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2018/02/02 00:22:38

Shanedmoore

Honda GX690

I have A GX690 on a barreto trencher..having issues with rough idle at times and backfiring when you throttle up. Sometimes it does this sometimes it runs perfect. Sometimes it’s like it’s running on one cylinder sometimes it’s perfect. I am looking for suggestions, in my area there are several “small engine” shops but knowledge of Honda’s around here is slim. I have a video of it doing it. Thanks!

11 comments Leave a comment

Roy

Welcome aboard, we will try to help you. It sounds like contamination in the carburetor, thoroughly clean it and the tank and replace the fuel line. Also check valve lash while you are at it.

2018/02/02 19:58:33

AVB

I don't get it any small engine mechanic that worth their salt should be able to handle the repairs. It is a basic v-twin engine.

With it appearing to have a two barrel carburetor as Roy said could be trash in or a dirty carburetor in general that could be the problem. If anything like the last Honda horizontal v-twin it is bear to get carburetor off as you got remove the intake to access the carburetor mounting screws.

2018/02/03 09:52:52

Shanedmoore

I have cleaned the carburetor, soaked it overnight and new gaskets, orings and float needle. It is crazy what it does. Run perfect for a bit then go to missing and backfire when idling / opening up the throttle. I am starting to lean to a coil acting up. Even when it’s running smooth the exhaust smells like raw gas. Most of the time when you open it up it runs smooth. But the gas smell is still there. The engine has around 320 hrs on it.

2018/02/07 09:37:40

AVB

Yes it is possible to have one the ignition coils bad or even just a bad plug. Since a v-twin can run smooth on one cylinder if not under a heavy load, try unplugging one plug wire. If stays running replace the plug wire and try the other side. With which ever plug wire pulled kills the engine then opposite side is the one that is dead.

2018/02/07 13:29:45

Shanedmoore

Thanks for the help....due to kids and sports and sick grandparents time to mess with it is hard to come by...the left cylinder is not firing or something...but goes to working when opening up the throttle. It is new NGK plugs in both sides. I will narrow down to plug/ coil hopefully in a while...I am beginning to think it all goes back to carb...flooding iybout at idle...the minute you open it up / raise the throttle it smooths out.

2018/02/20 20:52:22

Mikel1

Was old gas left in it?
Do spark plugs look the same after running?
You can also purchase one of those neon in line spark testers, don’t cost much.

2018/03/03 12:40:34

Shanedmoore

It was not old gas. New non ethanol gas. A certified Honda guy checked it yesterday. He also is stumped. He tore carb apart and cleaned it again and said everything looked ok. About to try and find the neon testers and see. Right now leaning to a weak coil. The way the trencher is built it is a pain to get the flywheel cover off to look at it. There is a Hydraulic oil cooler in the way and when you take it off no way to run the machine. Thoughts on a “weak “ coil ? Is it possible? Thanks!

2018/03/25 12:34:28

Shanedmoore

Update...started from scratch...new plugs , new gas filter , new engine oil still slight miss. Bought new coil..no change. New carb....no change. When it gets hot at hall throttle or less it backfires occasionally and at idle the engine lopes / surges. When wife open and trenching you can tell there is an issue ....low on power. The plug on the cylinder that is missing is white. PLEASE HELP!! Thanks!

2018/07/14 00:30:45

AVB

Either it ignition or fuel delivery problem. Let removing both ignition coil kill wires to see if it see a feedback from a bad steering diode in the coil that you didn't replace causing that cylinder to shut down. Be ready to kill the engine using the choke or fuel shut shutoff if available; otherwise, pull the plug wires. If the problem goes away then replace the other coil. Yes this can happen I repaired a Kohler back in Spring where both coils this way would not even allow the engine to run if the kill wires were connected as they were feeding back into each.

Also check the valves are opening and closing as they should be. with the valve lift the same as the other cylinder as you might have either valves out of adjustment, dropped a push rod, or a bad camshaft lobe.

A side note here V twins are know run fine on one cylinder until loaded.

2018/07/14 07:14:08

Shanedmoore

I think I know what you are talking about. I will try tonight. I ruined an engine several years ago with one flooding and don’t want to do that. Pushrod note ....I have 2 new ones thinking these were wore. Thanks!

2018/07/14 17:07:48

Shanedmoore

New push rods didn’t fix it. Haven’t tried the “kill wires”. There is an oil cooler behind the flywheel cover therefore making it a pain too get to and also to get to the coils it has to be removed and then you can’t run the engine. I would be willing to pay someone that I could send some pictures too and talk to that can help me get it running right. Thanks!

2018/08/07 00:11:22

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Honda GX690

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