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I have been reading on this forum and on pelican about the likely cause of dropped or snapped exhaust valves on the right hand cylinder. Usually threads end up a bit too scientific for me and discuss the weak fuel ratio and the fact that it is further exasperated by using a straight through exhaust. By trade, i am a car mechanic so i have reasonable knowledge of cars running weak - especially from the good old days prior to ECU's and knock sensors etc.

My experience in the car world is that weak mixtures would burn out the edge of the valve, and in severe cases would actually pit the head of the piston . Once knock sensors started to get deployed, it would just retard the timing and stop the pinking to prevent any damage.

My question is - do all R1200s owners use high octane fuel as per the recommendations - obviously you can run lower octane as the ECU just modifies the running with the knock sensors keeping an eye on any detonation problems?

I was recently reading a car mag where it was testing the various high octane fuels available on the forecourt. Whilst very little performance increase was evidenced, it did talk at length about the extra upper cylinder lubricants etc that the fuels contained. That said, the tests were on cars that didn't recommend high octane fuel unlike our bikes. Do you think that the better fuel will help guard against the valve issue?

Does the high octane fuel help the cylinder to run cooler - i recall when unleaded fuel was introduced that valve seats had to be replaced because the new fuel increased exhaust valve seat temps - is their any evidence it affects internal temps at all? For classic cars you can get octane booster instead of replacing the valve seats so it would seem logical that octane ratings have some impact on cylinder temps?

If it is a likely fuelling issue why does it only seem (on the rare occasions it happens) to affect the right hand side?

Any thoughts?

Hi
Run the high octane fuel .
Valve clearances need to be smack on. The exhaust valves will tighten up if left unchecked leading to possible failure.
It also pays to have the bikes fueling addressed. Helps if standard and is essential if a exhaust system is added or other mods to the inlet side.
Heat damage to the exhaust valves seems to be the common factor in failures, although over revving the engine on downshifts would be another possible cause. The lean running causes excessive heat in the combustion chamber weakening the exhaust valve through heat fatigue. Couple in how hard the bike is ridden and a exhaust failure may happen. The heads break off the valve stem , usually where they are welded to the stem during the manufacture process. It seems to be more common on the RHS , but there have been LHS failures also. I think the RHS runs a little hotter than the LHS. I will check this out with a temp gun one of guys use at the track next year just to see the difference if any.
There are lots and lots of 1200 boxer engines out there running without problems. In the scale of things it is a tiny percentage which fail.
All the best
Gus