Rotax wont idle

marc walsh · Joined: 11 May 2011 Posts: 130

Am I the only person who cant get his senior to idle? Screw all the way in and air mix screw doesnt help???

tony zambos · Posted: Tue Mar 19, 2013 4:39 pm Post subject:

Marc,

You can't be the only one. Don't believe I've ever had a kart engine that would idle. Maybe my driver will chime in, but can't remember if our Rotax will. Does the engine run ok on the track? If it does, don't worry. Other people willing to help might need to know how the carb is set up, so might want to post that.
_________________
tony zambos
ap kart racing
L.A.D Specialties

marc walsh · Joined: 11 May 2011 Posts: 130

Funny thing is I have two carbs. One has the adjustments on the drivers side then the other on the outside?? She seems to run ok just wont idle

Cory Ross · Posted: Tue Mar 19, 2013 11:57 pm Post subject:

Sometimes mine does. Does not bother me though. I have also heard the Rotax performs better on the track if it is set so it does not idle. Something about it helps with throttle response out of corners.

John Matthews · Posted: Wed Mar 20, 2013 6:10 am Post subject:

"It ain't an idling contest!" Mike Clements

Being an engine builder this is a common question asked. Reality is for a race engine if you're adjusted so you can idle by definition you're giving up horsepower. As long as there isn't something physically wrong with your engine you could adjust it so it idles nice and smooth but that wouldn't do you any good since you should be in the throttle 95% of the time.

Also remember that 2 cycles are very sensitive to air conditions, what works great in the morning could be really off in the afternoon. If you're competitive an air gauge will be a good investment along with jetting software.

If you really need the engine to "idle" just adjust the throttle cable so it's running at a higher RPM when you let off the gas pedal. Pretty soon you'll set it back and start "blipping" your throttle like everyone else does on the grid before going out.

Cheers,
_________________
John Matthews
Heartbeat Power, LLC.

Peter Zambos · Posted: Sun Mar 24, 2013 1:17 am Post subject:

Took me a while, but the driver will now chime in.

As John said, you're not running a race on the stand, so that's really not where your focus will be. Our FR125 will only idle for a very short period of time before it will require throttle input to stay live. This is normal.

I will have to disagree with John, however, when it comes to setting your throttle cable. If you set a Rotax with any baseline tension on the throttle cable, it often won't start. This is because the fuel will not be running through the proper idle circuit in the carb.

Marc, there are two accepted versions of the carb for the FR125, and you have pinpointed the only difference.