14 replies to this topic

[paul1380]

Hi guys I have just put my weber carb back on my engine.
Engine spec: 1380
Omega pistons
evolution 001 cam (from mini sport)
1.5 high lift rockers
duplex adjustable timing chain
lightened crank
123 distributor (set at 6)

Weber 40 dcoe
Jetted at:34mm chokes
Main jet-115
Air corr-200
Emul tube-F11
Starter jet-120
Idle jet-45F9
Aux vents-4.5
Acc valve-50
Acc pump jet-45
Float set at 15mm

OK now to the problem whilst running no real problem usual jets need sorting but once turned off I am getting fuel leaking from the carb manifold head side. I am using the standard machanical fuel pump not sure if the float is to wide or is it the fuel pump?

Thanks for any advice.

[nicklouse]

you do have the correct floating O rings and holders between manifold and carb and you are not over tightening the nuts?

[Northernpower]

How old is the needle valve and seat?

[nicklouse]

re read it and first thing poor gasket and yes sounds like the float chamber shut off valve.

[paul1380]

you do have the correct floating O rings and holders between manifold and carb and you are not over tightening the nuts?

Yep I have the correct o rings and no not tightening them up to tight down loaded a weber manual in pdf and found out just how tight to tighten them.

[paul1380]

New neadle valve and new seat what should I set it at?
And will the mechanical pump be OK as not sure what pressure it is as I have read for weber 3-4 pressure.
And thank you for the information guys.

[Northernpower]

New neadle valve and new seat what should I set it at?
And will the mechanical pump be OK as not sure what pressure it is as I have read for weber 3-4 pressure.
And thank you for the information guys.

 

Have a read of this

 

Needle and Seat, and Fuel Pump Selections.

The selection of the needle & seat size depends not only on engine horsepower, but also on the fuel pump output - which must be sufficient to supply these needs.

The standard new S.U.electric pump delivers about 7 gallons/hour or 32 litres/hour, which is adequate up to approx.90 to 95 b.h.p.- as a rough guide.

However, some opinions suggest a higher output of 4 to 4.5 litres/hour pump output is required per 10 bhp.in high performance conditions.

Up to 90bhp.- a needle & seat (n/s) size of 1.5 to 1.75 would be adequate, and at around 100bhp. a suggested size would be 1.75 to 2.00 (which possibly could require a pump output of up to 7.5 - 8 gals./hr.-borderline for the S.U. pump at sustained high power levels).

Above this level, a higher output pump will be needed. At around 110bhp a 2.00 n/s size, and around 120 bhp. a 2.25 n/s size is suggested, which would require a pump that could deliver at least 9 to 10 gals./hr.(40 to 45 litres/hr.).

 

Float Setting.

This is critical to avoid flooding, and to ensure proper functioning of the jet systems. Remove the carburetor float cover, remove the pivot lever and float, and check the condition of the needle & seat, and the suitability of the size.

Following this check and selection, reassemble, and hold the cover vertically with the floats hanging down so that the float tongue is in light contact with the needle valve ball. The distance between both floats and the cover should be adjusted to be a level 7mm. (with the gasket in place). The distance on full float movement should be adjusted to be 15mm. This leaves a full working float range of 8mm.

[paul1380]

Wow thank you Mr.7 port I will double check the size of the needle and I will rejust the float tomoz and I'll let you guys know.

[Northernpower]

Wow thank you Mr.7 port I will double check the size of the needle and I will rejust the float tomoz and I'll let you guys know.

No problem, if you're wondering how to calculate the 7mm just use the shank of a 7mm drill bit.

[paul1380]

Ok latest up date readjusted the float to 7mm and checked the neddle and seat they are 1.75 and it is still leaking fuel?

I have been thinking that it might be pumping to much fuel in via the fuel pump so will get a fuel regulator and see what happens.

Thanks again for all your in put.

[nicklouse]

mech pump normally has not enough fuel problems. which is why most people switched to electric with a regulator.

[paul1380]

Ok but wonted to run it with the manual pump less work lol

[nicklouse]

Ok but wonted to run it with the manual pump less work lol

yes an like i said we tended to find there was not enough fuel. so i would say you need to really check the float needle valve and what pressure it is holding pressure to.

[Magneto]

I have a friend who just installed a weber on his Sprite, it also leaked till he put a pressure reg on it set to 2.5lbs, with that in place he's had no further problems. Same mechanical fuel pump.

[paul1380]

Ok thank you ill get a regulator fitted :)