Bignothing

Fixed! The float needle was sticking closed. This explains why it felt starved of gas sometimes but ran well momentarily. Took it all apart and cleaned it. Float needle now drops under gravity to touch the float lever tang as it should. Runs perfect!

Thanks for the replies. Yeah, 100:1 seems too light on oil. However, a trials school with a fleet of mid 2000s Gas Gas 2Ts has run them for years like that without issue and they have a lot of hours on them. They also use 100 octane avgas. The more I think about it, I’m still leaning toward a fuel delivery issue. Electrical wiring issues tend to cause complete and abrupt shutdown and this problem is not like that. I had a bad ignition coil once that worked fine at idle speed but fell apart at higher revs. But it always malfunctioned the same way, not occasionally as is the current problem.

Thanks for the reply, stpauls. Negative. Main jet was removed and checked. Choke not on. Air filter not blocked and not that dirty. As noted, the bike runs great intermittently, so it points to something that happens occasionally, which makes it all the harder to diagnose.

Hi everyone, new to the forum. I picked up a 2005 Sherco 250 2T and I’m having an issue with it. It starts and idles fine, but it falls flat at half or greater throttle. No power and it won’t rev out. Strangely, on rare occasion it revs out normally for a few seconds but then goes back to poor running. What’s been checked: Fresh gas at 100:1, new plug, no water in carb bowl, float height right on, reed valve good. Stock 118 main jet at 700 ft elevation. Air filter is clean. I think I’ve about eliminated fuel so I’m thinking it’s an ignition issue. Anyone have anything like this happen on these bikes? Thanks!