RM85 2003 model problem

Good day to you all.I'm having some issues with my sons little rm85 its a 2003 model (with a power valve). As soon as I hit the gas it just boggs out on high rpm's ,when I change to 2nd ......good power but as soon as it reach high rpm's the same happens same in 3rd etc. The fuel tank is clean and the carb is clean new air filter and new plug new crank seals and new stock reed valves it has a fuel 2 stroke mix of 40:1 fully synthetic castrol oil.The bike starts very easy cold or hot. I've checked the power valve it seems that its functioning normally when revving it up the valve opens as soon as you get to 3/4 of the throttle +-.......... Please anybody any suggestions? Did anybody experienced the same thing in the past? Thank you .

have you tried tuning the carb and cleaning it sounds like the main jet is clogged

Thanks for the advice ,ill check it out and let you know.

Hi to all,oke I had another go with the RM85 ......I've re-checked the carby its clean and I've tried various jets too,leaner and richer moved the needle up and down but with no luck. I also cleaned out and repacked the muffler. So I put the bike on a stand started it up (warmed it up first) then hit the gas.....to my surprise (stock jetting) the bike revved up smoothly (in 1st to 6th) gear until WOT! So I jumped on it and took it for a test drive only to find out at WOT it was the same in every gear. Could this mean that if at W.O.T under load when its going BWHAWAW that its a lack of compression? Its driving me nuts already!

did you check the clutch and fluid

Thanks for the reply , yes clutch and fluid 100%

yea i would check compression might be time for a new top end 

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