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Missing/popping/sneezing at idle


Tinus89
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You really should balance the throttle bodies using the vacuum taps and a suitable balance device (TwinMax or carb sticks) using the white knob under the left throttle body

 

I was under the impression something changed when the gearbox was replaced?

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+1 on white knob balance method using manometer or other vacuum instrument....

 

Having done it every which way, I would:

 

1.

Back off the RH throttle stop. Unless you have some super high mileage bike where everything is worn out and sloppy, using both will make you crazy.

2.

Open bleeds one turn each. ("Micha's method") 1 turn is almost always right. Make sure the screws and ports are nice and clean.

3.

Sync using white knob at idle. Like I said, some frown at this. Guess what? If they are synced at idle, it will be synced off idle.

 

When the throttles are open (>3k) the white knob needs to be moved a lot to make any difference in vacuum. This is because the small adjustments the white knob makes gets lost in the large flow of air coming through, and tiny imbalances in throttle vanes will be hard to see on any kind of meter, even the expensive one I bought.

 

You can turn the white knob and the throttles will appear to be in balance at higher RPM's. But they're not, which you will see when it drops to idle. Then you can use the bleeds to try to even it out, which is what I did, and then it idles worse than ever.

 

In short, the ultra tiny differences in throttle openings will be revealed at idle but will be lost at higher RPM's. If the idle is balanced, then higher RPM's will be balanced too.

 

Try "JB's" method, and sync the throttles at idle using the white knob. Turn 1/8 and blip throttle and let it settle. Keep doing this until it smooths out and is in balance. The idle will probably creep up as it smooths out (you can adjust this later using the LH throttle stop screw). It will never be perfect but you can get it close. Check "off idle" RPM's as you get it smoother, I bet they will be in sync too.

 

Yes, this method is backwards, but since your bike runs like crap right now, why not try it? I went through ever "method" before doing it this way, and now my bike runs like a sewing machine and pulls like a locomotive.

 

If your bike still sneezes, then it's something else. But basics first.

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+1 on white knob balance method using manometer or other vacuum instrument....

 

Having done it every which way, I would:

 

(... whole story...)

 

This makes perfect sense, actually. Why would you want to add air to the mixture at idle without fuel?

I'll try setting it to 1 turn on both ABS's and then balance it using the white knob (and my CarbTune).

 

Question: if this is really the case, what are the air bleed screws for anyway then?

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+1 on white knob balance method using manometer or other vacuum instrument....

 

Having done it every which way, I would:

 

(... whole story...)

 

This makes perfect sense, actually. Why would you want to add air to the mixture at idle without fuel?

I'll try setting it to 1 turn on both ABS's and then balance it using the white knob (and my CarbTune).

 

Question: if this is really the case, what are the air bleed screws for anyway then?

 

You can tweek the idle balance with the air bleed screws. A little more air causes leaner idle mixture, and it speeds up, and conversely.

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JB - what you wrote above makes good sense. I'm going to try it at next opportunity. I found setting balance at 3,000 kind of tricky - then fiddling with the air screws to get a balance idle.  It all seemed like a compromise.  Good idle = good WOT...  Sound simple and it's working for you.  

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It does sound really simple and I am definitely going to try it.

But then my question remains: why would I want to start off with both air bypass screws 1turn open? And not fully closed?

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+1 on white knob balance method using manometer or other vacuum instrument....

 

Having done it every which way, I would:

 

(... whole story...)

 

This makes perfect sense, actually. Why would you want to add air to the mixture at idle without fuel?

I'll try setting it to 1 turn on both ABS's and then balance it using the white knob (and my CarbTune).

 

Question: if this is really the case, what are the air bleed screws for anyway then?

 

 

For the same reason men have nipples. Kidding. Probably a hold over from carburetor days, and see below.

It does sound really simple and I am definitely going to try it.

But then my question remains: why would I want to start off with both air bypass screws 1turn open? And not fully closed?

 

The long answer is that the ECU has two "maps": one at idle, and one off-idle. The idle map assumes the vanes are closed, and adjusts mixture with this assumption, and the mixture needs some air in it, thus the air bleed screws.

 

The short answer is: because, as Micha says, one turn is almost always right. 

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What I did:

 

- Cleaned, and set both air bleed valves to one turn open.

- Warmed her up and balanced idle with the white knob. Idle was around 1250rpm.

 

She was idling OK, but the clutch was very loud and could not be made quiet with the clutch leaver, indicating a disbalance.

I do not know whether she would still backfire or not.

 

I then got frustrated, turned back the white knob and solved the disbalance with the air bleed screws, giving me a more balanced, quiet idle (clutch quieter as well), but showed a hiccup again as well.

 

Then I got thinking: what has changed since the gearbox change-out?

