RUNNING RICH but NOWHERE TO GO!

[ANLAF]

Since the rebuild top end last week I've had several test rides to get the timing and carbs set-up correctly - I noticed black powder on the end of the exhaust pipes, and my fellow riders smell the unburnt fuel from my exhausts.

My 76/77 carbs are set-up correctly with 27.5 pilots, 135 mains, jet needle raised to #2 position (all to compensate for the pods and through exhausts), and the mixer screw is 1.5 turns out.

I don't want to simply mess around with the settings - the last thing I want is to run hot, but the plugs are getting pretty black, too, and shorting the spark coming off the throttle (to add insult to the injury of a hanging throttle).

Short of raising the jet needle to #1 and turning the mixer screw in to lean - there doesn't seem to be anywhere to go - or is there?

Can anyone help?

Anlaf

 

[5twins]

You might try leaning the float setting by a MM. The spec for that carb set is 25mm ± 1mm. Try them at 26mm. You could also go down one on the mains to a 132.5. Contrary to what many seem to think, straight pipes don't flow all that well. Massive re-jetting isn't usually needed for them.

The '76-'77 carb set I ran for a while on my bike was jetted like yours except I used a 132.5 main. That was the largest it would take. I have pods and the Mike's Commando exhaust, which probably flows better than your straight pipes.

 

[ANLAF]

Thanks, 5twins - just after I posted I realised I hadn't mentioned my 25mm float setting (the one you recommend in the Carb Guide), and wondered if float-setting could have anything to do with the lean/rich mix. You have answered my question there. I will go in and increase to 26mm as you advise. As always, much appreciated.

As for the main, I will order some 132.5s.

Anlaf