Replace piston and Sleeve or just the ring??

[j77456]

Hi all. I'm new to the forum as well as to Nitro cars so bare with me here if you will.

I've got a Nitro truck and it seems I've blown the motor. I was warming it with a heat gun to start it easier and it seems I've run it too hot. I started it recently and went for a run to warm it up. As soon as i opend the throttle full tilt it started dying at top end. I see i've now lost all compression on the engine. So here's the question. Can i replace just the ring or should i replace the entire piston and sleeve. I can't imagine that either piston and or sleeve are damaged?

Thanks in advance for the assistance.

 

[watertrucker]

Welcome to RCT. Most Nitro engines don’t have piston rings. The sleeve is tapered toward the top and that creates the compression. What truck and engine do you have?

 

[Littlemotor]

As was said above-no rings in nitro glow 2-smokes.. It would take a LOT of abuse to get it hot enough to lose compression, or all pinch in a single run.. I’m not saying it’s impossible, and it could’ve been crazy lean (likely with being to the point of breaking up on top-however I wasn’t there, and it could’ve been blubbery RICH), but 99.999% of the time-that wouldn’t kill the pinch, or the actual compression.. Seems more likely to me that the piston wasn’t brought down from TDC when it cooled off, and THAT will cause the compression and pinch to leave the chat every single time…

 

[Chubaka]

As was said above-no rings in nitro glow 2-smokes.. It would take a LOT of abuse to get it hot enough to lose compression, or all pinch in a single run.. I’m not saying it’s impossible, and it could’ve been crazy lean (likely with being to the point of breaking up on top-however I wasn’t there, and it could’ve been blubbery RICH), but 99.999% of the time-that wouldn’t kill the pinch, or the actual compression.. Seems more likely to me that the piston wasn’t brought down from TDC when it cooled off, and THAT will cause the compression and pinch to leave the chat every single time…

Some sand with no filter will do it. Better yet, putting in the wrong glow plug with dirt around the coil will be very effective. Ask me how I know. Had a brand new engine overheat a couple seconds. Traxxas said the new .15 lost compression and got scorched. On that one a drive shaft broke so I drove 50 or so feet spinning one wheel with a under 8mph top speed.

 

[Littlemotor]

Some sand with no filter will do it. Better yet, putting in the wrong glow plug with dirt around the coil will be very effective. Ask me how I know. Had a brand new engine overheat a couple seconds. Traxxas said the new .15 lost compression and got scorched. On that one a drive shaft broke so I drove 50 or so feet spinning one wheel with an under 8mph top speed.

Well that shiit wouldn’t require a post like the one we are all replying to, ya big ol’ walkin’ carpet, you…

 

[CertifiedMike]

The smallest actual piston and ring set I've personally seen is from this Husqvarna 2 stroke.
Its only 35mm diameter!
I thought of @Littlemotor & @johnnydmd for a psycho-nitro mod motor as soon as I unboxed it!

 

[TeknoJ]

I don’t know everything but I’m pretty sure it’s best to replace piston and sleeve as a set, in most cases it’s a good idea to do a connecting rod as well since they can stretch overtime.
I only have experience with one car and it’s somewhat vintage and the motor was shot so I opted to replace the entire thing since I couldn’t find parts.

 

[CertifiedMike]

I don’t know everything but I’m pretty sure it’s best to replace piston and sleeve as a set, in most cases it’s a good idea to do a connecting rod as well since they can stretch overtime.
I only have experience with one car and it’s somewhat vintage and the motor was shot so I opted to replace the entire thing since I couldn’t find parts.

You are correct! You replace them in pairs because there is no ring. They wear together, as a pair.

 

[johnnydmd]

This all will depend on the engine, and whether parts are available, or if buying a new engine is cheaper (sometimes it is).

 

[TeknoJ]

This all will depend on the engine, and whether parts are available, or if buying a new engine is cheaper (sometimes it is).

This is exactly where I was at in my situation. It was more cost effective to replace the entire engine rather than rebuild the old one, finding parts was almost impossible.

 

[j77456]

Hi all. I'm new to the forum as well as to Nitro cars so bear with me here if you will.

