+2 dellorto carbs & spark plugs

[Chris_3003]

Hi all, I have a 1972 elan +2, with dellorto 40s (non emishion). Sometimes it runs like a dream and then after a week (or even a day) it will find a way of not running correctly.

I have a feeling it is carb problems, as one day it will be fine, (start well, tick over etc), then the next it will either struggle to start or not at all. What has fixed this problem is either changing the plugs or cleaning the originals. So this leads me to the carbs?

The jet sizes are as follows; Main 120, Idle 50 and Choke/Starting 50. This last one is where the problem is (I think) as from different sources i read the jet should either be 30 or 70? The float levels are at 15mm (as they should be). Would the size of the choke jet be causing at least some of my problems?

[512BB]

Hi Chris,

Welcome to the forum. I would think it very unlikely that your problems are carb related. They may not be set up correctly, as you say your plugs condition is not ideal, but if the carbs were at fault, you would not have an intermitent fault, but one that is evident all the time.

It sounds like an ignition problem to me, so check all things in that area, particularly the dissy cap, rotor arm and points, and then the coil. All those things can produce intermitent faults, plus others. Let us know how you get on.

All the best,

Leslie

[terryp]

Chris
It may be that the plugs are fowling and not being burnt off. What plugs are you using? Do you do a lot of poodling rather than motorway driving or fast driving?
There's lots on the forum about plug choice but basically comes down to:-
Poodling and normal driving NGK BP6ES
Fast Road / Motorway NGK BP7ES
Track etc NGK BP8ES

Terry

[billwill]

It might well be that the accelerator pumps in your carbs are not working properly.


As with the Webers you should not need to use the starting device (choke) at all, just a few dabs on the throttle to pump fuel into the manifold and then twist the starter key.

[Chris_3003]

A great responce, thanks guys. It only gets a little use (once a week usually) and thats not fast use as well. I beleve the plugs to be NGK BP6ES. I am going to take them off soon and have a good look at them, could a hole in the the accelerator pump diaphragm cause extra petrol to be sucked in and upsetting it all?

Are the jets the correct sizes?
Main 120, Idle 50 and Choke/Starting 50

[Robbie693]

It might well be that the accelerator pumps in your carbs are not working properly.


As with the Webers you should not need to use the starting device (choke) at all, just a few dabs on the throttle to pump fuel into the manifold and then twist the starter key.

According to Mr Wilkins, for Dellorto's one should not pump the throttle when cold but use the choke, as the carbs operate differently to Webers. Apparently pumping can fill the airbox with neat fuel and cause a flash-back.

I have always used the choke from cold (just to get it running) with no ill affects (or explosions!)

Cheers

Robbie

[Daholmes19]

Hi there

Being intermitent it does sound like ignition but I had "intermittent" and permanent issues with the Dellorto's on my +2 and found/fixed the following problems which may be of help to you (some off this forum others from an expert in Italy), probably common faults given the age of the carbs and potential lack of maintenace. My issues gave a flat spot around 2700 rpm (transition issues between circuits) and a very rough idle with fouling on number 1 and 4 plugs. Looks like the PO had tried to fix the issues, receipts in the binder that came with the car, but never found the root cause. get yourself an exploded diagram and check the following;

1. Check that the idle jets are seating correctly in the carb body, and that they are idle jets and NOT choke jets (they are VERY similar). Idle jets have a waisted shoulder which seats in the holder, mine had choke jets (the right size 50) in number 1 and 4 which don't have a shoulder so fuel was leaking around the jet as it wasn't fully seating in the body. A trick here is to lightly crimp the end of the idle jet holder so that the jet is a tight fit, next don't push the jet fully home but allow the jet to seat itself as you screw the jet into the body for a tight seal.

2. If you get around to stripping the carbs down make sure you remove the cover that fits in between the acc pump and the main body. It actually forms the bottom of the float chamber and the 'top" of it can't be seen from above. Both of mine had 2 to 4mm of "crud" on them, some of which was floating around and probably blocking the jets as all 4 jets (idel and main) pick up fuel from that exact spot....!

