Engine Doesn't turn after thowing chain

S

scott16

New member
Hi,

Being a novice crew chief, I have no idea why the engine is no longer turning on my son's kart. At our last race, the kart threw the chain (reason unknown). Engine is a green plate clone and was turning about 5100 RPM when the chain went. RPM spiked to 6600, but it kept running for most of a lap until my son pulled into infield and the safety crew shut it off. (I have the data logs from the MyChron showing all of this.)

After the race we changed the oil, per our usual routine. Today we tried to start it up and it won't turn at all. Specifically the flywheel (easiest part to get to) will not move.

Any suggestions what to try? Obvious one would be to rebuild the engine, but that is beyond us for three races. I'm hoping for something basic so we can finish out the season.

Thanks!
 
sounds like motor is locked up rpms shouldn't have hurt it do to the fact that chain was off when rpm went up hate to say it sounds like motor is toast
 
scott16 is the chain altogether/intact (not broken-piece missing) that might be jammed between clutch and engine side cover or chain guard . I had jumped a chain before ,it was bound between the chain guard and clutch sprocket .
 
The chain stayed intact, but was thrown completely off the drive pulley and clutch. When we looked over the chain, found that one link was pushed together so the opening for the sprocket was no longer sufficiently wide. New chain was the easy part. Would really love to know what happened to the motor.
 
Easy enough to find out- pull the side cover. But first- pull the plug and try. Compression release ( I'm assuming clone) may have failed
 
If there nothing obviously wrong on the outside, I would pull valve cover. Make sure you didn't drop a valve. And then pull side cover. Or like said above check compression release.
 
Took the valve cover off first. The exhaust valve rocker was very loose (wobbled side to side) compared to the intake. I'm assuming that this means the exhaust valve failed. Valve still moves, piston is a little past halfway down. At this point just using the motor as a learning opportunity. Tried to remove the cylinder head, but wasn't possible without an impact wrench.
 
For 3 races a kit engine would get you points.
Should not need an impact. Slip a piece of pipe over the ratchet or give it a sharp blow with a hammer.
 
Never had a clone but do these motors have an oil dipper on the rod? Maybe the spike in rpm's snapped it off and the rod locked on the crank due to lack of lubrication. Several guys at the track including myself lost animal engines due to this when we played around with world formula cams that allowed the motors to rev higher.
 
You must log in or register to reply here.
Back
Top