Honda GX390 will not run.

[Jwilson22071]

Have a Honda GX 390 (GCBCT- QA2). Pulled it apart to put new piston rings in it. Got everything back together. When I went to start it it runs for a 5 seconds and dies. Will start right back up, but dies again. Will only start with the choke on. I don't even have time to turn the choke of before it dies. Can keep it running somewhat with starter fluid. Had a new carb on it so I pulled it back off and replaced with the same one that came with it- same result. Here is what I've done so far-
1. Changed carbs and checked all gaskets
2. Owner told me he had trouble with governor before so I changed governor gear and shaft. 3. Cleaned out fuel tank and put new fuel line on. Got good flow all the way thru the bowl on carb.
4. Checked valve lash several times. Engine starts really easy, just will not stay running. I can kinda keep it running if I hold the carb shut at idle but cannot open the choke. Seems like I'm getting to much air but it has new gaskets and insulators.
Can the coil be doing this? I'm not to familiar with these 4 post coils I believe they are called. Its the coil with the plug on it. I started it with the switch plugged in , then i unplugged the switch ( checking the switch)and put the red and black wire together. Would not start unless I did this. Oil sensor wire is unplugged. The engine is on my lift do I need to ground the block somehow with this different coil? I'm lost any help would be appreciated. Thank you

 

[bertsmobile1]

Some of these engines have a low oil shut down switch which grounds the spark if the oil level gets too low
So disconnect all the wires at the plug and see if the problem goes away.
Occasionally the kill switch wires can make a ground contact with steel blower cover when the engine is running and shoving wind around

 

[Jwilson22071]

Some of these engines have a low oil shut down switch which grounds the spark if the oil level gets too low
So disconnect all the wires at the plug and see if the problem goes away.
Occasionally the kill switch wires can make a ground contact with steel blower cover when the engine is running and shoving wind around

Ool sensor wire is unhooked already. If the kill wire is shorting out wouldn't it keep the engine from firing at all? In the current condition I can restart it as soon as it dies. I will pull the wires tomorrow and see if I can find any bad spots. Thank you

 

[bertsmobile1]

My go to for problems like this is a red in line spark tester.
Hook it up them watch weather it flashes all the way to the bitter end which indicates the spark is fine
next is a can of carb cleaner with very short shots down the carb throat.
If I can keep the engine running for at least a minute this way then I know it has a fuel problem.
I like to do both as they compliment each other.
Yes, kill wires kill but in order to do that they have to be touching a ground point some where

 

[Jwilson22071]

My go to for problems like this is a red in line spark tester.
Hook it up them watch weather it flashes all the way to the bitter end which indicates the spark is fine
next is a can of carb cleaner with very short shots down the carb throat.
If I can keep the engine running for at least a minute this way then I know it has a fuel problem.
I like to do both as they compliment each other.
Yes, kill wires kill but in order to do that they have to be touching a ground point some where

I understand how all that works. That's the same test I do. As stated before I can keep it running with starter fluid all be it badly. I have plenty of fuel going to the carb. Tank is clean and a new fuel line. Tank is gravity fed and I can open the drain on the float bowl and fuel is running just fine. With or without the fuel cap on. I have put on 2 different carburetors one new one used and have the same exact problem with both. If I hold my hand over the air filter opening it tries to run. Carb has brand new gaskets and insulator. In fact tank and hose came off a unit that is currently running. As soon as the governor tries to open engine dies. That's why I was wondering about the coil. I have spark all the way until engine stops turning but I'm wondering if the on/off switch needs to be grounded somewhere? My lift has a wood top and the engine is just sitting on it. But, if I have a ground problem why is it starting at all. Engine can die and I can start it right back up.

 

[bertsmobile1]

Ground means grounded to a metal part of the engine .
So now it is clear, you have a fuel supply problem
Can be as simple as the gasket blocking off the vent hole .
If air can not get in fuel can not get out.
Could also be a bd inlet valve not opening enough
And can be a governor hooked up wrong
People often get this backwards.
The Government puts a brake on you and prevents you doing what you want to do
The engine governor puts a brake on the engine and prevents it over reving .

The throttle cable pulls on a spring that is connected to the governor arm holding it WFO.
The governor arm is connected to the throttle butterfly via the throttle shaft
The governor mechanism works against the spring and tries to CLOSE the throttle
The faster the engine goes the harder the governor should be trying to CLOSE the throttle
Thus at rest the throttle should be wide open but as soon as the engine starts to turn the governor should move in the closed direction.

So check the governor adjustment
With the engine off push he governor arm to WFO
Slacken the governor clamp and rotate the governor shaft to the fully open direction as far as it can go then tighten the clamp

 

[Jwilson22071]

Ground means grounded to a metal part of the engine .
So now it is clear, you have a fuel supply problem
Can be as simple as the gasket blocking off the vent hole .
If air can not get in fuel can not get out.
Could also be a bd inlet valve not opening enough
And can be a governor hooked up wrong
People often get this backwards.
The Government puts a brake on you and prevents you doing what you want to do
The engine governor puts a brake on the engine and prevents it over reving .

The throttle cable pulls on a spring that is connected to the governor arm holding it WFO.
The governor arm is connected to the throttle butterfly via the throttle shaft
The governor mechanism works against the spring and tries to CLOSE the throttle
The faster the engine goes the harder the governor should be trying to CLOSE the throttle
Thus at rest the throttle should be wide open but as soon as the engine starts to turn the governor should move in the closed direction.

So check the governor adjustment
With the engine off push he governor arm to WFO
Slacken the governor clamp and rotate the governor shaft to the fully open direction as far as it can go then tighten the clamp

So.... governor is adjusted correctly. Carb has good gas flow from the tank to the float bowl. And, I have tried 3 different carbs. Double and triple checked gaskets and insulator installation. Same result. It will only run on starter fluid. Beginning to wonder if I didn't get the head in right and I'm sucking air thru the head gasket. Or if I'm one tooth off in the cam because it gets kinda tough to pull when the choke is open? I don't know guess I will tear it down again.

 

[HurstGN]

Not to be insulting, but you did verify the carb gasket holes are aligned for the airflow needed to have the carb run properly? It's easy to mess those up.

 

[Jwilson22071]

Not to be insulting, but you did verify the carb gasket holes are aligned for the airflow needed to have the carb run properly? It's easy to mess those up.

Yes sir I have checked a few dozen times. Lol

 

[Scrubcadet10]

have you tried using an alternate fuel tank/supply?