BSA B2 Pushrods / Valve clearances

[courtney]

1936 BSA B2 OHV

Hello,
I hope somebody can help with some advice.

I have adjusted the valve clearances on my B2 but the clearances, particularly those on the exhaust valve, are massive, around 1-2mm. The adjuster is at its limit and I can't get the valve clearance small enough. I suspect it could be that the pushrod ends are worn or the pushrod itself is too short. The pushrod has a cup on each end.

Will the cups wear deeper over time where the adjuster and cam follower sits in them? Could this wear be enough to affect the clearances so much?

The lower cup on the pushrod sits on the taper of the follower not tightly but enough that when you pull the pushrod off of the follower it will lift the follower with it. Is this an issue? I think the adjuster also sits quite deep in the pushrod end.

The pushrod end inside diameter is around 5/16", so how deep roughly should the ends be at each end? Does it sound like I am on the right track with my issue?

Does anyone know a good place that could make me a replacement or is it possible to source replacement ends for the pushrods to remove and replace mine?

Many thanks in advance.

[limeyrob]

The push rods are probably case hardened and once this wears through the wear accelerates fast.  This may be where you are.  The same can occur with the cups on the rockers.  If the bike isn't' doing a lot of miles then there are fixes.  On is to get some appropriate sized valve caps so you bring the adjustment back into range. Long term you probably need rockers and push rods as when the pushrods wear they wear the rocker cups out of shape.  How are the valve ends of the rockers?  These can wear a lot too.  You can re-face the valve end of the rocker and make up the difference with a valve cap

[Steve.S]

Hello Courtney,
As Mr.Rob says, the easiest solution is to fit a valve cap. Although this might put the rocker geometry out a bit, it probably won't matter much.
I wonder if your exhaust valve is the correct length of 3.802"?
!930's BSA rocker pads had a pronounced U shape to them. Due to lack of owner lubrication over the last 90 years, the thin case hardening will have worn away. This causes a circular recess in the pad, which makes correct valve clearance adjustment difficult. So they would have been ground down, probably many times, over the years, resulting in a very thin pad. Having them built up with Stellite or some such may restore your clearance.
Regarding pushrod cups, these were quite deep from new, and again would suffer from lack of regular lubrication. But I wouldn't know how to measure any wear without a new one to compare it with. The cup shouldn't grip the follower, although I doubt it matters much. Are you sure it's not oil stiction? You could make a new longer pushrod from 4130 steel tubing.
I find excessive cam wear is quite common in these engines. The overall height of the cams in the 1933 B2 engines was 1.228", but although the part number is different for the 1936 engine, I think it was just a wider cam. I think the valves should open about 1/4" which may give an indication of any cam wear.
As far as I can gather, I think the pushrod cups should be about 1/4" deep.
I think I would just fit a valve cap, and ride it while you can.
Hope this helps.