9 replies to this topic

[Someone called James]

Hello Guys and Girls,

 

Ever since I bought my mini, a 1989 998cc Racing Flame in February 2016, the Idle Speed has been too high, usually at about 1000-1200rpm once the engine has warmed up. The previous owner said that they had "modified" the carburetor (a single SU HS4) to make the engine more "reliable" or something along those lines. 

 

I've checked the condition of the spark plugs and these show the mixture seems OK and wound the idle speed screw out as much as possible until it makes no difference. The throttle and choke cables aren't too tight so I'm out of ideas. 

 

I'm going to strip the carb down in the future before fitting on my rebuilt engine but I don't want the same problem to happen once I've rebuild it!

 

James C. 

[Stiggytoo]

Try manually holding the throttle back to see if revs drop. Could be that the butterfly valve wasn't assembled correctly. Or a big air leak.

[cal844]

Try manually holding the throttle back to see if revs drop. Could be that the butterfly valve wasn't assembled correctly. Or a big air leak.

Or the return spring bent, bent jet... A lot of things

[Scousemouse]

My tick over went up from 1000-1100 to 1200-1300 after I had refixed the choke cable after it pulled out thru the cable nipple upon starting up one morning.

Evidently it was down to me rushing and not checking the choke was fully open when off.

(must get around to fitting new nipple) but on 1000-1100 the engine is quiet + smooth.

Question ...what is the correct rpm on tickover for a 91 998cc???

[cal844]

850+-50 rpm

[Someone called James]

Thanks for the suggestions, I'll try holding the throttle back and see if that makes a difference. I'm going to rebuild the carb at some point so some of the internals will probably be replaced. 

 

Thanks, 

James. 

[Scousemouse]

850+-50 rpm

I'm using the tacho(nippon) off the original 3 clock dash,wonder if this tacho is goosed as when it shows 1100 on t/over the engine don't seem to be racing??

[cal844]

Could be the voltage stabiliser(although I'm sure the tacho is a separate feed)

[Scousemouse]

Yep tacho is separate.

[cal844]

In that case I'd be verifying engine revs and tacho revs are the same

If not you have an issue somewhere

Edited by cal844, 21 November 2016 - 04:57 PM.