Idle OK, but TBs not balanced: Bleed Screws?

[tmcafe]

Set my idle to a little over 1k rpm. Got a Twinmax and checked the TBs' balance; the needle kept hovering left of the zero mark, around 1, as you can see in this generic pic:

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It seemed that the right idle screw didn't help the matter. Should I try again with the idle screws only, or should I reset the bleed screws according to Micha's method for the TPS? The bike runs fine, and I'd rather not mess with its settings if possible. Thanks in advance for any suggestions.

[Greg Field]

Perhaps it is the tool? Twinmaxes're third-rate.

[Tom M]

You shouldn't use the idle stop screws to adjust TB balance. I believe you should back the right (when sitting on the bike) TB idle stop all the way out and only use the left side to adjust idle speed. If you use both stop screws lash in the throttle linkage can complicate the adjustment process. The white knob should be used to adjust balance above idle. Some say use the bleed screws to adjust balance at idle. I used the Micha method, 1 turn out on both bleed screws and balance TB's with the white knob at 1800rpm, and I'm happy with the results.

[tmcafe]

Thanks for the replies. Didn't know Twinmax wasn't too reliable. What's better, mercury sticks? (I guess water mano should be pretty accurate, but kind of hard to use). Micha's method starts with adjusting the bleed screws first (1 full turn out from closed). Perhaps I should have done that (I assumed the bleed screws were set before I got the bike and didn't want to mess with them). I'll do it just to make sure. Also there must be enough lash in the throttle linkage that when I rev the engine the balance starts to shift toward 0 (balanced), at least as indicated by the Tmax.

 

Another question:

 

Should the engine start just by pushing the start button, or does it need some help from the throttle, as mine seems to (even with fast idle lever all the way on)?

[savagehenry]

Another question:

 

Should the engine start just by pushing the start button, or does it need some help from the throttle, as mine seems to (even with fast idle lever all the way on)?

My bike almost always needs a little throttle roll to fire. It seems to be fairly common here. I don't remember the exact name, but there was a thread on this not too long ago. S.H.

[gstallons]

Same here. Always 1/8 to 1/4 throttle to start.

[tmcafe]

Thanks. At least it's good to know it's not only my bike that needs some throttle to start. Perhaps the fast idle lever isn't acting as it should? I'll look into it, though if the cable is adjusted to open the throttle more, it's more likely that it won't be completely off when it should, with the engine warm.

[gstallons]

Check for .010" or .25mm air gap between the roller and fast idle cam with no "choke" . Since this is just a fast idle it does not enrichen anything. look to se if the idle increases with the lever pushed "full on". If it doesn't, start looking.

p.s. I use this only when I start the bike and get off to do something like putting on riding gear.

[raz]

Didn't know Twinmax wasn't too reliable.

Hey, does it say "Made in France" in that picture? I'm not going to tell ya what my conclusions of that is

 

Seriously I have no idea if Twinmax is generally reliable or not, but obviously it is an easy check: make up some kind of Y connection so both hoses are connected to the same port. Try running the engine at various throttle openings and verify that the meter sits fairly tight, right in the middle. After that, you can and will trust it to some extent

[fotoguzzi]

can you bring the needle back to neutral with a little turn of the balance knob for butterfly sync? with the control arm conected. I think it's the white thumb screw knob I'm thinking of.

[tmcafe]

Thanks again. From what I've read, apparently the white knob on the rod that connects the TBs should be used to tweak the balance at higher revs than idle (it may affect the idle, but there's some slack in the rod connection so it may not be a problem for the idle setting).

[richard100t]

I have a twinmax & it works just fine. Mercury sticks would be better because you can see both cylinders at the same time for balance level. BUT for general purposes the twinmax will get you to the same place.

The white knob can be used to tweak it with the rod connected, but you still have to know which way to turn it. Its very difficult to tell if you're going the right way without a measuring device hooked up. Also once you have the tb's balanced very close I use the bleed screws to get it just perfect.

I always set the tb's with the engine at idle. The idle screws are just a doorstop type of thing & dont do anything other than hold the throttle open a pinch. With the twinmax I can turn the sensitivity all the way to the highest setting & get it to barely move off center at idle speed, so once you get the hang of it you can get it dead on perfect.

[tmcafe]

Thanks. I'm a bit surprised that you're saying you fine-tune the balance with the bleed screws. Shouldn't they be set first and then left alone before adjusting the balance with the idle screws? Also shouldn't the white knob on the rod be used to adjust the balance at higher revs (like 3k)?

[dlaing]

I have a twinmax & it works just fine.

Ditto.

If in doubt, reverse left and right hose.

I have never seen any inaccuracy with mine.

What has thrown me off is that if bumped it can lose the zeroing.

Be sure to zero it before and make sure it zeroes after.

I imagine they are delicate and Greg Field has probably had problems with damaged ones....

[dlaing]

Thanks. I'm a bit surprised that you're saying you fine-tune the balance with the bleed screws. Shouldn't they be set first and then left alone before adjusting the balance with the idle screws? Also shouldn't the white knob on the rod be used to adjust the balance at higher revs (like 3k)?

That is a debatable question.

People get good results with all methods.

I prefer to balance with the bleed screws and am adamant that doing so produces better results.

I prefer not to use the right idle set screw because the transition to throttle on is smoother, but using the right idle screw may help keep a reliable idle, and give a more identical TPS reading with each closing of the throttle.

Yes, do use the white knob to adjust the balance at higher revs, like 2-3K.