High Idle

Wetwilly · Post by **Wetwilly** » Tue Apr 22, 2014 4:41 am

Hello everyone,

When I fire up my 1966 305 CA77 Dream the engine just takes off and idles at what seems to be 2500 RPM!

I have had the carb apart:
- I have checked numerous times that I have the slide in properly
- I have replaced the throttle cable and made sure that it slides easily and returns to the home position, the end of travel.
- I replaced the O-rings on the base of the carb and on the other side of the spacer
- Inspected spacer for cracks, there are none.
- My float bowl and carb top gaskets are in good condition and do not leak (not as far as I can tell)
- The air bleed screw has no effect BUT the idle screw does have a slight effect.

It behaves like the throttle is open. I can rev it up with no hesitation but I have a terribly high idle that I cannot bring down to a normal level. Any help would be appreciated. I have automotive experience but this one has me baffled at the moment.

Thank you all,

kirbb9 · Post by **kirbb9** » Wed Apr 23, 2014 12:28 am

Check your slides. There is a "bump" in the carb bore and a corresponding slit
in the slide. Or the slides are in the wrong carb. Hope this helps.

Brady

kirbb9 · Post by **kirbb9** » Wed Apr 23, 2014 12:28 am

Check your slides. There is a "bump" in the carb bore and a corresponding slit
in the slide. Or the slides are in the wrong carb. Hope this helps.

Brady

Wetwilly · Post by **Wetwilly** » Wed Apr 23, 2014 8:32 pm

I've checked my slide numerous times. It is in the correct way and seems to bottom out properly when installed. I checked for proper operation today with the carb installed using a mirror. It looks ok.

rustywrench · Post by **rustywrench** » Thu Apr 24, 2014 8:56 am

Spray a generous amount of a non flammable liquid at the base of the carb. Any change in RPM will tell you where the problem. Air leak causing a lean condition. Sometimes the carb base will distort from over tightening. If in fact that is the case, somewhere on this forum there is a thread designated to checking the flange for flatness and sanding to correct it. Also I remember reading a thread about a slide that was excessively worn and passing too much air. Just a couple more places to focus your attention. Rusty

Snakeoil · Post by **Snakeoil** » Thu Apr 24, 2014 9:48 am

If none of the suggestions given so far work, here are a couple things I'd check. These are separate things and NOT a list of sequential steps. Just trying to think of things that might cause this.

- Check the O-ring on the air mixture screw.
- Back the slide stop screw out all the way. This is what you are calling the idle screw.
- Remove the cable from the slide and reassemble the carb. See if the idle is still high.
- Drop the bowl and make sure the pilot jet has not fallen out.
- Check the centrifugal advance to make sure it is not stuck fully advanced.

Let know if you solve this and what caused it.

regards,
Rob

Wetwilly · Post by **Wetwilly** » Thu Apr 24, 2014 11:32 pm

Wonderful!

These are the ideas I needed.
- I checked the o-ring at the air bypass screw....it was missing! I think I may be on to something but I have a bit of a dilemma. My Clymer manual shows the o-ring between the spring and the threads of the screw. This doesn't seem to work. There is a groove just under the head of the screw and I assumed that must be where the o-ring went. Tried the bike with the new o-ring and no difference. I'm not quite sold that the o-ring is installed correctly though. Do you have a picture of an air bypass screw with the proper position of the o-ring?

I still have yet to check that my timing advance has not jammed in the advanced position.

I will go through the list this weekend.

Thank you very much!