Rich mixture - change jets but which ones?

I installed twin Weber IDF's on my type 4 2l engine a while back and altho it runs fine the mixture is too rich judging from spark plug colour.

The carbs are IDF 40's I think and off-hand I can't re-call the jet sizes etc. I used but I did follow recommendations from one of the carburettor suppliers. I would like to try a few things myself before perhaps going for a rolling road session so, in theory do I need to reduce the size of the idle jets or should I increase the size of the air correction jets, or is there something else that needs doing? I know that maybe I have over-simplified the problem here and the best bet is the rolling road but any advice as to what I could try would be welcome! Timing, valves etc are all fine so it's just carbs to worry about. I have a fuel pressure regulator running at 2.5psi which I believe is about right.

 

Did you get this sorted?

 

eurocarb are good for parts and advice

 

Thanks for the posts and apologies for not responding sooner.

Not sorted yet as I've been away but now I'm back and I'm thinking that the float level could have affected the mixture - I've checked one carb and float level was all wrong so I've adjusted it and found that the engine starts better now! A step in the right direction methinks, and, just maybe I don't have to change jets! Since putting that carb back I've now discovered an inconsistent slight petrol leak on it - just around the accel pump area. I believe that even a small pin-prick hole in the diaphragm can cause a leak there and a rich mixture so, maybe tomorrow, that carb comes off (again!!), perhaps gets stripped right down if I can build up the courage to do that, then a good soak in carb cleaner for 24hrs. A blow through from the compressor to clean out all the sh**, and finally re-assembly with new float needle, valve jet and diaphragm will hopefully result in 100% confidence that the carb is as good as it can be with the given jets. If I can achieve that and find that everything is better then I'll do the second carb as well.

Once all that is done then I'll look at spark plugs again and if no improvement will think further about the jets and possibly a rolling road session. Can't see the sense in changing jets and getting rolling road if carbs not A1.

Any further thoughts/recommendations/ideas etc most welcome in the meantime, especially in relation to carb cleaner - I assume it's good for both inside and out and that even a double strength one will not harm anything??!!

 

rule of thumb for main jets is 4x the vent size your 32 ventruri x4 =128 main jet

Is it just rich or does it not run very good ?, personally i dont know much about webbers but do they not have mixtures screws . float heights are critical with dells ! when checking spark plug colour you have to go on a good run ,turn it off ,coast to a stop and then pull a plug .
are they balanced ? i have a snail balancer if you want to borrow one ?

 

Hi Ihu1281 (sorry, I've forgotten your name!!)- thanks for that. Have checked my carb jets etc and I have 32 Venturi with 140 main jets, F11 Emulsion Tubes, 220 Air Corr and 45 Idles. The carbs were tuned (but no jets etc changed) some time ago by local guy who specialises in VW's and, apart from difficulty in starting the engine runs pretty well altho of course I have nothing to compare it with. I have a snail also and have checked the air flow to each barrel and that is fine. Yes, they do have mixture screws but because engine was running fine once it started I have not adjusted these. However I know that the carbs are dirty - there was no squirt from one accel pump nozzle until I cleaned it, so I think there may well be more crud in both carbs - hence the cleaning. And I don't think it's worth trying to adjust mixture screws, idle jets etc until I can be pretty sure the carbs are very clean inside. I then get a bit nervous that I won't be able to adjust them properly despite the fact there's no reason why I shouldn't be able to do it and I do have loads of printed advice from 'specialists'!! Confidence breeds confidence, I guess!

Still haven't seen your bus - is it up and running yet?? Would be good to see and compare if you have the time. PM me and maybe we can meet up again sometime.

John

 

John its steve ...... Its all mot`d taxed and insured but then i started taking bits off again and you know how it is ;D
We are going to camperjam in her tho so i must put the steering box back in .

There must be a stack of people who run webbers on a 2 liter who can advise on suitable jet sizes but i`d say they are all not suited mains too big and idles too small .

You were after a spare wheel a while ago , did you get one ? i have one if you need a spare

 

Steve - Cheers, yes all sorted thanks. Since we last met I've had new furniture, new roof lining plus a bottom-half respray. Just want to get my carbs sorted before we go to Ireland in her during June probably!!

 

As above - Can anyone tell me what carb setup they have on their twin Weber 40IDF's on a t4 2litre engine please? Would be an excellent starting point once carbs are cleaned out!
Many thanks

 

vzi can be helpful and so can Earlygay.com ...cover all bases
same colours ?