125cc laydown engine for 70's

[Mosh]

Well, my 81 70 engine lost spark and when I removed the flywheel, I found there is only 1 thread left on the crank for the flywheel nut..I could reassemble it, but the lil ole 3 speed 70 just aint getting it no more.

I have been wanting to upgrade my 70 to a 125cc for some time and I guess now is the time to do it.

So tell me guys, what is the best engine, for this deal..Pricewise durability,and ease of swapping.. Not to worried about the starting system, I think I am gonna get a adapter kit made for me to use the 70 pullstart..

So school me here..what is the best option, and I want to keep it auto clutch.
Should I just buy a 125cc pitbike and yank the whole deal from it? I want to keep this is cheap as possible..Dont we all? hehe
Thanks

[Vealmonkey]

It's a matter of budget and personal preferance. I like the lifans. I like manual clutch. The lifans are bolt in engines. If you know someone who can machine your pull start cage and flywheel, it's an easy mod for pull start. You may have to get a different intake. Intakes usually aren't a big deal on the suspension frames like mine, but clearance issues on the stock 70 frames. DrAtv has all kinds of wiring harnesses and intakes and lots of other things to help you out for adding a lifan engine. You can mod the atc70 stator side cover to fit the 125 engine, but a trx70 side cover has the plug to see the timing mark, but that is up to you. They are fun. But if you are gong 125, for a few dollars more, you can go 140! LOL And there is really no more work. For $400 you can get a 140 with a billet oil cooler right to your door. Maybe another $70 (or less) to get all the goodies for an easy install. Your only left with modding a pipe. Pipes may or may not take some tweaking and their cost is all over the board. Have fun.