Engine won't idle

[EvhCo]

Hi everyone. Excuse me if my writing is incoherent, but I'm psychically shattered as a huge lot of plans are about to go astray.
I recently cleaned up my GX-15 thoroughly, meaning lots of cotton pads and sheets of paper with a bit of soap on all of the engine. After roughly 2 weeks of sitting, I decided to but it back on the F2004 for a test drive. Engine starts good (from the 3rd pull), but it goes into full throttle as soon as it starts, with the throttle all the way down. To be honest it doesn't sound like full throttle, more like 2/3 throttle. There are two things that may cause this:

The line going to the exhaust pipe broke in half (don't ask), so I tightly plugged one in the other one. Since it's the exhaust line, I didn't think it might make much of a difference. Could this cause a leak?

There was a bit of fuel line material on the carb's fuel inlet. It looked like a tiny bit of fuel tube debris that somehow
broke when I pulled out the fuel line. I removed it before use. Was that more than just tube debris?

I know that engines with low compression do that, but it worked absolutely perfect the last day I used it before doing the maintenance. It never ran since. I've let the engine outside, I didn't even have the energy to do the after-run.
I'm bastardized. Any help is appreciated.

 

[EvhCo]

Problem solved. fiddlesticking idle needle was too lean

 

[cbaker65]

Problem solved. fiddlesticking idle needle was too lean

You should never alter the fuel tubing that goes to the muffler to the fuel tank ,an should never try to run
the engine with out it!

The engine relys on that fuel pressure ,otherwise the engine will run lean an higher revs.
I burned up a new 8.0 engine after the muffler fell off!...

 

[EvhCo]

I see, but what if I've got a fuel pump on it?

 

[Certified Mike]

Because you said that you tightly plugged in another one, I'm gonna go with, you DON'T have a fuel pump...

 

[EvhCo]

Because you said that you tightly plugged in another one, I'm gonna go with, you DON'T have a fuel pump...

Haha, I meant I thought of getting one, but I scrapped the idea. Thanks

 

[Certified Mike]

@cbaker65. Is 100% correct as far as not running without a proper working exhaust. The engine DOES rely on the line from the exhaust to the fuel tank. It uses the presure created (in waves) to make the engine run correctly. The engine itself needs the exhaust's back pressure in order to run correctly and safely as well. If you haven't done so yet, be SURE to get that ALL sorted and be SURE to do it RIGHT!

 

[EvhCo]

@cbaker65. Is 100% correct as far as not running without a proper working exhaust. The engine DOES rely on the line from the exhaust to the fuel tank. It uses the presure created (in waves) to make the engine run correctly. The engine itself needs the exhaust's back pressure in order to run correctly and safely as well. If you haven't done so yet, be SURE to get that ALL sorted and be SURE to do it RIGHT!

Thanks for the heads-up. It happened like a month ago when the muffler slipped off the tank. Luckily I've quickly noticed the sound getting unusually lean and stopped the engine. Now I've strapped some high-flow (large) tubes both for the fuel line and the pressure line. Required retuning, but worked awesome.

 

[EvhCo]

So yesterday I put back my engine back on it chassis after some extensive modding. Charged up the starter and poured some 20% nitro in the clean tank (previously used 16%). The engine was clean inside out, the tank fresh, and the lines brand new. Started it (takes some time to start until it heats up), and worked like a champ.

Today I strapped the Arduino and all the servos back on the chassis, and got it ready for the first run in 2 weeks. It took significantly more time to start, but I got it done. It started up, but it sounded extremely strange (like one of those old gasoline engines), constantly bogging. In the end, it lost power and shut down, refusing to start further..

I tried tightening the carb, replacing fuel, blowing through the fuel line, blowing through the pressure line. Nothing.
I took out the glow plug. Glows nicely. I poured down some fuel down into the engine and put the plug back in. Finally, it started. Worked for some time and then bogged down and stopped.

It never started again.

Fast forward 2 hours, I noticed that fuel barely goes to the carb when priming the engine, but when the fuel line is out of the carb, fuel goes right through. This got me thinking the carb got clogged, since I had no time to do the after-run last time. I blasted some WD40 on the plug and inside the carb.

Currently overcharging my glow starter. Any idea what causes this stupid problem?

 

[EvhCo]

UPDATE: Yep, it works now. Starts from the 3rd pull and has an even smoother idle than before. Looks like the carb was indeed clogged. WD40 did the trick.
I am never missing an after-run again.

 

[Rolex]

Same basic issue so both threads were merged.

 

[cbaker65]

UPDATE: Yep, it works now. Starts from the 3rd pull and has an even smoother idle than before. Looks like the carb was indeed clogged. WD40 did the trick.
I am never missing an after-run again.

One in dougt lead a scout ,after run doesn't really clean the carb.,it just makes sure the engine & bearings don't
rust an corrode up!
The corrosion in the carb is prpbably merely dried flakey fuel residue .in which is due o sitting a long period of
time ,WD-40 is fine to use to clear that out!...

Great job on figuring out that problem!....

 

[Certified Mike]

The only thing I could really add to your efforts would be to check out the o-rings on the needles in the carb. Replacing them is cheap and eliminates the question of condition. Make sure you use a good lube on them when they go back in. Associated's 'Green Slime' is great on o-rings! You can use that for your shocks as well.