125-200cc CR125 and 144 scored piston and cylinder (Pics and vid)

[High Society]

Could it be a jetting issue? Running too lean? I ride more high speed desert stuff at times.

 

[72racerx]

A leaking LH crank seal could also cause a leaning out problem, but this should show on a leak down test.

 

[GhostRider32]

I poured 10.2 ounces of oil in the fuel can and shook it up.

Are you talking about a 5 gallon can? How much gas did you mix the oil with? 24:1 is 5.33 oz of oil to a gallon of gas......

 

[Zomby woof]

I mixed 2 gallons of fuel .

 

[Motosportz]

3oz to a gallon of modern 2 stroke oil is good.

 

[Motosportz]

I mixed 2 gallons of fuel at 25 to 1. I poured 10.2 ounces of oil in the fuel can and shook it up. How long should I shake the can for? I used Maxima Super M. Is this a bad oil?ve a leak there. The rubber boot for the exhaust pipe and chamber seems a bit loose. I assume I have to rebuild the top end before I can do a leak down test? What do I need to look for around the reed block? The mouning bolts are tight.

Thats plenty of oil, kinda rich actually. If you shoock it even a little if should be fine. Super M is not my favorite but nothing wrong with it. Seems like you are doing it all rich but that sure looks like a lean / low oil issue as it is all around the piston.

 

[MOTORHEAD]

24:1 is very oil rich, but will lean the air / fuel mixture. There is no reason you should have to go any lower than 32:1, and I doubt that you need more than 40:1 to do the job.

If it's gotten significantly colder where you are and you went to 24:1 with the same jetting that you had at 80 or 90 degrees, then that might be your problem.

 

[MOTORHEAD]

Let me add, that if you need to run Super M at 24:1, then you should switch to 927 and back down to 40:1 or 32:1.

 

[72racerx]

I'm running Maxima 927 at 45:1 without any issues. Not saying that you should run the say mixture. Most of my riding is single trail so not a great deal of higher speed work involved. I also have the 150 kit fitted.

 

[MotoMarc36]

The difference between 24:1 and 50:1 is not even a jet size so isn't worth considering as the cause. While 24:1 technically leans the air/fuel ratio, in practical application it is a non-starter. Opinions vary, but most smallbore engine builders agree that a high-RPM (desert) smallbore needs more oil, and 32:1 is generally the leanest they'll go for that use. I think Wally's mention of the fuel and oil possibly separating is an interesting and plausible theory. I have nothing to support it scientifically except that it looks like no-oil damage but you are sure you added oil. I would do a leakdown test and, passing that, switch both oil brands and gas station locations/brands. Go one up on your main and one clip on the needle to be safe and have another go. Make sure your silencer core isn't broken and misaligned, raising the pipe bleed-down pressure dangerously high.

If it was a lean-jetting caused issue or airleak-lean issue I would have expected it to have seized tight at least briefly, which you didn't mention if it happened. Or eroded the front edge of the piston and coated the headpipe in aluminum. It really looks no-lube galled.

 

[High Society]

I'm running Maxima 927 at 45:1 without any issues. Not saying that you should run the say mixture. Most of my riding is single trail so not a great deal of higher speed work involved. I also have the 150 kit fitted.

Did you notice how much your connecting rod moved when you installed the 150 kit?

24:1 is very oil rich, but will lean the air / fuel mixture. There is no reason you should have to go any lower than 32:1, and I doubt that you need more than 40:1 to do the job.

If it's gotten significantly colder where you are and you went to 24:1 with the same jetting that you had at 80 or 90 degrees, then that might be your problem.

I just used the stock jetting. Temp was around 60's. So running that rich of a mixture will actually make it run hotter? I also read about riding WOT, and quickly closing it and allowing the bike to coast at a high speed is bad? I've been ridding 4 strokes for a long time and I actually used engine braking at times to slow me down. I'm riding the same way I would my 4 stroke. Can this be an issue?

Thats plenty of oil, kinda rich actually. If you shoock it even a little if should be fine. Super M is not my favorite but nothing wrong with it. Seems like you are doing it all rich but that sure looks like a lean / low oil issue as it is all around the piston.

This was after I used installed the kit, The manual stated 25;1 during break in. I was eventually going to switch to 32;1. Which the manual stated to use after break in.

