K 301 muffler glows

[brentwd]

I pulled the motor in my 125 to fix some oil leaks and to fix anything else. I found the carb shaft was worn and the head had a leak. The carb has a new shaft and rebuild kit. The head was sanded until flat on a piece of glass and a .003 gauge to mic it. The problem is after all was done it was running hot inside the muffler at full throttle for a short time and then would die. After a few minutes to cool down it would start back up and run fine till I revved it and would do the same.The timing was set with a meter and the carb was set per service man. All that was done to the motor itself was scrape the piston and valves. I don't know what else it could be.

[jsoluna]

I saw this on the exhaust pipe of my 129 a week or so ago. I could only see it at night, but the pipe was a reddish color where it met the head, only at WOT.

I thought it was a lean condition, so I played with the carb mixture screws, no change at all. Checked my air cleaner for obstructions, checked and re-checked my timing...none of those things ended up being contributing factors.

What I eventually figured out was that I had accidentally used 93 Octane fuel to run the Cub. I put 93 in my '99 Ranger with the 3.0L engine to solve the ever-present engine pinging that occurs with 87 octane gas. Didn't realize that I filled up my gas can with the same fuel.

After I went through the 93, I put 87 back in the Cub and haven't had the problem since. Just a thought. Probably not your issue here, but high octane gas can lead to over-heating the same as incorrect timing and lean conditions.

What spark plug are you using, btw?

[scleve]

If the muffler is glowing red you are running to rich. The new improved (garbage gas) is so different from the old leaded stuff. I think you will need to adjust the the carb to run a little leaner. Also if you find a station that sells non enriched gas (no ethenol) I have better luck with that. Just my opinion.

[Matt G.]

The carb settings in the manual are a guide...they won't work exactly for each engine. You want it to be set slightly rich, anyway, since the extra fuel in a slightly rich mixture helps the engine. Here's how I typically set the mixture on my carbs:

Let the engine warm up for 5 minutes or so, then at full throttle, enrich the mixture until you get an rpm drop and/or the engine starts stumbling a bit. Then slowly lean it...you'll notice an RPM increase, then a drop. After the drop, enrich the mixture again such that you're at the high point of the RPM rise. Then enrich it another 1/16 or 1/8 turn. Then let it idle, set the speed, then adjust the idle mixture screw in a similar way. Once you're confident you have that set correctly, quickly move the throttle from idle to wide open. If everything is set right, the engine should respond nearly instantly and run smoothly at full throttle. If you get bangs and flames out of the muffler, the mixture is too lean, and if it bogs down, stumbles, and blows black smoke, it's too rich.

Have you checked the cooling fins and the area under the flywheel shroud for cleanliness?

[Matt G.]

Originally Posted by scleve

If the muffler is glowing red you are running to rich. The new improved (garbage gas) is so different from the old leaded stuff. I think you will need to adjust the the carb to run a little leaner. Also if you find a station that sells non enriched gas (no ethenol) I have better luck with that. Just my opinion.

Absolutely not. Glowing muffler = too LEAN.

[brentwd]

Thanks guys for the reply, I have tried adjusting the carb and it does not stumble when you crack the throttle. It does blow white smoke when it goes from idle to WOT. It did not do this before. You can feel the air moving thru the motor, so I would not think that could be it. Just a quick question, When the manual says HIGH IDLE and LOW IDLE, does that mean the high idle is on top or main fuel needle and the low idle is the one of the side pointed to the reverse at an angle on the #26 carter carb?

[Matt G.]

You have the needles identified correctly. Take the flywheel shroud off and look for stuff...just because there is some air moving through doesn't mean that it is completely clear.

[Vince_o]

Glowing muffler is to lean, ask me how I know on my old 147. If you run it like that too long, youll warp the block, ask me how I know, one of my 100's from a PO

I also remember turning the fuel preasure up in our old diesel trucks and at night the stacks would glow a little.

Matt I think my dyslexia has rubbed off on you.

[Matt G.]

Originally Posted by Vince_o

Matt I think my dyslexia has rubbed off on you.

Crap...where?

[william1041200]

Im glad Matt said glowing = lean! Thats just a flat out fact(if timing is right).. I have yet to hear of a warped block... Not to say it can't happen, but do you mean head??? Usually the first to try to get away from the heat