HELP PLEASE Carburetor tuning question....

[mfrias2nd]

First off thank you all for taking the time to view my post. I can see this is a very tight and friendly community.

I'll try and make this quick and painless...When I first picked up my new (used) R65 the idle was so rough that every arm muscle was getting a workout. Also due to 1 carb leaking I picked up the rebuild kits and got busy. after 1 carb was done and put back together the bike fired right up and the vibration smoothed out significantly so went to work on the other carb...here's the problem....the bike didn't want to fire right up anymore. I had to hold down the throttle for it to fire up and when it did fire up thank goodness it stayed on. Now this next part may also be related to the faulty start up but the throttle response is very poor. When I quickly pull back to rev it up it has a slight delay and if I slowly start to rev it it revs up rough then evens out. However, it's idling beautifully. Any thoughts?

I've spent all morning reading up on carb rebuilding and tuning, timing, etc etc...figured I'd try here...

Thanks again!

[Barry]

When I quickly pull back to rev it up it has a slight delay and if I slowly start to rev it it revs up rough then evens out. However, it's idling beautifully. Any thoughts?
 

Sounds to me like it might be a throttle sync issue. ie the carb butterflies are not both opening at exactly the same time. Opening the throttle real slow is always a good test of  throttle sync.

[mfrias2nd]

Sounds like a good place to start! Maybe the throttle response was shaky before but I didn't notice because of the sever idle vibration.

[Bob_Roller]

What parts did you replace when you rebuilt the carbs ?

Can't tell where on planet earth you call home .

If by chance you purchased and installed 'pattern' carb diaphragms from Motobins, they have caused problems by not being flexible enough for Bing carb usage on BMW motorcycles .

[mfrias2nd]

I purchased the rebuild kit from Eubmw.com read somewhere this was the place to go. All the rubbers and gaskets seemed to match what was taken out. I didn't make any adjustments to the throttle.

[nhmaf]

Hmmm.  Chances are that the EUBMW parts are pattern copies, but, they may still work OK.  The major problem that people have experienced is with the rubber diaphragms - unless you buy the real deal from Bing, sometimes the rubber is good, sometimes it is too stiff/inflexible to work well.  Fingers are crossed for you - there are a number of things to checkout first before we get to that level of detail.

[montmil]

Might not be just a carburetor issue.

If you've not yet done so, check and set valve lash. Valve clearances can make a difference in starting and running performance.

Also, check ignition timing, spark plug condition, plug wires and caps, compression, fuel filter -you have one, right?- and condition of fuel lines as they can deteriorate and create fuel flow problems. Do you have the OEM coil? Commonly known as the Crack-O-Matic, this item has a nasty habit of developing hairline cracks that render both it, and a smooth running engine, a thing of the past.

Go ahead and change all lubricants: engine, trans, driveshaft and final drive. You will establish a needed baseline for future maintenance.

The links provided are excellent guides to the care, rebuilding and tuning of the Bing CV carbs.

My favorite for Bing synchronization; after a complete rebuild of both carbs:
http://www.airheads.org/content/view/183/98/

Snowbum is one of the high gurus among Airhead technical information. He knows of what he speaks and writes regarding BMW Airhead Boxers.
http://bmwmotorcycletech.info/technical-articles-list.htm

What is the model year of you R65? That info can be important in advice offered.
Where are you located?

Monte

[tvrla]

If I read this correctly, your problems started after rebuilding the second carb. Is this correct?

[steve hawkins]

HAve you put the choke circuit in back to front.  They are sided.....

[mfrias2nd]

Hi everyone...it's an '82.

Yes I noticed the throttle response wish iffy after the 2nd carb was rebuilt. I also replaced all the fuel lines, flushed the tank, soaked and rebuilt the petcock with new gaskets, filter and o'ring.

Now, the only thing I remember doing when I was putting the carb back on the bike was turning the screw on the throttle adjustment linkage when I thought I was turning the barrel screw into the carb. I don't know if that makes sense but I realized what I was doing and sort of eyeballed it back to position. Could this have tweaked my cable synch off enough to cause this problem?

[Bob_Roller]

If you turned the idle speed adjustment, most likely it needs adjustment to synchronize the carbs .