Float levels - Evaporation

Well it's not a new topic! but with the wet, cold & windy stuff outside I thought I'd address an issue I had in the 'summer'. New carb bodies & brass chromed slides transformed the mileage this year but I've experienced fuel starvation in heavy traffic (lots of idling). On the Friday Donnington NOC day it got really bad and refused to restart waiting for a track session (10mins tickover). Of course everyone assumed I'd flooded it but with nothing to lose a heavy tickling of the carbs got it started.
Now I have the tufnol spacers in place and that day it was about 20C. It has done it since after being turned off and left for an hour or so. The float levels are 080" below bowl edge. Nothing else has changed other than the new bodies and brass slides. Draining the carbs gets me 30cc from each but it takes 50cc to fully lift the float and shut the valve (bowl off the bike), I haven't figured why though it's probably obvious! Does anyone deviate much from the 080" setting? Cheers.

Keith1069 said:

Does anyone deviate much from the 080" setting?

Click to expand...

Apparently that .080" recommendation has been out of date for some time, and I've always considered it was too low.



According to Burlen what we should all be checking is this:

"The correct fuel level for all Mark 1 Concentric carburetters is 0.21” plus or minus 0.040” below the top edge of the float bowl. Thus when the needle valve is being held shut by the tangs of the float, the level of the fuel will be between 0.17” to 0.25” (4.33mm to 6.35mm) from the top of the bowl.


The 0.588” seating depth was modified in May 1972 to 0.579”. In April 1974 an adjustment to the slots for the float spindle also lowered the float. The seating depth was further reduced to 0.574” in May 1986 and has remained as that ever since. In this position the fuel level is correct when the top surface of the float is parallel with and just above the top of the float chamber when the valve is closed."

http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=13

Many thanks Les, I missed that update. With the 080" float position, bowl horizontal and the float shutting the valve, fuel is just below the edge. Angled down as it would be on the bike it 's just about to overflow.
Cheers and a Happy New Year to you and all for 2010.