that was in use slightly (it's not a match with the rest of the bolts in use here)


Always round off the end...


And, even though I'd spun the nuts back off the bolt to clear the thread ends, I also span a die down the bolt too.


Now it's a matching length


Test fitting


So - time to start on this side of things....


Cam followers going in.


Timing pinion and cam-shaft into the chest.


Push rods in. Bit of a git to get in tbh, the exhaust especially, the camshaft has to come out to get the pushrod in between the rocker and follower.



aaaaand that's where Saturday's fun ended.  I needed to do some reading to remind myself of the process for timing the valves.  This is, again, where my existing knowledge is completely lacking, I've never done this before, but I'm very aware of the risks involved in getting it wrong!

[Rockburner]

Aaaand I got into the workshop today as well!

I spent some time reading Fenner, Pitman, Irving and Greenwood... and while they don't disagree with each other completely.... there are some differences. :roll:

But - we'll get to that.

Back in the workshop I double checked the current setup:

This note tells me how the timing pinion on the crank-shaft was fitted prior to dismantling:


And that's how I fitted it:


The books had said that one trick was to fit the mag-platform/timing chest cover to check the backlash and to ensure that the gears weren't jumping about.

So I fitted the studs: using the double-nut trick to get the studs themselves nice and tight:


Timing chest cover in place (but not pushed fully home)
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This is what I was getting as backlash with both valves open.




2 degrees of backlash.  1 degree is what is mentioned in the books, so that's something to talk to the guru about... along with other things, but I'm not distubing him on Easter weekend!



I carried on regardless - it's all good practise.
You can't really see it here.... but the push rods are ever so slightly not straight.... which means they should be replaced.



I played with the timing wheel and piston tell-tale until I got the 0 degree mark right at TDC. 


The tappet clearance, according to one of the books should be 0.003" and 0.004", then reset to 0.002" once the timing is done: which seems a tad odd... but this comes from the Greenwood book - which is based, from my understanding, on racing experience.






Set both sides easily enough.

This is the timing numbers from the 4 books I've got....


I wanted to check the valve openings with the dial guages, so I dug out the ally bracketing I had found a few months ago and made a start on making up the 2 small brackets I needed.








Bit of heat to make the bend easier


Along with an assist from my number one, all time, favourite tool.


The holes for the small end are 1/4", and I ended up doing the other end 1/4" as well - turns out the dial guage lugs were exactly that size.


Guages fitted and aligned.



I lost count of how many times I spun this thing.
I marked the "correct" timings on the wheel in black, and the timings that I had, which were surprisingly close for a first go, in red. But I can't quite make sense of the offsets: I had expected that if they were "early" at one point, they'd be early all round.... but they're not... not quite... I am wondering if I've got a "sporty" cam here... but will be talking to the guru about it first.



One other thing I have seen a photo of, is a little handle on the timing wheel to make it easier to rotate, so I figured that might be worth adding.


I used an M5 bolt and a cork...    It may get improve upon in the future!


So - I need to talk to the guru next week, and buy new push-rods, along with the ends (which come separate), a new oil-union for the rocker box, some new oil-nut fittings, a spanner to fit the buggers (if I can find the right one),

I have another job coming in which necessitated moving a few things about in the workshop... and while doing so I discovered that the right side fork is weeping oil... and there was oil under the gearbox, which I think "might" have been coming from the kickstart shaft.  Goldarn it! GAH!