Scooter very slow after big bore

[cixikingringhini]

Hi guys last summer I bough a GY6 139qmb 50cc scooter. This winter I did the 80cc big bore swap and my scooter lost very much power. It starts right up and idles fine but wont go over 30-40km/h. I swapped the jet for an 88 and it runs much better but still not more than 30-40 and my top speed with stock cylinder was 60 flat 80 downhill. I tried to ride down the same hill and it wouldnt let me past 50 km/h gps. I tried to do almost everything with different results like better take off but no matter what I do it just wont go faster. My needle is raised to the max. The carb is tuned ok I have a race air filter in the stock box but without cover ( it bogs with the cover on). I have naraku variator with naraku rollers. I tried 5.3, 5.5, 6.0 g and no difference. Naraku belt and Naraku racing CDI. I tried stock exhaust, race exhaust even no exhaust and without differnce. The engine revs fairly ok when on the stand with the wheel off the ground. It just doesnt have any power to rev that high with me on it But why even downhill ? What else could be blocking me ?

[Happypancake!]

No power but revs on stand. I'd re-check timing.

[cixikingringhini]

Thanks !
I will do that.

[GrumpyUnk]

Given the mis-marked flywheel TDC indicator of a recent post, it would not hurt to check for mechanical TDC when setting the cam. Ignore the flywheel marks at first, and set the piston at TDC using a pencil or straw through the spark plug hole. Rock the flywheel back and forth to find the 'middle', where the piston seems to sit still, and consider that TDC. Set the cam holes even with the cylinder head top, and put the chain in place. CHECK that it stays correct after two complete crankshaft turns.
Might be a good idea to Sharpy mark the 'apparent' TDC position, whether it tracks with the "T" or not.
tom

[cixikingringhini]

Thanks for your help the timing was at least two notches from center. The scooter runned better but still very low speed. My problem is SOLVED and it was something whole different. The oil in the gearbox was thicker than honey and it litterally took about two minutes for it to even start to leak out haha. Changed the oil scoot now runs decent.