TB Balance problem?

[El_Gringo]

I have been trying to check the balance of the TB's on my V11. I followed the instructions posted, but a couple of points raised their heads.

 

What happens to the right side idle screw after adjustment. Presumably it is now superfluous? I guess as the bodies should now be balanced any adjustment to the lefthand side TB should drive the right hand side by the same amount. If so - begs the question - Why is it there? Is it the motorcycles appendix?

 

Whlist checking the balance..... I bought a balance kit on Ebay it comprises of two lengths of tubing the same lenght and diameter, with a ballbearing in each. The tube is wrapped into a loop so at rest the two balls rest at the bottom of the loop. When the engine runs the air moving passed the balls moves them slightly, if the TB's are not balanced more air moves passed one ball than the other, thus the balls are displaced . The TB's are said to be balanced when the two balls line up.

I noticed one ball was oscillating while the other was stationary - has anyone else used this type of kit? Is my oscillating ball normal!? Should they both oscillate?

 

Wot d'ya think?

[Guest ratchethack]

What happens to the right side idle screw after adjustment. Presumably it is now superfluous? I guess as the bodies should now be balanced any adjustment to the lefthand side TB should drive the right hand side by the same amount. If so - begs the question - Why is it there? Is it the motorcycles appendix?

El Gringo, while there are plenty of "wrong" ways to balance the TBs, IMHO there are many alternative, yet perfectly acceptable ways to do it that can all hardly be considered "wrong". This is just me, but I wouldn't remove it. The chances of it getting back in place again (should it ever be needed) may be about as good as getting an appendix back in place years after removal.

 

While the RHS idle stop screw is not used per the technique many (myself included) typically go about it, it can serve a purpose when going about it another way. Backed well off and out of the way, using the technique you followed, you or the next happy owner might consider it "available" as an option for a future balance.

Whlist checking the balance..... I bought a balance kit on Ebay it comprises of two lengths of tubing the same lenght and diameter, with a ballbearing in each. The tube is wrapped into a loop so at rest the two balls rest at the bottom of the loop. When the engine runs the air moving passed the balls moves them slightly, if the TB's are not balanced more air moves passed one ball than the other, thus the balls are displaced . The TB's are said to be balanced when the two balls line up.

I noticed one ball was oscillating while the other was stationary - has anyone else used this type of kit? Is my oscillating ball normal!? Should they both oscillate?

I'd never considered this before. Can't recall anyone ever posting here (or anywhere else) using this kind of balancer, so it wouldn't likely have come up. The manometer kind most use (myself included) wouldn't show differences between individual intake vacuum pulses.

 

But it's interesting to think about. Assuming the TBs are balanced correctly, why would one cylinder create a more pronounced vacuum pulse than the other? I'm thinking the 270/450-degree firing phase must be at the bottom of things here somehow, but can't quite imagine how this explains it?? The way I think about it, they should both oscillate the same. Unless you've got a restriction in the hose that doesn't have the oscillation that would damp out the pulse on that side? In this case, it would be impossible to get the balance right.

 

You did set the valves correctly before balancing, yes?

[gstallons]

Ratchet' was referring to the engine valve adjustment. That is the only thing I can see that would cause this "flutter".

Before you go too far swap sides with the hoses to see if the problem remains on the same side.

[dlaing]

Whlist checking the balance..... I bought a balance kit on Ebay it comprises of two lengths of tubing the same lenght and diameter, with a ballbearing in each. The tube is wrapped into a loop so at rest the two balls rest at the bottom of the loop. When the engine runs the air moving passed the balls moves them slightly, if the TB's are not balanced more air moves passed one ball than the other, thus the balls are displaced . The TB's are said to be balanced when the two balls line up.

I noticed one ball was oscillating while the other was stationary - has anyone else used this type of kit? Is my oscillating ball normal!? Should they both oscillate?

 

Wot d'ya think?

Dammmmit! They stole my invention!!!!

But I still have a top secret spring loaded version of the invention for onboard metering. (don't tell anyone).

Kinda disappointing to see it being problematic.

I thought it might be challenging to get the tolerance of the ball to adequately match the tolerance of the tube.

gstallons offered good advice by suggesting swapping the tubes. You might also try swapping the balls.

Another possibility is that the design needs more damping to stabilize the reading.

You may be able to find some adjustable inline valves from a hardware store or Aquarium supply store.

