Engine issues

My Daughter's Kawasaki Bayou 220 is causing me fits. She bought it with her own money but with my help and I'm feeling a bit guilty because shae hasn't been able to enjoy it yet.

We bought it cheap and it ran when we picked it up but it had a stumble as you advanced the throttle. I rebuilt the carb with no improvement. It has a nice bright blue spark but I changed the plug, wire and tried a good coil that I had in my shop. It has a CDI so no points to worry about. I've checked and adjusted the valves. I've checked and rechecked timing, float level, vacuum leaks, fuel lines, etc. It can be hard to start or it may start with a touch of the starter button regardless of engine temperature. It may idle like a dream or it may need you to fiddle with the throttle to keep it running. No matter where you hold the throttle the engine hunts. Every once in a while it seems to run well for a couple of minutes but it frequently dies and will not restart. After sitting overnight it may start right up or it may need a ton of cranking before it runs. The pull starter will pull really easy a couple of times and then will just about rip your hand off on the next pull as if the engine was locked up.

The only problem I can find is the compression is sitting at 149psi. The manual states 228- 146psi is normal. Could all these problems be caused by low compression? 149psi doesn't seem all that low to me and it still falls into the acceptable range (which seems really wide). Should I just pull the head and see what's going on or am I missing something simple?

Pull the exhuast and make sure its clean and full flowing. Shop vac on blow to check for mice nest or other blockage. shake pipe to see if theres a baffle that broke loose. Remove and clean spark arester.

Are motor mounts bolts tight? running motors that wiggle can mess with grounds.

It should run acceptably at 149 psi. Checking the grounds and for blockage in the exhaust is a good start.

Just because it has spark doesn't mean that the ignition is working correctly, the pick up or the cdi unit could be malfunctioning. Also I've found that its best to use high quality spark plugs like NGK or Denso. Never use Champion.

If its not too difficult, check the valve lash and cam timing.

Thanks for the suggestions but I've already checked and cleaned the ground wire as well as the exhaust. The cam timing was off by a tooth when I bought the bike but I fixed that on the first day. Same goes for the valves. They were set a bit tight when I picked it up but I adjusted them when I checked the timing.

I learned my lesson about cheap plugs years ago and only use NGKs on my Jap bikes. Having said that I've swapped a few diferent plugs in just to see if the heat range made a difference. No dice.

My experience with CDIs is they either work or they don't. Since I'm getting a nice bright blue spark I'm assuming that it's ok. I'm 45 and I've been working on my own bikes and cars since I was a kid but I'm always learning something new so I'm happy to be corrected on this point.

Is there oil under the fly wheel side cover? If not pop it off grab a timming light and a spare car battery and check the spark advance while running. Some CDI's are known to go bad at higher rpms but thats mostly the older units. my 74 yamaha mx175 is this way....there made of unabtanium too...I swaped in points for now.

Oh one more thing! i have seen a ATV with a second box in the wire harness that was a seporite rev limiter and it was bad ran fine unpluged that took me weeks to find out WTF was up. As i recall it was far away from the cdi box too. Lost labor hours big time on that repair.

Does it have a vacuum petcock? Try swapping in a standard manual petcock.