Hi, I have above engine in my Twister hammerhead. it is mounted sideways on the solid swingarm (non IRS) and there is a chain sprocket mounted where the original shaft drive U joint used to be. Chain obviously runs straight to the sprocket on the solid axle.

I need to gear the thing down for off road. I have put 24" mud tyres on the rear (larger than original twister 22"). If Someone knows the original YFM200 diff ratio I will be able to work out the correct sized sprockets to use.

Also How fast could a YFM200 go? I guess I can gear it so it's much lower than a standard bike so then it will conquer the hills even better.

Thanks for any help.

 

From my 1985 YFM200 Manual:
Primary reduction ratio : 73/22 (3.318)
Secondary reduction ratio: 19/18x46/11= 4.414
Gear ratio:
1st 3.181
2nd 2.066
3rd 1.428
4th 1.040
5th 0.821
Reverse 3.181

 

Thanks man, I actually just recently got this info from a local Yamaha dealer which really surprised me. As you say the diff is 4.414:1
I now have the fitters at my work rebuilding my axle for me and I've got a drive sprocket that's a pretty close match for the right ratio. hopefully I'll be mobile soon and actually get to use this beast. It's summer in New Zealand and it's a long dry one for us this year.

I'm also going to try using a car muffler on it to quieten it down a bit so I can take the kids out for a spin. Thanks again.