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Dellorto Carb Differences

Guzzi_don

Guzzi_don

Tuned and Synch'ed
Joined
Jun 2, 2012
Messages
27
Location
Sydney, New South Wales
I have completely rebuilt the VHB carbs on my T4 (same as T3), replaced all jets, needles, floats, needle & seat, etc.

I have synched the carbs with vacuum gauge.

I have set the timing, correct at 4000rpm.

I have set the tappets to correct size.

I have set the idle mixture screws using the colourtune and highest idle method and to obtain the correct colour and best idle mixture the LH idle screw is only 1/2 a turn out from fully bottomed whereas the RH screw is a full 2 turns out.

Can anyone suggest what might be causing this?

Thanks in Advance
 
I've noticed what you describe on many bikes where the idle mix adjustment is best with the screws at different settings. I believe it is due to casting/machining differences in the internal passages of the carbs. As long as you get her to run correctly, I wouldn't worry about it.
 
john zibell said:
I've noticed what you describe on many bikes where the idle mix adjustment is best with the screws at different settings. I believe it is due to casting/machining differences in the internal passages of the carbs. As long as you get her to run correctly, I wouldn't worry about it.
Click to expand...

Thanks John, my mind is at rest. Although it is idling very well now, I still need to take it for a ride to make sure it is running ok at all throttle openings.

Cheers
 
Did you check your starter cables for free play?
Did you also replace the starter valves, or at least checked the valve's rubber plugs for tightness?
Finally, you can change your idle jets cross-wise. Does the idle setting change also? Then you may have a wrongly stamped or faulty jet.

good luck Hannes
 
I have the same idle jet setting at very different turns. Problem remains for me that the bike idles well, but doesn't like to come off idle, hesitates to gain rpms until past 2k or so.
 
wicks said:
I have the same idle jet setting at very different turns. Problem remains for me that the bike idles well, but doesn't like to come off idle, hesitates to gain rpms until past 2k or so.
Click to expand...

This is an indication of the carbs not opening together. I know you have said you synchronized the carbs, but if you are using old cables, then may not allow the carbs to open at the same rate. Also with direct control of the slides, if you rapidly open the throttle, the engine will get too much air and bog down.
 
Just had a breakthrough - swapped idle screws (fuel and slide speed both) right with left, and suddenly the bike started up and idled great, with no "choking" revving up off idle. (new viewers, this is a PHF36 set up on an otherwise stock V7 Sport).

Then a discovery - screwing the left fuel mix all the way in revealed no change, so I pulled the left plug wire and with no change, it seems to be idling only on the right cylinder. Replace left plug wire, restart the motor, then pull the right plug wire (still at idle) and the motor stops immediately. Throttle the motor to 2K revs, pull the right plug wire, and the left is firing normally keeping the motor running.

Is this a clog somewhere in the idle fuel route in the left carb?
 
Difference between a VHB30 AS and a VHB30 CS ? Got a VHB30 CD and understand matching for pair would be a VHB30 CS, but wondering if an AS would work...
 
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