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Messages - windy

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British Bikes / Re: 1929 J.A.P 250cc Sidevalve engine problem
« on: March 13, 2013, 12:50:42 PM »
Yes, not so good. Caused by the PO bolting the crank together without any regard to it running true. The crank webs were closer together at the big end than at the opposite side, causing the main bearing pins to flex up & down on each revolution. This has also knackered the timing gear, but luckily I have managed to obtain one. The opposite main bearing is made up of loose rollers, so a new set should sort that out. Oh, and he managed to put the big end roller cages together wrong too, the double cage spacing washer was not in the middle between the cages as it should have been, but between one crank face & the bearings. Crank pin nut locks were made of pieces of cut off brass screws that were hammered over. They were only screwed in about 2 threads into the crank webs. "New" piston ring gaps were about quarter inch, not 8 thou as recommended. Cam & followers badly trued up, loose fasteners virtually everywhere inside the engine, the list goes on & on. This guy gave me a business card to say he rebuilds druid girder forks for a living. Heaven help those he has worked on!

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British Bikes / Re: 1929 J.A.P 250cc Sidevalve engine problem
« on: March 13, 2013, 11:19:23 AM »
Managed to find some shim stock this morning & used a sharpened gasket punch together with a block of (very) hardwood to punch a disc out. Thanks for the advice guys. Looks like we are getting somewhere now :)

Next challenge is to sort the worn timing side crankpin & bush out.

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British Bikes / Re: 1929 J.A.P 250cc Sidevalve engine problem
« on: March 12, 2013, 10:12:55 PM »
John,
thanks for explaining. I couldnt work out how a disc would work, and imagined it would be floating up & down & around all over the place if it was inside the valve body, but now I understand, it sits "between" the valve body & seat. The valve body you can see in the pic was fitted upside down, so caused a lot of confusion! The seat is screwed into the crankcase, hence fixed, not sprung in this instance. Thanks also for the link to the B&L tell-tale. I could do with one so will likely buy one from him when he comes to Stafford shortly.
Leon,
glad I didn't assemble it with a steel ball now.
I've pulled the engine completely to bits & thankfully caught a few other botches before they wrecked the engine. The "engineer" I bought the bike from, who "rebuilt" it less than 20 miles ago needs locking up!

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British Bikes / Re: 1929 J.A.P 250cc Sidevalve engine problem
« on: March 12, 2013, 04:39:43 PM »
Thanks for the reply Leon. The oil is fed from a "Best & Lloyd" oil pump, driven from the timing gear, with no sight glass, so I'm going to use a section of clear pipe to keep an eye on the oil supply in future. The disc valve idea sounds reasonable enough but i think its a ball bearing shown in the parts diagram, as far as I can see. I was just wondering if there should be a light spring above it but now guess its just gravity that does the job, with crankcase pressure lifting it on the downstroke? The pair of big disc valves between the timing case & crankcase are present.

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British Bikes / 1929 J.A.P 250cc Sidevalve engine problem
« on: March 10, 2013, 12:51:28 PM »
There should be a small valve that admits oil into the crankcase on my 1929 J.A.P 250cc sidevalve. Problem is there is nothing inside the valve casing. Looking at a very feint diagram I can just about see there should be a ball bearing in there, but my question is should there also be a spring?


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