Exhaust came undone....now wont start.

[flarcer]

While out bashing in a huge open field i noticed a change in the exhaust note of my engine. After bringing it back to me and removing the body, I see that one exhaust bolt is completey gone and the other is barely hanging on. The pipe is dangling loosely. Which means I was running for at least one minute with no exhaust. After Loctite and reinstalling pipe, motor would not start, sputer but not start. I later replaced the head gasket, no start. Replace the spark plug, no start. Any other ideas? Is the motor done? thanks

 

[BrawnFG]

with the pipe off it may have overheated (as it will have run lean)

did you inspect the head and ring when you renewed the gasket?

have you checked that teh plug is snug, and the carb is snug?

 

[flarcer]

Carb is snug, plug is snug. Top center of piston was black and thick. Is this normal? I don't know about this to know the difference.

 

[sperera]

may have even sucked in some crap being 2 stroke which may be assisting the problem. when you pull the pull start how easily does the piston slide up and down?

 

[flarcer]

Piston slides up and down as normal. I pulled the head back off, everythings lubed just fine. The ring is not as fluid as normal though.

 

[sperera]

hrmm very strange, any scratches or marks on ring or bore?

 

[flarcer]

The cylinder bore is smooth, nothing feels odd.

 

[BrawnFG]

i'm at a loss on this one.

if spark is strong, and plug is new, and the coil gap is right

is fuel getting through? does the carb need a clean out?

other than that, I'm lost on this one.

if you figure it out, let us know so we can add it to the list of things to check

 

[ANGRYEVO8]

Remember engines only need 4 things to start, air, fuel, spark and compression. If you have a good spark than pour a small amount of fuel into the top of engine through the spark plug hole. If it starts and runs for a little bit than you know that its a fuel delivery issue.

But i would say that running with the exhaust hanging off has let some dirt in, or as it would have ran lean the ring is no longer good. I would change the ring and see if that works. Are you getting a good seal around the head gasket??

 

[Timmahh]

losing the pipe wont neccessarily mean the motor will run lean, it will toss the needle settings. but most likey it allowed poop to get sucked into the motor (yes your exhaust suxs too.) and likely damaged the cylinder wall and ring.

take the exhaust off fully, and take a look at the piston/ring and cylinder walls (with piston at BDC). you ll likely find some scratches/scoring from dirt/sand getting in while the bolts were loose.

Locktite wont help hold the bolts. the heat from the exhaust will just melt it out. the best option is to use Permates Red HIGH TEMP gasket maker. this wont melt out, it just remains soft when it gets hot. so will still hold the bolts.

 

[flarcer]

UPDATE: Problem solved.....sort of. Because so many of you asked about the piston ring I decided to replace it. My LHS did not have a ring in stock but Large Scale RC had the 28.5 kit on sale, I got that kit instead and now I'm back at it. After installing the kit and using red Loctite as advised here on the pipe, I let it sit over nite. Then I ran it for 5 minutes, checked it and found that the exhaust was loose again just like Timmahh said it would. So Tim where can I get this high temp gasket maker?

 

[Timmahh]

any auto parts store.

its Permatex High Temp gasket sealer.

just squirt some into the exhust stud holes, smear a bit on the bolt threads, and put them in and tighten them up. again let them set for 24 hrs to dry.

once dry, the bolts shouldnt loosen up anymore. the gasket maker will soften when hot, but wont melt out.