new piston/rings and now its popping

[lon]

I just rebuilt my top end, the cylinder was ok but the head looked pretty chewed up, I smoothed the inside of it out decent enough but its far from perfect. Quad started up and ran great. I did a few break in cycles, still no issues. Went to the track,first practice started up ran great for the first 100ft the started popping, made it about half a lap before it died. couldn't get it to start so back at the truck checked the plug it was a nice brown color, I changed the carb back to the one I had on it before the rebuild and it started right up ran good until about a half lap into the race then it started popping again. He made it the rest of the lap like that so I had him pull off the track, when he got back to the truck I was a little frustrated so I let it set for a while so I could clear my head. After it cooled down I tried to start it, it took about 30 kicks and it finally did. He rode it around the pit area and it seemed good again. He turned it off and it started right up so now I have now idea whats going on so I let it set until his second race. It took alot of kicks to get it to started, it ran great for about 100yds and just died. Now it will not start. Any ideas?

[lon]

Well I just went out to the garage to mess with it, just for the fun of it I tried to start it. And wouldn't you know, it started on the firsrt kick so I had my son get on it and take it for a ride. He rode it for about 10 min. with no issues. So now I'm totally stumped.
Have I told you that I don't like mini quads. I mean come on man, really. !@#$%^

[LT80]

Sounds like a new wiseco squeaking in a LT80..
I wonder if was squeezing is why yours was quiting.
I'd prolly pull the head and take a look at the cylinder walls. It's prolly fine but I'd be curious. :)

[lon]

When I had it apart the first time I did notice that the cylinder had a couple small not really scratches but lines. What is squeezing and squeaking.
Thanks,
Lonnie

[LT80]

Sorry, basically the same thing.
It's when things get extremely tight for whatever reason. Tends to melt the piston. That's what's next on those "lines" you mention.
I literally take a medium sandpaper (80#) and sand the bageezus out of the piston on those areas.
It's a cross between clearance and dragging oil. :D

[lon]

I have a new cylinder on the way,should I keep running this one. Is it going to blow if I do. When I pull the jug, if the piston looks good do I put it back together and run it.

[LT80]

A few more "break in cycles" and it should be ok.

[selbygirl]

if it was up to me and had a new top end coming. I would wait and put the new one in , in case if something may brake off and fall in the case. like a skirt or a piece of the piston ring. but that's me I have the worst luck.. and if it was popping I would check the reeds for cracks and chips

[lon]

I checked the reeds before I put in the new topend,they looked good. I am gonna try out the new topend just to see the difference, I'll check the reeds again when I change over. I didn't break it in as much as I would of liked to. It was so wet at our house I had him do a few passes down the road, hoping that would be enough. I guess not.

[LT80]

I gotta ask... Forged (stock/pro-x/arts)or cast (wiseco) piston?
Cast pistons require more clearance and a meticulous break-in (on mini's) IMO.

[lon]

Sad enough but I'm not really sure. I pmed you more detail.