first four stroke build - advice needed

[SirLurksAlot]

And with a more aggressive cam you would need even stronger valve springs, which brings us right back where we were before.

Also, I bet I could figure out valve springs easy enough if I had the OE specs. It's not rocket science, just some math

Probably so. We're not all you, tho. Worth noting - high perf kart guys, having tried, say the lifan isn't a good choice for hopping up. My own experience with a 152f-3 is that after a pretty short time of completely ungoverned operation, it wore out. Burning oil, loss of power etc. Less than 2yrs of moderate use. I weigh 135lbs bike is 98lbs, so not heavily loaded. Well maintained, e0 gas, and hi zinc oil changes every 20hrs. Kart guys report similar results. Kept to 4k rpm max and they seem to hold up well. This is all very unscientific and casual personal experience. YMMV ofc

 

[Toby woodman]

if you can find another similar engine in the uk I will give it a try but at the moment. I can't see another option. if it's kept governed then surely it will last a few years. asides from the engine choice. is 2.5 hp enough for a torque converter / can you see any problems with the transmission I have thought might work

 

[ImpulseRocket]

Probably so. We're not all you, tho. Worth noting - high perf kart guys, having tried, say the lifan isn't a good choice for hopping up. My own experience with a 152f-3 is that after a pretty short time of completely ungoverned operation, it wore out. Burning oil, loss of power etc. Less than 2yrs of moderate use. I weigh 135lbs bike is 98lbs, so not heavily loaded. Well maintained, e0 gas, and hi zinc oil changes every 20hrs. Kart guys report similar results. Kept to 4k rpm max and they seem to hold up well. This is all very unscientific and casual personal experience. YMMV ofc

I wouldn't doubt that motor wears out when pushed. It's built for generator and pump duty, and it's built to be as cheap as possible.

I find it interesting that somebody would pick a 79cc Lifan for a "high performance" cart. I can only assume some size restriction in class racing.

 

[Toby woodman]

Regarding a torque converter it’s geared for slow top end about 24mph. With a torque converter that would make starts easier. Would this engine be powerful enough for a torque converter

 

[darwin]

Toby, with the amount of $$$ and effort to get what you want have you thought of a used gas scoot or an electric? Maybe things are different where you are? Here for $1500/2000 you can get a nice used scoot or new electric for those hills.

 

[Toby woodman]

My mother absolutely loathes motoribikes. This is as close as I can get to one sadly. Also the lifan is the only small engine of that size I can get in the uk. And larger engines won’t fit in a standard frame. I can’t get a beach cruiser style bike in the uk. Using the lifan and a torque converter. Is that the best I’m going to get to a reliable 4 stroke. As the 49cc kits seem terribly built

 

[Toby woodman]

As long as I can get the torque converter on the engine I should be okay. I can either mount it in the frame if there’s enough space or over the back wheel. Whichever option I choose. I will use a jackshaft. Here is the beginnings of it which I started today.

 

[Toby woodman]

 

[Toby woodman]

All I’d like now is for someone to look over the gear ratio and confirm that 2.5 horsepower with a cvt will be enough power to be practical and fun

 

[SirLurksAlot]

I wouldn't doubt that motor wears out when pushed. It's built for generator and pump duty, and it's built to be as cheap as possible.

I find it interesting that somebody would pick a 79cc Lifan for a "high performance" cart. I can only assume some size restriction in class racing.

Those guys will try anything...