350 cc side valve JAP engine parts needed

[john.k]

The interesting bit is missing from the pic...........I assume the mag is run at engine speed from the timing side mainshaft....so the motor appears to be from an Atco .with a extension for a crankhandle...........looks like you might need to keep your leg and the chain separated..........Funny thing ,I was given half a dozen Japs from rail  trolleys......only singles ,unfortunately,but they all had a ugly addition to the timing case for a crankhandle.....So I left them for the scrappie.I did snafle a 750 twin ,fortunately,who d a thunk theyd ever be selling for princely sums.............are so many people restoring Autotrucks.?

[Mobike]

Thanks 33d6 that information is very useful has been noted.
I have no expectations of breaking any speed records,just an interest and curiosity to try something a bit off the beaten track!
As much a part of this hobby is as you say not the destination but finding out and researching what it is !
Funny you should mention "Tuning for speed " I still have my father's copy and wish I were as skilled as he!
Once again many thanks for your help .
Regards David

[Mobike]

Hello,
I read on another forum that  it is 2" 20tpi ,not sure if that's correct but it s the only reference I have found at this time.
Thanks for your reply,regards David

[john.k]

There is a bit of JAP stuff on ebay from time to time............every now and again someone converts a V twin to OHV and offers the SV  bits for sale.......although the exhaust nuts are pretty rare............I would think you would have to make your own........20 tpi does ring a bell......Im pretty sure the motors only use two different pitches 26tpi for all the nuts and bolts,and 20 tpi for the intake spigot and exhaust nuts...........Its actually a very fine thread for cast iron,but seems to hold up OK.

[Grunt]

I read on another forum that  it is 2" 20tpi ,not sure if that's correct

2” x20 TPI is possible though I somehow think it’s a little on the large side.

[john.k]

i checked the thread on a 750 sv twin,and its 1 3/4",and thats a 70mm bore barrel............Ive also got a 85mm bore barrel,checked and its 2"....thats a 500sv.

[Mobike]

Yes,I thought it sounded a bit on the large side!
I will check it out later ,thanks for your reply,David

[Mobike]

Have nt had time to remove existing exhaust stub but approximately 1 5/8ths ?
I will remove it tomorrow and get a better idea,

[Grunt]

Is this the one
http://www.vintage-motorcycle.com/index.php?language=en&site=4&pid=24&id=26427&limit=0
If so then it probably is a 2” dia thread.

[chaterlea25]

Hi All
The OHV JAP engines use the 2in, thread even the 250cc
The British Only one linked to is priced at €99   

I already suggested "Meetens" who have old stock of JAP and Villiers industrial engine parts for the exhaust nut
or whittle one up on the lathe 

John

[Mobike]

Yes,that's the one I found  ! Looks like I better start a fund?
 After seeing their prices ,that was what prompted my request if anyone has an old useable one they might sell?not worried about the finish as long as thread is usable .
Exhaust is 1 3/4" .
I had the head/ barrel off today,bore looks sound slight wear but rings and piston all sound.Plenty of oil evident,so I have reduced the pump setting as it s still quite Smokey.
Gradually increasing  the running time now i know the pump is working,hopefully turning clockwise on the pilgrim pump does reduce flow?  it seems to be running/starting a bit more reliably now.

[33d6]

Funny isn't it. As with David I looked at the price of that new stainless steel exhaust nut but instead thought they couldn't be making much selling them at that price. To make things on my lathe I duck and weave buying cheap lengths of stainless from a bloke who deals in factory remnants, odd job lots and so on. I can't get it any cheaper. Given the diameter of bar stock required to make that size of nut is far too large to slide through the head stock of my lathe I'd also have to pay to have the bar stock cut in to appropriate lengths to suit. To make an exhaust nut for each of Davids engines I'd have made a severe dent in that 99 pound just to get the material to start.
All of this assumes I have managed to find a hexagonal bar stock of the right size. Reality is I wouldn't and would have to use round bar and mill the hexagon on as well. Another operation requiring another machine and taking more time and effort.
Of course a modern machine shop would use a CNC machining centre to combine these operations and could churn out exhaust nuts ad nauseam. Unfortunately to purchase and set up an machining centre of the size needed runs in to six figures. Just a tad beyond my budget. 
What I'm trying to say is that I find a J.A.P.  stainless steel exhaust nut at 99 pound to be very reasonable. Luckily they rarely wear out. Most are lost by careless owners.
Finally, Pilgrim pump. Screw the adjuster out to increase flow, screw it in to reduce it. This assumes no internal wear.
Cheers,

[Grunt]

Unfortunately I have to agree, making one out of mild steel or brass would be slightly easier but still involve a fair bit of organisation before any machining was done. Another problem would be that to ensure a good fit of the nut, whoever makes one would Be better off having an exhaust stub to use as a gauge.

[Rex]

Agreed. I wouldn't attempt to make something like that without being able to try the thread for fit.

[Mobike]

Ah well,it was a thought.
For my purposes an older slightly battered nut would be acceptable/preferable as it's only a bit of fun, and a new one would show up the rest of it!
l will hold off on that for now as it's coming up to the auto jumble season,my brothers always commenting on my " eagle eyes"you never know!
David