The Really, Definitely Completely Un-Authorized TBS

[Fred W]

Yeah, that's it. Trust me, Ha ha...

Sorry Thomas, I didn't take any pictures of the balanced condition after. It looked just like the before's except the 4 were all the same height.

Actually. my point in those pictures of the gauge was just to show how it showed one thing at idle speed and at 4k rpm it was different. If all I had done was balance the air screws per the FSM it could only have hurt the 4k reading (if anything).

 

[Constant Mesh]

On your tuner I assume that stronger vacuums will yield higher columns. Yet the columns are a bit taller for higher rpm operation. That's opposite of what I would expect.

On the earlier FJR's with the adjustable throttle stop it's probably better to have the air screws just barely opened. This ensures that the throttle valves will be opened a bit more at idle. When you are adjusting the individual throttle valves back and forth it's good to end up with a bit of space between each valve's tang and its stop set at the factory. It may be possible for a throttle valve's tang to bang into its stop before the #3 valve's tang hits the knob adjusted stop.

A butterfly valve is not a very good flow control valve particularly when it's opened more than a few degrees. So adjusting it at minimal openings should yield the most satisfying results.

I find that a good sync has a great effect on shifting. If the sync is off I'll notice it at the shifter long before I detect a noticeable increase in overall vibration.

 

[Fred W]

On your tuner I assume that stronger vacuums will yield higher columns. Yet the columns are a bit taller for higher rpm operation. That's opposite of what I would expect.

Yeah me too. Good observation. I wonder if I reversed the photos somehow. :blink:

On the earlier FJR's with the adjustable throttle stop it's probably better to have the air screws just barely opened. This ensures that the throttle valves will be opened a bit more at idle. When you are adjusting the individual throttle valves back and forth it's good to end up with a bit of space between each valve's tang and its stop set at the factory. It may be possible for a throttle valve's tang to bang into its stop before the #3 valve's tang hits the knob adjusted stop.

Another good observation. That would definitely be confuscating to anyone not watching out (or aware) of the possibility

 

[road runner]

I was being a smart ash in my last post, but seriously, I did try the method of revving and watching, and it takes much longer, and is a pain in the ash. With no load on the engine it can run away really quick, and you will find yourself revving your engine for hours trying to get it just right. Not saying it can't be done, but it is a PIA.

By doing it the way Fred W mentioned you are checking the plates at partial opening. Because the air screws are turned in all the way the throttle is opened a little to keep the engine running. If I were to guess, I would say the plates are open about the same amount as cruising speed even though the engine is at 1000 RPM. If you want to check the sync at more throttle opening you can also back off the idle screw a few turns (this will take more air from it) and keep the idle at 1000 with a vist or similar.

This is checking it at partial opening, which is where the engine spends most of it's time. So I think it is the way to go , but thats just me. And I think if you check it after by the rev technique it will be very close.

 

[dustyrains]

I wonder, do bikes with throttle by wire also need periodic TBS?

 

[Fred W]

edited to remove doubts about the procedure in post #1

 

[Patriot]

during a fit of age related insomnia,

ah yes...sigh :dribble:

this thread is really cool and in a good way, running what brain cells still fire in moi

carry on and thanx

Mike

 

[road runner]

Wow Fred,

That is a lot of bench racing, and all true, however I will agree to disagree.

I think Yamaha sets the throttle bodies up on a flow bench, not knowing the flow variations of the engine. Also the flow variations between cylinders is very insignificant, and that is what they concentrate on when designing an engine. Granted it is a production engine so you could do a little better, but we are not looking to get that extra 2.5 HP over the other guy. If the variation was a lot then you would have to do sync on a dyno at RPM like mentioned earlier, and I don't believe that is necessary.

Like I said earlier when doing TBS like you first said you are checking the throttle plates at an angle somewhat more than idle even though the engine is at 1000, because by closing the air screws you have to open the throttle to give it enough air to run. So say the plates angle is equal to, oh say 2000 RPM. If you want to check the sync at a larger plate opening then you can also back out the idle speed air screw, this will take more air away, and you would have to open the throttle more to keep engine at 1000 RPM, and maybe that plate angle would be something like while cruising at 3000 RPM, But I don't know for sure.

Maybe if we can see the diag screen while riding, check what the TPS angle is at say 4000 RPM, then check it again at sync time and see if it's close. If not then close the idle speed screw (by turning counter clockwise) and recheck.I'm thinking if the air screws are closed that the TP angle will be close to cruise speed, and that is where it spends most of the time.

