Help! What caused this scratch on the piston?

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Well, without seeing the cylinder head off and doing a quick check of what is missing, we could only guess.

From my experience, I seen a gouge on my the original HPI CY fuelie 26cc. At first I thought I could just sand it down and add a new ring and gasket. Nope, I found the wrist pin clip managed to crawl it’s way up to the top of the piston. Only to get pinched by the exhaust port and dragged back down the cylinder wall. I ended up dropping in a 36mm piston and cylinder kit.

To get the answer you are looking for, it has to come apart.
 
you should remove the engine from the car and put a little gas mix in the crankcase
slosh it around dump it out,make sure theres nothing in there.You will need a complete top
end with gaskets a and new circlips.if you have any questions about this,call steve at ddm
Looking at that pic of the piston looks like something caught the ring exhaust side.

If you find something please post ur findings here,What gas mix are you using/oil gas ratio?
i a rovan 36cc and 29cc so far no problems but i know im going g290 if they do crap out.
 
It actually dented the piston in against the ring. I cant get the ring off but would this cause the engine not to fire? Because it wont hit a lick :(
 
Scruffy said:
It actually dented the piston in against the ring. I cant get the ring off but would this cause the engine not to fire? Because it wont hit a lick :(
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Yeah its toast,never run that way piston/cylinder its done.
you need complete top end and real important to make sure nothing in the bottom of the crankcase
everything clean before installing new parts.

i never used lucas 2t anyone else here have experience with this oil?
25:1 is good for these engines.
 
So now its deciding whether to rebuild this engine or rebuilding my RCMK 28.5. About the same cost. This engine is 2 bolt and the RCMK is 4 bolt and if im going to rebuild, i think id rather go with Gizmo's 30.5 full mod head kit for the RCMK. Should be quite a bit more power over the current 27.2.
 
What sucks the worst is this engine didnt have 2 gallons thru it. Only had it since April
 
Thats a esp full mod 27.2. Cy or rovan i wouldnt be surprised but esp is supposed to be top notch
 
12 Bravo said:
i've used klotz super techniplate for years at 32/1 with zero problrms
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with the full synthetics 32:1 still spits oil out the ex which is good..
experience my 2 rovans is they like 25:1 and clean, oiled air filter with outerwears im using Maxima super M(jaso certified)
2.5 gallons compression still good.mite open one up to check the bearings...
i think they wont crap out because i really want a g290 or g240

Scruffy said:
Thats a esp full mod 27.2. Cy or rovan i wouldnt be surprised but esp is supposed to be top notch
Click to expand...
cy bottom end?
 
Buzzsaw46 said:
Did you find out what went through it to cause the damage?
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No i haven't had time to pull the engine off and flush the case out. I was running in sand at the time it quit on me but idk how sand got thru anywhere as i was running a freshly oiled foam filter with a redneck outer filter and prefilter
 
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