Scooterotica

Hi, my Jet 200 has: Gran Tourismo kit, 28mm Delly, BGM clubman. I changed front sprocket to 16 tooth. It pulls like a train through to 3rd gear, say about 85-90 kmph, then I get into 4th gear and the revs drop. Acceleration continues but noticably slower. I top out about 115 - 120 kmph but it takes a while to get to that. The engine feel like it still has power beyond that, that I am running out of gearing.

Is the solution to go to a 17 booth front gear? I already have a longer chain in it (used a tensioner to use up the slack).

Thanks
David

If you put a 17 on that will make it taller try a 15 what gearbox are using

After thought whats your ignition static or varitronic as if either is set wrong that could cause the same problem

I run a Li150 box 17/46 (4.6) on my GT200 with BGM clubman and 30mm Delly, pulls that gearing comfortably. Ignition is static set at 17 degress, on mine.

What gearbox and crown wheel are you currently using?

Jet/SX200 box would have been fine left with the standard 15/46 sprockets.

scooter has a SX200 gear box, BGM stator & flywheel set to static 17 BTDC, 46 tooth crownwheel.

From the table, stock 15/46 is 4.82, 16/46 = 4.52, 17/46 = 4.25.
and going up in front gear should be giving me 5mph each time. Or am I reading this wrong?

On similar set up but with an indian gp200 box and 4,8 final drive i reached 130kmph and were able to sustain the speed on full throttle last summer.

Davidsquaredson wrote: ↑Tue Feb 20, 2018 1:17 pm scooter has a SX200 gear box, BGM stator & flywheel set to static 17 BTDC, 46 tooth crownwheel.

From the table, stock 15/46 is 4.82, 16/46 = 4.52, 17/46 = 4.25.
and going up in front gear should be giving me 5mph each time. Or am I reading this wrong?

No, you're not reading it wrong. But it depends entirely on the ability of your engine to pull it. A quick calculation on a gearbox selector means my little LI150 should do 150 MPH with this and that gear. But it's pretty meaningless in reality. You're only taking it further away from the power which will be generated by higher RPM and lower gearing.

Go back to the original 15 front and see if it immediately resolves your current issue, which I think it will.

Adam

you say you changed to 17 front, which is clearly too tall, what did you have on the front before, which i presume revved out in top gear and made you think it would pull a bigger front sprocket ?