27 replies to this topic

[TopGearRules]

Hi there, I got a new HS4 carburettor fitted a few weeks ago but im suffering from a rough idle problem. I've had to set the idle RPMs to around 950 since it idles erratically (dropping to 700 then returning to 900, and then repeats). Can anyone give me advice to what could be causing the problem?? Apparently the carb has been 'reconditioned' so hopefully all the parts are new!

 

This video sort of demonstrates the problem, but obviously mine is more noticeable/worse:

 

 

Many thanks, Alex 

Edited by TopGearRules, 12 July 2013 - 02:20 PM.

[KernowCooper]

You mention adjusting the idle, but don't mention setting the mixture, what have you set the mixture to ? 2.5-3% at idle would be a good point to start with, and then adjust the idle when your happy the mixture settings ok, Up on the large Nut is weaken and down for weaken.

[TopGearRules]

You mention adjusting the idle, but don't mention setting the mixture, what have you set the mixture to ? 2.5-3% at idle would be a good point to start with, and then adjust the idle when your happy the mixture settings ok, Up on the large Nut is weaken and down for weaken.

 

Thanks i'll try and adjust the mixture and see if it makes a difference. Also doesn't screwing the large nut richen the mixture? Al

Edited by TopGearRules, 14 July 2013 - 10:50 AM.

[KernowCooper]

Up weakens and down richens it, use the lifting pin if you dont have access to a CO Meter, lift pin slightly engine falters/stalls = weak, should raise slightly in revs and settle down to a even idle, but ensure timing and points and tappets are correct before any carb adjustments

[TopGearRules]

The carb has been tuned just right now and seems to be running smoothly and doesnt bog down at idle. However, it seems to be really sluggish when you drive for at least 5 minuets after a cold start. Can anyone give me any advice to what is causing this? It doesnt want to accelerate at all, and if you put your foot fully down on the accelerator the engine bogs down. Only the carb idle and mixture has been changed so far....

 

Al 

[KernowCooper]

If its a cold engine are you using a bit of choke? does it clear once warmed up?

[TopGearRules]

If its a cold engine are you using a bit of choke? does it clear once warmed up?

Hiya, yep I usually pull the choke out about an inch. My mini has always been rather sluggish when starting from cold, but recently it's been a little worse than usual. If its just a normal characteristic of having a new carb then I'm sure I can live with it :)

Thanks, Al

[KernowCooper]

Once warm it should pull cleanly, if you push up the lifting pin do the engine revs rise slightly and drop back to where they were? if it stalls or revs drop a lot and run roughly its to weak.

[TopGearRules]

Once warm it should pull cleanly, if you push up the lifting pin do the engine revs rise slightly and drop back to where they were? if it stalls or revs drop a lot and run roughly its to weak.

Hi Dave, sorry getting back to you so late I've been doing a lot of overtime at work lately and been away the Internet! All I can say is that for the first few minutes of driving from cold it doesn't want to go anywhere and is extremely sluggish. I have no power at all when I pull away from junctions and it really bogs down when you put your foot fully down on the accelerator. After the first 5 minutes it drives beautifully and pulls really cleanly. It's started this problem when I adjusted the mixture (I might of set it too rich at the time). Perhaps I've done something wrong with the carb? Thanks, Alex :)

Edit: It sounds like it might be an over fuelling problem, but the mixture is not rich?

Edited by TopGearRules, 29 July 2013 - 01:46 PM.

[KernowCooper]

Poor performance when cold as you describe is usually weak mixture Follow the way in my post to check and adjust it and go from there, do it with a hot engine.Its not unusual for the engine to require a bit of choke when started form cold though.

Edited by KernowCooper, 29 July 2013 - 03:27 PM.

[TopGearRules]

Poor performance when cold as you describe is usually weak mixture Follow the way in my post to check and adjust it and go from there, do it with a hot engine.Its not unusual for the engine to require a bit of choke when started form cold though.

 I will richen the mixture tomorrow using your method and see if that makes a difference. Thanks for all your help!!

[TopGearRules]

I enriched the mixture slightly before setting off today and it didnt really make a difference really. I think I might try and put some carb cleaner through it since it could have been that I had it too rich before and has left some deposits. Its a really strange problem and is really bothering me now

[jaydee]

Last time you serviced your air filter?

[TopGearRules]

Last time you serviced your air filter?

 

It was replaced about a month ago since the exhaust manifold was blowing and got it clogged up (a new exhaust system was fitted at the time the new carburettor was installed). The car was running perfectly from a cold engine until I enriched the mixture slightly in order to solve the rough idle problem. After that its become undriveable (ie no power at all) for the first five minuets and is really sluggish. Kinda annoyed because I dont have the money at the moment to go to a garage and get it fixed. Thanks for all your help so far, I appreciate it. Alex  

[jaydee]

What needle in the carb for what engine?