- Different gearbox

- Different oil in the gearbox: the new one came with 85W140 vs 80W90 (old)

 

I know I have some wear in my piston rings (145/135psi compression test left/right - tested last year). Would the difference in compression in combination with more internal friction in the gearbox because of thicker oil, cause the disbalance and therefore popping/sneezing?

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Since the "white knob" actually sets the true relationship between the throttle plates, I cannot conceive that the throttle bodies could be in true balance any other way.  Certainly, we can get the idle smoother using the air bleeds, even if the throttle plates are out of balance.

 

Hence, the method of balancing the throttle bodies with the linkage (white knob) at "some RPM" closer to what we might be operating under way then "fine tuning" the idle RPM with the air screws to account for variances that are accentuated at idle. Also, I have found that setting idle a bit higher minimizes the idle stumbles and coughs.

 

There are several other *hiccup* makers in the system to be considered as well . . .

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Since the "white knob" actually sets the true relationship between the throttle plates, I cannot conceive that the throttle bodies could be in true balance any other way.  Certainly, we can get the idle smoother using them, even if the throttle plates are out of balance.

 

Hence, the method of balancing the throttle bodies with the linkage (white knob) at "some RPM" closer to what we might be operating under way then "fine tuning" the idle RPM with the air screws to account for variances that are accentuated at idle. Also, I have found that setting idle a bit higher minimizes the idle stumbles and coughs.

 

I fully agree, that's what surprised me as well, that it does not idle as nicely then. What do you call "a bit higher"?

Also keeping in mind mine has a Centauro flywheel mounted when it was converted to a 2-plate clutch, which may have a lower centrifugal weight.

Maybe I just have to re-set it using the "white knob method" and take her for a ride... Because in the end, how much time do you (should you) spend idling?

 

There are several other *hiccup* makers in the system to be considered as well . . .

Oh please, which are? :ninja:  :whistle:

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One way to ensure smooth tickover is the Harley mod, they shut down the rear cylinder when idling. So simple.

 

Problem: rear cylinder overheating at idle.

Solution: turn it off!

So only one cylinder running = smooth tickover.

 

A bit of fiddling with GuzziDiag and its done.

 

Myself I prefer not sitting around at idle and to ignore any unbalance.

 

Could not find a tongue-in-cheek emoticon.

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Since the "white knob" actually sets the true relationship between the throttle plates, I cannot conceive that the throttle bodies could be in true balance any other way.  Certainly, we can get the idle smoother using them, even if the throttle plates are out of balance.

 

Hence, the method of balancing the throttle bodies with the linkage (white knob) at "some RPM" closer to what we might be operating under way then "fine tuning" the idle RPM with the air screws to account for variances that are accentuated at idle. Also, I have found that setting idle a bit higher minimizes the idle stumbles and coughs.

 

I fully agree, that's what surprised me as well, that it does not idle as nicely then. What do you call "a bit higher"?

Also keeping in mind mine has a Centauro flywheel mounted when it was converted to a 2-plate clutch, which may have a lower centrifugal weight.

Maybe I just have to re-set it using the "white knob method" and take her for a ride... Because in the end, how much time do you (should you) spend idling?

 

There are several other *hiccup* makers in the system to be considered as well . . .

Oh please, which are? :ninja:  :whistle:

 

I like my idle closer to 1350. With a lighter flywheel, a higher idle is a pretty simple way to smooth out the power pulses. Other than it sounding like it's idling a little high, I've never heard that a slightly high idle has any downsides. (I started out wanting my Sport to lope at idle like a big block Chevy V8 with a big cam . . . :whistle:  )

 

I chased a "hiccup" for about 10 years.  There is a ten page thread that details the process of discovery.  Over half of it is about discovering the best relays for the V11. Looking back, I'd say I was chasing "The Hiccups", maybe a handful of different things. In short: inadequate /under rated relays, incorrect TPS baseline, incorrect CO Fuel Trim (both covered on the "Decent Tune-up" procedure), a damaged TPS right at the point I wanted to cruise along, broken/corroded coil wire connection to the right coil, erratic voltage from a marginal charging system/ battery/ connections/ melting 30 amp fuse.

 

Nasty Hiccup thread: https://www.v11lemans.com/forums/index.php?showtopic=19610  (lengthy)

Decent Tune-up thread: https://www.v11lemans.com/forums/index.php?showtopic=19610 (detailed tune-up procedure)

Best Relay thread: https://www.v11lemans.com/forums/index.php?showtopic=19755&p=216605 ("answered" post)

 

The Best Relays, Decent Tune-up, and TPS replacement were the key issues.

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Yeah I remember Docc tearing hair out over it until he tested the TPS.

 

I tore my hair out until I discovered the fuel return hose nudging the TPS ever-so-slowly out of spec. Over and over.

 

That being said, my bike, although running sweetly as ever, does occasionally hiccup....just once.....usually at idle.

 

I always freeze......oh shit...!.....then relax when it disappears and so I take off.

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