It runs!!!

[Ventodue]

I gather that rubber seat is not replaceable because I did install a carburettor kit from Dellorto and there was no such part in the kit...

Correct. It's not in the overhaul kit. It's sold as an integral part of the enricher piston, part no. 0615.27.238. Cheap and still widely available - Ducati Paddy, Ducati Vintage Store, Moto Guzzino etc.

Any suggestions as to how one would check if it is seating correctly?

Attach a small bore tube to the pick-up jet where it protrudes into the float bowl and try to blow up it. If any air passes, the seal of the piston is cooked.

Does anyone use a VHB carb with these singles?

(Not sure what you mean by "these singles", but ...) Yes, on my 450 SCR.
Idle jet size? 45.

On some forums (Laverda, Guzzi), I have read about the air passage being fouled and constricting air and causing a rich idle mixture or flooding. I am going to have a look in from the top and try soaking that passage with carb cleaner...

This is a problem most usually associated with the PHF range of carbs, and normally manifests itself by a lack of response when tuning the mixture screw.

[Ventodue]

<snip> Plug wetness has returned in full force.

(As well as having too big an idle jet ...) Flooding can be caused by the float height being too high (not to be confused with the float valve itself not sealing properly. That normally results in fuel leaking all over the place ...)

Here's the specification.

VHB float height.jpg

You need to have the carb on the bench to check it.

[MonzaMan]

Thank you Ventodue.

I did not mean to disregard your advice. I am also convinced the idle jet is (way) too big.

I just could not comprehend how it used to work in the first place (20 years ago the bike ran well) and did not want to compound problems by introducing a new variable. I will go ahead and order a couple new jets. In the mean time (will likely take several weeks), I will attempt to cover all other suggestions made here.

From what I have seen after a quick look, the suppliers have been in Europe. Are there any decent suppliers of Dellorto parts in the US that might be a bit quicker for me here in Canada?

Just saw your latest answer. I did adjust the floats lower (close needle at a lower level) arbitrarily without measuring and it did not change anything. I will do it again to spec.

Thanks.

[mrkprsn]

I think Bevel Heaven has carb parts https://store.bevelheaven.com/Jets/

[Duccout]

Moto Guzzino, or if you have trouble, I can recommend Eurocarb in the UK.

Cheers,


Colin

[Ventodue]

<snip> Are there any decent suppliers of Dellorto parts in the US that might be a bit quicker for me here in Canada?

My first port of call would be Guzzino (as previously mentioned! and subsequently noted by Colin).

And there's Eurotrash Jambalaya. He'll sell you an enricher piston for $7.60, I see. Altho' somewhat curiously, he's not listing any idle jets ...
https://www.eurojamb.com/collections/de ... zzi-ducati

And Steve Allen (Bevel Heaven), as mentioned by Mark. Just be aware that Steve, as a Ducrappi twin man, deals with the PHF range of carbs; so just check the Dell part numbers to make sure that what Steve sells fit the VHB range.

And in Canada itself, there's always my old mate Wolfgang Haerter over in BC. Wolfgang's a Laverda man, but some of the early Lavs used VHBs, so you could always check in with him:

Wolfgang Haerter
Columbia Car & Cycle
357 Shakespeare Ave.
Nakusp Canada

Tel.(G): 001 250 265 4502
laverda@lightspeed.ca

HTH

Craig