Engine died while breaking in

[CaptainNapalm]

Hi readers, while I was breaking in my Losi T 2.0 RTR everything was going fine, nice smoke, engine reasonably cool maybe around 70C, bursts of throttle to 50%.

I am up to my third tank of run-in fuel 5% nitro, high oil. Then (it may be my imagination) but it sounded like the engine was double firing, then before i could shut it off, engine died.

Flywheel is STUCK at about 90degrees from BDC. It will not move, tried warming the block up with hairdryer, but still stuck. Any ideas? or have I blown something inside the engine?

I have tried loosening the glo-plug and turning engine over but flywheel is stuck firm.

Cheers in advance.

 

[CaptainNapalm]

Update: Not willing to go down without a fight, I heated up the block again with the hairdryer and used a flat head screwdriver to lever the flywheel. Surprisingly it came unstuck gently, but felt like there was a 'lock' preventing the piston to return to BDC. I sprayed some WD40 into the chamber and gently massaged the flywheel back and forth. The piston now moves freely.

I was running in on bitumen and only a few times had to open the glo-plug for flooding the engine. I was careful not to get dirt down the chamber. And the piston movement while I massaged the flywheel didn't seem gritty at all. So I am puzzled to why the piston became stuck in the first place.

 

[olds97_lss]

5% nitro and high oil... that's a weird mix for many land vehicles these days. Most are setup to run at least 20% nitro with the head shims.

70C is only 158F, which means it's still very cold. By tank 3, you should be closer to 200 than that. I'd lean it out a bit.

The piston gets stuck at TDC due to the pinch of the sleeve. Doing the "break-in" wears this pinch enough so it will run and seal. With yours running that cold and on that low of nitro, it was probably so rich that it was "4-cycling" (firing every other time) which eventually usually flames out/stalls. In your case, it stalled when the piston was at TDC (top dead center) and in the pinch zone. The sleeves are tapered from top to bottom, so as the piston moves up, it gets tighter and seals. Once you have the engine up around 200-220, the sleeve expands slightly and the taper isn't so aggressive. Since your running so cool, I doubt yours is expanding enough yet.

 

[stevecz28]

with the nitro rating sooo low and the oil so high, i can almost bet its gonna be a pain in the butt to get tuned. you dont have nearly enough nitro to get the thing up to temp. so youll have to lean the thing out soooo much that i just think your gonna have problems the whole time with that fuel. i have a blend of 20%nitro and 14% oil...does great

 

[AxialLST]

The double firing sound sounds similar to when I ran my Axial out of fuel while breaking it in. It started running like that, sounded wierd so I brought it over, and the tank was empty. Killed it, and let it cool and continued on with heat cycling. I have figured out that when I pinch the fuel line to stop the engine it does the same thing as it runs out of fuel. Maybe this helps?


-AxialLST

 

[CaptainNapalm]

Thanks for your input guys. I did have the high oil mix ending up around 100C at the end of the runs beforehand. The time the piston got stuck was the start of a new run. But, I was only using the high oil mix to be gentle on the first two tanks. I'll run the rest of the break in on 25% mix i have, and start leaning it out.

Could the double firing have broken anything inside my engine that i should check first? Everything feels ok, but I am just an rc noob atm.

 

[AxialLST]

Only way to be sure is to pull the cooling head off and look at the cylinder and sleeve for any scores. You can also pull the backplate off and make sure the connecting rod is still tight around the crank and doesn't look twisted or stretched. As long as everything looks ok and the compression is still good you should be fine.

-AxialLST

 

[d8 rider]

hi

befor you start your engine use the heat gun and make your engine tep more than 200f

then start your engine it wel work very nice evry time preheat your engine befor starting it

 

[syphon68]

I personally have never had to preheat my engines to 200deg F before you start them and have never heard of anyone that has. Like Olds said just make sure that your engine is getting up to that 200 deg mark so that the sleeve can expand and you can get your proper tune and break in.

 

[olds97_lss]

I personally have never had to preheat my engines to 200deg F before you start them and have never heard of anyone that has.

I have, but not a losi mach engine. Only my LRP28S3's. They had a tight pinch when new so I heated them with a hair drier as hot as it would get it and it made starting it the first 8 tanks or so much easier.

 

[syphon68]

I learn something new every day, thanks