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Everyone missed something in Buck's original post.....
His bike has 100,000kms on it.......he has a simple air leak:wink2:

Buck;
Go to the auto parts store and buy 4 vacuum caps to fit the fittings on the throttle bodies, get a tube of
Form a Gasket silicone seal if you don't have one
Go to the hardware store and buy 8, M4x25 Allen screws and a 3mm BALL end Allen screwdriver
Replace the stupid Phillips screws in the manifold clamps, tighten correctly
If you want to sync the throttle bodies you'll need a vacuum gauge......
I use a Uni-Syn, and have been since '59 they're $20-30 on eBay
Remove the plastic air horns, clean them and seal the stupid holes closed with silicone seal, set them aside
You must do this if you use a Uni-Syn
Now look down your intakes.....does the gap between the throttle blades look the same on 1&2 and 3&4?
This is where you ignore the manual......you want to make 1&2 the same as 3&4, the human eye is great at discerning tiny gaps
or use a narrow feeler gauge
You use the left screw to do this......the one they tell you NOT to touch........Chuck and Donsy helped me do this at Bubba V
The left screw adjusts the difference between 1&2 and 3&4, I'm surprised Chuck forgot, I don't know if Ed saw me do this
Ed, There are no Nylocks in the MV throttle linkage, they don't move unless severely abused:wink2:
Pictures......the throttle bodies are upside down
 

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Discussion Starter #23
So this is how it went.
We found the screw with the paint and unpainted it. While it does control the blades, opening or closing them slightly, none of that has the desired effect on idle rpms. Meaning, you twist it a bit backwards or forwards, nothing changes, until you hit a certain blade angle where the engine would abruptly jump from 1100-something right to 1700-2000. There's literally nothing in between and that's how it's always been. There's no gradual throttle "mode" on Brutales that would have a nice curve going from idle 1100 onwards, instead it would sit at 1100 while it can, then jump to 2000 and then go smoothly upwards from there. Which means it's the ECU controlling the idle, after all? I was hoping for some analog magic but it doesn't work that way.

We did open the valves a bit, reset TPS and did the balancing which went pretty well (it wasn't all that bad initially, just the rightmost two were out of sync with the leftmost two and another screw fixed that). And then nothing changed. So we brought the painted screw back (the best we could) and upped the fuel mix which was set to "-10" before and set it to "8". After we did all that the engine started revving down much more slowly and "in waves". Like in a wah-wah-wah kind of way. We'd rev it up to 8k and it would go smoothly to say, 6, then go slow for a moment, then normally down to 4, slow down there for a moment, then normally down and so on. Never saw that happening before. It was always smooth up or down. So that's problem number 1.

Problem number 2 is that it has a hard time going back to idle now while riding. Most of the time gets stuck at 2k and after a bit of prodding it may or may not go to 1100, only to get stuck again after you rev it up. Don't know if it's because we didn't put the screw all the way back or if it's something else.

The bottom line which is problem number 0: stalls when revving down still keep happening.
 

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How are you observing idle speed?
What are you using to adjust Fuel Mix?
 

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Discussion Starter #26
Idle speed observed and fuel mixed changed in a software which name I didn't write down. It's not MV's but rather works for many brands and has a large silver box connecting to the diagnostic port. So you choose Brutale 1078 there and it shows a set of params it can work on along with sensor data in realtime. Throttle angle was there as well so we were observing it while twisting the screw back and forth. TPS reset performed there.

I don't think another set of plugs is in order, those were basically just changed and are NGK's regular iridium plugs. Fresh.
 

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On anther note...tight valves will cause stalling and hanging idle..... Have you checked valve clearances??
 

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Discussion Starter #28
No, we haven't checked valve clearances.
I'd like to know how folks have suggested messing with that screw when obviously it doesn't do what they say it does (controlling idle rpms).
 

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So this is how it went.
We found the screw with the paint and unpainted it. While it does control the blades, opening or closing them slightly, none of that has the desired effect on idle rpms. Meaning, you twist it a bit backwards or forwards, nothing changes, until you hit a certain blade angle where the engine would abruptly jump from 1100-something right to 1700-2000. There's literally nothing in between and that's how it's always been. There's no gradual throttle "mode" on Brutales that would have a nice curve going from idle 1100 onwards, instead it would sit at 1100 while it can, then jump to 2000 and then go smoothly upwards from there. Which means it's the ECU controlling the idle, after all? I was hoping for some analog magic but it doesn't work that way.

