[drnknmnky13]

I have been working on my project bike.The 80 yamaha maxim. I have her running pretty god (BTW she gets over 45mpg) Anyway everything seems to be right except for one thing. After she warms up the idle starts raising on it's own. If I put her in nuetral she'll sit at about 1k then after about 2 or 3 seconds she'll raise to 3k. Sometimes she'll start at 3k and raise up to 4k. When cold everything works and idle is perfect. I took the carb about and cleaned the chit out of it. I also found a ripped diaphragm so I replaced that. Any thoughts?

 

[jim schmidt]

air leak. Spray some contact cleaner around the intake spigots and see if it stops for a second. That's the first place I'd look, or else a loose or cracked vacuum line.

 

[drnknmnky13]

I sprayed WD40 on it today and no change. I turned the idle speed down and when cold it's just above dieng. When hot it's much better. I did find an exhaust leak at the head. Would that have anything to do with it? I'll check for any cracked lines tomorrow. Thanks for the input Jim.

 

[Redstar11]

Like Jim said, either an air leak, or the bike is running lean on the pilot circuit.

Does it run better with the choke on?

Definatley check for an air leak around the intake boots on the head. Spray with carb cleaner or something very combustible. It's easier to tell that way. Listen for RPM variations when spraying. Any variation is indication of a leak.

 

[drnknmnky13]

I'll give that a try tomorrow. I'll also see how it runs with the choke on. Are there any standard setting for lean/rich? Or a way to tell if it's running one way or another? I appreciate your help guys. I'm trying to learn carbs but i don't have any other carbed engies around to see what it's supposed to do.

 

[Mandres]

You might not have a problem after all. Set the idle adjuster so that the engine idles at the appropriate speed once it's warmed up. Use the choke when starting the engine cold. It's normal for the engine to stumble/almost die when it's cold, that's what the choke is for.

-M