Losi 5T Multiple Cylinder/Piston Failures

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XJman said:
Its either running really lean, or your mix is off. Try using a mixing funnel like a ratio rite https://ratiorite.com/

What is losi's break-in? I've literally broken engines in and just sent them out of the box and the difference in life is minimal honestly. When I do break an engine in, sometimes in the past but definitely the last few, i set the needles per the carb spec and take both about 1/8-1/4 turn rich. let it idle until the temp stabilizes then shut it down. Let it cool a few hours, then repeat.

After that I let it warm up for about 5 minutes and do an easy couple laps some WOT, then I beat the absolute poop out of it.

I am not easy on my 1/5 scales really, nor do I baby the engines. I literally just spent about an hour om my g320 wide open throttle blowing the tires to the belts in a single outing.

I'm thinking you've got a AFR problem. check the gaskets for the intake, thats usually the most likely failure. However if you haven't rebuilt the bottom you could have leaks around the crank seals.
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If my mix was off, wouldn't I see more consistent wear around the entire piston/cylinder diameter if that was part of the cause?

Here's Losi's break-in. "Allow the engine to idle for 2-3 minutes to achieve operating temperature. Drive slowly for the first half tank of fuel (about 25 minutes) to break in the engine."

That's the impression I got from all of my research on 2-stroke RC's. Glad to hear I haven't been driving this incorrectly.

I doublecheck the gaskets tonight, but I still don't know where the metal debris would be coming from.
 
jeepfreak1972 said:
Ok, I just looked up a genuine Zenoah G320 top end kit. Those circlips have no ears, which is a good thing. Not sure if you have a real Zenoah or not and are using genuine Zenoah parts. If you are, it should eliminate that as a failure if seated properly when assembled. This is odd...
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Yes, as far as I can tell this is OEM Zenoah. All of the replacement parts I've purchased have been from DDMracing.com, so they should also be OEM.
 
Rockfootball47 said:
Yes, as far as I can tell this is OEM Zenoah. All of the replacement parts I've purchased have been from DDMracing.com, so they should also be OEM.
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This is odd for sure. The debris marks definitely indicate something internal vs outside debris getting in. I used the DT1 filter as well. Properly oiled, nothing gets through them. The dents look like piston ring pin to me but if its still in the piston, it can't be that.
 
Ring gap always goes on the intake side of the cylinder. Just in case the pistons are marked incorrectly. I recall someone on here saying they had a piston with the arrow facing the wrong direction.
 
Well it is a little hard to tell but that score looks like it might be from the end of a piston ring, looks like it has a radius with a 90 degree end in the score.
 
jeepfreak1972 said:
Ring gap always goes on the intake side of the cylinder. Just in case the pistons are marked incorrectly. I recall someone on here saying they had a piston with the arrow facing the wrong direction.
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Ring gap needs to be somewhere inline with the cylinder that does not cross over a transfer port or exhaust port
 
smokinwheel said:
Ring gap needs to be somewhere inline with the cylinder that does not cross over a transfer port or exhaust port
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This isn't my first rideo lol. There is only 2 possible positions it can be. Somewhere near the intake side of the cylinder or the wrong side. Obviously not over a port but with a pin to locate the ring, it lands where the the engineer designed it to land.
 
Looking at pics on line, some look like the ring gap pin is on the exhaust side of the piston between the arrow and 3 o'clock. I haven't seen that on a single ring 2 stroke before but they've all been chainsaws.
 
n26tjosi.webp


It looks to me like the ring gap should be in an area like where the straight line is.
If you spin the piston 180 it would put it right about where my half azz arrow is and there would not be a transfer port in that area because it would be like where the line is?

Maybe , does that make sense??
 
1 to 25 or 25 to 1 on mix....... not a pro but looks extremely lean.....peppering because it's lean then getting to hot and breaking which causes heavy dents, damage.
 
smokinwheel said:
View attachment 111607


It looks to me like the ring gap should be in an area like where the straight line is.
If you spin the piston 180 it would put it right about where my half azz arrow is and there would not be a transfer port in that area because it would be like where the line is?

Maybe , does that make sense??
Click to expand...

I marked on the bottom of the cylinder where the arrow, piston ring locating pin and cylinder damage are oriented. The pin was in the same spot for all three pistons.

Marked Cylinder 1.webpMarked Cylinder 2.webp
 
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