Balancing the carbs

[RoSPA_man]

Hi

I use a home-made manometer - a basic u tube filled with Redex mounted on a piece of wood. Connected to each throttle body, it enables me to balance the carbs simply by adjusting the right hand throttle body crossover cable. By definition, it's always perfectly calibrated and clearly shows when the two carbs are in balance
When I mentioned this contraption to an independent pro, he said that belonged in a museum! While he may be right, it's always worked well for me. So, my question is what else does the all-singing, all-dancing gizmo used by BMW do that the manometer doesn't do?

I'm genuinely intrigued to know what other adjustments can be made - and where do these adjustments happen?

Thanks

[dirtrider]

Quote

 

I use a home-made manometer - a basic u tube filled with Redex mounted on a piece of wood. Connected to each throttle body, it enables me to balance the carbs simply by adjusting the right hand throttle body crossover cable. By definition, it's always perfectly calibrated and clearly shows when the two carbs are in balance
When I mentioned this contraption to an independent pro, he said that belonged in a museum! While he may be right, it's always worked well for me. So, my question is what else does the all-singing, all-dancing gizmo used by BMW do that the manometer doesn't do?

I'm genuinely intrigued to know what other adjustments can be made - and where do these adjustments happen?

Thanks

 

Afternoon RoSPA_man

 

So, my question is what else does the all-singing, all-dancing gizmo used by BMW do that the manometer doesn't do?-- The BMW computer can do a lot more, like lock the idle actuators, read stored fault codes, etc, but it won't balance the throttle bodies any closer than a good homemade manometer will if the homemade manometer is used by an experienced & talented person with care & precision.

[TTM3]

Has anybody tried these Dual-Port Manometer Gas Pressure Tester in lieu of a  homemade tube manamoter? See Amazon.com: Manometer, Professional Air Pressure Meter, Dual-Port Manometer Gas Pressure Tester,12 Selectable Units Differential Pressure Gauge, HVAC Digital Manometer, Gas Pressure Tester (Included Battery) : Industrial & Scientific

 

Thanks!

[dirtrider]

9 hours ago, TTM3 said:

Has anybody tried these Dual-Port Manometer Gas Pressure Tester in lieu of a  homemade tube manamoter? See Amazon.com: Manometer, Professional Air Pressure Meter, Dual-Port Manometer Gas Pressure Tester,12 Selectable Units Differential Pressure Gauge, HVAC Digital Manometer, Gas Pressure Tester (Included Battery) : Industrial & Scientific

 

Thanks!

No, never tried that one. Even at it's best it won't be nearly as accurate as a simple liquid manometer for the BMW 2 cylinder boxers.

 

The problem with those handheld devices is in how they damp then average the harsh opposed intake vacuum pulses on a boxer engine. Due to the fluctuating intake pulses it is difficult to verify the accuracy at any point in time. 

 

It might work but I wouldn't trust it until it's accuracy was verified against a true liquid manometer. 

 

 

[jjpen]

I do not think the pressure range is enough to measure intake pressure.

[dirtrider]

54 minutes ago, jjpen said:

I do not think the pressure range is enough to measure intake pressure.

Afternoon jjpen

 

That Amazon manometer can read to slightly over 80 inches of H2o so that is plenty of range to balance the BMW 1200 throttle bodies.   

[pwillikers]

Vehicle: '11 R12RT (K26, 0440)

 

My RT vibrates (at 90mph) through the handlebars a bit more than I think it should and I'm on a mission to find out why.

 

Balancing the throttle bodies is on the list of things to check however, my son's buddy borrowed my TwinMax and promptly moved to the other side of the state.  While pondering the dilemma I stumbled on this digital manometer.   Is it suitable for this purpose?  Does anyone have any experience with it?  (I particularly like the skull and crossbones, nice touch. :-).

 

Thanks.

