I just put a 350x motor out of an 86 3 wheeler on to my 91 250x I have everything done and it runs good, but it dosent have the speed I expected from the 350, what can I do to beef it up or what am I doing wrong? I used the 250x carb, and I think I am running a 140 main jet?? should I be using the 350 carb, or is the 350 carb any bigger, if not is there like a 38mm aftermarket or somthing that someone recomends. also I think it might be geared to high, I have the stock 250x sprockets on both the front and rear, I think the front is a 13 tooth, anyone know the size of the stock 350x sprockets? any help would be appricated,

the 350 dosent seem like it tacks out like the 250 did, I also changed the cdi unit to the one from a the 350, I adjusted the throttle as much as I could, that help some but she still aint moving like it should, I think. thankx, later

 

The stock gearing on a 350X was 13T front and 40T rear. I would definitely put the carb from the 350X back on. I don't know the stock carb size on the 250X but I would bet it has a smaller bore in turn restricting the normal air flow.

 

I have now learned again from Powroll, that the carbs from the 350x and 250x are the same size, 34mm, also, they said that the 250x carb accuactly flows better than than the 350x, (better design), they also said no airbox lid, the person I talked to seemed to stress this, also I am going to slap in a k&n filter, I am using the stock now, I am going to put on the 350x airboot (from box 2 carb) if I can make it fit.