13 HP (GX390) Honda Engine Problems

#1
I would appreciate any advice you folks might have. I have looked at some current treads and don't see my exact problem, so here it is:

When I start my machine it idles a little rough, but can stay running on its own fine. In fact when I'm not gunning it isn't obvious there is a problem (it almost sounds like a small timing problem). However, once I pull the trigger the machine can't produce any real horsepower. The engine sounds like it struggles, and it wavers. The pressure goes up and down, but even at its strongest the psi is very low. I looked at it closely with the trigger pulled and the thing I noticed was the wire and spring under the throttle bar were moving back and forth.

Any ideas? Thanks in advance.

Also... until this happened the machine was working perfect. This whole year I have been keeping very close tabs on it. I did just change my tips, but would that do this???
 
#2
I wouldnt think the tip would do it unless its too small for the machine then maybe. I think its a carburetor problem. Try running it with the choke in the half way position. I have to run mine like that or it surges up and down too. It still doesnt struggle like yours but its very possible the carburetor, probably the jet, is plugged up.
 
#3
Thanks Torque454 for replying. I'll try your idea tomorrow. Now that I think of it I did have some minor problems starting the engine a few times this summer. It was after I ran out of gas and refilled it. Maybe some dirt got into the carb. Anyway, I'll see how it goes tomorrow. Thanks again... I'll let you know how it goes.
 
#4
Torque454, I tried starting the machine and had the choke at over half for 10-15 minutes with no change. I am going to clean the carb, but I'm not confident that will fix it. Can't hurt though... I'll update the result. Any suggestions on the best way to do this? I'm going to google search how to clean the carb, since I've never done it myself before. Ahhh the joys of trying to do things on the cheap.

One other thing: today after I started and stopped the machine a few times it became very difficult to pull start and almost ripped my arm off. That sounds like a compression issue (but what do I know?).
 
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#5
Torque454, I tried starting the machine and had the choke at over half for 10-15 minutes with no change. I am going to clean the carb, but I'm not confident that will fix it. Can't hurt though... I'll update the result. Any suggestions on the best way to do this? I'm going to google search how to clean the carb, since I've never done it myself before. Ahhh the joys of trying to do things on the cheap.

One other thing: today after I started and stopped the machine a few times it became very difficult to pull start and almost ripped my arm off. That sounds like a compression issue (but what do I know?).
The nice thing about a Honda carburetor is you can take the thing as far apart as you want to clean it up and put it back together and you dont have to replace any gaskets. Its not complicated at all. However if youd prefer you can get a new carburetor for $50-75 max. The compression thing i dont know about. You may be right about there being a timing issue i dnt know. That could cause that sort of problem too. I dont really know how the timing would be off just enough to do that tho. The only way I could see it happening is if the flywheel key sheared, but then it just wouldnt run at all.
 
#7
Torque454, I tried starting the machine and had the choke at over half for 10-15 minutes with no change. I am going to clean the carb, but I'm not confident that will fix it. Can't hurt though... I'll update the result. Any suggestions on the best way to do this? I'm going to google search how to clean the carb, since I've never done it myself before. Ahhh the joys of trying to do things on the cheap.

One other thing: today after I started and stopped the machine a few times it became very difficult to pull start and almost ripped my arm off. That sounds like a compression issue (but what do I know?).
Release the pressure at the gun.
 
#8
Thanks for all the replies. Here is an update... I finally worked up the courage to take off the carb. It didn't take long to see someting odd. As soon as I removed the plastic air intake (below the air filter), as small flat peice of brass fell out. I wish I could have seen where it was eaxctly in the carb, but I didn't get the chance. Anyway, I didn't know what it was until I removed the carb and saw that it regulated the air. Somehow it had come off the choke shaft. Unless I broke it somehow when I removed the plastic air intake, it may have played a part. What do you think?

I tried sliding it back in the shaft and saw that the shaft was cracked and so that must have been how it came out. If it had been stuck and blocked the air do you think that could have caused the problem?

I can't get a replacement part for a few days, so is it safe to just put the carb back on without this piece? I assume it would just be like running the machine without a choke. I drained out the gas, so it might be hard starting it I guess.

Jetstream1, I have to admit I hope you are wrong... I had to replace both those last year and I have been real careful. I was considering the unloader too.

Douglas, I always try to start the machine with the gun pulled, and ran it with the unloader discharging water the whole time, but it felt like I wasn't pulling the trigger when I actually I was while reefing on the pull start.

Thanks again for the interest and ideas. I'll keep an eye on the thread and update as I go.
 
#9
I want to thank you guys for the help you gave. I sure appreciate you spending your time to help me.

Here's my last update: I put the carb back on without the butterfly air "flap" and the machine was able to pump out the power I needed. However, it still ran rough so I only used it for about 30 minutes. I was going to check a couple of things when I noticed it leaking some gas around the seal between the carb and the engine. I tried tightening the lower screw on the float chamber, then tried to start the engine. I couldn't turn the engine over... period. It still was leaking gas so I tried messing with the machine a little more and overtightened the screw that pushes the air intake onto the carb. I broke the bolt. At this point I gave up and left it for a local professional to do.

It was a learning experience I guess. Thanks again.
 
#11
Big Jon, did you get your machine straightened out? What was the problem?

As far as the trouble you were having with the motor not wanting to turn when you tried to start it up I had the same problem. The problem for me was that I had left the gas valve in the "ON" position instead of "OFF" for an extended period of time without the engine running. What happens is that gas will continue to seep into the carburator and into the combustion chamber of the engine. There's no spark to ignite the fuel so it just stays there in the combustion chamber causing the motor to lock down, I guess due to too much compression.

The easy cure for this is to take out the spark plug out and pull the starter rope a few times until all of the gas has spewed out of the spark plug hole. Put the spark plug back in and the engine will no longer be locked down. Pull the rope and the engine starts right up.
 

Mark

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#12
After having cylinder loaded up with gas
it is best to drain and refill engine oil, as
it is likely contaminated with gas.
 
#13
After having cylinder loaded up with gas
it is best to drain and refill engine oil, as
it is likely contaminated with gas.
Extremely great info! Thanks!

When I had the above problem I ran my machine a couple of hours on the gig I was on but I changed the oil after that. I hope it didn't cause any damage.
 

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