carbs

Post by **Lukey** » Tue Dec 30, 2008 2:42 pm

Hi all, my idle is a bit lumpy. Checked everything but the carb. Can I take the carb off/apart with out having new gaskets? Also somebody's donated a carbs of a late BL mini, how can I identify it?

Post by **MarkyB** » Tue Dec 30, 2008 2:57 pm

Can you define lumpy a bit?
Is it missing or are the revs not constant?
Probably worth checking the tappet clearances first.
Also with the engine running lift the little pin under the carb dashpot and see what happens to the revs.
If you have a timing light shine it on the timing marks and see if they jump about (this shows wear in the distributor)

Post by **Lukey** » Tue Dec 30, 2008 3:51 pm

I've done all of this, even replaced the dizzy because of wear. In fact this very second I have just sat down from adjusting the valves because I had to re-torque the head last night. In the 4 months I've had the car the only thing I haven't looked at is the carb. I've adjusted it but never checked for wear.

Basically at idle the car misses quite badly but as soon as you jump on the revs the car runs a peach. I can take a video if you want? It's been like this since I've had it but other things with the car had priority.

I shall see what happens to the revs and report back.

Post by **Matt** » Tue Dec 30, 2008 3:59 pm

late BL mini... probably a HS4

Measure the carb throat (inlet side), If the float chamber is on the side it will be a HS something if its 1.25" is a 2, 1.5" a 4, 1.75" a 6. ie. HS4 would be a 1.5" throat with a float chamber on the side

HS4:

If the float chamber is integral (and underneath) then is a HIF, the size is then denoted by the diameter of the throat in mm. For example a 1.5" HIF carb would be a HIF38.

HIF38:

(note there are some interim carbs known as HIF4 and HIF6 - these arnt very common and use the same rebuild kits as the appropriate later HIFS)

New gaskets are a good idea and not expensive, but if you are really short on cash you could make them out of cereal boxes

Post by **Lukey** » Tue Dec 30, 2008 4:04 pm

Ah thank you for the info, it is HS4. What carb would a 1098 67 moggie have standard? I need to stop being such a cheap skate but I just can't stand ordering things like £2.50 gaskets from ESM. It drives me nuts that the postage is almost the cost of the gasket (stubborn bloke thing).

Post by **mike.perry** » Tue Dec 30, 2008 7:05 pm

The 1098 Minor would have an HS2 carb with an AN needle and AUC 4387 spring.

Post by **Lukey** » Wed Dec 31, 2008 12:06 am

When I push the pin up the engine cuts out, also I'm disassembling the HS4 how do I take the throttle disk out of the body?

Post by **picky** » Wed Dec 31, 2008 12:21 am

Ideally if you push the pin and hold it up, the revs should rise a little but then go back to idle. if yours cuts out then you are running too lean I think...

To take out the throttle spindle:
With the throttle closed slowly unscrew the two screws in the throttle spindle. then open the carb to full throttle, and the throttle plate should slide out. Make sure you put it back in the right way round, as the edges are NOT straight they are angled, if you put it back in the wrong way round you will never get a good idle as it wont shut properly. Notice that the screws have a cut in them at the end, you should splay the ends of the screws a little once u have put it back in, this is to stop them coming undone and being swallowed by the engine (not good!)

Hope that helps,

Picky

Post by **Lukey** » Wed Dec 31, 2008 12:27 am

Ta picky the bloody thing still won't slide out I'll give it a bit of force. No matter how I've ever adjusted the mixture even if the plugs look spot on if I lift the piston the engine has always cut out.

Too cold out side now but I'll take it apart tomorrow and finally get to the end of this problem.

Post by **picky** » Wed Dec 31, 2008 12:30 am

yeah its a tight fit, try pulling it with a pair of pliers but try not the damage the edge. also try shifting the spindle in and out a bit to loosen it off. it will give in eventually

Picky

Post by **mike.perry** » Wed Dec 31, 2008 10:37 am

The HS4 carb should give you improved performance on the 1098 engine, especially if you cough up for a decent exhaust manifold.

Post by **Lukey** » Wed Dec 31, 2008 11:24 am

The carb seems fine, which is rather annoying. I guess I'm looking for a vacuum leak somewhere. I don't know what else It could be.

I'll take a video for you all to see.

Is there a classic tried and tested manifold? Could I just port the originals and remove the hot spot? I'm planing a 12G940 swap so this would be a much better carb?

Post by **bmcecosse** » Wed Dec 31, 2008 8:52 pm

The larger carb is only any use if you have the larger bore matching inlet manifold - do you ? When you lift the little test pin - you must only take up the initial slack - and then lift the piston about 1/8" - if you push it all the way up it will always stall! Have you checked if the vacuum advance unit on the dizzy is working - if it's failed the idle timing will be too retarded - and the engine will feel 'dull'. I wouldn't bother taking the throttle disc out - what will you gain by doing this ? Unless of course you are going to Vizardise it ??

Post by **Lukey** » Wed Dec 31, 2008 10:30 pm

bmcecosse wrote:The larger carb is only any use if you have the larger bore matching inlet manifold - do you ? When you lift the little test pin - you must only take up the initial slack - and then lift the piston about 1/8" - if you push it all the way up it will always stall! Have you checked if the vacuum advance unit on the dizzy is working - if it's failed the idle timing will be too retarded - and the engine will feel 'dull'. I wouldn't bother taking the throttle disc out - what will you gain by doing this ? Unless of course you are going to Vizardise it ??

Yup working OK, I will say though there is hardly any vacuum from the vac nipple at idle. The carb had a bit of oxidation in the bore which was causing the disk to not move freely, I could not clean it properly.

I do have the larger manifold, I tried setting the mixture once by pushing the piston up by 8mm as instructed by the haynes manual and it did the same thing.

Post by **bmcecosse** » Wed Dec 31, 2008 11:18 pm

Well -if it stalls like that then that's because it's too weak! The 'pin' test does work. 8mm sounds a bit too much - depends how much slack there is before the piston actually lifts. Can just use a thin blade screwdriver in the mouth of the carb - then you can see how much you are actually lifting the piston.

Post by **Lukey** » Wed Jan 14, 2009 8:58 pm

Got some new gaskets. From the inlet does it go: insulator, gasket, throttle linkage plate, gasket, carb?

Post by **bmcecosse** » Wed Jan 14, 2009 9:04 pm

Should probably be a gasket between insulator and manifold. I think also the throttle plate goes nearer to the manifold - then the insulator then the carb - with paper gaskets twixt them all! Thjis gives a bit of space for the throttle links to swing without fouling.