Help with carb balance & tuning

[williamemack]

Anybody out there who can help me tune my carbs. If you're within an hour of Moultonborough, NH, I'll come to you. Most of the problem seems to be idle.

Will   603-253-6436

[Barry]

Hi Will,

I'd be glad to help if I wasn't several thousand miles away.  Looks like you are in a nice part of the world.

[montmil]

Hi, Will

Your sig line would indicate you've owned a passel of Airheads, too.

Couple questions that I assume you're asking about your 1980 R65:

1. Have you checked valve clearances? Incorrect valve lash has a bearing on idle quality.

2. Same question about ignition timing. All good there?

3. Are the vacuum takeoff screws (or rubber plugs) in place on both Bings?

4. Are you experiencing high idle rpm's or a low idle stumble? High idle -not returning to the proper and calmer revs- can sometimes be traced to sticky advance weights in the bean-o can.

5. Have you recently been into the carbs?

I've attached a pdf at the bottom of this post. I have found this to be my "go to" technique for carb balancing. Hope it helps you.

let us know a few more details and we can provide better answers.

[nhmaf]

I'd be willing to give you a hand but I've just started on a new contract, so I've less free time than I have had earlier this summer.   I'm thinking of going to a club picnic on Sunday, but maybe we can shoot for sometime on Saturday?  You can PM me and I'll give you my phone #s, etc.   I've been thinking of coming up with an excuse to stop over at the police motorcycle museum in Meredith sometime this month anyhow.

Mike

[quixotic]

Until about a month ago, I had never tuned any carbs at all.  If you find no one close by, I would heartily advise building a cheap manometer.  I made one out of an old yardstick and some clear tubing and some ATF fluid.  Then I distilled the important bits out of Snowbum's page on the matter.  Then I started practising.  The only real screw up occurred when things were so out of balance initially that the ATF fluid snaked around where it shouldn't have gone (but not into the engine).  Now I know enough to quickly turn the engine off if the fluid is REALLY unbalanced, and then adjust.  Then turn the engine back on and quickly observe if my adjustment went the right way or not.  

It's just a bit of trial and error.  I'm still learning, but I did it again last night after installing sport bars (and shorter throttle cables).  Now at least I have a bit of confidence under my belt.  

But check all the stuff that Montmil mentioned first.  

[montmil]

... I would heartily advise building a cheap manometer...  The only real screw up occurred when things were so out of balance initially that the ATF fluid snaked around where it shouldn't have gone...  

Had that same issue after rebuilding the carbs on the '81 R65 and attempting the initial balancing.

I eventually clipped the vinyl tubing in the area of the Bings, inserted a one-inch length of smaller i.d. tubing, then replaced the last bit that matches the Bing vacuum take off attach.

Slowed down the movement of the ATF (also BMW fork oil) which allowed additional time in tweaking the low speed circuits.

I have had some of the fluid get sucked into the carb. No harm, no foul but a helluva lotta smoke.

Told my neighbor I was fogging the mosquitoes.  

[georgesgiralt]

I own a manometer once used in jet aircraft engines (for some sort of tests). Of course, due to it's age it uses mercury as the liquid but it is made using the U tubing principle as are the homemade variants.
The thing really good about this unit is that it has two reservoir at the top of the tube. (A pair of cylinders around 3 cm dia and 10 cm length ).
This way, if really out of balance, the mercury will be sucked on one side and accumulate into the reservoir instead of being sucked into the engine. Clever design !
Also, it has a bolted connection to the U tube. The part of the U tube entering the reservoir is affixed by a nut, and has an Oring on top of it. When you screw the nut, you compress the O ring reducing the passage for the gaz so damping the instrument ! If you screw it fully, the seal becomes air tight and the mercury column is not moving anymore, whatever the depression is.

[nhmaf]

I gave up on messing with messy liquids and invested in a Morgan CarbTune (it uses stainless steel slides inside glass tubes - a rotameter, if you will).  Especially handy when working with 4 cylinders' worth of carbs!

[williamemack]

nhmf kindly gave me a hand this afternoon. We concluded that the problem most likely lies with the right carb float and/or float needle, but the bike now runs well enough so that I will wait until winter to get into the carb. THANKS MIKE.

[nhmaf]

Hi Will,

It was a pleasure to meet you in person and chat!   I probably should have spent more time working on your problem than chatting, but I'm happy that I was able to be of some help.   Perhaps we'll get in a ride or two before your southward migration.

[williamemack]

Call Duncan of Duncan's Beemers this afternoon and he said that I might be able to drop the bike off with him on short notice and he could do all the good things Mike and I didn't have time to do. Hopefully I will be able to return to NH with the valves checked, the floats checked and an engine that is as smooth as it should be.

[nhmaf]

OK Will - whichever way you'd like to do it is fine!
Keep me posted, we've got some good riding time yet.

[Luca]

a 3/16 vacuum restrictor (usually available at big box auto chains) will also calm the vacuum fluctuations and slow the oil down a bit in manometers.  Plumb them as close as you can to the carb end of the manometer.

Got them on my liquid filled grade A 0-30" hg vacuum gauges and they read super smooth.