The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: rob650 on March 23, 2015, 12:43:08 AM
-
Thanks in advance for any advice.
After rebuilding both carbs, my right one doesn't want to fill up its float bowl. Fuel flow to carb is good. Check for obstructions with the carb body, none found. Im thinking i am incorrectly connecting the float needle (The triangular shaped "plug" with the springy post) to its floats, via the thin wire clip. Si there a predetermined amount of space that is supposed to exist between float and spring when assembled? or just keep at it with Trial and error?
Thanks.
-
sound like the tab has been bent and the level is set too "low". Most manuals have a section on setting the float level. It is a fiddly job to reassemble, but difficult to get wrong I would think.
Wish I'd seen you post earlier as I had the float bowls off mine this afternoon to fit new bowl gaskets and to also check that the alcohol laced fuel I had to feed it on the weekend has done no harm, I could have taken photos as I did check the levels.
-
The float should be level without pressure on the spring
If you hold the carb upside down the spring is going to compress giving you a incorrect setting.
So you want to check the float level by holding the carb at an angle were the tab touches the needle but does not compress the spring
-
mrclubike, are you saying that as i hold the carb upside down and level, the floats should also hang level and NOT be compressing the float needle in any way?
-
Make sure the small wire clip is not between the plunger on the needle and the tang on the float.
mrclubike, are you saying that as i hold the carb upside down and level, the floats should also hang level and NOT be compressing the float needle in any way?
He's saying that while the float should be level when the needle seats, you can't turn the carb upside down because it compresses the plunger in the needle. Just hold the carb upright and then slowly roll the carb over until the float starts to swing the other way and presses on the needle. The carb will be rotated slightly past horizontal.
-
Make sure the small wire clip is not between the plunger on the needle and the tang on the float.
mrclubike, are you saying that as i hold the carb upside down and level, the floats should also hang level and NOT be compressing the float needle in any way?
He's saying that while the float should be level when the needle seats, you can't turn the carb upside down because it compresses the plunger in the needle. Just hold the carb upright and then slowly roll the carb over until the float starts to swing the other way and presses on the needle. The carb will be rotated slightly past horizontal.
Luca is correct
Maybe "level" is not the best way to say it but the float and bowl mating surface should be parallel when the float tab touches the needle without compressing the spring
-
My two cents worth.
Setting float bowl height is a pain in the bum. The smartest thing I've ever read on the topic is:-
"fuel dripping on foot, level too high. Other R65s passing you, level too low".
My method of setting fuel bowl height :-
1/. remove carb from bike
2/. place carb in bicycle service clamp (around diaphragm chamber) and ensure that it is held level.
3/. Connect a remote fuel tank.
4/. Remove float bowl bale and empty float bowl.
5/. Hold float bowl onto carb body with one hand, turn fuel on with other hand - wait 10 secs.
6/. Turn off fuel and remove float bowl and note fuel level.
7/. Depending on whether too high or too low, adjust "tang" and repeat 4, 5 & 6 as necessary until perfect fuel bowl height is obtained.
It is my opinion that getting both carbs as near to equal height is a little more important than the actual height, that is to say if the height is in the ball park I concentrate on getting the two carbs equal rather than both pedantically set to the "correct" height.
Additional steps that may or not be necessary.
Ensure that float needle actually seals - if not and there is an apparent "rim" near the top of the float needle, or you have been forced to use Government mandated alcohol contaminated fuel, swear and curse a lot and order new float needles - no riding for you till they arrive.
I used to laugh at Snowbum's admonition to buy a few spare clips - until I lost one that was, now I keep a couple of spare clips, you probably should too, stick them in the same baggie as the spare alternator brushes, alternator brush springs, seat hinge retention circlips and spare fork damper rod piston rings - you will use them all one day.
While waiting for your new flat needles, buy toothpicks from different sources until you find a brand that approximately matches the taper on the float needle (or whittle your own). coat end of toothpick sparingly with valve grinding paste and apply to float needle seat whilst turning rapidly. Clean up carefully.
-
On the basis that it's the actual operational fuel level that counts I'll add that if you do it with new floats at 12.5 grams and then again with old floats at say 15 grams it will produce different operational fuel levels and therefore different mixtures even if you follow the exact same method and set say 24mm in the float bowl
Just like old Archimedes in the bath, old heavy floats displace more fuel than lighter ones. With floats heavier than new it's not that you can't make them work but with the 'remove the float bowl method' you have to aim for a lower level than with new floats. I suggest at least 1mm lower for every extra gram they weigh over new. This effect is very real and produces a significant difference in mixture strength. Trust me I learned it the hard way.