Post by ilovenxstage on Oct 20, 2013 10:29:38 GMT -5
My NC50 has been sitting for about three weeks and it won't start. I've put fresh fuel in it, premixed 32:1. It's getting fuel, air, spark, and compression, but the most it will do is occasionally backfire. I've tried starting fluid and it does no good.
Post by ilovenxstage on Nov 13, 2013 16:20:19 GMT -5
I finally did a compression check and I was only getting 40psi. I took the top end apart and my piston is fried to a crunchy crisp! There are also deep gouges on both the piston and the cylinder, and both rings are seized in their grooves. Looks like it's time for a rebuild. I've always used good oil, but I think the big bore and the higher flow exhaust were just too much for the stock jetting in the carb and it was running too lean for too long.
Compression should be around 120 PSI on a fresh engine . Yes running too lean ( more so on a 2T ) will fry the piston . Since you have it apart I would spend the extra and get a BBK which will also require upjetting but will put out more power and be more fun to ride . Many 2Ts use Mikuni VM11/22 main jets
Post by ilovenxstage on Nov 15, 2013 5:35:10 GMT -5
The piston that got cooked was a 70cc that the previous owner had put on, but the carb is original with non-replaceable jets. I had a stock 50cc piston and cylinder that are in fair condition that I put on until I can afford a new BBK, intake manifold, and new carburetor. Its running now, but I do miss the acceleration that I had with the BBK!