13 replies to this topic

[twackler]

I have a bog standard HS4 carb and have always had problems with idling speed. I've recently had some starting issues an gave the carb a bit of a revamp ,a good clean oil change e.t.c. She's running well except it seems the throttle disc doesn't close completely this is proven because when i force the throttle return lever closed by hand the engine note drops and becomes normal (it barely moves about 1mm) i've tried wd40ing both ends of the throttle spindle but it doesen't make any difference as soon as i rev it goes back to the accelerated idling. Could this be a deformed throttle disc or a bent spindle ?

Edited by twackler, 08 June 2010 - 12:31 PM.

[liirge]

Have you put the throttle disk (if touched) round the right way, it chamfered so will only close completely if round the right way, the little hole in the disk should be above the shaft not below.

[twackler]

Thanks for the quick reply .i didn't touch the throttle disc i cleaned the dashpot and piston checked float clearance sent air down the jet in both directions. I can live with the problem it's a shame that's all,and I presume it 's giving me bad fuel economy although the spark plug color looks ok, i'll have a colortune in a couple of days.

[AndyMiniMad.]

There are two small screws which hold the disc to the spindal. they are split at the back to stop them coming loose. If you squeeze the spilt bits together and then loosen the screws a bit the disc should go all the way closed. Then tighten it all back up and split the screws again...before you do this though i assume you have tried to adjust the idle screw? and checked the throttle return spring is ok. Sorry for the stupid questions but you never know.

[twackler]

Please keep the stupid questions coming. I'm going to check out the return spring (it is there i know that)as far as the fast idle screw is concerned ,what position should it be in ,in relation to the cam lever, with the choke off.

[Big_Adam]

Mine throttle spindle used to bind.

So I cut the throttle spring in half and make a new hook on the end. Problem solved.

[AndyMiniMad.]

Your idle screw. just keep turning it anti clockwise untill the car idles at about 850-900 revs. if you turn it untill the revs no longer drop and they are still above normal. then you need to follw the instructions in my earlier reply.

[Brigbeale]

My Racing Green's HS4 used to have the same problem.
It turned out to be the spindle had a lot of play in it and the disc would catch as the throttle closed.
I had a HIF carb at the time and the local garage (a mini fanatic as well) told me to ditch the HS4 in favour of the HIF.
He fitted it and set it up.
The car has run fine since.
Only thing he recommended was to keep a close eye on the top engine steady rubbers (poly in my case) as when they wear, the carb may touch the bulkhead as it is closer than the HS4 setup.

[twackler]

Thanks for all the answers guys,revs are still above normal with the idle screw fully unscrewed.
So i'm gonna take the carb off and have a fiddle, may modify the spring whilst i'm at it.
One thing that did make me wonder,when i sprayed wd40 on the ends of the spindle there was a change in the engine note as if the wd40 had found it's way inside the carb is that normal ?

Edited by twackler, 08 June 2010 - 07:42 PM.

[cooperrodeo]

This is a common problem, but usually only with twin carbs where the throttle has to be closed further than with single carbs. Problem is usually worst when carbs are hot. As already indicated, it is due to the disc binding on the carb body. You probably do not need to squeeze the butterfly fixing screws as you can usually turn them enough to loosen the disc in order to centralise it. Do this with the throttle stop screw wound off.

[twackler]

Cheers i know what i'm doing tomorrow.
Has anyone got a tip for threading the choke cable back through it's little hole on the cam lever mine is a bit frayed and i haven't got enough play to be able to cut it.

Edited by twackler, 08 June 2010 - 08:13 PM.

[AndyMiniMad.]

Cut some of the sleave away to release more cable. then trim away the frayed bit and re fix. This only works if you have a spare inch or so length on the whole cable.

[toni6669]

Maybe your butterfly spindle or carb bushes are worn, does it have play in the butterfly?

[twackler]

Have you put the throttle disk (if touched) round the right way, it chamfered so will only close completely if round the right way, the little hole in the disk should be above the shaft not below.

I've just taken my carb off and the hole in the disc is below the spindle shaft !!!!what would the consequences be ?

Edited by twackler, 25 October 2010 - 11:21 AM.