View Full Version : Honda GX390 not running at full speed?

01-17-2012, 01:15 AM
Just took my pressure washer out of storage from about 2 yrs, drained old fuel, took carb apart and cleaned with carb cleaner including jet. Engine starts and runs great with choke at 1/2 position but when open choke and full throttle it dies within 3 seconds or so. Ive cleaned carb 2x and refilled with fresh gas. Could it need a valve adjustment? I didnt see a lot if any oil in carb? It runs good with carb at full throttle and 1/2 choke for as long as i need it to. Any suggestions?? Its a honda gx390 13hp.

01-17-2012, 01:21 AM
just read the earlier post about cleaning carb, but I failed to push out nozzle and clean that...could that be problem? Ill try again tomorrow.

01-17-2012, 08:00 AM
Could be Lou, If all else fails you can get a new carb and other pressure washer parts HERE (http://www.watercannon.com/p-2217-carburetor-assembly-gx-series.aspx).

I haven't had any issues with these Chinese carbs.....

01-17-2012, 11:48 AM
Just cleaned carb for the 3rd time and removed and cleaned nozzle and cleaned everything well, but still only runs good at 1/2 choke. Could this be a carb issue, I've never adjusted valves? where can i find specs for valve clearance?

01-17-2012, 01:17 PM
Could this be a carb issue

It sure sounds like something isn't fully open inside the carb,
Have you replaced the spark plug (BPR6ES) ? I've seen fouled/weak firing plugs cause a issue such as this....

Valve adjustment if you want to check;


01-17-2012, 01:49 PM
the spark plug?? wonder why? I'll change that out to see if that helps. then check valve adjustment. If still not running right, ill have to order replacement carb. I just assumed that it was a carb issue, but it runs great at half choke so I know fuel is getting though ok. Ive cleaned it 3x! thanks for help!

01-17-2012, 01:51 PM
when im looking at valves...which one is intake and exhaust?

piston slapper
01-17-2012, 06:18 PM
Remove the fuelbowl drain screw. Check the gas flow.
You may have a clogged fuel screen in the tank.
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01-17-2012, 06:37 PM
Ditto what Slapper said ^^^^

The intake is the one closest to the carb....

01-17-2012, 07:02 PM
ok will do, tried a new spark plug but still not running right. I cleaned out jet and nozzle holes with a small wire to make sure they aren't clogged and ran air through again. Still not good. Definetly not clogged, should i run machine with drain screw out and plugged with thumb. everytime i've taken carb apart there is fuel in the bowl.

Now I can run machine with no choke and full throttle but under load, when I pull trigger on gun, with fluctuates from high to low to high to low , etc.....

piston slapper
01-17-2012, 07:20 PM
Don't try to run it with the drain screw out.
If you have good flow it should be ok.
Surging with no load is somewhat normal.
When you pull the trigger it should level off.
Only other thing to check is the intake gasket for damage.
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01-18-2012, 08:36 PM
compared fuel flow with drain plug out and it runs like another pressure washer i have, so I have good flow. My mechanic friend and I adjusted valves and it runs a little better but it still is running lean. Has anyone heard about buying a bigger jet or maybe drilling hole out one size better? My friend thinks this will help will the carb starving for fuel at full load.

piston slapper
01-18-2012, 08:58 PM
You wouldn't want to tamper with the emmisions, would you?
If the jet was so clogged that you had to clean it with a torch tip cleaner.
Well that's another story.
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01-18-2012, 09:31 PM
umm dont really understand.....the jet is clear, is cleaned it with carb cleaner and a wire from a brush. Just wondering if drilling it out would work or not.

piston slapper
01-18-2012, 09:43 PM
If you drill it ,you may as well replace it.
If you clean with a mini round file (torch tip cleaner)
You might get it close. A centimeter is a mile on fuel jets.
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01-18-2012, 09:52 PM
got it, I may grab a "torch tip" soon. Lemme run a couple of tankfuls and see if it gets better. have you had any luck with sea foam in the fuel?

01-18-2012, 10:47 PM
have you had any luck with sea foam in the fuel?

Sea foam will fix ANYTHING !!!!!

Just a private joke..... :rolleyes: