Dellorto Carburettors

byron · Mar 31, 2020

I’m just in the final stages of completing the restoration on my 76 R90s. I had the carburettors professionally rebuilt about three years ago at the beginning of the project and now I’m installing them. I have set the mixture screw at 1 1/2 turns, the idle screw at one turn and the needle at the third notch from the top as a starting point. Also each throttle cable has about 1 mm of play in it.
My concern is I have no experience of these pumper carburettors and I am wondering if they need to be primed or will the pumping orifice fill on its own.

Khulu · Mar 31, 2020

A '76 R90S

What colour? :bow

byron · Mar 31, 2020

Khulu said:
A '76 R90S

What colour?

Orange

byron · Mar 31, 2020

Here is the Dellorto

Khulu · Mar 31, 2020

Lovely, my poster on my bike stable wall is the silver / grey smoke but I don't have the bike yet!

One day, hopefully!

theoneandonly · Mar 31, 2020

take out the screw , at the top , on the far side of the bottom picture , next to the triangle, and with a clear bit of hose suck the fuel up. battery overflow pipe works well.

change the plastic fuel inlet for a metal one.

byron · Mar 31, 2020

theoneandonly said:
take out the screw , at the top , on the far side of the bottom picture , next to the triangle, and with a clear bit of hose suck the fuel up. battery overflow pipe works well.

change the plastic fuel inlet for a metal one.

Thanks for the information, in the Haynes manual it is described as the accelerator pump valve ? Which looks like a brass valve with a screwdriver slot on the top left of accelerator pump.. Does it need to be full to the top with fuel ?Do you have the plastic caps break down quickly then?

mikeyboy · Mar 31, 2020

Just wind the throttle from closed to wide open,1/2 dozen times,they will (edit should)prime them selves,
You will be able to see the fuel coming out of the jet,
Have a good look at the pattern of the “squirt”.
The non return valves (both in the float bowl and the brass one pictured)can be problematic it they get gummed up .
Also worth a looksee is the plastic actuator lever for the pump,they can wear and reduce the stroke of the pump causing flat spots on pick up.

byron · Mar 31, 2020

Thanks so much for all the help Fellas

harry the cat · Mar 31, 2020

So that's a proper thread with helpful responses from people who know what they're talking about. Well done :thumby:

Deleted account 220319001 · Mar 31, 2020

Usually the jets are brass with a screwdriver slot.

Dellorto Carburettors

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