GX390 carb issue-VIDEO

And u better change the OIL if I'm correct you were drowning that thing the more I THOUGHT ABOUT IT
 
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Yeah i dropped the main back down to the factory one it came with which was a 107.5

Ive read that tuning thing over and over, and I still have a hard time understanding parts of it.

So since me just giving it a little gas will kill it, Im not even up on the main jet yet anyways.

Maybe the pilot needs to be bigger? Its a 90 right now.
 
What did you set ignition timing to? It acts like really low timing, like a sheared key.
If it was too fat it would black smoke.
You say been playing with carb and no change, I would be looking else where.
Just trying to help
 
Double checked cam and flywheel yesterday, it's good.

It's around 32 degrees of timing

It has to be the carb

If I give it gas, it dies at this point.
 
you have no return.................. nothing to regulate fuel pressure............... your drowning it------------- open the return to the tank
 
That helped by venting the return line

If I ease into it I can get to 4k again

But that's it

If I mash the throttle it dies
 
Bob, I don't believe so.

Here is how it sits right now

The fuel return was blocked again just to keep crap out of it.

 
Try a different coil. It might be bad. If you don't set the coil gap right it can burn it up.

Just a thought even tho it don't make sense. Lol
 
I'm wrong it's mounted correctly. It's a pumper carb though and blocking the return will make it too rich though.
 
some times the best thing is to start with what you know... you know you have spark... whats the plug look like??? you know you have air... that leaves you with timing, and fuel.. make sure you didn't pop a key... ive had them jump time and run that way... 2nd (ive never run a tilly!!! but I believe there like weed eater carbs???) take your jetting so you know its lean!!! high and low side... work 1 side at a time!!! 1 step at a time... wish you luck nice lil bike and it sounds good too...
 
Brand new coil and plug

You do see arrows, that's the block off plate to use an external pump. I've started it up both ways, with that return line blocked and unblocked. Runs a tad better unblocked.


But still stalls when given gas. If I ease into it I can get it to rev up to 4000 or so. Im thinking the pilot jet is lean.

Timing has been verified on both the cam and the flywheel.

I'm going to make some calls today to guys I know that work with these carbs and see what they have to say.

Haven't done a leakdown test yet. But just rolling the engine over by hand, it feels like its sealed up pretty good.

Thank you guys for all the help
 
Have you had a timing light no the flywheel?
I'm guessing that your timing is not where you think it is.
You are aware that there are different coils available (about a year and a half ago Honda came out with a new coil that wasn't compatible with most billet flywheels.) Make sure you aren't hitting a rev limiter or something in the coil itself. If you've got the standard ARC flywheel, you need to use the old style Honda ignition module with it only. We got into a long haired problem with reverse polarity and all kinds of stuff a couple years back right when the first new coils / ignition modules came out.

Sneaks suggested a leakdown test -- a leaking IN valve will do what you are experiencing here as well. Simple test to perform even with light or breath if you don't have a good leakdown gauge to do the test "properly."


Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
765-339-4407
 
Big thanks to Brian at Carlson

Problem should be solved

Apparently an NR racing non rev limited coil will not work with a Billet flywheel.

Puts you around 60-70 degrees of timing

Was told i was around 32 but they obviously didnt use a timing light

HAd to order a UT1 coil

HOLY CRAP

Been battling this since August
 
Glad you got your issue resolved.
The Briggs twins have the same issue,the 2 coils offered are 42* different.

Put another vid of it running good when you get a chance.
 
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