I have a 1989 Moto4 ATV...Barn Find....Just got it for something to tinker with....Started right up, Idles fine but has no engine power what so ever....Installed brand new OEM air filter, Brand new Intake joint tube. All new exhaust gasket because it leaked pretty good..exhaust silencer has a small whole in it and i welded that shut.. NO more leaks.. Bike just sounds like its starving for air to me...THe headpipe is also glowing cherry red up towards the motor also...I know that can be somewhat normal sometimes but its pretty red.. Is it lean? Dirty Carb maybe? Running out of ideas.. Any help would be great...

 

It sure sounds lean to me. Something that old probably needs the carb rebuilt.

 

I worked on my Father in laws moto4 when he had the exact same issue. Turned out one of the jets backed out and fell down into the carb bowl and it was running super rich. Might be a pretty specific thing but worth checking out. If you have never had the carb before I would recommend looking at a parts breakdown to make sure you arent missing anything.

 

Could running rich cause the pipe to glow cherry red? I thought it only got that hot if it was running lean.

 

I would think so if its rich enough and dark enough. Steel glows bright red at 900F and exhaust temp averages 750F so if its rich enough I guess the temperature curve could come back up if compression is high enough (or low enough) and depending on engine rpm and ambient temperature and barometric pressure and altitude and humidity...There are alot of variables involved so just saying red pipe means lean is rather pretentious if you ask me. Red pipe could also mean perfectly fine just hot outside. I dont have any data to go off but I would venture to say red pipe means nothing. Check your plug color, check all your jets and that your carb is assembled correctly. Some carbs have a plastic piece that can either be put on the top or the bottom of the E clip on the needle and that could cause it to rich out, I have made that mistake recently. A good parts breakdown will tell you where everything is supposed to be.

 

He didn't just say "red pipe". He said "glowing cherry red" and that could be 1,500-1,600 degrees or more depending on whose definition of cherry red you use. I never heard of a pipe getting anywhere near that hot when the engine wasn't running lean. If you say it's possible to run rich and get that hot I'll take your word for it until I hear otherwise.

 

The weatherman said the ambient temperature is dropping and the barometric pressure is rising, so maybe everything will be okay if it doesn't get too humid.

Alright, I couldn't just sit here and not say anything else about it. Well, I could, but I had a little time to kill. I was just giving my honest opinion based on my own experience earlier.
I wasn't pretending not to be pretentious, while misusing the word pretentious. But I could if I wanted to.

Pretentious: Trying to appear more clever than you are. Trying to give the appearance of great importance, especially in a way that is obvious. Making an exaggerated outward show: ostentatious [characterized by or given to pretentious or conspicuous show in an attempt to impress others, (of actions, manners, qualities exhibited, etc.) intended to attract notice]. Full of pretense or pretension; having no factual basis, false. Making claim to or creating an appearance of (often undeserved) distinction or importance. Intended to attract attention and impress others. Attempting to impress by affecting greater importance or merit than is actually possessed. Behaving in a way that is intended to impress other people but seems false or too deliberate. Making usually unjustified or excessive claims (as of value or standing). Expressive of affected, unwarranted, or exaggerated importance, worth, or stature.

 

Have you checked your spark plug yet Brandon B.? What's it look like?

It may (or may not) be worth mentioning that I had a snowmobile that I couldn't get to run right. It fired up, idled good and ran, but didn't have much power. I didn't see what the pipe looked like when I was out riding and it died on me, but it was running lean and burned a hole right through the top of the piston. The mechanic who told me that also said it it would cost more to rebuild the engine than what the snowmobile was worth. Then I took my first and only snowmobile, dumped on our property in the woods and used it for target practice. So even though I'm no expert on the subject like someone else is, I know that running lean can get an engine hot enough to destroy it. And it can make the pipe glow red-hot.