Yet another jet question, with a difference.

[Guest]

My son has a 50cc 2T motorbike (Derbi Senda X-treme SM 2006) and will not go above 5000rpm going through the gears normally, in top (6th) it does between 25mph and 30mph, but if you knock it down a gear or two and can get it to 8000rpm she then flies, and as long as you keep the revs above 8000 while changing gear she will hit 50mph+, it has been de-restricted by the PO and the exhaust has been changed, it has been re-jetted as well. I think the carb has been changed as well but I am not sure. I can not find out what carb is supposed to be fitted, so I was just wondering if any one could help with any of the above. Cheers

[hampshirehog]

All those Minarelli engined bikes come with a 17 or 18 mm carb as standard - I can't remember the standard size for a Senda. They're too small for a de restricted 50 and a lot of nippers put on carbs which are way too big.