Hello.
I cleaned my carbs and set the fuelscrew right 1 7/8 position. I did not touch needles or anything else..
To problem: When firing up runs right about 1500 rpm:s. Running couple seconds, idling rises around 2000 rpm. It stays around 2000 if i dont touch the throttle. If i even touch the throttle idling cames down to normal 1500 rpm..
Did i set the throttle cable too tight or what ?? Never before done that and clean carbs first time.
I cleaned my carbs and set the fuelscrew right 1 7/8 position. I did not touch needles or anything else..
To problem: When firing up runs right about 1500 rpm:s. Running couple seconds, idling rises around 2000 rpm. It stays around 2000 if i dont touch the throttle. If i even touch the throttle idling cames down to normal 1500 rpm..
Did i set the throttle cable too tight or what ?? Never before done that and clean carbs first time.
FJViper
New member
Check cables, boot clamps, Make sure your slides are all equal, choke plungers are all the same and releasing. If you have to, pull the carbs again and make sure everything is tight. Make sure that each fuel screw is set at 1 7/8 or a little richer.
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Did you clean out pilot jets? I had the same idle hang and found 2 of the 3 jets plugged up. Also set the slides low (as per spec in sevice manual mine is 1.2 mm) and then adjuist idle RPM from there (once the motor is warmed up). My slides at idle were sitting way too high and the Yamaha tech guy told me that I can get 1,800 RPMS with the slides way too high up or way down as well (if that makes sense).
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Yes i cleaned all 3 pilots and everything is surely tight and properly set.
Fuelscrews i but exactly 1 7/8 turns.
Works great otherway..
Fuelscrews i but exactly 1 7/8 turns.
Works great otherway..
Try turning the screws 2 turns out. My Viper idles much better at this setting.Also make sure that you have atleast 2mm of free play in the throttle cable.
If you are sure everything is good and clean then adjust your idle screws. Those are not as accurate as you might think and every sled is a little different. As with most carbed engines, that setting is just a middle of the road starting point. All that said, the idle speed of a sled usually doesn't matter as long as it isn't way off.
One thing about the Viper engine (and others as well) is that once the engine is heat soaked (fully warmed up) they tend to idle high because they can. They have very little resistance and the normal idle air flow is sufficient to run faster once fully warm. I have read a number of perspectives on this, and even experimented a bit myself. I am convinced that warm carbs and warm engine let more air flow through.
Some simply choose to fatten the idle mixture, others simply drop the idle down to 1300 or so, others simply live with it. Myself, if I want it to settle down I simply blip the starter (choke).
One thing about the Viper engine (and others as well) is that once the engine is heat soaked (fully warmed up) they tend to idle high because they can. They have very little resistance and the normal idle air flow is sufficient to run faster once fully warm. I have read a number of perspectives on this, and even experimented a bit myself. I am convinced that warm carbs and warm engine let more air flow through.
Some simply choose to fatten the idle mixture, others simply drop the idle down to 1300 or so, others simply live with it. Myself, if I want it to settle down I simply blip the starter (choke).
I think you are right about what you sayd. Cold engine and iddlle is normal but when warmed up for good iddlle start to rise.
I think i can live with that.
Thanks guys
I think i can live with that.
Thanks guys
02Viper24
New member
I have had the same problem all season. Pulled the carbs four times, set air screw to 2 turns and turned the idle down. Thought I had it fixed and last time we rode the idle went back to 2100. I can burp the choke and it goes down for a couple seconds and then right back to 2100. Have to wait till next season to try it again.