# Honda GX120, HELP ASAP!!!



## MoparAndy04 (Aug 4, 2006)

Ok, I race quarter midgets, basically it's a go-kart. I run a Honda GX120. The motor had been rebuild at the end of last season (around October of 2005) to Honda specs. The only mods done for racing is the stock fuel tank was removed and the whole air cleaner assembly was removed (only the carb remains). It has been running great, and I have been doin darn well thus far into the season. Now, all of a sudden it runs like crap. The idle has to be purdy high for it to stay running and it seems to jump around rpm wise alot at idle. Also, when reving it up and letting it decelerate it backfires more than it has in the past. And, it seems to spit a little gas out of the carb when running. 

Firstly, could weak valve springs cause this? I would think that it could because when the motor completes the compression stroke it would blow out a little air threw the intake valve which could explain the little fuel blowing out and the pour idle due to it not getting fuel plus a little gas could be getting in the exhaust pipe due to the exhaust valve not closing all the way which could be the backfiring. Sorry if that was confusing but it's really hard to explain.

Secondly, what do you think it is? It is not the spark plug (Bosch Platinum +4 4477, just FYI), it's getting fuel and it is brand new (filled the tank an hour ago). It's not the kill switch. I don't know what else to try and I need it running good by Sunday which is when I'm racing. Please trey and help me and please do it quick! Thanks!


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## bugman (Aug 12, 2004)

If it has no air cleaner? I'd say carb problems right now... as for the plug, NEVER overlook the obvious.... try another just in case.


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## MoparAndy04 (Aug 4, 2006)

Thanks. I have changed the plug and that didn't help what so ever. No, it doesn't have an air cleaner. For whatever reason nobody at the track runs them, I guess the figure it restricts airflow. As far as carb issues, what might be the problem? Thanks!


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## bugman (Aug 12, 2004)

Plugged jets with dirt, bugs, whatever can crawl or be sucked in, really needs a air filter to get the most outta the engine though.


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## big ed (Jul 29, 2006)

sounds as if you may have a timing issue say a broken flywheel key , bad ign. coil, or even with it being mostly stock a cam or crank problem it will take some time to troubleshoot but will be related timing some how good luck


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## peppy (Jul 19, 2006)

Could weak valve springs cause this? 


Yes

I would also take a look at the exhaust valves and make sure they are seating and are clear of carbon buildup


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## inch_from_crazy (Jul 30, 2006)

big ed said:


> sounds as if you may have a timing issue say a broken flywheel key , bad ign. coil, or even with it being mostly stock a cam or crank problem it will take some time to troubleshoot but will be related timing some how good luck


if you even SCRATCHED a flywheel key in a honda you will have accomplished a feat i have never seen.they are a good 1/8 of an inch steel half moon key unlike the aluminum alloy tecumseh or briggs keys, so dont waste your time removing your flywheel. as for your fuel problem, i'd say your scking air from somewhere, check for a crack in your carb adapter.


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## mitchell (Jan 15, 2006)

Blowing fuel out of carb, or compression coming back through carb is intake is not closing fully, I MEAN INTAKE VALVE,find your valve specs and check tolerance on your intake valve,if not valve tolerance or still wont run right within tolerance, then a possible worn lobe on cam.


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