Took to Shop: "Stuck Valve", rejet, Dyno - $275

[The Buddha]

I've run it from canada in winter to central California in summer with a O2 sensor in the pipe. It wont work with anything bigger than 152.5. And there is a loss in performance from 150 to 152.5 and actually there is a loss from 147.5 to 150 but its a much smaller loss, the O2 sensor reads 147.5 as a shade lean and the 150 as a shade rich.
I'd say the sweet spot is under 150. That is if you have a normal pipe and a K&N. Do funky stuff like a 4" header pipe or a set of velocity stacks are yea 150 may be lean. Else 150 is just what it can handle. BTW how did it run before the intake manifold got eaten like it was.
Cool.
Buddha.

[ben2go]

If the bike is jetted to maybe 3-4 sizes over the main you need, you will not run past 6-7K and get worse than 33 mpg. The thing is it also will be soft and gutless when accelerating, and possibly smell like gas all the way across.

I have a feeling this is it. I had already rejetted to 150 main, and the shop guy told me that he needed to go up in size, which tells me that they are now too big. Couple that with the fact that he told me he ran this on a Dyno, but yet somehow missed the fact that it does not accelerate past 6K rpm makes me think this guy is bulls***ing me.

I will install my CRF petcock, test the max rpm at each gear, do a proper plug pull to see what color they are, and repost with my results. I am hoping the petcock is the issue, but oversized jets seem to be a likely culprit as well.

I really don't want to mess around rejetting the carbs again myself since its running better now (despite the rpm problem) than it ever was before, which really isn't saying much, lol, but overall it still runs decent.

Thanks again for the help guys, I'll report back when I get more info.

Over 150 mains is way overkill.I have never been over 145 on mains.I currently have two GS motors running.One is a spare.The motor in my bike is running 145/40/2 washers/3 turns, and my spare is running 142.5/40/1 washer/3.5 turns.Both used the same exhaust and same lunch box filter.I think maybe the engine I currently run has had some internal work because it takes a more aggressive jetting to run smooth.