125-200cc help need after bottom end rebuild...please

i had two cr125 engines that ran fine,one broke the manifold and needed new barrel but it still ran well,my engine in my bike has always been perfect till the 3rd gear went,i had a mechanic open up that engine n found it had been welded b4 n one bearing could be pulled out with his finger,so i use 2nd engine with new barrel,ok for 3 weekend n bearings started knocking in the bottom,so i now have had new bearings done and the better parts from both made into one....now i got it back just without topend as i know how to do that,the problem is now my bike wont run on higher revs,it will tick over and sounds great until its in gear then after 2mins riding open throttle and it just bogs n dies,ive tried both topends n results same,it also smokes alot,any ideas before i send it back?

put in a new plug.....check the carb, what main jet is in there...check the reeds...make sure your gas is flowing free from the tank...do you have one of those silly "one way" valves...take it off. pipe/silencer clogged?

Are you sure you put the correct piston in?

BTW, I have a spare cr125 transmission.

cheers for reply,ive now used both set of reeds, both barrels with the old pistons that were running fine b4 bottom went,with there correct carbs.both engines were fine on topend and bike ran super,never had jet issues before,nothing has changed except the rebuilt bottom end,ive had cap off tank while ticking over n it still died with throttle so its not that,its like its oiling up plugs,would crank seals cause this or could he have put power valve on wrong in the outer clutch cover?power valves are smooth n free running,put new plug or clean/dry plug and itll fire up n tick over again n rev for a bit but once open it up properly just wwrrr ddead.please any thoughts,im pulling my hair out,got to go out now but im back later n will try anything.

sounds like it could be stator fault, mine had similar fault and that turned to be the stator.

would stator do that?only affecting higher revs?

It can...not typical....but it can.

When the motor was rebuild the stator was taken off and handled.

Check all your electrical connections.

stators fine as when first started it will rev up to full,then its choking up thick smoke and dies,ive droped gear oil n its lost 200ml since ive been testing things so it looks like crank seals not in right n im burning loads oil starving the engine of fuel n oiling plug up,im going to send it back but the guy who did it hasnt offered to check it,should he do it for free,i paid 260 and supplied husky parts,seal kit gasket set n main bearings.

fuggin oath he should do it for free!

Take the right side cover off the motor and check the crank seal ...replace if needed. It might be not put in right.

It's not hard to do and you do not have to split the cases to change a seal.

$20 bucks the oil side seal was rolled putting in crank,I've done it myself. You have to pull the seal to see if it was rolled,Do NOT resuse the seal once pulled. This would explain all the smoke and no top end.

yeah iwas sure the seal had gone,really pissed off as the mechanic swears he put new one in,but in the seal kit there was still a crankseal init and it didnt look like it had been pulled out of a case that been used at least 3 years!i sent it back n he charged me 140 quid to check his work out n fit another seal!
its back now and ive rebuilt it and had a run round fields n it seems ok,no thick white smoke n powerband opened in each gear,fingers x'd.