Quirks of Mikuni/Solex's and Webers

[joey]

Is there a really loud and noticeable hissing sound when engine is idling?

Nah no real hissing sound so to speak of, it would be hard to hear over the electronic fuel pump and engine noise anyway

[Stock_22]

Joey, I had a similar problem to yours, not quite as bad (mainly between idle and 2500rpm). From memory the guy at carb tech said that the accelrator pump on the rear carby was blocked and not allowing enough fuel through into the carby. After replacing that she runs fine now through the entire rev range. Hope this helps as its a bit vague...

edit: I also had the carbs rebuilt at the same time.

[mike1980ra40]

hi all,
Another question, any one here have thick yellow goop building up on the bottom of the
carbs? Both carbs on mine do it, rear carb drips onto the starter (yuk)
have had the bottom gaskets changed a couple of times.
if it's not a common thing, are the diaphrams kaput?
it's worse when the engine is cold. checked the screws there tight?
any thoughts?

cheers.

[Rodger]

mike,

I suggest a close inspection of the pump diaphragms. They can split or the seals around the central metal plunger may have perished.

Both these problems allow fuel to slowly or quickly flow out the bottom of the housings. The one dripping is bad and both show up as fuel stains and congeled fuel.

The leaking fuel will also hinder proper operation of the pump circuit so the engine could show signs of hesitation as Joey and Stock_22 discribe above.

Regards

Rodger

[mike1980ra40]

thanks Rodger exactly the same fault, hesitation.
I'll be ordering diaphrams fairly soon then.

cheers.

[joey]

If my solexs are running rich at the top end but are running perfectly when at idle and up to about 4.5k rpm what jets/mixtures need to be changed?
Cheers, Joey

[Rodger]

Joey,

What have we ended up with in those Solexes.

We can play around with things a bit. Try a bigger #60 Pilot and a #180 or #200 Main Air. This may move the Pilot to Main system transition further up.

How is it on cruising at say 3500 in fifth gear?

It is rich up high mostly because of the small size of Main Air Jet running out of flow. It takes a whole book about how each jet effects the other and its effect on mixtures up and down the range of load and throttle position.

Carbs are a compromise but those Solexes should still run well, and I still swear by them.

BTW Joey you do realise that when you go to those planned 45mm Webers on your 3T-G or 4A-G you may well be going down the same path setting them up.

Regards

Rodger

[joey]

BTW Joey you do realise that when you go to those planned 45mm Webers on your 3T-G or 4A-G you may well be going down the same path setting them up.

In what way do you mean this? The fact that it gets richer as the rpms go up, or its quite laggy at low rpm?
Cheers, joey

[Rodger]

Joey,

What I am saying is. It could take some time to sort out the jetting, venturi/choke sizes of the Webers and if you have lumpy cams in the 4A-G then you may well still have low down problems. I guess you need to choose your Webers carefully and preferably buy a new or reconditioned pair.

I am yet to look at your Dyno graph on your Car's page as my Network Policy at work does not allow some graphics. 66kW is rather low, compared to one of my 2Ts with a mild cam and 44mm Mikunis (would have been better with 40s) of 74kW and very drivable. Definately need to sort it out.

Regards
Rodger

[joey]

I'm not looking to put big lumpy cams in the 20v if i go down that path, would probably go something that starts to kick in around low-mid rpm unlike the 2tg so hopefully that will help a little bit with the tuning.
It didn't even get 66kw, it got 49kw. The tuner did say it was running mega rich up high, but as i wasn't there i couldnt be sure he was revving it out to when the cams kick in although i did tell him the motor doesnt really start producing power till 6000rpm

[mike1980ra40]

mike,

I suggest a close inspection of the pump diaphragms. They can split or the seals around the central metal plunger may have perished.

The leaking fuel will also hinder proper operation of the pump circuit so the engine could show signs of hesitation as Joey and Stock_22 discribe above.

Regards

Rodger

I have checked diaphragms they seem ok, I also found a spare pair which seem to be in
good condition also, one thing i think i should be kicking myself for is the type of material
used for the pump body and pump body cover gaskets. I should have realised this before

dark grey gasket paper not suitable for areas in contact with petrol, light tan paper should be used.

it looks like the petrol leak is through the gasket paper not the diaphragms because the
dark grey paper is to porous for a thin liquid like petrol. oops how embarrassing.

cheers.

edit: even though diaphragms seem to be ok i'll still change them for new ones anyway,
I don't trust them, if in doubt replace it ... whats the colour of red ay? ...

[Turdinator]

Hi Guys
I'm having a small problem with my webers. I've changed over to 45DCOEs and i've found the idle mixture screws are moving due to the engine vibrations. It will drive fine untill i rev the motor out then it won't idle nicely untill i re-tune the idle mixture.

They currently have the standard spring setup to try keep them in tune. I am going to replace my soft mounts this weekend incase they've gone hard and are causing the problem. I've also been told i should remove the spring set up and put lock nuts on the screws.

What are peoples thoughts and experiences with this?

[Rodger]

How many turns out are your Mixture screws turdinator?

If more than 2.5 then the springs are getting loose. Also would indicate a lean idle and may need to go up to the next size Low Speed/Pilot/Idle Jet, (what ever Weber call it).

Measure the free height of the springs, I may have longer ones.

Regards

Rodger

[Turdinator]

How many turns out are your Mixture screws turdinator?

If more than 2.5 then the springs are getting loose. Also would indicate a lean idle and may need to go up to the next size Low Speed/Pilot/Idle Jet, (what ever Weber call it).

Measure the free height of the springs, I may have longer ones.

Regards

Rodger

Good suggestions Rodger from memory the screws are less than one turn out but i will check. I will also check the height of the spring. My concern is that the screws wind out with the vibrations, so i'm wondering if the springs should be weaker?

[Steve M]

We had the same issue with loose idle springs, so we stuch washers under them, then they were tighter and still easily adjustable. It made the engine lose tune less regularly.