motor dying when hot, greyhound clone

[friction]

I am thinking I may need a rejet of some sort, but what do you think?

Motor is completely stock, with a helper spring on the governor spring, stock air filter and airbox, stock exhaust pipe but muffler box is broken off. Essentially just a closed end pipe with 3 holes drilled in the side of it.



When cold, the motor fires right up on the first pull and I can open up the choke completely almost immediately. Rides around good and is responsive.

After a little while, once the motor gets up to temperature, It wants to die when it drops back to idle. Fairly often it will just cut out at full throttle (as if I let off the gas) and die, and when it dies it is hard to get started. When I do get it running after a bunch of pulls, I usually have to have the choke half closed or so and the throttle cranked a little bit in order to keep it from dying.

Oil level is good and oil is pretty fresh 10w30 synthetic. Oil sensor is disabled. 87 octane fuel.

I want to say this seemed to be more prevalent when the welds on my stock muffler broke and the box came off...but its been a few months since i had it out so thats just a guess more than anything.


I need to read the plug and see whats goin on, but having to close the choke halfway to help keep it running when hot makes me think its not getting enough fuel?

 

[texasfabguy]

have you changed the plug? have you re-set the valves?

 

[friction]

yes, its not the stock plug, its an ngk that was replaced the last time i changed the oil. has only a few hours on it.

ill look into re-setting the valves, ive read a lot lurking here but havent read about that yet.

 

[1BadFox]

I am thinking I may need a rejet of some sort, but what do you think?

Motor is completely stock, with a helper spring on the governor spring, stock air filter and airbox, stock exhaust pipe but muffler box is broken off. Essentially just a closed end pipe with 3 holes drilled in the side of it.


When cold, the motor fires right up on the first pull and I can open up the choke completely almost immediately. Rides around good and is responsive.

After a little while, once the motor gets up to temperature, It wants to die when it drops back to idle. Fairly often it will just cut out at full throttle (as if I let off the gas) and die, and when it dies it is hard to get started. When I do get it running after a bunch of pulls, I usually have to have the choke half closed or so and the throttle cranked a little bit in order to keep it from dying.

Oil level is good and oil is pretty fresh 10w30 synthetic. Oil sensor is disabled. 87 octane fuel.

I want to say this seemed to be more prevalent when the welds on my stock muffler broke and the box came off...but its been a few months since i had it out so thats just a guess more than anything.


I need to read the plug and see whats goin on, but having to close the choke halfway to help keep it running when hot makes me think its not getting enough fuel?

What do you mean a closed end pipe?

If exhaust is not exiting the pipe at a high enough rate.... your exhaust valve is prob near melting with heat from all the back pressure.

 

[texasfabguy]

What do you mean a closed end pipe?

If exhaust is not exiting the pipe at a high enough rate.... your exhaust valve is prob near melting with heat from all the back pressure.

I know what he means.if you take a stock muffler apart, the first section or baffle is a pipe with holes on the side.if you look at a stock muffler. on the top of it you will see a welded cap looking thing, That is the end of the pipe.

 

[friction]

Exactly. The weld broke at the end of that pipe, and the box came loose. I had to ride it like that for a few miles for lack of a better solution, the box portion is pretty much ruined.

Anyways I figure its halfway between a straight pipe header and the stock muffler. That's how it sounds.

Sent from my Ally

 

[roccosbike]

No back pressure,now your engine is running lean.Put a new muffler on it or rejet it.

 

[TomH]

your plug should look pretty white if it is running too lean..lean is hot..could burn a hole in your piston if it is too lean. you want your plug to look like moca coffee color, light to medium brown.

 

[DuVoisin]

No back pressure,now your engine is running lean.Put a new muffler on it or rejet it.

Back pressure aint got nothin to do with it. Get on that bike ride the hec out of it. When it starts to die , crack the gas cap loose, it's not venting correctly most likely. Pull the fuel line off the carb, make sure you have a steady flow.Also ,stay away from any Ethanol gas , this draws moisture right out of the air we breath. Look inside the carb bowl for any grey or white jelly substance. May even have some water droplets in it. I think it's heat related, probably a ignition coil. Coils break down sometimes when they get hot,causing intermittent fire to the plug or a weak fire. This would explain having to choke the carb when it's hot. It takes more fuel to ignite with a weaker spark.If everything checks out fuel related, put coil on it. Also make sure of any wires that have insulation that may have rubbed through touching metal.Coils are cheap and they can sure cause a headache. Thanks, Tommy DuVoisin ,30 year Briggs/Tecumseh MASTER TEC.

 

[badtec]

I was also going to mention the gas cap. Good luck.

 

[friction]

These are all great tips, ill find some time this week to look more into it. Hard to get some good seat time these days after work when its dark outside!

Sent from my Ally

 

[1BadFox]

These are all great tips, ill find some time this week to look more into it. Hard to get some good seat time these days after work when its dark outside!

Sent from my Ally

Thats my favorite time to ride. I got one of those l.e.d. lights that straps on your head. Its 180 lumens and takes 3 triple aaa's. It is super bright. Lights up the whole trail. I got mine at Lowes for 38.00. Way better than any headlight on the bike. Plus you can see turns and curves in advance because you have the ability to turn your head to whatever you want to see.

 

[dave dickson]

The exaust tip is a good one,, personally I would change that oil back to straight 30wt, I would run 10 w 40 in the winter, I would check my fuel for water, I would also suspect your coil, they will fail after they become warm.
Dave Dickson

 

[friction]

I think it may in fact be the gas cap. When I first got the bike running the cap wouldn't seal and leak fuel like crazy. So I put plumbers tape on the threads. That stopped the leaking.

I partially unscrewed it and rode around tonight with no issues, but not that long of a ride. But when I shut off the bike immediately unscrewed the cap more and I could hear the air suck in.

Really need to get a new muffler. A little too loud for my liking without it.

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