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Balance TB's


joeb

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Kwik question. Having trouble balancing tb. Rebuilt rt side tb.

Set so both right side and left side butterflys lift off stop at same time. Idle screw on rt side has been messed with before so need to know aprox setting. Tried to check left side and duplicate on the other side, but, left side is frozen solid . Starting to strip out slot so will leave alone for now.

Does this rule of thumb work ? Screw all the way in then back off 1 1/2 turns ?? Thanks.

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Kwik question. Having trouble balancing tb. Rebuilt rt side tb.

Set so both right side and left side butterflys lift off stop at same time. Idle screw on rt side has been messed with before so need to know aprox setting. Tried to check left side and duplicate on the other side, but, left side is frozen solid . Starting to strip out slot so will leave alone for now.

Does this rule of thumb work ? Screw all the way in then back off 1 1/2 turns ?? Thanks.

 

Evening Joeb

 

That is a good place to start but you really should remove & clean the other side as it might have restricted air flow due to coking.

 

Edited by dirtrider
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Thanks. Will try to pull out and shoot some carb cleaner in it.

 

Evening Joeb

 

On those frozen BBS screws I usually hit the screw head with a small pin-point torch to heat the screw (& soften the internal "O" ring)-- After that they usually come right out.

 

If yours is frozen be careful that you don't ruin the screw slot.

 

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Took two of us to loosen. Me pushing for all I was worth on a big screwdriver, the other torqueing the driver with a wrench. Got it ! Some numbnutz put locktight on the threads. Cleaned out with carb cleaner , reinstalled and am now getting close to balancing tb's.

I'm seeing differing versions of procedure for balance. HAYNES says to set idle speed then get to 1500rpm and use cable adjust to balance. It also says that individual idle speeds can be adjusted by the idle screws. ???

On this forum I've read to set butterfly s till they open at same time, adjust with idle screws till vacuum is even, run to about 30000rpm then adjust even vacuum with cable adjuster. Of course that may affect the " at rest point on one tb " but you can't have perfect at idle and high revs ".

Any thoughts or suggestions ( if it's about my personality, I've heard many....... I'm kinda thinkin about tb syncs here ) on which procedure ? As always, VERY appreciative of ALL your input. Thanks guys.

 

PS.

Helping a bud with a K1200lt check valves. I'm the guy spinning rear wheel to rotate engine.

Thought I'd be smart and grab rear wheel spoke with left hand , instead of grabbing tire to get better purchase on wheel.

If you do that and pull real hard on spoke, left hand " driving "

finger " gets jambed in brake caliper. It is not as much fun as it sounds. Hope my pain is your gain.

Edited by joeb
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As long as that K12LT was zinged up to redline a few times every thousand miles or so, the valves are not likely to need adjusting.

The high rpm helps keep them clean of gunk. The use of a top tier gasoline like Chevron or Shell helps keep carbon deposits down.

Not saying one will never have to adjust one or two, but the chances are pretty slim.

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Well.....trying to adjust TBs according to link that was provided (thanks Roger ). I didn't mess with TPS adjustment so most of it seems to be dealing with cable adjustment. Think I have them set properly. Both sides are resting on the stops. Initially set to open at same time. Both idle screws turned in then backed out 1 1/2 turns. Start bike balance both sides with idle screws, rev it up and balance by backing off cable ( clockwise so as not to interfere with idle stop point per directions ). Only trouble is, I can't get idle speed down below 1500 rpm. If I lean the mix, keeping them balanced, no appreciable rpm drop till the right side is all the way in, then it chokes of the right cylinder. Seems like the left side needs to be more open than the left by almost full turn. Should I be turning them to a richer setting to slow engine ? As I mentioned earlier, it seems someone put thread lock on left side screw. Could a blockage from the lock residue be causing the imbalance? Thanks .

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Well.....trying to adjust TBs according to link that was provided (thanks Roger ). I didn't mess with TPS adjustment so most of it seems to be dealing with cable adjustment. Think I have them set properly. Both sides are resting on the stops. Initially set to open at same time. Both idle screws turned in then backed out 1 1/2 turns. Start bike balance both sides with idle screws, rev it up and balance by backing off cable ( clockwise so as not to interfere with idle stop point per directions ). Only trouble is, I can't get idle speed down below 1500 rpm. If I lean the mix, keeping them balanced, no appreciable rpm drop till the right side is all the way in, then it chokes of the right cylinder. Seems like the left side needs to be more open than the left by almost full turn. Should I be turning them to a richer setting to slow engine ? As I mentioned earlier, it seems someone put thread lock on left side screw. Could a blockage from the lock residue be causing the imbalance? Thanks .

