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Rebuilt VHB 29 Carbs don't run real well

SirKeppa said:
Hi Amboman.. i am by far no expert with carbs. I understand how they work and thats it. By saying this is the correct srew you mean it is a working replacement screw right?
I am asking because the original mixture screw looks slightly different from that newer one WE are talking about. It basically has a shorter nose tip as the original screw that can be found in a untouched VHB-29.
View attachment 29161
Left is the new one and on the right the factory one.

Now my question is if that contour change effects the air adjustment? If you guys say it should work fine with that different nose tip i have to look further why my Eldorado wont run now.

I am a bit confused because i get messages from "it wont run with that screw" to "wont make any difference"


Thanks!
Click to expand...
The one on the right is not the correct screw for a VHB as used on an Eldorado. The one with the long tip was referred to here in the US as the "EPA adjuster screw" - it was part of the modifications done to PHFs to help Guzzi meet emissions standards in the early '80s.

I'd be looking for other reasons why your Eldorado won't run.
 
Okay, thank you very much for that information! Thats interesting.
The reason why I mentioned that longer tip version is because its shown on Greg Benders site and it looks like the one that was installed in my VHB-29 before.
Anyway that tells me the carb should run with both mixture screws so I will stick to that newer ones now.

Edit: I can still use that shorter tip screw with the factory Eldorado jets setup right?
 
Someday, I will have to write a guide here about carburetors.

To understand why your bike is doing what it is doing, you need to understand what part of the carburetor does what and when. This knowledge will tell you which part to focus on.

The mixture needle only affects the mixture in the carburetor at idle.

The slow jet controls fuel delivery at Idle - 1/5 throttle.

The main jet and needle affect 1/5 throttle and above.

Do you have the Dellorto manual? You can grab it free from my Google Drive here:

 
Last edited:
SirKeppa said:
Edit: I can still use that shorter tip screw with the factory Eldorado jets setup right?
Click to expand...
The VHBs on an Eldorado came with the shorter tip screw, so yes. The rest of the jetting from the factory: 45 idle jet, 145 main jet, 265 atomizer, V5 needle (middle notch), 60 slide, 80 starter jet.
 
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