Engine trouble

[Brock3]

New to the go kart world. I have a used go kart. the 150cc motor was smoking and lost a lot of power. I replaced the rings and piston and the smoking stopped. Took it on a test run and it still had low power. Then it died and won't start again. Could it be the valves? Or what are y'all's suggestions? Timing was still fine. Was still getting gas.

 

[Soapbox kid]

Did u Chang ur spark plug??

 

[Johnnym]

I would suggest:
spark plug test
compression test
make sure it has sufficient oil
you could check the valves by shining light on the top of the valve and see if you can see light coming through(if the head is still off, if not try and diagnose the valves otherwise)
make sure the gas is good and you positive its getting through the carb and into the engine

 

[OzFab]

Silly question but, you never know: Are you 150% sure the piston went back in the correct way?

Other than just checking the valves, clean them & the combustion chamber with a wire brush, remove them & lap them in.

Double check the cam timing, refit the side cover using the correct gasket & check the end play of the crank, refit the head using a new gasket & new spark plug & you should be good to go.

Before you attempt to start it, turn the engine over by hand to make sure nothing is binding

 

[landuse]

Are you sure you set the valve lash with the piston at TDC?

 

[datsbooksleia]

It could also be the carburetor being dirty. could be so many different things

 

[Brock3]

First off, thank u everybody for your replies. As far as the spark plug goes, it could probably use a change, it seemed to give a sufficient spark when I tested it, but it is dirty so I'll deffinately give that a shot. As far as testing the valves, I tryed the light test and didn't see anything but I did turn the head, valves up and put fluid in the "dome" and it did leak thru, don't know if that means anything. The piston is in correctly, not a silly question at all. The piston was marked kind of like the claymore mine, lol, this side faces enemy. Timing is on, good gas flow, i know the previous owner and he cleaned the carb right before i took it, but im going to take it apart and check it anyway. Vibrated when i first started it up after the ring and piston change, but turned like a top after it warmed up. It did seem to run really hot tho.

 

[fowler]

Anougther silly question but did u remove the whole piston and rod

Did u install the bearings back in right

Does it turn over really easy?

The only extra thing I can think of is insufficient oil pressure caused wear

Did u fit standard rings?

But these are a bit extreme
Try the other solutions first

 

[OzFab]

I tryed the light test and didn't see anything but I did turn the head, valves up and put fluid in the "dome" and it did leak thru, don't know if that means anything.

That means your valves are leaking, therefore, you're not getting full compression.

As I suggested, lap the valves

 

[devino246]

I see no mention of cylinder honing. You DID hone the cylinder when you replaced the rings, right?:toetap05:

 

[falcon52]

I would suggest a compression test. Sounds like the rings haven't seated to me. If the compression test comes out bad I would double check the valve lash. But I would put money on the rings not being seated. Sounds like you'll need to give her a good hone to me.

 

[datsbooksleia]

First off, thank u everybody for your replies. As far as the spark plug goes, it could probably use a change, it seemed to give a sufficient spark when I tested it, but it is dirty so I'll deffinately give that a shot. As far as testing the valves, I tryed the light test and didn't see anything but I did turn the head, valves up and put fluid in the "dome" and it did leak thru, don't know if that means anything. The piston is in correctly, not a silly question at all. The piston was marked kind of like the claymore mine, lol, this side faces enemy. Timing is on, good gas flow, i know the previous owner and he cleaned the carb right before i took it, but im going to take it apart and check it anyway. Vibrated when i first started it up after the ring and piston change, but turned like a top after it warmed up. It did seem to run really hot tho.

The spark plug change is a good idea. My engine would not start even after trying to start it with my cordless drill. Finally, i pulled the plug and found it to be black. I sandblasted it clean with a HF pneumatic spark plug cleaner and the motor fired right up.

 

[Brock3]

Hey guys, sorry for not gettin back on here sooner, I have a newborn keepin me pretty busy lately. I got the buggy running good. First thing I found was a vacuum line coming from the gas tank that kept coming loose and killing the motor. Then I found a split in my fuel filter. And finally, after fixing those minor problems, the buggy was still running rough, so I put new valves in. The thing runs like new now, and I'm probably out only 40 bucks. Well worth it in my opinion because the whole family has enjoyed runnin around in it. Thank you all for your suggestions on what was going on with it.