1983 phazer 485 engine crazy erratic idle issue HELP ME!!! - Snowmobile Forum: Your #1 Snowmobile Forum

phazerbuggy · 06-16-2012, 08:15 PM

i just bought a 1983 yamaha phazer 485 that was sitting for over a year... i took the engine out to use in my honda odyssey ATV. got everything hooked up correctly and cleaned the carbs.. i then started the engine for the first time.. it started right up but only ran on one cylinder for a bit then the other kicked in... when it idled decent for about 30 seconds then the RPM went through the roof and the machine took off then died... what could cause this crazy increase in idle with no throttle being applied at all. does it every time, starts right up... idles for a few sec then takes off. what do i do??

**kccats** · 06-16-2012, 08:35 PM

Lean or run out of fuel!

yamadad4 · 06-16-2012, 08:37 PM

or crank seal/air leak

phazerbuggy · 06-16-2012, 08:42 PM

Could you explain how I maybe able to tell? Everything LOOKS ok...! And if its too lean, why? And how could I fix it? Let me explain I just got it. And when I got it, the lines were empty, and it wouldnt start, or suck fuel. I cleaned the pump, and the carbs which looked decent. Then, I switched gas tanks, so it is now not sucking it with the filter thing it had, the line is now Direct feed from the tank to the pump. Which made it run after I cleaned the carbs, but again, now is doing this!!!

yamadad4 · 06-16-2012, 09:05 PM

since the carbs are a butterfly type(stock) unless they are sticking or the throttle is sticking, theoretically your sucking air somewhere. could be the boots from the carbs to the engine, could be the idle screw, could be the synchronizing screw between the carbs, hard to say.

usually an erratic idle, especially to your extreme, is caused from upsetting the fuel to air ratio, or leaning out as kc mentioned. lean meaning more air, less fuel.

hard to visually inspect the seals, ones behind the clutch and the other is behind the recoil. depending on the time lapse from your idle to wide open, if you have time, spray some carb cleaner behind the clutch and see if your revs increase prior to it doing it on its own. you can also spray around the recoil and the carb boots as well. even easier to spray the recoil side if you have an e-start machine.

phazerbuggy · 06-16-2012, 09:16 PM

thanks for the tip, will try that tomorrow, and i forgot to mention that it has no muffler just 12" straight pipes, going to put mufflers on but didnt know if that could be a problem too

yamadad4 · 06-16-2012, 09:28 PM

lack of exhaust wouldnt cause the high idle, but its not real healthy for the engine. are you using the stock y pipe?