EDIT: Great post, so stickied, but too many rude words, so edited

have you done the shake test?

hold the air filter in 1 hand, try to wiggle it

if it moves without the engine moving, your carb bolts are loose (which will mess up all manner of things to do with smooth running) and need tightening

if you put your foot down hard, is there occasionally like a jolt, like you get no power for the first ~1/2 second?

carb bolts are loose then, sort that and the idle will fix itself

tighten up the carb bolts and you get more power, better response and more economy

reason not to do it? uhhhr, none?

how to tighten carb bolts -> take off air filter cover. you'll see 3 nuts (probably) or screw heads (less likely). undo whatever is there, and remove lower air filter housing, be careful not to damaget the rubber tubing and the funky metal spaceage lookin stuff (both just pull off, or you can leave the space age stuff off and just move the housing away, but be careful, cos its fragile (But it can be swapped with some off a 700)

you'll see another host of nuts or bolts below the housing - 4 or 5 maybe. tighten them all up to a reasonable level, like pretty tight, but not super tight

then try to undo, if its easy, your threads are knackered and you need a newer carb, or you can simply drop a shitload of superglue down the holes and try again (cheaper, will last a while). if not, re-tighten (to be on the safe side)

Replace the air filter lower housing, making sure you put the little rubber pipe back on (cos the fricken thing is alwasy forgotten) and the silvery stuff then replace the lid and treat the thing to a new filter, it probably hasn't been changed since the dark ages

You may well want to do a tune up, as you've now fixed the air leaks, if you've adjusted the screws to try and make it run properly you'll have screwed up the tuning, but DO make sure the engine is completely warmed up, ie: first time the fan comes on cos the oil heats up slower than the water, and the engine aint fully warm till all the oil is warm. The oil won't be fully hot even when the fan comes on, but its certainly well warm enough for us to do our adjustments.

The best way to do this is using a gas analyser, and you'll want to set the CO to about 2.0%. If you haven't got one of those, there's a way round it. Screw the mixture out until the idle speed is at its highest and smoothest. Readjust idle to about 950 RPM or so. Then screw the mixture in until the engine revs JUST slow down about 50RPM or so. This should bring you to under the 3.5% needed to pass an MOT. It can always be checked or corrected later.


tadaaa! your problems are fixed, and you dont need to be a postwhore to do it (thats my job)

Part II: how do you adjust the carb

Want to continue 5lab? lol

STEP 2: read the haynes manual

(i'm hungover and cba)

Everyone who mentions to tighten the carb screws always talks about the ones on the top of the carb only, What about the one under the first heat shield before the cooling plate? Does anyone bother to check this one to see if it's tight, IT'S THERE!! I know, as I found it by chance while cleaning the carb, and has probably worked loose as well, this one was. First time I've seen that on all the carbs I've stripped and cleaned.

Check it out if you don't believe me, because if this is loose you will still have an air leak.

morgan105,
is that the 1.4 carb your talking about? (webber twin downdraft)

Only the 1.4 carb is 'famed' for shaking loose, so I'd assume we are indeed talking about the Weber DIR32.

Incidentally, I understood that the problem was often that the threads ripped out, so tightening does no good - if it gets to that stage you need to retap the threads, or get a replacement 'unshaken' carb!

cheers

James

That's the one!!!

If they keep shaking loose but the threads are good, try a bit of loctite on them, and I mean a bit.

As for the nuts that hold it on to the manifold, use NYLOCK nuts. There a pain when you want to take it off or putting it back on but they don't come loose.

It must be a general fault on cars with weber carbs or conversions, Those who attended Gaydon will know that Francois and his pal sorted out my carb in the pub car park and mine is a 1.7 on checking the cars extensive history I found a bill dated July 99 for a carb replacement,I know its a twin choke or dual venturi weber but there is no mention of what model it is (how would I find out ?) it cost the guy nearly £315.00 supplied and fitted five years ago so keep checking your nuts guys ( should be bolts but not nearly as funny LOL )

The 1.7 has a Solex CISAC 32-34 carb - very similar to the one on the 360 B200K. It was most likely replaced because of the carb-base warping problem.

cheers

James

Foggy,

Where did you get your information from that the 1.7 has a Solex CISAC 32-34 carb? my records have it listed as the Solex 28/34 Z10 CISAC from 86 - 91, this is the same one as fitted to the 89-91 440,460 1.7.

I think that Solex CISAC 32-34 is used in older B200K models, not sure though.

For the B200 from 85-89 was the Solex 34/34 Z11 CISAC as fitted to the 740 2.0 from 87-88 and the 240 2.3 87-90

You're quite right - the barrel diameter of the first choke of the B172 carb is indeed 28mm, making it a CISAC 28-34....but I was nearly right

Interesting that it was fitted to the 2.3 240 - that must seriously stifle it!

cheers

James

well my 1.7 has deffo got a weber

It is possible to obtain a Weber replacement (which is a superior quality carb!), but AFAIK it was never factory spec on the 1.7. Think yourself lucky though - it's an upgrade!

cheers

James