I posted this in the technical forum but then realized this might be better off in the Honda forum, so here's my question....

My brother and I went riding today with his used (new for him) Honda 250R quad. We rode for only a few minutes and it began to bog down after he would start to give it some throttle out of first. We knew since this was the first time taking it out that it would have some problems, but just didn't know what. After a few minutes it bogged down and stopped running, then wouldn't start. I road back and got a few tools along with spark plugs and tow rope. I got back and he replaced the plug which wasn't dry, and then it started right up. We headed back to the truck and were almost all of the way back when it just shut off, no bogging or anything. When he went to kick start it there was absolutely no compression at all and had to be towed back, and our day was over pretty much before it even began! He thinks it might be the top end of motor....just seeing what others might think. Thanks for any feedback

 

What mix was he running? Has it been modified at all, shaved head for more compression? If so it needs race fuel or a race fuel mix. What color was the plug he pulled out and have him pull the plug that's in it and check it's color. It should be tan, if it's white or grey, it was running lean and got too hot, burning the piston.
Sounds like it may have been running lean and possibly holed a piston. More than likely with loss of compression. Time to rebuild the top end. Luckily it's easy and fairly inexpensive.

 

I believe he was running 32:1 and not sure if it has been modified since he just got it and this was the first trip out. The end of the plug was a dark gray color, and he told me after he changed it that this was 2nd time he changed it in the past few days, the other being a couple of days ago from just idling in his driveway. Yeah, we both figured the top would have to be rebuilt....thanks for the feedback, much appreciated.

 

Sounds like a lean condition. I would tear down the top end and you'll prolly find that the exhaust side of the piston is scorched. In addition to improper carb. jetting a lean condition can be caused by an air leak somewhere at any of the many gasket surfaces on the motor. A friend of mine had a tiny crack in his expansion chamber and he smoked a couple of top ends before he realized what the cause was. Once he rebuilds and starts the break-in procedure be sure to jet the carb a little on the rich side and once break-in is complete you can jet a little leaner for optimum performance.