R100 RS Tappets

PW Cymru

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Checked the tappets this afternoon and was alarmed to find no gap on either exhaust. Inlet was perfect at 0.004" so needed no adjustment.

I used the clamp method to torque the rocker shaft posts down prior to setting the exhaust to 0.008" and re-checking the inlets.

My question is the bike is twin plugged and would asume that during the conversion the harder valve seats would have been fitted to allow it to run on unleaded. The bike was new in 83 and unleaded was introduced in 86 so its a fare bet that it is modified.

Could the valve seats be receeding, I'll check them again after say 500 or 1000 miles to see how they have settled.

Bringing the bike home I hit reserve at 170 miles which is about 30-40 miles short of what it should have been.
The tight exhaust valves could have accounted partly for this mpg.

If the exhaust seats are receeding whats the fix ?
 
Contraversial, but - You don't need new valve seats on an old engine.

The original valve seats are work hardened by being smacked with a valve x times a second for 10 years when they are red hot.

the valve seats will be harder than a hard thing - unless you recut them :blast
 
Contraversial, but - You don't need new valve seats on an old engine.

The original valve seats are work hardened by being smacked with a valve x times a second for 10 years when they are red hot.

the valve seats will be harder than a hard thing - unless you recut them :blast

that could well be the case, and then there's "lead memory" to consider. but if they are found to have closed up next service time, i'd say it's time for new seats.
 
I'd say monitor them after 500 then a 1000 miles and if they show tightening think about getting the seats done! and the exhaust valves replaced too!
 


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