XR70 w/ TB88 I need more torque

[surveywaters]

I have an XR70 that I installed a TB88 kit on. I put the TB cam in and the 20mm carb. I don't care about top end, just torque for my son on the track. I need any tips available. I currently have a 14t front sprocket and 36t rear. I am considering putting the stock carb back on for more bottom and/or putting the factory cam back in which has a shorter duration. What are the experienced thoughts on either of these routes? If I replace the OEM carb, any tips on jetting with a stock exhaust?


My problem is 1st and 2nd have such a big gap that my son (7years old @ 54lbs) tends to stay in 2nd which is to tall coming out of the turns and up the hill.

[PlanetMinis.com]

[TheFiddyMan]

Re-gear it to a 13 or even 12 tooth front sprocket. That should help tremendously

[GAjonn]

if you drop to a 12 tooth it becomes a 2 speed tranny, just 2nd and 3rd. Was he racing at durhamtown?

[PTECH]

Theres always the takegawa 3 speed transmission. About 200 bucks but you'll have 3 close ratios work with inside the trans so you're not left trying to work around a lousy transmission with your final drive like you are now. I run one in 70 and its brillant, I hate riding bikes without it now.

[traut811]

Agreed with GAjonn, first gear would be useless going down. If you want more torque, adding the trail bikes 51mm stroker crank helps tremendously!

[Jordo]

Putting a 13th on is the ticket! It finds a happy medium which is noticibly better. It's only a $10 part so it can't hurt to try.

[kimanjay]

takegawa or kitaco 3 speed kits are the only way to lose the massive gap between 1st and 2nd, gearing it will just make 1st gear useless

Putting a 13th on is the ticket! It finds a happy medium which is noticibly better. It's only a $10 part so it can't hurt to try.

[doopsx3]

stroke and punch it to a 108