carb balancing

[manxr65]

can someone in plain english tell me how to balance the carbs on r65 as i have never done it before , i have mercury gauges
thanks

[Bob_Roller]

First thing, is to make sure the carbs are in good condition internally, no leaky or degraded seals, partially clogged jets, passageways, diaphragms in good shape, rubber hoses between the carbs and cylinder head in good condition, not cracked .

Do a valve clearance check/adjustment .

If you have any fuel filters in the tank at the fuel tap, make sure they are clean, if you have a fuel filter in the fuel line, make sure it's still good .

Check air filter for condition .

Check spark plugs for proper gap and general condition .

Now you can get to the carb synchronization !!!!!!!!!

Get the engine up to operating temperature .

Back off the adjusters for the 'choke' cables, and throttle cables, so the cables are slack .

Next turn the idle mixture screws on both carbs until they stop, don't force them closed, just a gentle 'snugging up', back them out about 3/4 th's turn .

The throttle, back the idle adjustment screws out until they are clear of the throttle arm, then place the thinnest feeler gauge you have between the throttle arm, adjust the idle speed screw, until it catches the feeler gauge, remove the feeler gauge, and then turn the idle speed screws in one half turn .

Start the engine,  then adjust the idle mixture for highest rpm, when you go past the optimal setting, the rpm's will decrease .

Next, is to adjust the idle speed screws so the columns of mercury are the same, then adjust for proper idle speed, general consensus for this is around 1200 rpm .

After this is done, you need to adjust the throttle cables back to where they are supposed to be, then run the engine and open the throttle, and see what the mercury levels are doing, you may have to adjust the cables to get optimal synchronization with the throttle off of idle .

That's about all I can think of, I'm I may have missed something, and other members will add, what works for them .

Good luck in your synchronization effort !!!!!

[montmil]

... and the l-o-n-g version:

http://bmwmotorcycletech.info/synchcarbs.htm

Monte

[raypond]

G'day  manxr65,

All of what Bob said. I built the $4 synchronizers from this article - http://www.airheads.org/content/view/183/98/ - (they cost $7.50 in Oz) and they work a treat. I'd never synced carbies before but had no trouble at all. Your mercury gauges should make it even easier. I think the article confirms what Bob says, the only thing I can add is that the bike needs to be really well up to running temperature. Otherwise you'll be sitting at some traffic lights one hot day wondering why your bike is idling at 2500rpm. Cheers, Ray

[Barry]

Worth pointing out that a typical $4 manometer using say auto transmission fluid is at least 15 times more sensitive than a mercury manometer due to the differences in specific gravity.

The mercury manometer benefits from being 15 times shorter.

[Ed Miller]

The only thing I would add to Bob's list is that the points gap (if pre-81) and ignition timing need to be set correctly.  And Ray already emphasized that the carbs are adjusted on a thoroughly warm engine, not one that has just sat and idled for a while.  

[montmil]

Throttle cables should be synch'd first. The manometer will be very helpful to adjust the idle rpm and confirm carb balance at approx 2500 rpm. Then you can address any idle mixture adjustments, if needed.

The Boxer will run so much smoother, particularly at higher cruise speeds, with throttle cables "tuned". Lots of good help in the Airhead Beemer Club archives plus Snowbum's site.

Monte

[Semper Gumby]

I set my carbs with the procedure from the Bing manual with the help of the Colourtune Plug in place of the spark plug.

http://www.gadgetjq.com/ctune.htm

[manxr65]

i tryed balancing as you all said and i got the carbs balanced ok but i cant get it to tick at all unless i hold the throttle open a fraction ,  if i turn throttle screws it revs up and and will not come down ,got mixture good and cables free ,also sometimes it revs up and is slow to return down again, im ordering new carb kits to rule out problems with inside the carb and new cables.

was thinking about changing to mikuni carbs , has anyone changed there r65 to this. if so what size carbs and jets
thanks

[Barry]

got mixture good  

How many turns out from gently closed did it take to get the mixture good. ?  

The revs hanging up can be caused by a sticking ignition advance but I would explore your carb settings first. You should have ended up with the throttle stop screw approx. 3/4 of tun in from fully closed and the mixture screw around 1/2 to 3/4 out from gently closed.  If yours vary significantly from these settings there is something wrong.

[bubby-joe]

Go slow, very small adjustments they are one of the most sensitive to setup I've ever seen final setting for me are 3/4 mixture and 1000 RPM but getting down to 1000 took a long time to get it right and the yard stick balance tube with 2 stroke oil was a big help and very very sensitive.  It starts very good from cold, near freezing (SPRINGS COMING) I live in the NORTH but it takes a very long time to warm up and give me a good steady idle without the choke lever open full to 1/2, minimum 5 -7 minutes to warm it up just sitting from cold to steady idle.  If you go the Mikuni route stay with 32mm's, pick a pair from a 650cc twin if you can they should be close but jet kits are readily available and there not as sensitive to tune but the idle may take as much fooling with to get just perfect.  There tuned right with a dusty light brown plug after a good run checked right after shut down careful there HOT.  I feel a road trip coming on....