Hey I have a z50a that wont start, I have 140psi compression and its timed correctly, valve clearance is ok, i have a good spark, points gap is ok and its backfiring threw the carb.
any ideas

Help Thanks

This is more of a bump than any kind of suggestion, but how about a little more background on the bike.  For example, "The bike ran perfectly before it sat for three years with gas in the tank and carb".  Or, "It was running just fine before I took it apart to [fill in the blank] and when I put it back together, it wouldn't run".

Here's a WAG.  How's the coil?  I had a weed wacker that wouldn't run, except for when I sprayed carb cleaner down the carb throat.  When I tried to start it on the carb cleaner, it ran briefly and then stopped.  I had checked the spark and thought it was good because when I turned the engine over with the plug removed, I could see a spark.  I thought for sure it was the carb.  So, I cleaned the carb and no luck.  Then, I got a rebuild kit, but still no luck after the rebuild  I was about to order another carb, but one wasn't available.  Besides, the cost was getting to my pain threshold for a free piece of equipment.   I gave it to a co-worker who was a mechanic for 20 years and is still a tinkerer.  He got it running.  When I asked him what he did, he said he replaced the coil.  I asked him how he knew the coil was bad when you could see the spark with the plug removed.  He told me that he didn't get shocked when he held the plug and turned the motor over to check for spark.  I guess that was his way to check for a weak spark.  He replaced the coil and it fired right up.  Just a thought...

hbtaylor16, on 28 April 2012 - 01:01 AM, said:

Sounds like you need to clean up the carb. Pull it apart, order a rebuild kit from CHPUSA and get it going. Usually you can get it running at least a little by pulling apart the carb and cleaning the heck out of it. I use high E string from a guitar to feed through the jets and stuff. Usually it's just that.