What to try next?

[bob654]

Its stock except the V and H exhaust. and they say to change  the jets to what I have in, atm. Air Filter has a rubber 'snorkle' type thing on the back which is clear. Floats today.

[Poldark]

Stock jetting is wrong.  He said it is a US import bike.  They came from the factory jetted too lean in order to meet US environmental regulations.  The idle mixture screws were pre-set and capped off (easy to remove caps though).  Our fuel content has changed a lot in the past 40 years.  I don't know much about fuel in the UK, other than it's probably better but more expensive.

If your bike is a US-California model, may God grant you patience to work on it.

[bob654]

This morning I checked the float height, which was correct. I checked the plugs which were very sooty, so figured even with the Airbox side opened it was too rich. So I  cleaned the plugs, reset the air/fuel screws and replaced the 115, ( V and H recommended main jet size), with standard (?) 102.5 main jets.

Trial run with the Airbox open showed  great acceleration and easily exceeded 100mph, on a private road, so I was very pleased. I replaced the Airbox side and set off again fully expecting a poorer performance this time.

Fantastic result even more responsive if anything, revved right through the range quickly and easily, I backed off at 105mph in 4th. 

I still have fine tuning to do, no doubt

Thank you all. Although some opinions have been divided, all have been useful, and I am grateful for all the advice and information. Ride on.

Edited July 7, 2022 by bob654

[Poldark]

Glad to hear it's running well.  Sounds like your fuel runs well with the stock jetting.  Does your fuel contain corn-based ethanol?   

[bob654]

As little as I can buy our best fuel is 5% most is !0%.

[Gixer1460]

1 hour ago, bob654 said:

As little as I can buy our best fuel is 5% most is !0%.

If you use ESSO Synergy Supreme 99 . . . . . . 

Quote

Although our pumps have E5 labels on them, our Synergy Supreme⁺ 99 is actually ethanol free (except, due to technical supply reasons, in Devon, Cornwall, North Wales, North England and Scotland). Legislation requires us to place these E5 labels on pumps that dispense unleaded petrol with ‘up to 5% ethanol’, including those that contain no ethanol, which is why we display them on our Synergy Supreme⁺ 99 pumps.