More hesitation

[Robbie693]

Hello,

Recently a posted about a hesitation problem with my Plus 2S/130. It coughs when coming back on the throttle at low rpms.

Several of you concurred with Paul Matty's suggestion of blocked jets so I have taken them out and given them a blow through. They all looked fine but I found that the starter jet had dropped off the emulsion tube when I took it out and wondered if I had found the problem.

Running the car afterwards I found it to be better but still the hesitation persists.

It was mentioned that the progression jets could be blocked but it's just a plug - no jet under it, just a hole in the casting (dellorto). Forgive my ignorance (I know very little about carbs) but, where's the jet?

The only thing that is different since Paul Matty tuned it is the timming is set to 12deg static whereas I always used to set it to 10deg. Could this be the cause?

Robbie

[tdafforn]

Have had similar problems on my +2S130 with Dell's...
This is despite a full overhaul of everything (engine included)
The problem can be dialed out to some extent by careful changing of the idle mixture vs idle RPM..
In particular, I have noticed that if you set the idle mixture using the suggested method in the Dell'l manual or using something like colortune the mixture is way lean..
(I know this from my wideband sensor)
a bunsen blue flame on colortune is typically >20:1.
If I richen the mixture to 14:1 or even 12:1 and alter the idle speed (which usually means opening the butterflies, then most of the hesitation is dialed out..
the only issue to watch out for otherwise is a BIG hesitation if you boot it when it is still cold (which probably means I should have th choke out!)
Tim

[tdafforn]

Have had similar problems on my +2S130 with Dell's...
This is despite a full overhaul of everything (engine included)
The problem can be dialed out to some extent by careful changing of the idle mixture vs idle RPM..
In particular, I have noticed that if you set the idle mixture using the suggested method in the Dell'l manual or using something like colortune the mixture is way lean..
(I know this from my wideband sensor)
a bunsen blue flame on colortune is typically >20:1.
If I richen the mixture to 14:1 or even 12:1 and alter the idle speed (which usually means opening the butterflies, then most of the hesitation is dialed out..
the only issue to watch out for otherwise is a BIG hesitation if you boot it when it is still cold (which probably means I should have th choke out!)
Tim

[andyhodg]

Robbie

Where are you located? I know a guy near Banbury who I use to set up my carbs. I first went to hi when I had a problem that I could not diagonse and he had it sorted and running better than ever afetr having the car for a few hours. He also mentiined a very slight flat spot between 2 and 3000 rpm that he said he could fix if I felt it necessary.

I would fully recommend him. If you are close enough to make it worthwhile I can put you in touch with him.

Andy

[peterako]

Just a comment on the 'progression jets'.

If you're talking about the Progression 'Holes' then there should be a number of holes under the plug.

A sort of progression of holes (3 or four I think) that allow for smooth progression from the Idle jets to the mains.

There is a fine line between these working right and working terribly.

Rohan can comment much better than I on this. And much clearer.

But, basically, the throttle butterfiles need to be open just enough at idle (idle adjust central screw) to allow the progression holes work correctly.

Another side effect of having this adjustment incorrect is that teh engine will return to idle revs slowly.

Hope I haven't either confused you more or sent you off in the wrong direction....

You can check the progression from jet to jet by increasing the revs very gently and seeing where it happens.

If, on the other hand, the hesitation happens only when you 'jump' on the throttle the problem could be with the accellerator pumps. (Squirting too much fuel intro the engine)

Peter

[Robbie693]

Thanks for the replys,

Tim - Interesting you mention richening the mixture, I have two plugs that are black and two dark brown. Have you managed to get all yours to the same even brown colour?

Andy - I'm in Birmingham so Banbury not a huge distance, could you give me this guy's details please?

Peter - I am easily confused when it comes to carburation! The revs return to idle well and the hesitation happens on small throttle openings and larger ones from low revs. It seems worse when the engine is hot

Robbie

[tdafforn]

Hi,
If you really want some advice on carburation then become a member of Sidedraft Central on Yahoo. The discussions on there are really intense and in pretty much all cases very informative..
Would also be interested in the name of the guy in Banbury. I have used Aldon in Dudley and have had good results..
Currently I have the +2 wired up to a wideband mixture sensor, throttle position sensor and rpm monitor. Gives me lots of info on how it is running.
(I can bore you with excel files of a twink on the road!)
Anyhow for mine the slight ( and it is slight, I think many people may not notice) hesitation is due to a slight part throttle lean spot. probably need to play with some jets, but haven't had time over the summer
Cheers
Tim

[andyhodg]

Robbie, Tim

The Guy I use is John Salt in Mollington, just north of Banbury. His contact number is 01295 750719.

He is semi retired and does all the work from home. He was responsible for designing carburation systems for the production cars during his working life. He certainly improved the running of my Webber engined +2.

Regards

[jimbo]

Robbie, Tim

The Guy I use is John Salt in Mollington, just north of Banbury. His contact number is 01295 750719.

He is semi retired and does all the work from home. He was responsible for designing carburation systems for the production cars during his working life. He certainly improved the running of my Webber engined +2.

Regards

Robbie,

Your problem sounds very similar to the issue I am having with my Sprint. Are you planning on using John Salt? If so, I'd really appreciate your feedback as I may well do the same!

Cheers,

James

[Robbie693]

Thanks Andy for the contact details.

Hi James,

Yes I think I will. I have to take the carbs off to fix an oil leak from the drain tube first, so may be a while before I can get around to contacting John. Will let you know as and when.

Regards

Robbie