G50B Runs bad after 30 minutes. Ignition?

[Panella]

Superchief500,

I didn't notice anything too hot, but otherwise the symptoms were identical, except that I didn't have a compression tester to check the compression. Regarding the one wet plug, I was able to remove the wet one without a wrench, so a loose plug probably would explain the wet plug.

If it's running hot and airflow is unimpeded ( blower in good condition, cooling fins clean, etc.) it might suggest a lean mixture. A plugged bowl vent should run lean until the heat causes enough vapor for a rich condition.

Flooding also might suggest a bad float needle or dirty seat.

How ratty is the exterior of the carburetor? The exterior condition might suggest the interior condition. The exterior of my carburetor was filthy when I pulled it, and the interior had varnish and other dirt. I'm overhauling it.

[Panella]

Screenshot_20200701-083319.jpg

Dirty carburetor.

Screenshot_20200701-083338.jpg

After some elbow grease.

[Panella]

Although, failure to charge the battery probably indicates a problem with the stator. Have you tried a spark tester when it's hot?

Check all your wiring, too. When I recently acquired the '91 Max II, I took it for one ride on my driveway and then couldn't get it started. I cleaned the battery terminals. No dice. I looked closely at the wiring, and I found a wire that was caught behind the shifter. I taped the wire and relocated it, and it started right up.

A wire with compromised insulation might not be problematic until the engine gets hot.

In other words, check everything.

[Panella]

Panella thanks for the reply. This is a 2 stroke engine. It vibrates bad enough that gas will start to dribble out of the over flow tube. At low rpms the motor doesnt vibrate real bad and the carb will stop dribbling. I dont know if this is part of the problem or not. I am hoping to learn what the stock carb is. Float type or diaphram type. I vapor lock could be an issue I suppose. I cant believe how hot this thing gets. The plastic hood can burn a person very easily

Vibration at high RPMs might indicate loose or otherwise compromised motor mounts, though a problematic fuel mixture might also be an issue.

The carburetor has multiple fuel circuits, with separate [overlapping] circuits for idle, partial throttle and full throttle. A dirty nozzle (idle to partial throttle) might cause a lean mixture at partial throttle, and a dirty main jet might cause a lean mixture at 80% to full throttle.

A lean condition can lead to excessive heating.

You might have multiple issues here, with fuel mixture and wiring or stator (charging failure) being separate problems.

For the suspected fuel mixture issue, open up the carburetor. Inspect it for dirt and varnish, and look closely at the needle valve. If there is evidence of dirt or varnish, pull the carburetor and clean or overhaul it.

For the charging and possible ignition issue, check all of your wiring, cleaning terminals and looking for anywhere that a wire might be rubbing against anything. A compromised coil or stator might not be problematic until the engine is hot. Try a spark test with an inline spark tester when it's hot.

[racerone3]

The temp you mention certainly sounds like it is running lean. as soon as it starts running bad, reach up and unscrew the gas cap. Vent may be plugged. I would also replace all the fuel line, it could be sucking shut somewhere and starving the engine for fuel.

[Panella]

The temp you mention certainly sounds like it is running lean. as soon as it starts running bad, reach up and unscrew the gas cap. Vent may be plugged. I would also replace all the fuel line, it could be sucking shut somewhere and starving the engine for fuel.

A bad gasket or a loose bolt (carburetor to intake manifold or intake manifold to cylinder head) that leaks air might also lead to a lean mixture.

Check everything.

[Panella]

In fact, if one cylinder is hotter than the other, one side might be leaner. This might suggest a leak at the cylinder head on that side. Check your intake manifold gasket and bolts on that side.

[Panella]

Also, running too lean can present another symptom.

Have you noticed any audible pinging?

[Panella]

Also regarding one side being hotter, check your valve clearance. One side out of adjustment can cause problems.

Air. Fuel. Spark. There has to be the right mixture at the right time, so each component must be functioning correctly. Start at the air filter, gas tank and battery, and trace each to the cylinder heads.

One thing at a time.

[Don]

I'd check the crank seal on the PTO side as well. This engine has a reputation for blowing that side out occasionally. (no valves in the G50B).