Thread: 3 speed to 4 speed trans conversion questions

I am getting ready to start my 3 speed to 4 speed conversion on my k3. I have complete 4 speed trans setup the gears, shift fork, and drum already. my question is how long should this take me? what else should I tackle on the motor while I have it apart? what else do I need to purchase to have everything for the swap?

thanks for any replies!! any tips and pointers welcome I have never had one of these engines apart and will take all the info I can get.

Don't forget that the front and rear sprockets are different between 3 and 4 speeds.

K3: 15F/35R
HK0/HK1: 14F/45R

Originally Posted by hornetgod

Don't forget that the front and rear sprockets are different between 3 and 4 speeds.

K3: 15F/35R
HK0/HK1: 14F/45R

good point, but if I just leave it as is I will have better top speed right?

I would need a full seal and gasket kit for the trans conversion right? anyone know where to get this on the cheap

These engines are sprocketed fairly close what the engine can pull. I doubt 15/35 set up will work well on a 4 speed.

+2.i doubt you can off road up a steep hill in first.you might get by with 88cc kit.i have 15 38 on a 88cc bike.easy fix for you though.it really depends if you want bone stock 4 speed gearing or tweak it for your paticular riding situations.

Don't forget that the kick start gear is not the same between a 3 and 4 speed. You'll need that gear...and they are not available by honda and near impossible to find. I have one...but it won't be cheap.

Originally Posted by fatcaaat

Don't forget that the kick start gear is not the same between a 3 and 4 speed. You'll need that gear...and they are not available by honda and near impossible to find. I have one...but it won't be cheap.

could you please provide a picture of what you are talking about? I have never heard that. I know what a kickstart gear is but don't know how this change would affect it. I thought as long as I stuck with the automatic this would not be an issue.

If you are using a ct70H cl70 sl70 xl70 transmission, you MUST change the kickstart shaft gear to match. If you are using an ATC70 transmission or one from trailbikes you will be ok. The first gears are different sizes in teeth and therefore need a different sprocket to accomodate. Trust me...better find yourself a manual...

yeah I have alot of reading up to do I just opened up some pdf manuals and going through, how much were you looking to get for the gear?

Originally Posted by JPct70

yeah I have alot of reading up to do I just opened up some pdf manuals and going through, how much were you looking to get for the gear?

30 shipped on the gear.