classic motorcycle forum

"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

Oh dear.

Re gasket sealant, I've used Loctite Aviation Gasket Sealanf No. 3 https://autopro.com.au/ap/Autopro-Category/Brands/Loctite/Loctite-Gasket-Sealant-No-3-Aviation-50mL---3JA/p/DI01199 for may years. It's a bit old fashioned, but is has many properties that I like. It doesn't set (surely it's best feature - I hate nothing more than to find bits of sealant crap floating around in an engine), it seals well, it's cheap, and it's a dark-blackish-brown colour. Just a thin layer on any gasket, or machined metal-to-metal faces, wipe excess off with a rag - looks good and works well.

Avoiding things clanking is the ancient art of "fitting". Lots of measurement and care required. Often forgotten is that things expand when they get hot, so clank-free  on the bench is not enough - correct clearance is important. Make sure the rod is central to the crankcase opening, and double check that the piston is precisely at 90 degrees to the cylinder base. (You can do the latter with an engineer's square on the crankcase mouth, remembering that the piston is not round, and probably tapered! If you do a trial fit of the cylinder with no rings, the gap between the piston and the cylinder should be even.)

All good fun!

Leon

I'll have a look at that gasket stuff - The 3Bond seems to have separated in storage, I think that's why it's so runny and not working well.  I'l have to try to re-vitalise it a bit!

Yep - the heat expansion needs to be born in mind etc.  All good points!

Lewis project  (ex-Adelaide)
Said to be 1910
What engine is that

https://scontent.fbne6-1.fna.fbcdn.net/v/t39.30808-6/656653990_936403695650586_909555156376747768_n.jpg?stp=cp6_dst-jpg_tt6&_nc_cat=106&ccb=1-7&_nc_sid=e06c5d&_nc_ohc=1Byd0ztidSIQ7kNvwHLz3eK&_nc_oc=Adr2QXIju4D6UVj1SdEDGn8PkC5lOydZKbZmxiQMrhTum3_fh1n4is6iboMt0Deo-uI&_nc_zt=23&_nc_ht=scontent.fbne6-1.fna&_nc_gid=9V5lj1zNrTJq0sz6APrccg&_nc_ss=7a30f&oh=00_AfxhHqDjdEoBu-rsT0HRi3oNRBueq8leAUHIJwoPIOJhSg&oe=69C9629C

Have some vague recollection of some discussion of this - with those twin bolts in the exhaust stub like that.
AJS  ??

Soooo, I hopped and skipped into the workshop on Friday afternoon, full of the joys of spring!

First thing I did was remove the larger half of the head-steady so the bracket that goes onto the head would be easier to fit...
My Dad's choices here are clear... this nut is NOt coming undone!


Then I undid the Rocker  box again so I could document the assembly process properly (as promised).
First: Assemble the rocker arms and bearings into the bottom half of the box like so: Note the "outboard" bearing liners have been pushed "down" out of the box body, so the rocker arms have next to no end-float:


Gently put the top on.


This is what the push-rod side of the box should look like - the rocker-arm bearing liners will be proud of the box face:




Fit and tighten down the "inboard" fixing screws, This will lock the "inboard" rocker-arm-bearing-liners in place, but allow the "outboard" bearing liners to still move: when the cover is fitted on, it won't meet the box edge, because the stubs on the inside face of the cover are meeting the outer end of the rocker arms: 


You can see the gap all around where the cover meets the box.


Tighten up the cover.  This pushes the rocker arm against the bearing liner, and pushes the bearing liner into the rocker box.


Most of these engines have a single-sided wing-nut/bolt for the rocker cover, but I just have a plain set-screw (bolt)


The bearing liners have now been pushed into the box, and the end-float of the rocker arms is limited by the stubs on the inside of rocker cover face.


Note - this bearing liner (exhaust side) is still a little proud.


Now fit and tighten the "outboard" fixing screws to lock the outboard bearing liners into position.


The assembled rocker box: the rocker arms should "flop" about freely, but without rattling around.  With that in mind, it's worth remembering that they only need a small-ish amount of movement  in actual usage.


Fitting the Rocker box to the Head:
The lower valve covers go on first, then the Rocker box:


The Washers on top of the Rocker box are spacers to allow the head-steady bracket to fit easily.


