250-500cc Power issues wr300...

Had the bike out for its first long ride after picking it up a week ago. Seemed to run fine on the low end. After getting on the fire roads with my ridding buddies i found it falling off at the top of every gear(buddy with a 13 txc 310 was pulling on me). I've never owned a 300 and haven't had a 2 stroke in the garage in 10 years. Is this normal? The guy i picked it up from seemed super knowledgable about the bike and its setup. Said hes running a 420 main jet in the carb and to run it at 40:1. Any input would be awesome guys

somethings not right. I can barely hold on to mine when i open it up. Thing pulls to the moon.. I assume compression is good? Got it jetted so you got the perfect color with spark plug? Which carb? Bike used or new?

verify power valve functions at top end throttle openings. remove PV cover and visually verify that it's opening.

Has the stock carb on it. I haven't checked spark but it starts and runs great on the low end so i didn't think it was an issue

How do I do that? Can it be checked on a stand running in gear?

yes on stand but in neutral with PV cover removed.

There are stops that limit how far the pv open, take a look at that as well. Maybe the po wanted to tame it a little. I also have the 420 main jet, and my 300 pulls alll the way through. I'm at sea level.

Does anyone have pics of what the power valve should look like when set correctly?

$ Float level too low, needs a bigger main jet, air cleaner over oiled or silencer needs re-packing .
$$ Cracked inlet boot, chipped reeds.
$$$ Ignition
$$$$ Compression