125-200cc 125 Piston Dome - Detonation or Normal?

Decided this weekend to install the 144, and I'm glad I did. The old 125 appeared to have been cold seized at some point. I'm not sure if I was responsible but the previous owner put on 30 hours running 100:1, and based on the rear tire that was on the bike, he rode a lot of roads, burnt out a lot, and didn't take extremely good care of it. I ran it about 3 hours at 32:1 trail riding. I'm not saying he's responsible for the cold seize, but you can do the math. The bike started and ran fine, in my other "first impressions" thread I mentioned that the jetting seemed off, but that may be a wrong assessment now that I know it was cold seized.

Anyway, it looks like a cold seize (exhaust and rt side transfer port) but the piston dome looks burnt as well. Does this look like detonation to you, as well as a cold seize? Is this a jetting issue that I should be concerned about with the 144, or is it simply a cold seize due to not warming up?

I don't see any detonation, but I think it wanted a bit more oil. Hard to tell from pics.

100:1? was he running interceptor?

Based on that my guess would be loss of lubrication, especially if that's the only spot with wear.

Did he tell you he seized it?

Yeah he was running amsoil. No he didn't tell me. I'm not sure he knew about it either.

I think Sabre is 100:1

I don't care what oil you run, if you think 100:1 is sufficient, you are BEGGING for problems. The 32:1 you chose to run it at is what you need for extended high-RPM operation, 40 to 50:1 is sufficient for average woods use and trailriding, and I'd never go below 50:1 for any operation, anytime, any RPM, any conditions.

I'm not seeing detonation damage in the provided pictures. Cold seizure is usually a "4 corner" seizure. That looks like a lubrication seizure, possibly with a bit of cold-seize element to it. Not to upset or alarm you, but I'd be fearing for the lifespan of my crankshaft's Big-end bearing.....

I had the same thought, but there is no evidence of any issues in the bottom end as if now. I'm making myself feel better by thinking that it has very low hours, he didn't race it (hence he probably didn't ride that hard, except for very short periods of time) and that the oil IS rated for 100:1. A lot of people run it.... Would I? He'll no. But it has been done and some people have no issues

At least that's what I'm telling myself *crosses fingers*

I have never blown a top end in my life, so Im not terribly experienced when it comes to identifying reasons why a piston looks the way it does.

Never

Never thought about that before. The circlips were seated properly though. I know because when I removed them, they flew out of the seat and hit my forehead.... BOTH of them. Lol

That's why you use eye protection when working with tools right ?



With oil ratio the guy was running, I agree with MotoMarc. I'm not a wide open guy in the woods but when I'm in the sand it's wide open. I'm running 40:1 and hopefully it will extend the top end life for me.

i know its just another story, but i have always run 40:1...always had longevity and good performance..i dont race hard, maybe i would go 32:1 for that...

100-1 would be fine in the appropriate application. I run my chainsaw at 75-1, but I wouldn't do that with my bike.

I agree......it all depends on the load on the motor. I bet you could try to hone off that aluminum from the cylinder, slap in a new piston and probably run it for 2 more years!

The alternative is to split the cases and replace the rod and crank bearings...is there any play or roughness there?

There is zero movement at the flywheel or the connecting rod - i checked when I had the jug off. There is the normal side to side play, but nothing out of the ordinary. No roughness either, and visually, the crank didn't look toasted or scuffed in any way - I think it's fine. Honing the cylinder is definitely a possibility - I'm sure after honing it, it'd be fine.

My plan is to turn it into a 165, or trade it + my WER steering damper for a 165 anyway. Either way - it's all still perfectly usable.

Did you ride it yet? How does it compare?

You can also use muriatic acid to remove the aluminum from the cylinder. It'll eat the aluminum but not the plating. Dab it on with a q-tip and wipe it after a few minutes and repeat until it doesn't smoke when applied. Wear eye protection and be very careful, it's pretty nasty stuff.

Never heard of that, i'll have to give it a shot when I get a chance.

I did ride it, but only for about 5 minutes - I won't get on it hard until I break it in. It sounded deeper (read: awesomer) though!

By the way - should there be an o-ring beneath the PV seat? I'm pointing to it here with a pick. My power valve chamber was 1/2 full of liquid exhaust residue. I wasn't running it too hard before I quit the last time I was out riding it, so I guess I could see why it filled up, but holy crap man. lol