 

[dirtrider]

On 5/19/2023 at 11:00 AM, pwillikers said:

Vehicle: '11 R12RT (K26, 0440)

 

My RT vibrates (at 90mph) through the handlebars a bit more than I think it should and I'm on a mission to find out why.

 

Balancing the throttle bodies is on the list of things to check however, my son's buddy borrowed my TwinMax and promptly moved to the other side of the state.  While pondering the dilemma I stumbled on this digital manometer.   Is it suitable for this purpose?  Does anyone have any experience with it?  (I particularly like the skull and crossbones, nice touch. :-)

Afternoon pwillikers

 

If you are chasing a 90 mph vibration then you are barking up the wrong tree with a throttle body balance check.

 

While it is never a bad idea to verify TB balance, at 90 mph that is so far above the range  (throttle plates  so far open) that a basic TB balance has little if any effect. 

 

At 90 mph are you chasing a vibration or chasing a buzz. A vibration is more wheel rotation speed & buzz (higher frequency) is more engine mechanical related.

 

Your camhead motorcycle as well as all camhead motorcycles have a 2 cylinder boxer engine with a single balance shaft.  That engine design has a basic built in higher RPM buzz as the engine in inherently primarily balanced but the pistons/connecting rods  are offset on the crankshaft so they do produce a normal boxer buzz (rocking couple buzz). 

 

In any case that digital monomer that you picture will work as as long as it can read differential pressures. With 83+ inches of H2o resolution that is plenty to use to check your camhead boxer.  Just keep in mind that those things don't have nearly the accuracy of a simple homemade "U" tube liquid manometer so if you want perfect then build a liquid  manometer.    

 

[walton66]

On my 2013 camhead I also had a vibration that was really annoying and started about 80mph.  One shop I stopped at inferred that I shouldn't be going that fast.  I lived with it until I got back to Texas in the spring of 2015 and took it to a shop with a mech that I had known since airhead days.  He found a bad wheel bearing.  He had a term for the problem with the bearing, that I can't remember, but after the replacement, it was perfect for the next 60k miles.  

[pwillikers]

Thanks for the replies.  Yes indeed, the effect of throttle body synchronization on engine smoothness diminishes as a percentage and quickly becomes irrelevant as RPMs increase.  The vibes were a conscious red herring to motivate me to sync the throttle bodies.  The device I referenced above interested me and appears to have many functions and it's cheap.  I think I'll order one.

 

In any case, I did get out to the garage and quickly discovered the source of the vibration.  Ewwww, how did that happen?  It's off to Woody's Wheel Works...

 

 

 

[DBULL]

I thought this topic was about food, and balancing how many carbs I ate today........   I'll leave now

[009jim]

I used to ride a 4 cylinder. At idle speed, the #1 cylinder was doing nothing. Several times I took it to a shop and they used their fancy gizmo to balance the carbs. It never fixed the problem. Eventually I made my own manometer and put on the bike. Instant;y I could see that #1 throttle cable was lagging. I performed the adjustment and after that all pots contributed equally to the idle.

[dirtrider]

6 hours ago, 009jim said:

I used to ride a 4 cylinder. At idle speed, the #1 cylinder was doing nothing. Several times I took it to a shop and they used their fancy gizmo to balance the carbs. It never fixed the problem. Eventually I made my own manometer and put on the bike. Instant;y I could see that #1 throttle cable was lagging. I performed the adjustment and after that all pots contributed equally to the idle.

Morning  009jim

 

Interesting, what motorcycle was that? I can't recall a 4 cylinder motorcycle that uses the actual throttle cables for a curb-idle throttle stop. Due to cables slightly changing lengths as they heat & cool most use a dedicated idle stop screw for the curb-idle stop/adjustment not the cable.  

 

I have seen a few that use a solid rotating rod or similar hard linkage that tie all the carbs or throttle bodies together then use a single idle stop screw on one of the carbs or TB's to adjust the idle stop on all of the carbs or TB's as a group with individual adjusters on each carb/TB to equalize.      

[pwillikers]

moved to new thread