To anyone who is facing this problem, here is my story and solution. I bought a 2005 Bayou 250 that was very difficult to start. It would usually take about 30-40 cranks to get it running. The piston would fire once for each crank past about the 20th crank, and then fire twice past the 30th crank, etc. Once it was started the engine would run perfect. When it cooled down to ambient temperature, the starting problem would return.

The first thing I did was check the valve adjustment because I was sure it had probably never been checked since new. It was only off by a very small margin. Adjusting the valves didn't help the starting problem.

The next time the engine was cold I took out the spark plug and dribbled a few drops of gas into the hole and reinstalled the plug. The engine fired up quickly but died within a few seconds after that fuel was burned off. That verified that it was defintely a carburation problem.

I had already had the carb apart 4 or 5 tims and had sprayed every orfice in the body. I had also backed out the mixture screw and had cleaned the white corrosion off the tip (be careful not to lose the small washer above the spring). That corrosion comes from ethanol in the gas sitting over time.

Here's what I missed. The problem was in the carb bowl...not the carb body. There's a vertical hole and passage way in the carb bowl that was still clogged. I couldn't unclog it due to the depth of the hole so I used a #60 drill bit and just drilled through it. I carefully sprayed out the shavings and debris afterward to make sure nothing got reingested back into the system.

That was the problem. The engine fired up on the second crank after sitting overnight in a very cold garage. It may have fired up on the first crank if I had known exactly how much choke to apply. That will come with experience but I'm satisfied with the results.

I hope this helps. I'll attach a photo later.

 

Good find!

"There's a vertical hole and passage way in the carb bowl that was still clogged"

Any photos to show the hole/passage?

 

I'm reading this with great interest because my 87 Concours street bike exhibits a similar trait, though it doesn't take as much cranking to get it going.

I've had the carbs apart and didn't notice anything in the bowls that I thought would have any effect on how it runs but maybe this carb is different than an ATV.

If anyone has pics of the atv bowl, please post.

 

I have photos but haven't figured out how to post them yet. I just joined yesterday to pass this information along.

You can't miss it...the vertical passage is the only one in the carb bowl. The reason I missed it is because I did what probably 9 out of 10 people might do by mistake...I removed the carb bowl and set it aside...then very carefully examined the carb body. Of course I gave the carb bowl a quick glance to look for crud in the bottom, etc., but I didn't give it the full examination it required. It was just an oversight on my part not to see that it had a passage that was part of the starting circuit.

I'm really happy that it's fixed...but the whole problem started with ethanol gas and the corrosion it causes.

 

i can't remember how many posts you have to have before you're allowed to post pics. in this reply box, you'll see the paperclip command, that's how you do it and then find your pics on your PC.
OR, make an album under your profile name, reference you have album pics, and we can go there to view those photos.

 

ZG1000!
Man, that brings me some good riding memories from 90's!

If it's not happen to be a carb related issue, check the cam lobes for excessive wear, especially if the bike has lots of mileage.

 

Okay...here's an attempt to post a pic or two.

If by chance they come through, the idea is that the passage way shown should be open. If you spray in the bottom, it should come spraying out the top.

 

Thank You! Choke works like it should, and it starts right up.