3. The acc jet circuit can "bleed" back fuel into the float chamber if the steel ball which acts as a one way valve is not seating properly in the carb body, so the acc jet takes a couple of pumps to prime rather than working straight away. To fix this drop the ball into the carb body and using a drfit carefully tap it down into the body so it creates a proper seat again in the aluminium.

After all of the above, plus a rebuld kit my engine is rock solid at idle and smooth through all the rev range.

Cheers
Dave

Woodstock, ON
Canada

[billwill]

It might well be that the accelerator pumps in your carbs are not working properly.


As with the Webers you should not need to use the starting device (choke) at all, just a few dabs on the throttle to pump fuel into the manifold and then twist the starter key.

According to Mr Wilkins, for Dellorto's one should not pump the throttle when cold but use the choke, as the carbs operate differently to Webers. Apparently pumping can fill the airbox with neat fuel and cause a flash-back.

I have always used the choke from cold (just to get it running) with no ill affects (or explosions!)

Cheers

Robbie

Yet in this book
http://www.amazon.co.uk/Build-Power-Del ... 273&sr=8-1
he doesn't even bother to tell you how to service the cold start device as he says you never use it.

I was having cold start problems, lots of them even using the 'choke' I bought that book and a set of gaskets & diaphragm etc and did a systematic clean out & re-assemble.

I seem to have no cold start problem now.

(though I couldn't try for long as the head cracked again).

[alaric]

Hi. Could you explain a bit more about how it's not running correctly - is it just hard to start but fine once going? Have you checked the earth strap on the engine and to the battery? If that circuit was loose it would make it run roughly as I think you describe.

All the best.

Sean.

[rgh0]

A possible cause of the problems you observe is the following sequence


Plus 2s that are used infequently suffer from fuel evaporation. This leads to loss of the lighter more easily vaporised fuel elements. This leads to the plugs getting wet when starting and fouling when running if it does start. This leads to starting and running problems that are only easily resolved by swapping out the plugs or taking them out and cleaning them. You also may need to drain and refill with fresh fuel in extreme cases.

cheers
Rohan

[Chris_3003]

Once again, thanks for the responce. I have now taken apprt the carbs and found that in the bottom of the float chamber (above the accel pump) there was stuff that is best described as mashed up weetabix. So I have cleaned them and they should be going back on later today. Hopefully so much crud was getting around and upsetting the jets and so sometimes it was ok and sometimes it was just getting in the way. Fingers crossed

[billwill]

Check that your accelerator pump jets are clear. They are very tiny holes, Don't poke anything into them use compressed air to blow them through.


But with fuel in the bowl the acc jets should be capable of making a 3 to 6 foot jet of fuel from the manifold side.

If you have that much crud in the bottom it really is probably best to get a new set of gaskets and pump diaphragm and a can of compressed air and do a proper carb overhaul.

[Daholmes19]

Hi Chris

I agree with Bill if you had that much "weetabix" in the bottom of the float chamber, about the same as I had, you will have to clean out ALL of the carb body with compressed air. More than likely its found it way into some of the passages. Use a hand nozzle for the compressed air and hold it tight to the passage and keep squirting it until it blows clean and clear.

The bottom plate also has a one way valve in it which stops the fuel going back up into the float chamber when the acc pump is activated, you can unscrew it to clean it and also the passage in the plate itself. In mine the "weetabix" found its way there too.

Don't forget to "re-seat" the other non return valve steell ball, there are two one either side of the choke jet. Point 3 of my first post.

Cheers
Dave

[Chris_3003]

I have now managed to clean the carbs properly (with an air compressor) making sure that all of the jets and fuel/air ways are clear, and will be looking to put them back on over the week end so will let you all know how it goes.

[billwill]

Before you mount them try some fuel in the bowl and check that they are not dripping underneath.


First time I didn't check before hand and had to take them off again to fix the leak.