Dellorto 14mm sha problem

[Benny88]

Hey all.

I was running a dellorto 14mm rep on my cag until it suddenly snaped of where it attaches to the intake manifold so I bought an original dellorto 14mm sha (cheers daz). However since attaching it the bike struggles to run. It will start with the choke on only. After starting the revs will slowly drop. This can be stabalized by slowly opening the throttle to keep the revs a constant idle untill it is fully open and the choke will snap off and the bike dies. It is clearly not getting enough fuel through but the main jet is the same size (if not larger) than the one that was in the rep carb i was previously running. The carb is brand new. I am thinking that there is not enough fuel getting down into the float chamber and it is simply drinking all the fuel up in the chamber (or it is flowing in too slowly) the fuel lines are fine.. I thought I should hit you guys up for advise before I go buying new jets or bending float needles and stuffing things up.

[RD RACING]

by the sounds of your discription this new carby is wanting either more fuel and or less air intake. normally when an engine only wants to run with the choke on it means its got enough air intake or it wants more fuel. i would firstly drain the fuel bowl to see how much fuel is in it, this will indicate fuel to the carby then remove the fuel bowl to check the float is working up / down [ do not bend the float to seat fitting ] if the float is moving freely then you will need to check the main jet for correct size plus you need to make sure there are no air leaks from the carby to manifold and manifold to reed block. check to make sure the manifold is not cracked aswell.

[Glen]

i didnt think the main jet would have a single thing to do with the idle on an SHA, but perhaps im wrong. i cant remember mine at all. but yes start the bike let it run for a few seconds (until it starts bogging) then turn off the fuel tap and unscrew the fuel bowl without spilling any and see how much is in there.

wierd though as all my bikes seem to pick UP revs when they start to drain out of fuel. if its only running when you choke it, seems like theres too much air perhaps from a leak at the manifold

[Benny88]

Well its definatley not the manifold. I managed to jam the old sha rep carb on, (even with a broken attachment) and it runs like a dream. The current main jet has 78 stamped into it. Slowly opening up the throttle will maintain idle speed even tho by then you are bypassing the idle jet. Maybe the tube that runs up through the bore is stuffed or blocked so opening it up is not helping because its running soley through the idle jet and opening the throttle especially with the choke off is then giving it way too much air.

Why would an allegedly high quality italian made carbie be shipped with A: a blockage or B: a jet that is too small for even the smallest of engines?

[ringo]

If it runs better with the choke on (you are artificially richening it up) it is running lean, you need a bigger main jet. Do not ride like this if you can at all you WILL seize your motor! get a jet kit.

[Benny88]

Oh and I have pulled the bowl off and it is full. Ive also attached fuel to it with the bowl off checked the fuel flow in. It all apears fine. Next step I may try and pull every component out of it and put it back together. Maybe ill come accros something.

[Benny88]

Originally Posted by ringo

If it runs better with the choke on (you are artificially richening it up) it is running lean, you need a bigger main jet. Do not ride like this if you can at all you WILL seize your motor! get a jet kit.

If this is the case it should continue to idle with the choke on but it doesn't the revs run down until it stops. opening the throttle can counter this but only till you run out of throttle to open and again it revs down and dies.

Dont think this wasn't the first thing that I thought of

[Glen]

can you not simply swap the jets around then

[Benny88]

you mean from the del rep carb? no cos they have different treads, plus it has a slightly smaller jet anyway, which is also making me think that the problem is not the jet.

[ringo]

try winding the idle screw in a bit some times the idle speed is not set up