I've got a Nitro truck and it seems I've blown the motor. I was warming it with a heat gun to start it and it seems I've run it too hot. I started it recent and went for a run to warm it up. as soon as i opend the throttle it started dying at top end. I see I've lost all compression on the engine now. So heres the question. Can i replace just the ring or should i replace the entire piston and sleeve. I cnt imagine that eith are damaged?

Thanks in advance for the assistance.

Welcome to RCT. Most Nitro engines don’t have piston rings. The sleeve is tapered toward the top and that creates the compression. What truck and engine do you have?

Thanks for the response. Its an Acme Conquistador with a Thunder Tiger Pro 15 engine

 

[j77456]

A lot of info here. Thanks a lot. Appreciate it. So the reason i think it got too hot. I read on some forums and also watching some Youtube vids that you should heat with a heat gun before starting. I think i might have cooked it by over heating it before starting it.

 

[Littlemotor]

A lot of info here. Thanks a lot. Appreciate it. So the reason i think it got too hot. I read on some forums and also watching some Youtube vids that you should heat with a heat gun before starting. I think i might have cooked it by over heating it before starting it.

99% not likely. About the only way if you did not suck dirt is to have the engine cool without rotating the piston down from TDC.

Also no sense doing a piston, and sleeve as they’re RTR only, and long since discontinued. Just find another RTR grade .15-.18 small block for the vehicle.

When heating the engine to ease unnecessary force on the rod, when there is still an abundance of mechanical pinch (not to be confused with actual compression), you want to be around 235F.

EVERY time you grab your vehicle after a run, you MUST rotate the crankshaft to bring the piston down from TDC. If you don’t, it WILL ruin the sleeve, and you’ll lose at LEAST pinch, but sometimes all compression as well.

This is one of the cardinal rules to nitro RC operation. It’s a MUST-not a suggestion.

 

[j77456]

99% not likely. About the only way if you did not suck dirt is to have the engine cool without rotating the piston down from TDC.

Interesting. How do you rotate the piston down / make sure it is rotated down?

 

[Littlemotor]

I edited/updated my previous post btw.


Rotate the flywheel by hand to find TDC, or top dead center. It’s where you feel the most resistance. Rotating back and forth as you determine the “center” of that resistance, then turning the flywheel 180deg. You are now at BDC, or bottom dead center. THIS is wear the piston needs to be inside the sleeve EVERY time the engine cools.

Some folks like to “mark” their flywheel with a Sharpie, bit of paint, or even a small mark with a dremel. I’ve always just gone by feel, as EVERY nitro RC owner should know how to accomplish this, and flywheels WEAR on the outside, thus losing any “marked” notation.

 

[j77456]

I edited/updated my previous post btw.


Rotate the flywheel by hand to find TDC, or top dead center. It’s where you feel the most resistance. Rotating back and forth as you determine the “center” of that resistance, then turning the flywheel 180deg. You are now at BDC, or bottom dead center. THIS is wear the piston needs to be inside the sleeve EVERY time the engine cools.

Some folks like to “mark” their flywheel with a Sharpie, bit of paint, or even a small mark with a dremel. I’ve always just gone by feel, as EVERY nitro RC owner should know how to accomplish this, and flywheels WEAR on the outside, thus losing any “marked” notation.

Thanks. Whats RTR please

 

[Littlemotor]

Thanks. Whats RTR please

Ready-To-Run. Base model, introduction to the hobby grade nitro engines. Not typically serviceable. Run it ‘til it’s junk, and replace with a new engine.

 

[fstnd]

You are correct! You replace them in pairs because there is no ring. They wear together, as a pair.

I have two same nitro .12 engines, and the pistons from one engine would not fit in sleeves of the other

 

[j77456]

Ready-To-Run. Base model, introduction to the hobby grade nitro engines. Not typically serviceable. Run it ‘til it’s junk, and replace with a new engine.

Ok great. So are you suggesting the Thunder Tiger pro 15 engine i have is not worth repairing and should be replaced?

 

[Littlemotor]

Ok great. So are you suggesting the Thunder Tiger pro 15 engine i have is not worth repairing and should be replaced?

I’m saying it’s not even ABLE to be repaired.. It’s long since been discontinued. Even if they DID offer routine maintenance parts for it, such as piston & sleeve sets, connecting rods, crankshafts, circlips, or bearings-you’d likely never be able to find them today.. They’re just not a popular engine, and meant to be replaceable as a complete engine. Sorry to be the bearer of bad news..