running great but surprised by carb settings

[StephenG80]

Hi - Just been out on my '54 G80 after doing a final tune of the carb, as the last plug chop from 60 mph things looked a little lean. The Carb is brand new mono block supplied and jetted etc by club spares (as standard on '55 I think). Anyhow I ended up with the needle on its highest setting (lowest groove). Engine runs really well, low tone exhaust note, picks up beautifully, cruises effortlessly at 6o - 65mph on pretty small throttle opening once up to speed. Little bit of vib at 50mph but clears at higher speed and nothing to worry about. On throttling off lots of engine breaking and no hint of any popping. So, not intending changing anything as I am a happy bunny now, but I am surprised at where my needle has ended up. Is anyone else running their needle on the highest setting (ie lowest groove)?

[Harry44]

As in another thread I've adjusted the fuel level on mine and gone up two main jet sizes. Modern fuel has Ethanol in it which contains an oxygen atom in its molecule so it makes sense to run a richer mixture.

[Groily]

Am having to run a 389 on the richest needle setting on my Model 31. Which surprises me too. And that's having upped the pilot jet a size too. Plugs about right and pick-up etc like your G80. Float level correct, no air leaks, so no faults that the settings are trying to compensate for as far as I can see. I've been happy running it this way, but have wondered about it from time to time.

[StephenG80]

Oh well, learn something new re the ethanol and extra O2 being available, thanks for that insight Harry. As everything seems running so well, first gear is not really engaged for any length of time at all - I am sure she could handle a bit more gearing without much depreciation in acceleration - so starts another journey!

Am I correct that standard engine sprocket is 21 teeth? - has anyone tried a 23 tooth one?

[raffles]

You wont find a 23 tooth sprocket unless you have one made. Try going up one tooth on the final drive sprocket
Tony

[StephenG80]

Tony - would I not need to go down in number on final drive sprocket i.e. on the rear wheel or were you referring to the gearbox output sprocket?

[SPRIDDLER]

Tony - would I not need to go down in number on final drive sprocket i.e. on the rear wheel or were you referring to the gearbox output sprocket?

Yes. To be pedantic, the gearbox sprocket is generally described as the final drive sprocket since the one on the rear wheel is a 'driven' sprocket.
Although the gearbox sprocket is a driven sprocket relative to th'engine sprocket........



(Now, where did I put that anorak? ).

[StephenG80]

love it - a pedant within the pedant - OK so if one wants to up the gearing is the general consensus to change the most hard to get at sprocket then ie the gear box output sprocket? by a tooth or two teeth? - or do some folk take the route of reducing the final "driven " sprocket on the wheel by say 2 teeth? (I was thinking with the latter it would be relatively easy to get a sprocket made up or adapted and then put onto the hub (obviously old sprocket would be machined off).

Anyone "knowledge" gratefully received.

[SPRIDDLER]

love it - a pedant within the pedant - OK so if one wants to up the gearing is the general consensus to change the most hard to get at sprocket then ie the gear box output sprocket? by a tooth or two teeth? - or do some folk take the route of reducing the final "driven " sprocket on the wheel by say 2 teeth? (I was thinking with the latter it would be relatively easy to get a sprocket made up or adapted and then put onto the hub (obviously old sprocket would be machined off).

Anyone "knowledge" gratefully received.

(It's o.k. I've found my anorak under a box of the wrong type of rivets).
.
If a finished rear sprocket sprocket isn't available this company will supply blanks for others to machine..........maybe give them a call?

http://www.sprocketsunlimited.com/

[StephenG80]

thanks Spriddler -that link may prove useful. However, I have sussed out that modern equivalent size of chain is 530 (I think) and 40 tooth sprocket for that chain size is used on a duke - so should be quite simple and I don't have to strip down the primary drive (again). Dropping two teeth at the rear is about 4.8% increase in gearing. Which means plodding though town in 3rd as opposed to 4th but slightly less frantic at 60mph when cruising. I am sure others on here have tried similar changes but can't find anything on the forums