I just recently tore down my engine to replace a crankcase gasket due to an air leak. When I pulled the jug I had noticed that the entire piston was black! I run Amsoil Saber 1.5oz per gallon and Opti2 1.5oz per gallon, (it is easier to measure 1.5oz than 1.3oz for a 100:1 mix.) I think this is a result of not running the engine hard enough during the first few miles. I am going to put new rings on it and re-jet for a 32:1 conventional mix. Is there anything I should do to prep the old cylinder? Sorry I do not have a picture to post of the piston. It got soaked in chem-dip and looks new again already!
Breaking in to softly
- Thread starter chris8686
- Start date
A black piston shouldn't be a big deal, but when you say black is it a thick coating or a thin coat?
carbon build up is normal on the piston. like where patchy was going... if its thick thats a problem. if its just a thin layer you have nothing to worry about.
Regardless of your fuel/oil ratio, if you're fuel/air ratio is on the rich side you'll get carbon.
Is the engine breaking into a good 2 stroke when under load or is it 4 stroking most of the time?
And you're right. You can be too easy on these little Chinese engines during break-in. Let it run a little. You won't hurt it and it will break in faster and better with some wide open throttle (WOT) runs. Putzing around at half throttle and not allowing the engine to run isn't doing it any favors.
I wouldn't start replacing parts until you have a couple of hundred miles on the engine. 300 is even better. I would suggest you not mix an old cylinder with new piston rings. That usually results in bigger problems than you're having now. Put it back together and ride it. And don't baby it.
Tom
Is the engine breaking into a good 2 stroke when under load or is it 4 stroking most of the time?
And you're right. You can be too easy on these little Chinese engines during break-in. Let it run a little. You won't hurt it and it will break in faster and better with some wide open throttle (WOT) runs. Putzing around at half throttle and not allowing the engine to run isn't doing it any favors.
I wouldn't start replacing parts until you have a couple of hundred miles on the engine. 300 is even better. I would suggest you not mix an old cylinder with new piston rings. That usually results in bigger problems than you're having now. Put it back together and ride it. And don't baby it.
Tom
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The piston had a thin coating of black carbon that was very soft. The majority of it was easily removable wiping with a shop rag. The engine had 600 miles on it. I intended on reusing the rings but one of them snapped while removing it....
I just got done rebuilding the engine and taking it for its first ride and rode it hard! I replaced the 6202's with ones I ordered from Fastenal for $1.50 a piece. They are made in China but the quality is much higher than the Yimmyangs or whatever that came in it. I can't justify spending $40 for a set of SKF bearings.
I just got done rebuilding the engine and taking it for its first ride and rode it hard! I replaced the 6202's with ones I ordered from Fastenal for $1.50 a piece. They are made in China but the quality is much higher than the Yimmyangs or whatever that came in it. I can't justify spending $40 for a set of SKF bearings.
I was concerned with the carbon below the bottom ring. After looking at a lot of pics of 2 stroke pistons it seemed like any carbon build up below the bottom ring was an issue
This may have been from before the rings sealed properly?
Otherwise your rings didn't seat properly?
Is there an even wear band all the way around the ring?
Ring may have been sticking or bent?
Otherwise your rings didn't seat properly?
Is there an even wear band all the way around the ring?
Ring may have been sticking or bent?
The rings were not sticking and there was not an even wear band around the ring. I think it is a result of not wearing in motor properly and it did not create a good ring seal. I putted around in this motor using cheap Dino 32:1 for 100 miles then switched to Amsoil saber 80:1 and putted around now with 600 hundred miles. This motor has never been run hard. After the new rings and switching back to Dino 32:1 I noticed that the compression was higher and the power was back. I ran in hard varying the throttle between half and full for 20 miles with a good load on the motor. The next start up I had noticed that the engine was much quieter and idled very steadily. I am going to run the Dino oil for a few hundred miles this time around, unless you suggest otherwise.
I run my motors hard from the start, Top end rebuilds are cheap, and I'm always keen to try some changes to the top end port design, So longevity is not my main concern.
I run my motors on Synthetic Oil, at 40 to 1 for break in and hot humid weather conditions.
I find the rings seat quickly under these conditions.
What I have noticed is some rings are not round.
When you put your new ring in the bore to check ring gap then hold it up to the light and look for gaps between ring and bore. If you can see light, get another set of rings, cause the ones you got are bent.
This sounds the case if the wear band on the ring was not even.
I don't think it maters too much what oil you use if it is mixed as to manufactures specs.
Synthetic has it's advantages at a price.
For the amount of oil I use price isn't a big factor too me and I don't mind paying for synthetic, it will make your motor last longer, be less messy and likely give improved performance.
Break the motor in to the revs you intend to use the motor at.
Main thing during break in is to keep an eye on the temp.
I run my motors on Synthetic Oil, at 40 to 1 for break in and hot humid weather conditions.
I find the rings seat quickly under these conditions.
What I have noticed is some rings are not round.
When you put your new ring in the bore to check ring gap then hold it up to the light and look for gaps between ring and bore. If you can see light, get another set of rings, cause the ones you got are bent.
This sounds the case if the wear band on the ring was not even.
I don't think it maters too much what oil you use if it is mixed as to manufactures specs.
Synthetic has it's advantages at a price.
For the amount of oil I use price isn't a big factor too me and I don't mind paying for synthetic, it will make your motor last longer, be less messy and likely give improved performance.
Break the motor in to the revs you intend to use the motor at.
Main thing during break in is to keep an eye on the temp.
Thank you very much for the advice! I normally run my bike between 3500 and 4000 rpm. It is just a daily commuter and I am looking for engine reliability and longevity not so much performance. I run opti-2 in my motors and have never had a lubrication related engine failiure.
In my other bike I had a crankcase bearing fail at 1500 miles but I would consider that a quality issue not a lubrication issue.
In my other bike I had a crankcase bearing fail at 1500 miles but I would consider that a quality issue not a lubrication issue.
With those kind of revs you should have a good long life with your chinadoll.
I run a 36 to reduce revs at cruising speed and I have great results with many thousands of miles on my various bikes.
Treat her right and she will love you long time.
I run a 36 to reduce revs at cruising speed and I have great results with many thousands of miles on my various bikes.
Treat her right and she will love you long time.
