GX270 misfiring

[ConnieP]

I have a GX270 that came off of a generator with the tapered output shaft. I replaced that crankshaft with one that has a keyed output shaft. Along with this, I put in 50lb valve springs, an upgraded fuel jet for the carb, an aftermarket air filter, and I also removed the governor.

The engine will idle- though it’s not great- but it really bogs down when you open up the throttle. The spark plug indicates that it is running rich.

I have triple checked the timing marks on the cam, verified the proper spacing for the ignition coil, and completely gone through the carb. What in the heck am I missing here???

 

[Denny]

Put the original jet back in the carb and see how it runs.

 

[panchothedog]

Your upgraded jet is too big. If you have a low restriction air filter and a header pipe, you will usually need a bigger jet. But bigger by a few thousands of an inch. Put the original one back in there ( as suggested by Denny ) it should run O K. Then figure the size of the stocker and in minut increment work up from there. You have passed what is optimal.

 

[ConnieP]

Thank you guys for the responses. I will try the original jet when I get home. I should note that I got the jet in a stage 1 performance kit from go power sports along with the air filter.
Is there any reason why this shouldn’t work?

 

[Denny]

It came from Go Powersports.

 

[bob58o]

Still using stock exhaust? Then I agree the jetting is probably too large. Usually open pipes are used with those kits. Air filter, exhaust, and jet. If you only do two of the three, probably will have issues.

Valve lash was set correctly after changing springs? Lash set when both valves are closed and springs relaxed?

 

[bob58o]

Get one of these and some ear protection.

 

[ConnieP]

Yes. I have double checked valve clearance. (This is the same as valve lash right?). I do not have that header pipe. Right now I’m still using stock exhaust. But I’ll order one.

But for now I switched the jet to the original one. When I did this it sounded way better at idle. But wide open it almost sounds like it’s hitting a limiter- video included. I shut off the engine and attempted to start again. No matter what I did it wouldn’t fire. This voodoo small engine stuff got me beat, man.https://files.fm/u/htt6ghfgsy

 

[bob58o]

I haven’t watched the video yet. Do you still have a low oil sensor connected? Is there gas in the tank? If you test for spark first, then you can try starting with starting fluid. It’s always one of a few things… Spark, Fuel, Air, Compression, Timing… those 5 categories make the lawnmowers go vrrmmm

 

[ConnieP]

I do still have that connected.

 

[ConnieP]

I also never took the governor arm out. I saw in videos most people doing this and tapping the hole and plugging it with a bolt. Is there any harm in leaving that arm in there?

 

[bob58o]

Low oil sensor could cause problems. It kills the spark when tripped. I’m not familiar with gx270 configuration for the governor arm. I think the governor gear assembly is on the side cover side on bigger engines. Hmm I’m not sure if free to spin if it could impact other moving parts like connecting rod? If the engine turns over freely without sounding like it’s eating itself… it’s probably ok? Maybe?

 

[ConnieP]

Okay I will try unplugging it. Would this be why I couldn’t get it to start after I ran it?

 

[bob58o]

Okay I will try unplugging it. Would this be why I couldn’t get it to start after I ran it?

Maybe, just a guess. Or maybe some other ignition / kill switch wiring issue. Phone dying.

 

[bob58o]

Check for spark. If you don’t have a tester, pull the plug and lay it on the block after attaching the cable again. Pull the cord and look to see if it sparks. Checking for spark is always a good place to start when diagnosing “won’t start.”

 

[Karttekk]

Are you able to move the governor arm coming up through the block by hand while the engine is running? The arm might be hitting the governor gear inside the engine. The governor should be completely removed including all internal and external parts if you do a gov delete.