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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11444
Experience:  25+ yrs. experience
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1985 Yamaha phazer 480 carbs are clean but will hunt idle

Customer Question

1985 Yamaha phazer 480 carbs are clean but will hunt for a idle then idles too high, like it is going to runaway. i have not looked at the reeds, the carbs are clean and every clamp is tight and i dont see any splits in the intake, sprayed with carb clean when running and nothing changed. im stuck.
JA: Thanks. Can you give me any more details about your issue?
Customer: thats about it, never had this happen on anything i have owned.
JA: OK got it. Last thing — Motorcycle Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 10 months ago.
Category: Motorcycle
Customer: replied 10 months ago.
sorry, i did not say this is a yamaha snowmobile.
Expert:  Louie replied 10 months ago.

Hi and welcome to JustAnswer,

Thank you for the question and your patience. Should you still need assistance for information purposes only...

Initially and almost always, the described "...hunt...idles too high..." with a "...carbs are clean..." would point to a most likely vacuum leak; i.e. after the carb to the intake (manifold).

Other than to re-check the coupling, check the spark plug burn. It black and sooty, then the overly rich/vacuum leak is confirmed.

Customer: replied 10 months ago.
It only makes sence that with the idle being smooth for a few seconds then the RPMs start to rise then drop down for a few seconds then the idle will take off and the sled will engauged the clutch. Could it be a crank seal? The sled did sit for about 5 years before I bought it. The carbs were in bad shape before I cleaned them. I have never had a 2 stroke do this.
Expert:  Louie replied 10 months ago.

A leak in the crank seal would also affect the compression. Consider a compression or better yet a leakdown test.

Customer: replied 10 months ago.
Louie, i will do a compression test and see what we get. I will let you know. I sprayed the intake area with brake clean, the engine did not change. More to come.
Expert:  Louie replied 10 months ago.

Yes please; an update when able on the compression test.

...and the color of the sparkplug(s).

Then consider spraying with water the intake area.