We did open the valves a bit, reset TPS and did the balancing which went pretty well (it wasn't all that bad initially, just the rightmost two were out of sync with the leftmost two and another screw fixed that). And then nothing changed. So we brought the painted screw back (the best we could) and upped the fuel mix which was set to "-10" before and set it to "8". After we did all that the engine started revving down much more slowly and "in waves". Like in a wah-wah-wah kind of way. We'd rev it up to 8k and it would go smoothly to say, 6, then go slow for a moment, then normally down to 4, slow down there for a moment, then normally down and so on. Never saw that happening before. It was always smooth up or down. So that's problem number 1.

Problem number 2 is that it has a hard time going back to idle now while riding. Most of the time gets stuck at 2k and after a bit of prodding it may or may not go to 1100, only to get stuck again after you rev it up. Don't know if it's because we didn't put the screw all the way back or if it's something else.

The bottom line which is problem number 0: stalls when revving down still keep happening.
I would say back the throttle stop screw back more and re-set TPS again.
Also check those vacuum caps like Noel said for vacuum leaks.
You can check for vacuum leaks easily by spraying some Aerostart around all the vacuum connections/caps and if the revs rise there is your leak.
 

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Exactly what italia said, any play between where the 2 throttle body sides meet and you'll get stalling. Easy fix
 

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@Buck: What are you using for guidance? Here are some excerpts from the appropriate manual dealing with idle speed:

476460

476461

476462


It also occurs to me that some have had issues with "slow" idle return when the rubber hand grip contacts the throttle cable housing and drags on the return.

As a request, could you please put the year and model of your bike in your signature line. Right, now the only identifier in the thread is 1078RR...that could be F4 or B4. The longer this thread goes on, the harder it is to figure that out.
 

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Discussion Starter #33
Added the signature.

We do look at the same manual, however at least in the images that you posted @silentservice703 idle rpms are not mentioned as configurable. That part concerns balancing the bodies and tightening or loosening of the throttle cord. I've played with that. The latter can be controlled with the painted screw, setting the idle throttle angle. But beyond that there's nothing you can seemingly do, as it appears that the angle is an absolute value that is passed over to the ECU. So it will always "idle" at 0-2.5° and will always momentarily switch to "live" at >2.5° (give or take, I don't remember the exact number) meaning there's nothing inbetween. It's either 1100rpms (idle) or 2000rpms (live, or what they call a "fast tickover"). You can't adjust the idle to, say, 1400rpms just by balancing the bodies or using that screw. Much like you cannot achieve said rpms by using the throttle lever when not moving. Unless I'm severely misunderstanding something there.

My issue with going back to idle is most definitely tied to not putting the screw back into its original position, but that's fixable. I was thinking more about how people were sure one could contol the idle speed with that screw.
 

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It’s a simple concept, add fuel and air and you get speed.
 

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I’m in no position to go out and tinker, or I would. It will be a month before I have my Brutale...or any other bike...out of the trailer to play with.
 

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I went through and read the whole thread.
A few things to make you stop and think about the situation:

So from what you have written, after a spirited ride, you are pulling up to a stop and pull the clutch and it stalls?

From what I understand, you have a bike with relatively large kms.
The stalling has gradually become worse, so it is not related to some recent mechanical work you have done to upset things?
There are no stored error codes, so the obvious diagnostics have been covered?

From what I can see everything you are doing is addressing the symptoms, rather than the cause. Fiddling with mixtures shouldn’t be necessary unless something has changed. You need to establish the cause - check, check and check again.

To rule out air leaks, have you properly checked every rubber hose and plug related to the intake system? Not just visually, get messy and spray the plugs and hoses with wd40 or similiar while it is running and listen for a change.

Have you changed the CCT or cam chain at all? Have you checked the valve tolerances as per the schedule and the method as in the workshop manual? Have you done a compression test, looking for differences between cylinders?
 

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What he said ^^^. Valve clearance comes to mind. Tight valves cause idle issues.

That said, I successfully adjusted idle speed on my 910R using the throttle stop screw. It is basically the same thing as the idle speed screw on any other bike. You do have to reset TPS after changing it so the ECU fuel map knows what is the base point.
According to the manual, you should be able to adjust idle speed with the air bleed screws, but that didn't work for me either since the butterflies were closed too far.
 
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