Final drive gears

[Bakeman]

Been wanting to install the 49/17t gears . they can be bought prepressed . how much more power @nd top end can I expect
? My engine has bbk 100cc all upgraded parts . was seeing if its worth it or not ! Thanks in advance .

[humanshield]

Not only is it not worth it.....the loads placed on the motor at the same time less ol is being pumped can ruin the bearings in a hurry.

Only use taller gearing if your motor has sufficient power to push the gears and maintain rpm.

You'd pretty much need a stroker 139QMB to get enough HP & Torque.   100cc kit is not enough.

As always....YMMV and that's just based on my observations

[ratdog]

Don’t know what you have now, but imho, the only reason to go to a lower gear ratio is if your topping out you RPM after a good run. I’ve got two bikes that are running wot in the 8500 rpm range. I know at least my bike will turn more, so imho it is a good bike to change the final drive. The other bike (the first bike we did the BBK in) is really struggling to do 45 mph. That bike is not going to get a different final drive, but I think it will get a High performance variator from scrappy dog scooters. That is supposed to have a larger drive face. Of course if it basicly has a larger front pull, that gives you a slightly higher gear without giving up the low end. Do you/have you driven a stick? Changing the final drive would be like never using 1st gear. Just think about taking off from the light in second all the time... i is your bike strong enough for that?

The third bike I have been working on , the earsplitingloudenboomer, is pulling over 12,000 rpm at top end. And that even after changing from a 10” rear tire to a 12” rear tire. The earsplitingloudenboomer will get both the High performance variator, and a final drive change. But keep in mind, that bike is already doing over 50 mph. Walt the guy that owned the bike is 5’9” and about 135 lbs. and he rides a 105 inch Harley!