 

Morning Joeb

 

There really isn't a richer or leaner setting on those BBS screws as ALL they are is air by-pass screws. So backing a BBS screw out lets in more air on the engine side of the throttle plate. If you back the screw out (letting in more air) the o2 sensor sees that extra air then simply adds more fuel.

 

It sort of sounds like you didn't get the throttle plate properly centered when you installed the new throttle shaft. It is VERY DIFFICULT to properly center a throttle plate if the base idle screw was not backed out to allow FULL throttle plate closure.

 

Also did you check the valve lash? -- That can have an effect on idle TB balance.

 

Same with the TPS voltage, high TPS voltage at idle can increase the idle speed.

 

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Dont know what a properly seated throttle plate looks like. When i set it, the plate was vertical in opening and seemed to have an even slight gap around it. Not an air tight seal. Is that normal ? As far as valves go, I'd just adjusted them . Valve lash ??? Top dead center and feeler gauge. What valve lash ?

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Dont know what a properly seated throttle plate looks like. When i set it, the plate was vertical in opening and seemed to have an even slight gap around it. Not an air tight seal. Is that normal ? As far as valves go, I'd just adjusted them . Valve lash ??? Top dead center and feeler gauge. What valve lash ?

 

Afternoons Joeb

 

To be properly set the throttle plate needs to show the least air gap all around it with the throttle plate COMPLETELY CLOSED not with it on the idle stop screw.

 

If you didn't completely close the throttle plate (back idle stop screw out) then there is a good chance that it isn't centered properly.

 

 

 

 

 

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Little confused. What are you calling completely closed if NOT at idle stop ? I'm probably misunderstanding your reply. So...... as I said I set it centered perpendicular in opening. Sounds like I should have set it at the stop ?? Think I'll have to go back in and check it .

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Little confused. What are you calling completely closed if NOT at idle stop ? I'm probably misunderstanding your reply. So...... as I said I set it centered perpendicular in opening. Sounds like I should have set it at the stop ?? Think I'll have to go back in and check it .

 

Afternoon Joeb

 

Back the stop screw out exactly 3 turns (that should easily then be out of the picture but be easy to screw back in 3 turns to be where it is now).

 

Then loosen the throttle plate screws until JUST loose enough to allow the throttle plate to slide.

 

Then hold the TB up to a light or bright sky.

 

Then lightly open & close the throttle cam while looking though the TB bore. (sometime tapping the side of the TB with a plastic hammer helps)-- It also sometimes helps to lightly slide the throttle shaft in & out a little as you wiggle & close the throttle plate.

 

The throttle plate is centered when you can't see any light (or very very light little top & bottom & the sides of throttle plate show as little light as possible & even on both sides. (kind of subjective & you want to end up with as little light showing around the throttle plate as possible but still have the throttle open & close without the plate dragging in the bore).

 

Sometimes they will stick just slightly when opening from fully closed & seated but that won't be an issue when you turn the idle stop screw back in.

 

Once centered properly I tighten both screws, then remove one throttle plate screw, then put some lock-tite on the screw, then reinstall tight, once that one is tight I then do the other screw. (you don't want a screw coming loose & ending up embedded in a piston top or under a valve margin).

 

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So far centering plate is a royal PIA. Is there an up or a down, inside of outside on plate ? It has a number 5 on the plate. Does it matter where it is. ?

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Morning Joeb

 

So far centering plate is a royal PIA.

 

Is there an up or a down, inside of outside on plate ? -- Probably, some plates have a light bevel on the top & bottom edges as the plate closes at an angle to the bore. Then you have wear to account for.

 

It has a number 5 on the plate. Does it matter where it is? -- A used plate should go back in the same orientation that it was before (I always mark my plates so I can re-install them the same way as they came out)-- Maybe remove the intake boot on the other to side to see where the number is on that plate.

 

 

 

 

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Got the bike running. Flipped that plate every which way till I got the tightest fit. I think that the darn thing still has too big of a space around it. Installed it, balanced it at idle, screw turned all the way in which kind of confirms that the plate isn't sealing too well, but, got the idle where it needs to be. Balanced up thru the rpm range, . Done with it for now. Thanks again for all your help.

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Quick follow up.

The shaft I replaced was badly worn. I think it had to move around so much that it probably wore down the throttle plate on the edges so that a tight seal was impossible.

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