Is this common with DCOE's?

[John Reay]

Just been out for a blast so it should come as no surprise that I now have to ask a few questions ;-)

 

Yes it that favourite old technology again. I have just fitted a newer pair of 40's on my X-flow.

 

 

Car runs beautifully on light, medium and full throttle. Nice 'clean' crisp throttle and progression is good but I have noticed the following 'symptoms' Are these common or not?

 

1. Set idle speed when properly warmed up to 1000rpm. Go for a blat and idle speed increases to 1200rpm. Have to turn idle speed screw anticlockwise even though it hasn't moved to regain 1000rpm idle speed. (there is a spring on the screw to maintain tension.

 

2. I get about 1-2mm of fuel in the well that sits above the left hand venturi of the carb. This is the fuel bowl vent.

Is this normal? (I never noticed this on my last pair of 40's but I can't say I was looking.

 

3. After blatting along some of the dual carriageways on my home and entering the estate I live in I have to navigate a sharp 90 left corner which then goes up a steep hill the car stumbles on light throttle going up the hill (now in a 30mph zone). A few blips of the throttle clears this and the cars is back to normal.

 

I have checked that the needle valves are shutting off (they are) and when fuel bowl is full the fuel level is about 6mm below the hole that would feed the aux venturi that would feed the main circuit.

 

Could it be that some fuel is slopping around the fuel bowl and possibly dribbling down the aux vent. I don't get this problem if blatting down a dual carriageway and then slowing down for a roundaboout, it only happens on this very tight corner.

 

4.After switching the engine off fuel drips from between the carb and inlet manifold on cylinder 3. The other 3 are fine.

 

 

Fuel pressure is 2.5psi.

New needle valves

Float height is 12-13mm shut off (DCOE 151's with plastic float)

Carbs are properly balanced using the Weber thingymebobby

New Misabs and new cup/rubber/cup mounts

 

No spitting. farting our coughing from the carbs or exhaust whatsoever.

 

Over to you guys.

 

Thanks in advance

 

JOhn

[Roger King]

Variable idle speed is often caused by incorrect setting of the idle mixture screws. It may also be due to an overtight or sticky throttle cable.

 

I'm afraid that it is possible to suffer from surge in the carbs which can let some fuel out of the vent under extreme provocation - make sure that the internal baffle plate is in place. Likewise dripping is quite common. The official float height is 14mm with the gasket in place; it may be worth setting to this although a lot of engine builders prefer 12mm

[John Reay]

Thanks Roger.

 

I have set the idle mixture screws to the highest idle speed and then trimmed back using the idle speed screw.

 

I'll look into sticky throttle cables. I have replaced those as well so that's a good place to look as well

 

I set the float heights to 12mm (gasket in place) as that is what it says in the Weber Tuning manual but setting at 14mm will certainly help.

 

I never had this problem on my old brass float DCOE 18's. Ho hum one of the joys of twin 40's!

 

JOhn