1975 32mm bings

[chasbmw]

My r90/6 seems to making progress, it got through the vehicle test today (MOT). I have been chasing a big flat spot from around 2000rpm - 3500rpm, the engine picks up after that. I have taken the carbs apart again and have spent a merry hour poisoning myself with carb cleaner and it looks as if the idle circuits are now clear.

The bikes bings (64/32/12) do not have springs above the diaphragms, and they are not shown in my parts book, would they be of benefit and if so is there a choice of which to fit?

Charles

[Garnet]

The springs from a /7 would be the ones to try.

Are your carbs at the correct base settings? Needle position, needle jet size, idle jet and idle mixture all at base?
There should be no need for springs unless you are experimenting with different mid-range settings. Do you know if the slides are correct? I do not know where the numbers are stamped on them, and there are different ones. They will also affect mid-range.

[chasbmw]

All is at base, the springs question was more of a musing wondering whether or not the springs would work.

I seem to be fairly sure that all the mini holes are clear in the carb body, so hopefully the bike will run good after the carbs go back on in a couple of hours.

Charles

[Roy Gavin]

I have found that auto injector cleaner cleaner works fine to clear the passages on Bings - just add a stiff dose to a full tank and you will probably notice the difference before the next fuel stop.

The Bings with springs above the pistons have different jets and needles to those without, and there is a possibility that someone has fitted the latter items without adding the spring.

So add the spring, the latter one is stiffer and works better, and see how you go. If too rich raise the needle a notch or two..

The speed that you open the throttle has an effect on mixture too - you dont want to open the throttle much faster than the revs are picking up, particularly if your mixture is on the rich side,

[chasbmw]

Thanks Roy, I should be off to Greece in a week or so so will leave mucking around with springs for now, it is running much better now, hopefully even better after I rechecked the float heights !

[Roy Gavin]

Yes, fuel level makes a big difference to running and smoothness, but it doesn't get a lot of air space.
Getting it right probably makes a bigger difference than twin plugging , and it costs, err, a lot less.
Snowbums site has the procedure for setting the fuel level in the bowl which is the bit that counts

[Garnet]

Yes, fuel level makes a big difference to running and smoothness, but it doesn't get a lot of air space.
Getting it right probably makes a bigger difference than twin plugging , and it costs, err, a lot less.