kdx250 no top end power

[smoker]

I have a problem that for now I can't find a solution. First of all the bike was running good it had a lot of power everywhere but it smoked allot and I thought crank seals where gone. I had the engine off and send it to an idiot who used the hammer and a screw driver to take it apart when I saw it I almost had a stroke...... .... He put the new crank seals in and everything else, then I put the engine back on, the crank case wasn't leaking anywhere outside... I cleaned everything and put it together... the bike starter and run really high in rpms after some time it settle down rode it some time easily and after some time I tried w.o.t bud it seems like it has a rpm limiter right where it should pull really hard this happens in every gear at same rpms..... it still has some oil going out the exhaust like it did before....
I have cleaned the carb multiple times and tried different settings nothing works
Spark has some oil on it but nothing drastic
The timing is on the same spot
There are no obstacles in the exhaust or air filter
I run 50:1
Any help??????
Sorry for my English it's my second language

[royadams]

My guess is the case is leaking oil and air into the crankcase. Definitely not a good idea to split cases with a screw driver.

[smoker]

Is there any way I can check for leakage?

[royadams]

You will have to pressure test the motor. There are a few threads on here how to make you own. Basically you plug the intake and exhaust and put a little air pressure into the spark plug hole and see were it leaks out.

[smoker]

Gonna try it as soon as I can. If there is leakage, what is the next step ?

[bufftester]

First when you saw him split your cases you should have grabbed that motor and ran....2 strokes are always going to smoke some and spit some oil out the exhaust, it's just the nature of 2 stroke engines. IF it is running okay on the bottom end and just falls flat check the KIPS valve. It is supposed to open ~6000 rpm, and if it doesn't the engine will feel like you described. A leakdown check like Roy suggested is an extremely good idea and will give you an idea of the condition of the motor overall. If there is leakage then you have to determine where it's coming from. A little soapy water will help you see bubbles, check around the crank seals and around your block offs, base gasket, head gasket, all the usual places.

[smoker]

I saw the marks when he returned the engine it was already late, what an idiot ........I have checked the kips it moves when I give it some throttle could it be it's set up wrong or something like that.... I would love not to have to remove the engine again....