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Hi everybody...

I know someone who told me than he had a 02 XC 800, and he was breaking VES every 500 miles...

I know than this engine was not perfect, but fine tuned, I never broke a VES... I updated to the Stainless steel valves this year only, I was running the old aluminium one... And never broke a VES before...

What can cause the VES to broke every 500 miles ? Even with bad maintenance, that VES should do a little longer, no ???

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its a combination of several things that contribute to take out the VES valves.
- missing coolant passage above the ex. port - the valves has nowhere to get rid of the heat
- lean/hot running mid range - spending too much time here leaves the valves in the hot exhaust gases, causing the valves to warp or break.
- incorrectly set TPS - should be 4.0 volts, was often set at 4.2 - 4.35 volts. This seemed to cause preignition/deto in the 5500-6000 rpm range on some sleds - which I suspect could cause the valves to develop cracks and break off. On my sled, I avoid to run around 5800, where the engine sounds like its "full of marble balls"

Could be me that had VES valves go bad at less than 500 miles. On the original valves , I had around 4000 miles, 1500 with a SLP single. Replaced the valves because they were warped and badly worn. My dealer put in the 03-spec valves with black coating. Took out 2 sets of those in around 1000 miles. Last time I lost the PTO piston and cylinder too.

Then put in Ti valves along with green/yellow springs, these have done around 3000 miles and still looks ok.
I also run the needles at #3.5, trading some performance for peace of mind.
 
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