This is the part that that I wished I had known about, 5 years ago. From KLRChris,
What does the KLR650 MC Mod do?
KLR650 MC Mod exhaust cam timing for the Gen 2 looks like this:
Open 57 + 15 = 72° BBDC
Close 37 – 15 = 22° ATDC
Cam Center Line 115 ° ((72 + 180 + 22)/ 2)-22) = 115°
Peak combustion pressure = 19°
The effective power stroke from the point where peak cylinder pressure occur is reduced from a 104° duration to 89°. This cause EGT’s to substantially increase. In some cases as much as 320°, an indication that combustion has not fully completed. Again, large piston moderate compression, poor squish and relative moderate ignition timing.
Overlap decreased by 16°, from 57° to 41°. This will also reduce cylinder fill. Reduced cylinder fill will also cause lower peak combustion pressure.
No evidence exist that someone other than the author has actually taken the time to take a degree wheel and dial indicator to the engine to verify the cam timing before and after the advancement of the exhaust cam. Not verifying modifications is the same than target shooting in the dark.
With the above information of the effects of the MC Mod, combined with the AIS to the exhaust system, particularly to the LH exhaust port seat & valve, combined with the overly-rich mixture from being forgotten fast idling with full cold start enrichener, burning in the exhaust port area is what I believe caused the excessive wear of the exhaust valves and valve seats in this case.
I could be wrong.
Hopefully we can revisit this thread in another 10,000 miles.
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