Head steady bracket:


Rocker box fitting bolts - getting these aligned is a bit of a git:


Test fitting the upper half of the valve covers:


Ah - yeah... the oil feed banjo fitting - that would have been easier to fit EARLIER....
I may need to find another one of these, it's brass, and the hex "head" is knackered.


And as for these little gits....


These are the oil feed into the valve-guides, and they are a pain in the arse to fit, so I took the Rocker box off again to fit them!


They're just  a push fit into small holes in the head, so sealing them wo'nt happen. :roll:

At this point I was pondering something and happened to be rolling the crank back and forth....

when I heard and felt a distinct "clunk" coming from the movement of the crank. :wtf:

Video:
https://youtu.be/_VnexesDQKA?si=NvSMuXI4gSz3eD10

So... I started stripping everything down again! GAH!

A rather unpleasant discovery  when I took the barrel off was this oil weep under the base gasket:




To be honest, I'd had a nasty suspicion that I'd seen dirty oil at the bottom edge of the barrel, looks like I was right.   I think the 3Bond had soaked into the gasket, or maybe it just wasn't thick enough??  Don't know: but when I fit the new base gasket (I'm going to make another one because this one is very tight around the barrel base), I think I'll use Blue Hylomar instead of 3Bond, maybe, don't know, we'll see.  I'm not impressed because this was weeping with zero provocation whatsoever, there's not even any crankcase pressure at the moment - the timing side is still completely open so this was weeping simply through capillary action.  It is interesting though that the weep lined up with edge of the barrel base that is broken (see earlier photos).  I think pulling the gasket away from the barrel base may help, hopefully!

This time I took the barrel studs off before the piston - makes it easier to get to the gudgeon pin circlips.


Another shitty video...
https://youtu.be/mW1prhFqC4U?si=zz84myipwydojLNr

(Apoloies about the portrait videos, I set things up in a hurry, will do better next time!)


So - the cases were split again!



I did figure it out though...
THIS:


is scraping on THAT:


I think the big-end-shaft nut is hitting the main bearing liner locating screw:


really not sure how the design would even allow for that.. but, it appears to be what's happening. I can only assume that previously, the thrust washer on this side was thick enough to create a clearance: IIRC the two thrust washers fitted were a 0.040 and a 0.050: because I've fitted a new liner on the output side the clearance in the cases is (I think) now a tad smaller, so when I did the crank end-float I ended up with slightly thinner overall thrust washers fitted.

I played around with the thrust washers: simply moving the fitted ones around (ie, moving one from the output side to the timing side), and this did seem to create enough clearance:

Video:
https://youtu.be/iPZ7o_STyd0?si=gztkDB_r870HtbDh

But, I think I'm going to do some more checks before I start the assembly process again: I'm going to make sure that screw is down as far as it will go, and I will likely do a touch of grinding to take some metal off the top of the screw head, just to increase the clearance a bit more.
Then, I'll fit a thicker thrust washer on that side, and re-do the end-play by fitting the correct thickness thrust washers on the output side.


Funnily enough... the output side of the bid-end shaft has the nut and shaft ground away slightly in a fashion that would indicate that this issue has happened on the other side.  While pondering this over the weekend (I've thought of nothing else), I did wonder if maybe the fly-wheels got swapped over when we replaced the big end bearings, but I'd be very surprised if this was the case, the crank wasn't completely disassembled: the output and timing shafts were not removed from the wheels, (and it's not a reversable assembly), so I am slightly confused.


Output side crankcase cleaned up nicely:


This stuff rocks!



So - all this weekend I've been pondering my options.

I think I'll start, as mentioned, by trying to take some material off that locating screw (won't be much, just enough to make it less of a prominence),
cleaning up the rest of the sealant from the cases,
Re-doing the crank end play with a thicker thrust washer on the timing side to ensure clearance,
Make a new base gasket (maybe with a thicker bit of paper... not sure really)
Then restart assembly.

few steps forwards.... several steps backwards.... hey ho...  it's all a learning experience!

Interesting, I always thought the petrol engine would require more finning because it burns hotter than cool running dope.