valves

[RDfella]

Well, actually for a B34, but has anyone else had this problem? Not sure what to do.
Second time I've had valve cotters sinking into the collar. First time it actually pulled nearly right through and it was only the valve spring fouling on the rocker that stopped us short of carrying on to destruction. This time strip down was for a different reason, but getting exhaust valve to release its cotter was a struggle. They had already started sinking in. Given no NOS cotters / collars are available, might have to do a full sort=out and change to Gold Star valve/spring/cotters/collar.

[Triton Thrasher]

Sinking into a steel collar?

[RDfella]

Yes. Sadly, it's a problem, but never seemed so bad in the 60's & 70's. Pattern parts perhaps?
I fully expected the inlet with its DBD alloy collar to be iffy, but it's fine.
The problem appears to be the shallow angle BSA used on its earlier cotter / collar fit. Looking at the cotters,  it's difficult to see which way up they go, whereas today the standard is 7deg.
Have decided the answer is to convert to a better set-up, but where do you get exhaust valves that big these days? DBD inlets are fine, but in order to accommodate them, they made the exhaust smaller so they're no good. Need a supplier of valves to choose from. Are Alpha still in business?

[JulianS]

Check out G & S valves in Godalming.

[chaterlea25]

Hi RD,
Yes had the same problems on B31/33's
Luckily I had enough bits to pick out a workable set, they were all original BSA bits as far as I could see.

John

[Peter in Aus]

Was talking to a friend of mine who is a renowned motorcycle racer about the cotters wearing into the collar, he came straight up with what causes it. The valve springs are to week, causing valve bounce, and allowing the cotters to rotate in the collars. What he did, was to fit another spring in the middle with the spring winding in the opposite direction, this allowed much higher revs without valve bounce and cured the problem.   

[Catz]

That sounds like a good idea.  That's the set up on the FJ and maybe other more "modern" bikes.

[Triton Thrasher]

Was talking to a friend of mine who is a renowned motorcycle racer about the cotters wearing into the collar, he came straight up with what causes it. The valve springs are to week, causing valve bounce, and allowing the cotters to rotate in the collars. What he did, was to fit another spring in the middle with the spring winding in the opposite direction, this allowed much higher revs without valve bounce and cured the problem.   

Thanks.  I learned something today!

[RDfella]

Springs are already a contre-wound pair, but could probably benefit from renewal.
However, given the poor cotter / collar arrangement, currently searching for an alternative valve with modern cotters/collars.

[berger]

just read that these B44's had a problem with valve keepers from over hardening or keeper angle of 7 degrees or 6 degrees and miss matched parts can cause a problem at high revs , now where's my black& tan thankyou for listening have a nice day, good luck rd  googly mentions some bike links about this subject .

[RDfella]

After some research, seems my original suspicion of cotter angle wasn't far off. Maybe sufficient when using cooking cams, but start destructing themselves when loaded with race cams.
My research shows that the included angle for vehicles' cotters varies, but moderns tend towards 14deg, whereas Gold Star and A10 with alloy heads are 10 deg. Early BSA's use 8 deg. At present a cut down Porsche exhaust valve with KK9 cotters (14deg) is looking good.

[muskrat]

G'day RD.
When I converted my A7SS head to take SR valves and collets I had to machine the keepers to accept the SR collets. Can't remember the angle.
Fun when we start modifying things for extra performance.
Cheers

[RDfella]

Have settled on Porsche 911 exh valve - will need shortening and I'll use KK9 collets. Will either find a collar to fit (possibly Vauxhall as they use 14 deg) or machine out the BSA one. The steeper angle should stop the constant creep of cotters into the cap.
Re fun - I started racing this bike in mid 60's and now repair it for my son's use. This state of tune keeps you on your toes ....