[Ryland3210]

Interesting. If I understand it correctly, each TB has its own tube and ball and the tubes are not connected to each other.

 

If that is the case, the annular area between the ball diameter and tube's inside diameter must be matched on both tubes to yield equivalent readings. Obtaining precision balls is not difficult, but I have to wonder about the consistency of plastic tubing as it is made, not to mention the thermal expansion of each if their temperatures differ considerably. If the tube I.D. is increased so the annulus has larger area, in order to make each 0.001" variation less significant, there will be increased airflow to the TB, which would act as if the air bypasses were opened more, which would affect the balancing one is attempting to achieve. Therefore, this should be done with air bypasses closed. Also, the loop in the tubing should be oriented such that each ball is in a straight enough part of its tube where its I.D. is circular, and not in a bend where the tube assumes an oval shape.

 

Manometers have the advantage that they rely solely on the density of the liquid used, and they do not add air into the intake.

[Guest ratchethack]

Good point, John. I would throw a small (10 mm or so ) combo wrench into this (valid!) observation by noting that the intake barbs by which the balance readings are taken have a .030" dia. lumen (aka annulus ) by my measurement, IIRC. This was the size Guzzi engineers chose to provide airflow through the charcoal "petro-badness" recovery canisters. It would seem that the airflow chosen would be negligible relative to that provided by the air bypass screws, since plugging them off has typically made an imperceptible change in both A/F and running at idle -- or at least one so tiny that no one seems to've ever noticed. . .

 

And still the Q remains as to why one cylinder would show a fluctuation in pulse and the other . . .not??

 

Oh yeah. Since wot we're doing here by balancing the TBs is to set the butterfly plates relative to each other so that we achieve equal relative vacuum in the intakes -- IMHO, leaving the air bypass screws properly set should have no detrimental effect on achieving that balance wotsoever.

 

But o' course. . . (well, you know).

[Ryland3210]

Good point, John. I would throw a small (10 mm or so ) combo wrench into this (valid!) observation by noting that the intake barbs by which the balance readings are taken have a .030" dia. lumen (aka annulus ) by my measurement, IIRC. This was the size Guzzi engineers chose to provide airflow through the charcoal "petro-badness" recovery canisters. It would seem that the airflow chosen would be negligible relative to that provided by the air bypass screws, since plugging them off has typically made an imperceptible change in both A/F and running at idle -- or at least one so tiny that no one seems to've ever noticed. . .

 

But o' course. . . (well, you know).

 

And still the Q remains as to why one cylinder would show a fluctuation in pulse and the other . . .not??

 

I'm kinda tired, and figured others would weigh in on the oscillation question. It does appear that the .030" orifice restriction is in the same neighborhood as the ball/hose annulus.

 

How do you mean "plugging them off"? Are you comparing plugging them off to when they are connected, or open to atmosphere? If it's the former, the question would be how restrictive the canisters are relative to the .030 orifice.

 

By the way, my erudite friend, is the plural of orifice, oral feces?

[Guest ratchethack]

How do you mean "plugging them off"?

Plugged off, as in wot most of us do (myself included), relative to the flow achieved thru them via the canisters, as designed and shipped from Mandello.

[El_Gringo]

Ah it seems I have misled you all....

 

The tubes which are connected to the head ports are actually each end of the same tube, so the reason why the ball is wiggling is beacause as Rach points out, the pistons are out of phase with each other by x number of deg. As the revvs increase this oscillation stabilises. It seems this type of balance tool is quite easy to use - when you read the instructions properly!

 

I reserve the right to say I have completely balanced the TB's until I get a few road tests under my belt but I followed the instructions to the letter and the bike seemed to follow them too!

 

Thanks one and all, if anyone is interested I bought it on Ebay under 'manometer'

 

Cheers

 

Still not sure what to do with the RHS idle screw though

[raz]

Still not sure what to do with the RHS idle screw though

I too worried about that poor screw having no reason for existence. To avoid it getting emotionally depressed I gave it the important task of stopping the throttle plate just barely off completely closed, when the rod is disconnected. That is: I backed it out, let the plate shut completely, and screwed it in just up to contact. The reason I wanted this is it's not very healthy to snap the throttle plate shut with nothing stopping it. It may deform the plate or the mating surface. My screw took the bate and now lives very happy, knowing it has the important job of protecting the TB once a year or so.