CN250 Idles fine, stalls under load
 

Problem: Kandi 250cc buggy. Recently had to replace the left side engine casing. Afterwards the engine starts and idles better than it ever has, in neutral it runs up rpms great, but put the FNR (forward neutral reverse) box that it drives in gear and it stalls 95% of the time, yet a few times ran 10 laps around the yard fine.

Whats driving me nuts is that it would appear gas/carb related because I have had one test drive where I went around the yard 10 times and stopped, then it wouldn't go. Idle for 3 or 4 minutes and do it again, go 2 times around and stop, same thing. So obviously gas/carb. But I have switched out the gas tank, gas lines, vacuum lines, and carb (including elect choke) from an identical unit bought at the same time that runs fine. No change. Also verified the elect choke is activating correctly ie: extends about a 1/4 inch after 5 mins.

I can't think of anything in the engine assembly I could have done wrong that would cause power loss with intermittent power return, ie timing, valves, gaskets etc.. I have no prior experience with working on a variator, but it looks like it operates correctly when I run rpms up and down in neutral.

Welcome-Sounds like a tranny or bearing issue-(never owned one) do the cv pucks look OK?
Are you in Eastern NC?

Hi, well I live in Raleigh NC. Busco Beach is exactly 1 hour door to door, thats were we do most of our riding. Going to try BearWallow trails at Hatfield and McCoy in WV this fall. If you know anyone that has been, I would appreciate their opinion.

You had a good idea, especially since I had to replace the FNR box at the same time
as the engine casing, and all the reduction gears as well. So I did in fact have the
entire drive line off, wheels,brakes,cv's,axles,swing-arms, etc...
So to test that idea I jacked the buggy up off the ground and tried turning everything while in gear engine off, no problems. Fired it up and could run everything while in gear no problems, high rpms etc... But dropped it back onto the ground and could not even go a foot forwards or backwards... dang.

I thought heard a metalic bang back near the variator housing while it was just sitting at idle, not really sure. But because this whole thing started when a dime sized hole got punched into the casing right next to where the final output shaft of the engine is, which caused the reduction gears to shred their teeth, I am going to remove that clutch/driven pully assembly tomorrow and check those reduction gears for peace of mind.

If you didn't look at the rollers in the variator since the damage case cover I'm thinking you have some flat spots or broken/damaged ramps.
I want to try and play a Busco beach, never been to Hatfield & Mc Coy's but have many friends that have ATV'd and 4x4'd there and said the land is endless.

might be a roller out of its spot too.

Not sure how old it is but if I heard a metallic banging sound coming from my engine I'd start disassembling it until I got to the root of the problem. It could be anything from a broken piston ring, a c-clip that came loose or problems with the variator or the clutch and also something in the transmission behind the clutch. Sounds like you replaced the differential? Is that what you mean by the FNR box? Unless I'm mistaken there is a C clip that holds the output shaft of the transmission to the differential. That is how my buggy is set up. If you left that out...Not sure what would happen.