Hello everyone
I'm looking for opinions on my ring wear, I seem to be going through rings too quickly and can't nail down the root cause.
I'll start with the bike...
2007 Honda CR250 that I ride mostly in tight and steep single track / x-country riding.
Engine is leak-free and gets pressure tested every time I assemble it. Jetting is safe-rich, mixed @ 32/1, air filter always clean.
Piston #1 I started the season with a brand new oem cylinder and top end, the bike ran awesome to 60 hours when I changed the top end as a precaution (admittedly a little past my usual 40 hours) At this point the compression was still good, but the ring showed wear on the exhaust side... not shocking for 60 hours. Everything else internal looked brand new.
Piston #2 lost compression at around 10 hours. One day I noticed a lack of compression at the kick starter, and looking back... I seem to recall it had been running a little rich leading up to this.
-ring worn very thin on exhaust side, and has collapsed into the ring groove
-spark plug reads very rich
-looks to me like good piston wash, a little on the rich side
-no scrub marks on the piston sides
-cylinder plating and cross hatch in good shape
With no found cause, I second guessed my ring end gap, and replaced the top end being more careful with my measuring and filing.
Piston #3 just lost compression again at around 15 hours. Same as last time... engine has seemed slightly richer the last couple rides, and I noticed low compression at the kicker yesterday. I will tear it apart this afternoon, expecting to find the same situation. I had done a compression test a week or so ago, and it was still good.
I am left wondering what is causing this. Tight ring end gap seems like a suspected cause, but I was very precise setting it last round. The only other two things I can think of are:
1- Overheating. I do boil my bike over pretty regularly trying to climb nasty hills in the trees, possibly the exhaust side of the cyl is swelling when hot?
I would expect to see piston scrub marks if this were the case, but there are none.
2- High speed transfer sections. We are forced to cover some ground on old roads at times, and I am geared very low so the bike sees a little time cruising in top gear at moderate RPM (5000 - 6000).
Although I monitor my RPM and try to keep it low, I always hate sustained RPM riding like this. Even at rich jetting, is this a possible culprit?
Any insight would be greatly appreciated.
I'm looking for opinions on my ring wear, I seem to be going through rings too quickly and can't nail down the root cause.
I'll start with the bike...
2007 Honda CR250 that I ride mostly in tight and steep single track / x-country riding.
Engine is leak-free and gets pressure tested every time I assemble it. Jetting is safe-rich, mixed @ 32/1, air filter always clean.
Piston #1 I started the season with a brand new oem cylinder and top end, the bike ran awesome to 60 hours when I changed the top end as a precaution (admittedly a little past my usual 40 hours) At this point the compression was still good, but the ring showed wear on the exhaust side... not shocking for 60 hours. Everything else internal looked brand new.
Piston #2 lost compression at around 10 hours. One day I noticed a lack of compression at the kick starter, and looking back... I seem to recall it had been running a little rich leading up to this.
-ring worn very thin on exhaust side, and has collapsed into the ring groove
-spark plug reads very rich
-looks to me like good piston wash, a little on the rich side
-no scrub marks on the piston sides
-cylinder plating and cross hatch in good shape
With no found cause, I second guessed my ring end gap, and replaced the top end being more careful with my measuring and filing.
Piston #3 just lost compression again at around 15 hours. Same as last time... engine has seemed slightly richer the last couple rides, and I noticed low compression at the kicker yesterday. I will tear it apart this afternoon, expecting to find the same situation. I had done a compression test a week or so ago, and it was still good.
I am left wondering what is causing this. Tight ring end gap seems like a suspected cause, but I was very precise setting it last round. The only other two things I can think of are:
1- Overheating. I do boil my bike over pretty regularly trying to climb nasty hills in the trees, possibly the exhaust side of the cyl is swelling when hot?
I would expect to see piston scrub marks if this were the case, but there are none.
2- High speed transfer sections. We are forced to cover some ground on old roads at times, and I am geared very low so the bike sees a little time cruising in top gear at moderate RPM (5000 - 6000).
Although I monitor my RPM and try to keep it low, I always hate sustained RPM riding like this. Even at rich jetting, is this a possible culprit?
Any insight would be greatly appreciated.