carb settin gspd
- Thread starter Valker
- Start date
This one comes up so often... Can someone who knows all the wrinkles
put this on the tech section then it will be there for everyone.
put this on the tech section then it will be there for everyone.
nud1e
Registered user
Valker, have at look at this thread
avrolancaster
Guest
(I have not read the thread, sorry)
The haynes manual is very good on this, if you choose to to follow it, it is the official procedure after all.
However, remember that any tuning of X component requires that Y is tip top.
Before trying to tune the carbs. you must have the valve clearences within tolerance and the valve timing and ignition timing spot on.
I have found that if you follow the procedure in Haynes (re: BMW) you can get the setting as near as perfect. Manometers help, for sure, but the modern commercial ones with their solid bars are pants. You are better off making your own.
If you can not get it right with the above it may be because you lack experience with old school set ups and simply need to find someone who can set up carbs. by ear. I remember how humbled I was when my twin weber Mexico Mk1 roared like it had never done before after....blah blah blah
The haynes manual is very good on this, if you choose to to follow it, it is the official procedure after all.
However, remember that any tuning of X component requires that Y is tip top.
Before trying to tune the carbs. you must have the valve clearences within tolerance and the valve timing and ignition timing spot on.
I have found that if you follow the procedure in Haynes (re: BMW) you can get the setting as near as perfect. Manometers help, for sure, but the modern commercial ones with their solid bars are pants. You are better off making your own.
If you can not get it right with the above it may be because you lack experience with old school set ups and simply need to find someone who can set up carbs. by ear. I remember how humbled I was when my twin weber Mexico Mk1 roared like it had never done before after....blah blah blah
i had to balance a pair of guzzi carbs yesterday. to satisfy my curiosity, i used a twinmax, an old style mercury carbtune, and a carbtune II with the solid bars you mention.
i preferred the carbtune II. it was the easiest to use by some way, with no significant error in the reading compared to the others. in fairness, i should mention that i am far more familiar with this device than the others.
the twinmax was easily the worst.
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Rob Farmer was providing this excellant facility FOC at Lumb Farm...I purred all the way home 
Top man
Anyway, as above..the Haynes manual is OK for this procedure...just don't rush it and blip the throttle a few times until you get the 'perfect' balance..................they'll soon go out of sync anyway !!!
Top man
Anyway, as above..the Haynes manual is OK for this procedure...just don't rush it and blip the throttle a few times until you get the 'perfect' balance..................they'll soon go out of sync anyway !!!
Carb balancing without gauges
A good trick I used was to just raise the throttles off tickover so the butterflies were hanging on the cable, not sat on the stops. Then gently push the throttle cables a little to one side, one at a time, if the engine runs more smoothly, that cable neededs adjusting up slightly, if it runs worse it needed letting off a little.
Do this on both carbs so you get a good feel for how the engines responding to the small adjustments deflecting the cables makes before breaking out the spanners.
If your not sure, get the gauges
A good trick I used was to just raise the throttles off tickover so the butterflies were hanging on the cable, not sat on the stops. Then gently push the throttle cables a little to one side, one at a time, if the engine runs more smoothly, that cable neededs adjusting up slightly, if it runs worse it needed letting off a little.
Do this on both carbs so you get a good feel for how the engines responding to the small adjustments deflecting the cables makes before breaking out the spanners.
If your not sure, get the gauges
how i do carb balancing without gauges:
warm engine
disconnect one plug. some bikes with electronic ignition (bmw airheads) need the plug grounding to avoid damaging the ignition module.
raise tickover on other side, then gradually decrease until just above stall point.
repeat for other side.
reconnect everything.
tickover will now be too high. decrease by equal increments (1/4 turn at a time) until tickover is correct.
works best on slide carbs, but should get you in the ball park on CVs too.
additionally, slight corrections can now be done by ear. some
experience needed for that bit.
warm engine
disconnect one plug. some bikes with electronic ignition (bmw airheads) need the plug grounding to avoid damaging the ignition module.
raise tickover on other side, then gradually decrease until just above stall point.
repeat for other side.
reconnect everything.
tickover will now be too high. decrease by equal increments (1/4 turn at a time) until tickover is correct.
works best on slide carbs, but should get you in the ball park on CVs too.
additionally, slight corrections can now be done by ear. some
experience needed for that bit.Pd Carbs
The only other thing I can try ... is to hit it with a very big hammer
In my trade (bricklayer) this is how we get over a problem
first, thanks to every one for there help... bought a carbtune form motor works.. My first problem even before I start.... the L/H side carb throttle screw adjustment is as far down as it will go and I still dont have the 1 mm gap!!! I have tried to adjust the R/H side throttle to see if it will make any differents to the L/H, but it dont... also turn the throttle stop all the out to make sure that it's not stopping me from getting the 1 mm gap on the throttle.
The only other thing I can try ... is to hit it with a very big hammer
In my trade (bricklayer) this is how we get over a problem
Carb balancing without gauges
A good trick I used was to just raise the throttles off tickover so the butterflies were hanging on the cable, not sat on the stops. Then gently push the throttle cables a little to one side, one at a time, if the engine runs more smoothly, that cable neededs adjusting up slightly, if it runs worse it needed letting off a little.
Do this on both carbs so you get a good feel for how the engines responding to the small adjustments deflecting the cables makes before breaking out the spanners.
If your not sure, get the gauges
Absolutely agree - there was always a lot of potential for the carbs to go out of sync and I always found the easiest and quickest was was to do it by ear. If ever I felt that the motor was 'hunting' all I would do would just put a bit of pressure on the cables coming out of each carb in turn until it smoothed out. That told me which one would need a little 'lift' on the adjuster. I have had a set of Davida gauges for 18 years and seldom used them!
first, thanks to every one for there help... bought a carbtune form motor works.. My first problem even before I start.... the L/H side carb throttle screw adjustment is as far down as it will go and I still dont have the 1 mm gap!!! I have tried to adjust the R/H side throttle to see if it will make any differents to the L/H, but it dont... also turn the throttle stop all the out to make sure that it's not stopping me from getting the 1 mm gap on the throttle.
The only other thing I can try ... is to hit it with a very big hammer
i have seen bmw throttle cables with too short inners that produce the problem you have.
Thats how i do all the airhead carbs, for idle and under load -
i can also do the oil head idle, but can't get the under load quite right
i get to practise twice a day everyday so hopefully will see some improvement on my oilhead ear calibration
Bingo!
Steptoe.. Where can we buy one of those ear calibration thingies
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