Granted all this I describe will account for the TP opening at higher RPM, but it will not account for the engine variations at 4000 RPM (which I think will be very close). So when your all done do a gentle roll on the throttle and see if it's close., but you may want to check it before you put the air screws back so your checking apples & apples.

I'm done splitting hairs

My .02

Art

 

[Fred W]

Hey Art,

Bench racing and hair splitting beats actually working most any time. Well, except for when it's time to pay the bills that is...

I agree, the throttles are set on a flow bench, but doesn't that mean that they will be compensating for the manifold's flow characteristics? And that this will result in them not being perfectly parrallel? I honestly do not know.

But it makes me wonder, if that is not the case, then why bother having adjustable air bypass screws?

 

[road runner]

Hey Fred

I'm not 100% sure of any of it either. But I would think the air screws are there so we have a way to fine tune the idle sync for each engine. There may be slight variations from one to another, so this will give a way to compensate. It is an extra bonus to have them. My brothers Huabusa didn't have air screws, it was synced using the throttle link screws. So if you sync it at RPM it may not be perfect at idle and vise versa. It's like in the boat world some outboards have adjustable idle mix screws and some are fixed. It is nice having the ability to adjust both at RPM and at idle so we can have the best of both worlds.

 

[S76]

Here is my twisted understanding:

I think your original posting is correct, exept for some words that I didn't even understand. (vivo?)

Except, when you sync the throttle plates at 4 or 5K you are not syncing the plates. You are matching the inidvidual intake runner's vacuum. And this is what you want to do. The vacuum in the runners is directly proportional to how efficiently that cylinder is firing. * (See footnote.) The throttle bodies and intake runners are pretty much all the same, but the airbox is the fly in the ointment here. That is why if you ever did the Barbarian mod you found the factory mixture settings at like 5, 18, 18, 22. The 5, is #1. The air has to make a sharp corner to get there. Less air less fuel. The 22

is #4, which is a much straighter shot, better airflow needs more fuel.

So you are correct to just sync the intake vacuum at speed. But this means the butterflys are not equal at idle, so you fix the idle with the idle air bypass screws. Now both are pretty good.

I do it a little different. I set all the idle screws one turn out and then set the throttles at speed. Then make minor adjustments to the idle screws last. Then go back and check it at speed again to see itf the minor air screw changes changed the speed adjustment. Couple times back and forth and you have it.

However, let me throw this one fly in the ointment. I did a sync on a gen I, setting the idle to about 12oo RPM's. The owner said no put it back to 1000. OK. I just turned the main idle screw to obtain the 1000 and then rechecked the sync. It was all off. I don't know why this happens but it did on more than one bike. So from then on I recheck the sync at the very end to make sure it is not FUBAR'D.

*Vacuum is a funny thing. I've messed with it to the point of confusion on several occasions. Any given engine will have x amount of vacuum at idle. If you rev it to 4 or 5 K the vacuum will be higher. Why? Yes, the throttles are open more and it would seem that would reduce the vacuum, but the thottles are only open a little bit more at speed, and the increased RPM causes the pistons to draw much harder than at idle, more than compensating for the increased throttle opening.

On the other hand if you were driving at low RPM and opened the throttle wide open your vacuum would go to zero, or there about. That's easy to understand.

 

[Zorlac]

"and the increased RPM causes the pistons to draw much harder than at idle"

Nah, they can only suck 1298cc's total, just more often above idle.

 

[SacramentoMike]

". . . I'm modifying my position that the throttle plates should be adjusted at idle. I have edited my original post in this thread to that effect. I will do some further experiments with 3Dogs' procedure of throttle variation, and maybe try a few other things (like balancing at ~2k rpm?), but in the interim, you are on your own. You have been warned.
By the way, on a test ride after adjusting the throttle plates at idle, my bike didn't run horrible. In fact, the difference (on my bike) was very subtle if any. But I think there is a potential that it could become worse on some bikes by following my prior procedure.

I feel much better now about my earlier confusion. I'm still confused; I just feel better about it now.

 

[Fred W]

Thanks to the many folks that have contributed to the discussion thus far. Especially to roadrunner (whose professional expertise I value greatly), Jeff Ashe and 3dogs.

I wrote this procedure up thinking that I had it all figured out, and as usual I was wrong. Maybe. Definitely maybe.

Yeah, I'm 100% sure it's maybe. :blink:

My point is, even if I did have it right to begin with, so what?!?

