06 belt is a 7/8 07+ is 20mm so I don't see a reason the extra 16th of and inch width on the rear sprocket would hurt anything but im not sure on the belt size fitting you may need to go to an 06 belt as well as I think the 133 tooth stocker would be to small for the 70 rear

 

Do you have to change the belt or is there enought ajustment? If you have to change belts ,change the front pulley 1t instead. Both good for around 225rpm or so. You will need about a inch of adjust ment to change pulley. I changed my fxr from 70t to 65t. belt it worked but only about 1/8th inch of ajustment left.

 

This is what I KNOW, the belt for the 06 200 rear was a 135 tooth belt and is 7/8 width the belt for the 07+ is 133 tooth and 20mm wide (About a 16th narrower than the 06) the front pulley is the same 32 tooth pulley (All though the 06 softail still had the 5-speed so I think the spline output is different) the rear sprocket is a 70 tooth on the 06 and a 66 tooth on the 07+. If you change out the front tranny sprocket to the 30 tooth on a 07 you need to change the belt to the 132 tooth to have enough adjustment(I have heard some squeak by without changing the belt (but you should do it).

Here I am taking a WAG. If you went to a 70 tooth rear from a 66 I would say you need the 135 tooth belt from 06, if you did the 30 tooth front sprocket and a 70 rear I would bet you could get away with the 133 tooth belt but again this is a WAG.


Doing a 30 front and 70 rear also gets you to 3.15 final drive

 

I did the 70 rear 30 front on a 07 street glide stock belt ok.What a change Pulled so much better .Not reving too hard either

 

Im sure it did..makes 1st even deeper than a stock 5 speed. This new ratio is just WRONG for these bikes especially with a stock motor.

 

It really brought that 103 build to life.113# torque.And im gonna do the same change to the fatboy 103 also

 

Hey..i know its been a couple of years on this thread. Hopefully you can give me some insight. I have a 2016 Fatboy s 110 SE..and while it is only my 3rd Harley it seems as if this bike with a bigger motor just doesn't pull like my last stage one 88? i can only assume it has to be the gearing. So my thought is change out the rear to a 70 as opposed to the 66 tooth pulley? And can i use my cuurent belt? also do i have to change the front to the 30?