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PK.
PK., Small Engine Technician
Category: Small Engine
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Experience:  Retired Owner of a full service shop and national parts sales website.
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I HAVE A HONDA GX390 13 HP ENGINE AND IT WILL ONLY ROTATE ABOUT

Customer Question

I HAVE A HONDA GX390 13 HP ENGINE AND IT WILL ONLY ROTATE ABOUT 300 DEGREES THEN IT STOPS. ANY IDEAS?
Submitted: 6 years ago.
Category: Small Engine
Expert:  PK. replied 6 years ago.

If you remove the spark plug does it do this?

Customer: replied 6 years ago.
i have not removed it yet
Customer: replied 6 years ago.
is pk there?
Customer: replied 6 years ago.
iremoved the plug and it spins freely
Customer: replied 6 years ago.
what is going on here iam not getting any answers to my replies
Expert:  PK. replied 6 years ago.

I won't always be able to reply back immediately but I will get back as quick as I can.

 

It's a very good thing that it will spin freely with the plug out. If you put your finger tightly over the hole you should feel pressure both try to suck your finger in and blow it off. If you can check that let me kno0w what you get.

 

Also, does this have an electric starter?

Customer: replied 6 years ago.
yes i feel suction and pressure and no it not a electric start
Expert:  PK. replied 6 years ago.

Okay, then the first thing to do is check the oil.

 

And can you tell me what this engine is mounted on? Have you had any other trouble with the engine or had any work done lately? How did this trouble begin? Like did you notice it has been getting hard to start or it hasn't been running right or has been making unusual noises?

Expert:  PK. replied 6 years ago.
I have to run out for a little bit but I'll be back in an hour or so. Let me know about the questions above and we'll go from there.
Customer: replied 6 years ago.
ok. what about the oil do you want me to check? and it is a power washer motor no recent repairs and no previous problems i just tiried to start it and could not pull the start
Expert:  PK. replied 6 years ago.

Just check the oil level and see that it looks okay. That's just a normal cautionary thing I always do when doing any work on any engine.

 

It sounds as though you may have a valve adjustment problem. Is adjusting the valves something you would want to try? I suspect that they have gone a little out and the compression release isn't working properly. This is fairly common and isn't a difficult job but does involve some pretty good mechanical aptitude.

 

I'm not going to suspect the washer pump because it turns over with no plug, but you should be sure that the pressure is turned down or off, however yours is set up.

Customer: replied 6 years ago.
yes i would like to adjust the valves if thats what you think it is. before i contacted this sight i cut the belts off in frustration because i could not remove the pullies so right now there is no worry about pressure
Expert:  PK. replied 6 years ago.

I can't guarantee that it's the valves but it would be the most likely thing to do next.

 

What you do is remove the valve cover and then rotate the engine over by hand to Top Dead Center, (TDC). You will probably have to remove the starter housing or the flywheel shroud to be able to turn the flywheel. TDC can be found by sticking something like a wooden dowel into the spark plug hole so that you can use this to gauge the height of the piston. Do not stick anything into the plug hole unless the piston is near the top or you will get it jammed up and cause yourself problems. TDC is defined as the very highest position of the piston after the intake valve closes. So if you've not done anything like this before, rotate the engine over by hand a few times to get the idea and then when the intake valve closes and the piston is at its highest, you're at TDC.

 

On the following, you only want to do one valve at a time. So completely finish one before starting on the other because you don't want to mix up parts.

 

Before you loosen the nuts, use the feeler gauge and check what the clearance is. It only takes a few thousandths to cause a problem. Remove the lock nut and the retaining nut and the rocker. Then pull the pushrod out and roll it on a nice flat surface. Glass is perfect. If it isn't perfectly straight, it will need to be replaced. Look at the rocker very carefully and be sure there aren't any cracks in it. Same for the nuts. Check that the stud is straight and tight. Don't try to remove it, just eyeball it or put a straightedge alongside it. Look at the valve springs and see that they look good and have good tension. Look everything over and pay attention for any spots that look burnt.

 

What you do then is replace everything on the rocker arm stud and insert a .006" feeler gauge between the rocker and the tip of the valve stem. Tighten the retaining nut down so that the feeler gauge just barely slips in and out. Leave the gauge in place and tighten down the lock nut. Repeat this on the other valve.

 

Rotate the engine over by hand and see that everything looks good with no binding or odd movement. Put your valve cover back on and put the plug back in, but leave the plug wire off, and try pulling on the starter. Hopefully this will have fixed things.

 

Customer: replied 6 years ago.
ok i will try it please be on the lookout for my reply. also is there an easy way to put the belts back on the pullies i tried to remove them but i could not so i cut the belts off to see if it eas the pump or the engine
Expert:  PK. replied 6 years ago.
If it doesn't have an idler pulley then it's kind of a pain. I'm assuming it has a two belt pulley? You can maybe walk them on, just keep your fingers well away. Probably you should loosen the pump, it should have some slots cut into the mounting base that let you adjust the belt tension.
Customer: replied 6 years ago.
i did the valve adj. and put the plug back in and i turned the engine by hand it turned and i still felt resistance but it disapated as i could hear a hiss of air as i kept up pressure on the plastic fan (ah yes that would have been smart to check if the pump had movement before i cut the belts (3) ) before i put the pull cord back on i wanted to see if this resistance was normal
Expert:  PK. replied 6 years ago.
Yes there should still be a good bit of compression. Don't be discouraged if the engine pops back or sneezes or doesn't start. You may have to go through this process several times until you get the hang of it. Valve lash is a very finicky thing to adjust and you might not get it just right the first time. Also, there could be another problem hiding in there. Let me know what happens. Thanks, PK.
Customer: replied 6 years ago.
i buttoned it back up but still met too much resistance on the pull start
Expert:  PK. replied 6 years ago.

Then I'd try setting the valves again. Also, check your starter when you have it off and make sure that it's not binding. You may try using a .004" feeler gauge. This will open the valve a little faster.

 

What was the measurement before you took the rockers off the first time?

 

If you're unable to get it after a few times then I would suggest you take it to a Honda shop and have a compression test done. If you have a compression gauge you can do that yourself. You can't get a true compression reading on an engine with an automatic compression release but it can give you an idea.

Customer: replied 6 years ago.
i did not check the valves before i took them off
Expert:  PK. replied 6 years ago.

Okay. Do you remember how loose they were? Were they looser than after you adjusted them?

 

Pay real close attention to the movement of the valves when you have it apart. They should move very evenly and freely. Any binding is bad.

Expert:  PK. replied 6 years ago.
I gave you the wrong valve lash. Use the .005" on the intake and .007" on the exhaust. Try those numbers and see what you get.
Customer: replied 6 years ago.
i have to shut it down for the night. i cant see straight any more. can i contact you tomorrow eve? how do i do that?
Expert:  PK. replied 6 years ago.

Just reply back to this same question like you've been doing. If you don't have any luck with the .005 and .007" lash, try tightening it up a little. Try .004 and .006. The rockers, pushrods and tappets may be a little worn and this may help.

 

I'll be on and off here until late afternoon as I have a couple of jobs out of the shop to go work on but I'll check back when I can. Thanks and good luck. PK

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PK.
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Retired Owner of a full service shop and national parts sales website.