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valve lifter wear

Posted: Thu Jun 04, 2020 11:08 am
by FGF
Hello ,

when you find an exhaust rocker scratched by the valve lifter like this :
decomp_us.jpg
what is the better way ?

forget it and run like this or weld it and grind it with what kind of welding ?

Thanks
Francois

Re: valve lifter wear

Posted: Thu Jun 04, 2020 11:47 am
by minetymenace
FGF, this is a "bump" for a question you asked in your Project Bikes topic, but without your own solution!

As you say, RR suggests welding it up, and if you have the means it would be quite easy to do if you can be arsed. Remove the ball on the end of the rocker (it is a push fit and can be drifted out) and fill the hole with weld (don't ask me how, to me welding is a black art practised by simians in the frozen north), then dress it back flat with a file. Re-insert the ball end making sure the cross drilling lines up with the oil way in the arm itself.

The indent is unlikely to be normal wear as the decompressor is only used to position the engine when starting, I guess the ding has been hammered in when the lever was pulled while the engine was running.

Re: valve lifter wear

Posted: Thu Jun 04, 2020 2:35 pm
by Jeff K
I am not sure if the area or the entire arm is heat treated or not. But, be aware that welding on it will change all of that. Best to find out before taking it to a welder.
Jeff

Re: valve lifter wear

Posted: Thu Jun 04, 2020 6:49 pm
by Momus
:?: Just run it.

That mark will be totally inconsequential.

Re: valve lifter wear

Posted: Thu Jun 04, 2020 8:58 pm
by beat
FGF wrote: Thu Jun 04, 2020 11:08 am with what kind of welding ?
if welding, use TIG for this small point.

Re: valve lifter wear

Posted: Fri Jun 05, 2020 1:14 am
by koncretekid
The indent on the exhaust rocker is quite common, as there is no return spring on the decompressor lever. If you look at the motor when it's running, you can see the lever bouncing back and forth because the cable doesn't retract fully on some and even leaving excess slack won't solve the problem. And there can be consequences as the indent gets larger, the decompression lever has to rotate further and can cam over if worn badly. I just replaced one on the B44 parts bike because of this, but I haven't tried welding one up. I am considering putting a return spring on mine.

Tom

Re: valve lifter wear

Posted: Fri Jun 05, 2020 1:39 am
by Canberra
On the B50 there are two designs for the valve mechanism. The later is spring loaded to release the valve lifter. I changed mine many years ago so am unsure of the parts involved.
I agree with Momus. Welding may bring up more issues with heat treatment than you're trying to cure. I believe Stan did weld up rockers on one of his specials but he knows what he is doing.

John