 

[High Society]

The difference between 24:1 and 50:1 is not even a jet size so isn't worth considering as the cause. While 24:1 technically leans the air/fuel ratio, in practical application it is a non-starter. Opinions vary, but most smallbore engine builders agree that a high-RPM (desert) smallbore needs more oil, and 32:1 is generally the leanest they'll go for that use. I think Wally's mention of the fuel and oil possibly separating is an interesting and plausible theory. I have nothing to support it scientifically except that it looks like no-oil damage but you are sure you added oil. I would do a leakdown test and, passing that, switch both oil brands and gas station locations/brands. Go one up on your main and one clip on the needle to be safe and have another go. Make sure your silencer core isn't broken and misaligned, raising the pipe bleed-down pressure dangerously high.

If it was a lean-jetting caused issue or airleak-lean issue I would have expected it to have seized tight at least briefly, which you didn't mention if it happened. Or eroded the front edge of the piston and coated the headpipe in aluminum. It really looks no-lube galled.

My main now is 460. When you say go up, should it be in increments of 5 or 10? I will check the silencer. It's a Pro Circuit Type 296. While I was riding the bike stuttered, shut down, and a few moments later I kicked it over and it started up.

 

[MotoMarc36]

460 "should" be about right. Next up would be a 470. If you are holding it wide open for 10 seconds etc in cool temps don't be afraid to start at a 480 or so and work backwards. I ran a 490 in mine last year iceracing in 5f temps, holding it wide open for extended times. Start rich and work back.

Was it tight when it shut down or did the kickstarter move immediately?

 

[Motosportz]

Did the bore, piston and ring end gap all get measured before each install? I'm100% with Marc and it sure look like was no oil.

Oh and Amsoil is the best I watched my buddy ride my 125 all day with ZERO coolant in the summer on big long hills. Still ran but he kept complaining about power loss and we wrote it off to choked air filter. The next day we went to start it and no compression. When I took it apart it had got so hot the powervalve actuating arm had melted and was in a lump at the bottom of the cavity. WOW. Even after all that you could have dislodged the ring from its burnt groove and rode the bike. Cylinder looked OK, piston was burnt but still intact. No seizure. I was using Amsoil then and I will never use anything else after that. True story.

 

[wallybean]

With that rich an oil mix, it is hard to see how the bottom end could be that dry. Something happened to leave you with no oil film or residue.

 

[High Society]

460 "should" be about right. Next up would be a 470. If you are holding it wide open for 10 seconds etc in cool temps don't be afraid to start at a 480 or so and work backwards. I ran a 490 in mine last year iceracing in 5f temps, holding it wide open for extended times. Start rich and work back.

Was it tight when it shut down or did the kickstarter move immediately?

It moved freely when I kicked it. I didn't kick it over right away. I looked down to make sure fuel valve was on, and choke was off. Maybe 30 sec to a minute before I kicked it back over.

Did the bore, piston and ring end gap all get measured before each install? I'm100% with Marc and it sure look like was no oil.

Oh and Amsoil is the best I watched my buddy ride my 125 all day with ZERO coolant in the summer on big long hills. Still ran but he kept complaining about power loss and we wrote it off to choked air filter. The next day we went to start it and no compression. When I took it apart it had got so hot the powervalve actuating arm had melted and was in a lump at the bottom of the cavity. WOW. Even after all that you could have dislodged the ring from its burnt groove and rode the bike. Cylinder looked OK, piston was burnt but still intact. No seizure. I was using Amsoil then and I will never use anything else after that. True story.

I didn't measure those items. Interceptor or dominator?

With that rich an oil mix, it is hard to see how the bottom end could be that dry. Something happened to leave you with no oil film or residue.

How vigorously do I need to shake the fuel can? I will switch oils and rejet. Wally, can you watch my connecting rod vid one more time to be sure it's not that? Around the 47 sec mark, it seems to move back and fourth too much?

 

[72racerx]

Did you notice how much your connecting rod moved when you installed the 150 kit?

It was fine it has the usual side to side movement that I would normally expect from any 2 stroke. I would be more concerned with any straight up and down clearance in the big end bearing.

 

[Motosportz]

I didn't measure those items.

you should to make sure everything is in spec and your not running to tight a piston.

Interceptor or dominator?

I use interceptor but both are fine and work great.

 

[High Society]

It was fine it has the usual side to side movement that I would normally expect from any 2 stroke. I would be more concerned with any straight up and down clearance in the big end bearing.

Zero up and down, and the movement of the crank feels butter smooth

.

you should to make sure everything is in spec and your not running to tight a piston.



I use interceptor but both are fine and work great.

I will look into Amsoil, thank you. I figured since everything was brand new OEM it would have been ok?

 

[Motosportz]

I will look into Amsoil, thank you. I figured since everything was brand new OEM it would have been ok?

the oil you are running is fine as well. Most oils are I just prefer Amsoil.