Dellorto advice

[JohnP]

thanks Simon, but I doubt it is a blocked filter. I have loads of fuel in the rear carb. Its running out of the carb into the airbox!

John

[ericbushby]

John,
It seems that the rear carburettor inlet valve may be leaking allowing the fuel level to rise too high. Or the float is leaking and has sunk.
It could just be grit and may respond to a clean out.
Best of luck
Eric in Burnley
1967 S3SE DHC

[JohnP]

Hi Eric.

Thank you.

That sounds more likely.

Do you think it is simple to check out those things with the carb in situ, or do I have to whip them out?

I've just bought 9but it will take a few days to arrive) a book about Weber and Dellorto carburettors by a guy called Des Hammill which may help me understand what I'm looking at a bit better.

Cheers
John

[billwill]

The Des Hammill book is good, though he says little about the Cold-Starter device and not a lot about the accelerator pump.

[ericbushby]

john,
I am not familiar with dellorto,s to be able to help much, but they should come apart a bit while still mounted on the head. Take the tops off and compare some things. (if that is appropriate)
Eric in Burnley

[JohnP]

So I popped the top off the rear carb with my first thought being that there may be something stopping the regulator valve closing properly and to check the float wasn't sinking.

I'm interested that I was able to blow air (from the lungs) a little through the valve when closed, and easily when open.

Finding nothing else obviously amiss, reassembled carb and she started on the button and now seems to be fine, so I guess crud in the carb inlet valve was the answer.

Thanks for everyones help.

John

[alan.barker]

Maybe it could be a good idea to buy 2 Viton tipped Float Valves and have them ready if it happens again.
You don't want the front carb to start leaking petrol all over the Dissy.
Alan

[john.p.clegg]

Seeing as this thread has been dormant for a while, I know about setting the float level/weights etc ( 14-16mm )but to take it to a finer tune what I would like to know is the working fuel level in the float chamber. as measured by taking the Main Jet assembly out .

I have read about 27mm with the cover off and 25mm with the cover on but these don't seem to compute..

any help out there ?
Thanks
John

[alan.barker]

I think with the cover in place the level is higher because the floats are in the fuel and raise level.
When you check without cover the level is lower by the volume that the floats deplace
Alan

[john.p.clegg]

Thanks for the quick reply Alan,will set the floats tomorrow and check the working level ( 25mm ) from the top plate , ( 35mm from the jet block.) ..with the top cover in place .

John

[john.p.clegg]

Just an update, set the float to 15mm and dipped the fuel level and yes,35mm
Remove this jet

this is the ref. surface

slide the vernier ( OK? Vince? ) down slowly till you see the fuel surface distort ( not easy,you need to peer down with a good light )

and this should be the reading ( 35mm )

John
P.S. I have read of two ways of setting the float height,the correct one is with the float chamber lid held vertical and allow the floats to just close the needle valve but not compress the internal spring in the needle valve..
( bench vise and magnifying glass needed for the over '60s ) , and it's a doddle if you have an electric fuel pump..

Makes me wonder why I ever stripped the EFI off it...