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General Forestry => General Board => Topic started by: Bigmikessmallen on October 29, 2017, 04:54:50 PM

Title: Honda gx390 problem
Post by: Bigmikessmallen on October 29, 2017, 04:54:50 PM
Sorry if this is the wrong place to post but i couldnt find the correct sub. Anyways my honda gx390 has an electric start problem it sounds like the battery is not giving it enough power to turn the starter. So i replaced the battery with new and the problem still persists. Could this be a bad solenoid? Any help would be greatly appreciated.
Title: Re: Honda gx390 problem
Post by: DelawhereJoe on October 29, 2017, 05:31:05 PM
How corroded are your battery wired and hows your ground wire, both will cause electric delivery issues. You can check the solenoid by jumping the contents with a screwdriver, if you complete the circuit across the top and it tries to start then the solenoid is the problem.
Title: Re: Honda gx390 problem
Post by: Kbeitz on October 29, 2017, 05:56:22 PM
Easy check... Just hook a jumper cable between the pos. on the battery and the large
lug on your starter. If that don't work hook the jumper to Neg. on the battery and clamp
the other end to the engine block. Caution. The engine will try to start on it's own when
doing the first one. The first will one find a solenoid or wiring problem and the second will
find a grounding problem.
Title: Re: Honda gx390 problem
Post by: North River Energy on October 29, 2017, 06:42:07 PM
Did this problem come 'out of nowhere', or has the motor been cranking slower and slower over time?
If the easy stuff yields no results, make sure the brushes are making good contact with the armature, and that the armature is still 'round' in the area of contact.

Also, would help a little to know what the motor is turning.
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 29, 2017, 07:50:31 PM
I tried jumping the solenoid earlier from the positive terminal to the little clip on the solenoid and it sounded like the starter wants to engage but doesnt.

What do you mean by what the engine is turning river?
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 29, 2017, 07:52:17 PM
And yes it has been crankin slower and slower over time. Thats what made me think the battery was bad which it was anyways so i got a new one and its still acting as if the battery has no juice.
Title: Re: Honda gx390 problem
Post by: North River Energy on October 29, 2017, 08:29:37 PM
What kind of machinery is the motor powering?

Compressor, power washer, log splitter, generator trash pump, elevator/stacker, ferris wheel, etc.

Brother once had a Honda street bike that cranked poorly, and it turned out the armature was worn into 8(?) lobes rather then being round.
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 29, 2017, 08:47:59 PM
Ohh its a cormidi 85 mini dumper. Hrmm so would it be worth just buying an entirely new starter with solenoid attached instead of just getting an armature?
Title: Re: Honda gx390 problem
Post by: North River Energy on October 29, 2017, 10:34:10 PM
^Don't know, but it's worth checking the condition of the brushes and armature if the simple tests don't reveal an easy fix.
Does the  motor spin easily with the pull cord, and does it run well otherwise? Is there anything in the dumper driveline that could be engaged when it shouldn't be, thereby loading the starter?
Title: Re: Honda gx390 problem
Post by: sawguy21 on October 29, 2017, 10:41:23 PM
Does the engine have a lot of hours on it? Check the valve clearances, should be INT .006" EXH  .008" If they are excessive the automatic compression release won't work.
Title: Re: Honda gx390 problem
Post by: btulloh on October 30, 2017, 08:59:19 AM
Quote from: sawguy21 on October 29, 2017, 10:41:23 PM
Does the engine have a lot of hours on it? Check the valve clearances, should be INT .006" EXH  .008" If they are excessive the automatic compression release won't work.

