21 replies to this topic

[Benito_S6]

Bit of a strange issue, idle set at 800 rpm. Go for a drive and the idle increases to about 1600 rpm. I then have to pull the choke out and push it back in. Then the idle drops back down to normal. Sometimes only drops to 1000 rpm. But when the idle is high I looked at the choke and it isn’t making contact with the screw on the throttle. Blipping the throttle doesn’t make it drop. And it doesn’t look like the throttle cable is sticking at all. Tried wd40 but no joy. Any other ideas? (1986 mayfair, hs4 carb)

Edited by Benito_S6, 20 May 2019 - 08:46 AM.

[unburntfuelinthemorning]

It's likely to be a worn throttle spindle and/or throttle spindle bushes.

[Benito_S6]

It's likely to be a worn throttle spindle and/or throttle spindle bushes.

thanks for getting back to me, is there a way to check for sure that thats the issue and what’s it like replacing them.

Edited by Benito_S6, 20 May 2019 - 09:55 AM.

[unburntfuelinthemorning]

Is there any obvious movement up and down of the spindle?  Even if there isn't there can still be enough wear to allow air in.  Try spraying WD40 or carb cleaner or the like around the bushes with the engine running and note any changes in idle speed.

 

As for replacement, it's probably worth trying the spindle first as it's easy to replace and sometimes all that's needed.  If the bushes need replacing then I refer you to these other threads with people more knowledgeable than I commenting in:

 

http://www.theminifo...ng-replacement/

 

http://www.theminifo...spindle-bushes/

[Benito_S6]

Is there any obvious movement up and down of the spindle?  Even if there isn't there can still be enough wear to allow air in.  Try spraying WD40 or carb cleaner or the like around the bushes with the engine running and note any changes in idle speed.
 
As for replacement, it's probably worth trying the spindle first as it's easy to replace and sometimes all that's needed.  If the bushes need replacing then I refer you to these other threads with people more knowledgeable than I commenting in:
 
http://www.theminifo...ng-replacement/
 
http://www.theminifo...spindle-bushes/

nice one thanks a lot, I will check for play when I get home and see what I can find. Thanks for your help

[Benito_S6]

Good news is the spindle is completely solid, no free play what so ever, and wd40 make no difference to the revs. Still trying to find out what the problem is but at least it’s not that as it sounded a pain to replace. Thanks for your advice though urburntfuelinthemorning

[dyshipfakta]

Sounds to me like the throttle cable or choke is getting stuck/ caught up. Check the routing of the cables and that they are free to return fully/don’t get stuck

[richmondclassicsnorthwales]

Try the return spring / s   -Again, an over looked item

 

Main pull back spring from carb to exhaust clamp / abutement plate.  Return spring on the side of the carb ?

 

Also, is the choke dropping down / jet / likely to increase fuel input ?

 

Ideas for the pot !

Edited by richmondclassicsnorthwales, 20 May 2019 - 06:33 PM.

[Benito_S6]

Thanks again for all your reply’s. Definitely not the choke cable as the choke is off when I drive and the idle increases. Also it’s not in contact with the throttle Screw. The idle sticks at 1600 every time. the pedal fully returns and so does the lever on the carb. Spring seems fine aswell. Might take throttle cable off and see what it’s like. Only other thing I can think of is dashpot oil. It’s got a good amount but I’m not sure what oil is in it. Dunno whether that would make a difference.

Edited by Benito_S6, 20 May 2019 - 06:50 PM.

[phillrulz]

Any sign of burning oil? Just thinking in theory could be burning some oil once hot enough 

[Benito_S6]

Any sign of burning oil? Just thinking in theory could be burning some oil once hot enough

no oils been on max on dipstick for few months. Check it every week. Also idle sticks high when engines cold aswell

[phillrulz]

 

Any sign of burning oil? Just thinking in theory could be burning some oil once hot enough

no oils been on max on dipstick for few months. Check it every week. Also idle sticks high when engines cold aswell

 

 

Ah well all the best then, mine did it sunday was in a line up at a mini  rally and sounded like i had the choke out. Tried blipping the throttle but nothing. Hasnt done it since however. 

[Zami]

Had a similar problem recently with a refresh rebuild. Set idle at 1000 go for a drive and idle would be at 1500. Discovered the two top nuts on my HS4s to manifold were not tight. Fixed the problem. idle is steady 1000.

[Zami]

Had a similar problem recently with a refresh rebuild. Set idle at 1000 go for a drive and idle would be at 1500. Discovered the two top nuts on my HS4s to manifold were not tight. Fixed the problem. idle is steady 1000.

[Zami]

Had a similar problem recently with a refresh rebuild. Set idle at 1000 go for a drive and idle would be at 1500. Discovered the two top nuts on my HS4s to manifold were not tight. Fixed the problem. idle is steady 1000.