1989 Honda CR250 Loss of Compression

[ChumScrubber]

Hello all, I have owned my bike for 4 or 5 years now and it has never failed me until last weekend. I was riding out in the dunes and all of a sudden second gear started losing power. It did not happen super quick, but more like over the course of 30 seconds to a minute or so. Just now power when I throttled up. So I shifted into first and it felt better, then I shifted back into second and the motor died on me. After that the bike was extremely easy to kick over and it would not fire. I immediately thought loss of compression. I am pretty experienced when it comes to working on small block Chevy’s, but I have never torn down one of these 2 strokes.

How likely is it the rings vs. the pistons? Or maybe even something else?

Can anyone give me a good idea of what you think the exact problem is? Or is this something that just has to be opened up and looked at to figure out?

I won't really have time to mess with it until this weekend so any help anyone could offer in the mean time would be much appreciated. Thanks! :nod:

Also, is there a good thread around here for some good general maintenance tips? I got the bike when I was too young to touch the ground while sitting on it and I probably could have treated it better over the years. I changed the trans oil often but haven't really done anything else. Now that i'm older I want to keep it as tip top as I keep my car.
Thanks again.

 

[2strokerfun]

Hmmm, 18-year-old bike being ridden in dunes, which I'll assume is sand, since I don't know of any other type of dunes. Loss of power over 30 seconds to a minute. I'm guessing you have a piston problem resulting from a too lean condition in that environment. Piston overheats, expands, you lose power. Keep riding and something's got to give. Probably exhaust side meltdown. If you can work on a small block chevy, you can work on a two stroke. Same concept, no valves. Pull the cylinder and inspect the piston and rings.

 

[ChumScrubber]

Thanks for the help. I only hope it's just rings and not the piston. I checked the spark plug and it seemed normal. So hopefully there is not a lean condition that will make this happen for another 4 or 5 years. It had been sitting for a long time though, so I don't know if something else led to the problem.

 

[2strokerfun]

Could be due to age/top end was worn. Could be the conditions you were riding in. I have heard a lot of people say they up their jets a size before riding in sand to avoid this as the sand puts tremendous workload on the engine. I try to avoid sand as much as possible.
My guess is that it is more than rings. Usually the piston causes these seizures. Piston, rings, top bearing and gasket will set you back about $130-$150 or so. If there is a problem with cylinder, it will be more.