X2.  Had this happen on several engines.  Should make it part of annual maintenance.
Title: Re: Honda gx390 problem
Post by: Kbeitz on October 30, 2017, 01:49:56 PM
You can buy a new starter off Ebay sometimes cheaper than buying brushes.
Title: Re: Honda gx390 problem
Post by: Magicman on October 30, 2017, 07:27:40 PM
Follow Kb's Reply #2 above and do some troubleshooting before you start throwing parts at your problem.
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 31, 2017, 08:08:14 AM
So KB just so i understand hook the jumper cable from positive battery terminal to the large lug but there are 2 lugs on this starter im assuming connect it to the ground lug on the starter? Sorry ive never jumped a starter
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 31, 2017, 08:09:14 AM
Also sorry for the delayed response thank you all for your input it definately gives me some direction on where to go from here.
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on October 31, 2017, 08:11:46 AM
The machine runs fine , there is no load on the motor. Runs well with the pull cord its just a hassle having to pull this thing everytime especially when the motor kicks back and rips the pull cord out of your hand lol.
Title: Re: Honda gx390 problem
Post by: btulloh on October 31, 2017, 09:09:04 AM
Jumping the starter is a great place to start.  It answers a lot of questions with minimal time invested. 

Don't discount the possibility of the valve clearance causing a problem with cranking.  If it's still cranks slow with the starter after jumping, it would be my next thing to do.  There is a de-compression lobe on the cam that works at low (cranking) rpm.  It has a big effect on starting torque required.  Adjusting the valve lash is easy and takes ten minutes or so.  It doesn't take a million hours before it gets out of whack.

Valve lash doesn't seem like it would be such a factor - until it's happened to you a couple times.

Good luck with the problem.  It's a good engine and you'll get it sorted out.
Title: Re: Honda gx390 problem
Post by: Magicman on October 31, 2017, 09:28:53 AM
And remember that being absolutely sure that you have a good ground is of the utmost importance.
Title: Re: Honda gx390 problem
Post by: sawguy21 on October 31, 2017, 11:57:22 AM
Quote from: Bigmikessmallen on October 31, 2017, 08:11:46 AM
The machine runs fine , there is no load on the motor. Runs well with the pull cord its just a hassle having to pull this thing everytime especially when the motor kicks back and rips the pull cord out of your hand lol.
That is also a sign the valves are out of adjustment
Title: Re: Honda gx390 problem
Post by: btulloh on October 31, 2017, 04:45:10 PM
True that ground check MM.  That's certainly the first thing to check before the other first thing.
Title: Re: Honda gx390 problem
Post by: Kbeitz on November 01, 2017, 08:34:00 AM
The 2 lugs on the starter is the starters solenoid. That's nothing more than a heavy duty switch.
Inside the solenoid is an electric magnet that pushes a solid copper bar up tight against the
two large bolts making like a big switch.



 (https://forestryforum.com/gallery/albums/userpics/39553/solenoid~1.jpg?easyrotate_cache=1509539265)

So the first thing I would do is to jump with a large screwdriver across the two large bolts.
Take care because the engine should try to start.

Then If this does nothing run a jumper from the pos. on the battery to the big bolt on the
solenoid that has the wire going into the starter. Something should happen.

If nothing then check for lost ground. Run a jumper from the Neg. on your battery to the
body of your engine and try starting.

If none of this works you probably need a starter. Use a heavy wire when jumping.
Title: Re: Honda gx390 problem
Post by: Bigmikessmallen on November 06, 2017, 12:39:29 PM
So all my grounds are good. I took the plug out today to see if theres spark just to make sure 100% and there is. The machine without the plug in turns of amazing full power to the starter as soon as i put the plug back in the juice to the starter drops 98% and will barely turn over.
Title: Re: Honda gx390 problem
Post by: btulloh on November 06, 2017, 03:53:12 PM
Sounding more like valve adjustment.  Hard to believe valve lash can have that much impact until it happened to me a couple times.
Title: Re: Honda gx390 problem
Post by: starmac on November 06, 2017, 05:52:36 PM
One other thing to check as far as grounds go. The starter grounds to the engine where it is bolted and mated up, I have run across them where it has corrosion between the starter housing and the block itself, causing slow problems. I would not discount the valve clearance if these do actually have an automatic compression release, the starter will be built to use the comp release and will never turn it as fast without it working. Kind of like the old small cam cummins.