It's much better for folks to be actually thinking (you remember how to do that?) about what it is they are doing, or adjusting, or attempting to do, and consider the ramifications and consequences, rather than just blindly going out and following procedures from some knucklehead chump that says: Hey This is the next best thing since sliced bread.

Yeah, that should be interpretted to be me,

or it could be someone else

Definitely.

 

[road runner]

Like Fred W just said about thinking. Thanks to you all for getting me to think some more about it.

I was hung up on taking play out of the linkage and the throttle opening at speed, when the real factor is vacuum at speed. I forgot about restriction would have more effect at higher RPM.

So I agree syncing the vacuum with the throttle plates at speed would be more accurate. I don't know how much different it will be to doing it at 1000 RPM, but I'm sure it will be different. I have tried it and it is a PIA, because the engine will run away revving it with no load, plus you can't watch the tach and vacuum gage at the same time. I will try it again next time I check the sync, although I don't think it's important to try to do it at 4000 RPM, because it will run away. If I just role on the throttle until about 4000 RPM and watch the vacuum that should do it. I think this is what 3 Dogs said.

 

[Patriot]

Like Fred W just said about thinking. Thanks to you all for getting me to think some more about it.I was hung up on taking play out of the linkage and the throttle opening at speed, when the real factor is vacuum at speed. I forgot about restriction would have more effect at higher RPM.

So I agree syncing the vacuum with the throttle plates at speed would be more accurate. I don't know how much different it will be to doing it at 1000 RPM, but I'm sure it will be different. I have tried it and it is a PIA, because the engine will run away revving it with no load, plus you can't watch the tach and vacuum gage at the same time. I will try it again next time I check the sync, although I don't think it's important to try to do it at 4000 RPM, because it will run away. If I just role on the throttle until about 4000 RPM and watch the vacuum that should do it. I think this is what 3 Dogs said.

throttle lock ??? ...

 

[Fred W]

Yes. Rolling on the throttle and watching the gauge, making note of the balance, then going back to idle for a quick linkage adjustment is the essence of the 3dogs method.

Patriot, using a throttle lock to hold it at 4-5k rpm with no load on it seems like cruel and unusual engine punishment to me.

I guess it might help determine if your CCT is OK though...

(sorry )

 

[08FJR4ME]

I might as well contribute to the confusion. :blink:

A) Has one thought about the throttle plates being out of sink on purpose? Maybe MaMA Yamaha wants them this way to alloy for uneven air box distribution.

B) What's the pluses to doing this? Other than eliminating some vibes from the bike is it worth it? At WOT I got all I can handle and some.

I have seen an increase in brain cell growth recently though.

Thanks Fred,

Get some rest, eh!

Now if only I can get help with spelling and grammar.

Edit: Admin's, every time I do a b with parenthesis I get a cool smiley. What's Up?

 

[Fred W]

I might as well contribute to the confusion. :blink:
A) Has one thought about the throttle plates being out of sink on purpose? Maybe MaMA Yamaha wants them this way to alloy for uneven air box distribution.

B) What's the pluses to doing this? Other than eliminating some vibes from the bike is it worth it? At WOT I got all I can handle and some.

I have seen an increase in brain cell growth recently though.

Thanks Fred,

Get some rest, eh!

Now if only I can get help with spelling and grammar.

Edit: Admin's, every time I do a b with parenthesis I get a cool smiley. What's Up?

In answer to A ), I think that is the consensus we are now reaching (that my plate adjustment at idle isn't a great idea)

The answer to B ) is: Strictly in search of the ultimate turbine-like, vibration-free engine.

It is unlikely to increase total power any appreciable amount. One could also argue that when/if the engine was in complete balance, and there is a minimum vibration then the engine will wear less. But that would be a stretch. It is also possible that a balanced intake would result in better fuel economy, but I don't think that effect would be great enough to measure.

If you look at the code for the cool smiley it is capital B followed immediately by a right parenthesis mark.

Lower case b won't work either: B)

Trick is to put a space between the letter and the paren.

 

[RadioHowie]

Patriot, using a throttle lock to hold it at 4-5k rpm with no load on it seems like cruel and unusual engine punishment to me.

So, Fred, what's the difference to the motor, as if it knows, between running at 4k WITH load and 4k with NO load?

You imply that some disaster is wating in the wings. If that was true, wouldn't there be also be a difference between 4k rpm in first gear as opposed to 4k in fifth? No load, or different load....what difference would it make?

Just curious to your reasoning.