MV Agusta Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
876 Posts
Discussion Starter #1
On the right side of the #2 throttle body there is a spacer approx. 5/16" wide (appears to be aluminum) between the throttle body casting and the nut on the end of the shaft the butterflies are mounted on. The spacer will move side to side about 1/16" and spins on the shaft when I rev it. I'm wondering if it could be the source of an air leak causing the bike to stall when throttle is closed while riding. It doesn't stall when revs drop from any level when in neutral.

Please note I have already removed the charcoal canister, replaced the fuel filter and checked hoses for damage, replaced the throttle cables, had the injectors cleaned, thoroughly cleaned the throttle bodies, replaced the TPS (in that order), synced throttle bodies and reset the TPS using VDST numerous times. Lambda sensor readings look good. I have manually confirmed 2.3 degrees on the butterflies, I have tried it at 3.0 degrees with same results. Barring a confirmation of my suspicions regarding the spacer, I'm going to try closing the butterflies below 2.3, don't know what I expect that to tell me but I'm running out of ideas. I'm considering replacing the throttle bodies but I would like the next move to be based in logic and reasoning rather than desperation.

The bike has 28,000 miles on it so I am looking for wear-related issues at this point. It started as a rarity and became progressively worse over the last 2-3000 miles till it is almost every time. From 3000 rpm and lower it is less likely to happen. Haven't checked the valves but it starts immediately and runs great otherwise. Oh yeah, 08 910S euro 3. Stock other than cat delete with a bung for the Lambda sensor.
 

·
Registered
Joined
·
1,660 Posts
What is the idle speed according to the vdsts?
What ecu are you running?
The ecu normally has differences between neutral and in gear with clutch released. Also, there will be default mapping if the ecu is looking for an O2 sensor reading and getting nothing.
 

·
Registered
Joined
·
876 Posts
Discussion Starter #3
The ECU is the original that came with the bike. VDST shows Lambda volts moving between 0 and 1000 as the manual says, percent moves up and down between -6 and +12. Idle is 1180 to 1240. 1-3 air screws are at 2 1/4 - 2 1/2, 4 is 1 3/4. #4 always ends up lower than the others.
 

·
Registered
Joined
·
1,660 Posts
So if I read this right, you are running the std ecu and mapping, and have done a decat. What I am confused over is whether you are using the lambda sensor?

Is it stalling when you pull the clutch in, like coming up to a set of traffic lights?
 

·
Registered
Joined
·
876 Posts
Discussion Starter #7
So if I read this right, you are running the std ecu and mapping, and have done a decat. What I am confused over is whether you are using the lambda sensor?

Is it stalling when you pull the clutch in, like coming up to a set of traffic lights?
I welded a bung on the midpipe and installed the lambda sensor. The vdst shows it reading properly and making adjustments.

Yes, when I pull the clutch in it stalls.
 

·
Registered
Joined
·
876 Posts
Discussion Starter #8 (Edited)
It won't let me download pics from computer, says they're too big. I put 3 pics in my photo album but I can't see how to put them in the message.
The screwdriver is on the spacer I'm referring to in one photo. It is filling the gap that represents how far it will move side to side in the other photo. One close up without the screwdriver.
 

·
Registered
Joined
·
1,660 Posts
Bit of a guess, but I think your std mapping is not coping with the lower back pressure from the decat. The way to find it would be on a dyno to check the afr on the overrun.

Is this something that has come on after a change you have made to the setup? How old are the plugs and what type are you running?
 

·
Registered
Joined
·
3,424 Posts
It won't let me download pics from computer, says they're too big. I put 3 pics in my photo album but I can't see how to put them in the message.
The screwdriver is on the spacer I'm referring to in one photo. It is filling the gap that represents how far it will move side to side in the other photo. One close up without the screwdriver.
If you copy the links from the albumpage it looks like this:





the shaft of the butterfly valves does not move, as there is no room within the throttlebodies.
Spacer is only for cabling guide and cable alignment, not very critical
 

·
Registered
Joined
·
3,494 Posts
Hi Augusta 17,I have a brutale 1078 and I replaced the throttle bodies with new, I had movement when standing in front of the bike looking at the left hand butterflies the ones on the tps side,there was were in the shaft , and so when turning the throttle. the tps side butterflies would slightly open first before the RH hand ones . you can actually see that the stem which holds the butterflies has worn the outer casing.

hope this makes sense

changing the tps position will do nothing,Tried all that.

cheers eddy
 

·
Registered
Joined
·
876 Posts
Discussion Starter #13
If you copy the links from the albumpage it looks like this:





the shaft of the butterfly valves does not move, as there is no room within the throttlebodies.
Spacer is only for cabling guide and cable alignment, not very critical
Thank you for the help with pics, I don't even know what "copy the links" means. I find computers boring. I only use it to buy ATV parts. But if they ever put wheels and a motor on one I'll be on it. It would seem the spacer is not an issue.

eddy/revhead, thank you as well. I forgot about the plugs. Iridium plugs was the first thing I did. Cat delete was several thousand miles before the problem started. I did consider putting the original exhaust system back on it but I can't see a logical reason why it would matter as long as the lambda sensor is working properly now.

Now I am wondering about the secondary air valve on the euro 3 models. I'm not finding any info about it so far. MV manual is no help.
Google search yielded nothing.

Anyway, my belly is full and the sun is shining. Time to start day 3 of the "It Can't Be That Difficult" campaign. On Wednesday I said this time I'm not doing anything else till I solve this problem. I may have to eat those words.
 
1 - 13 of 13 Posts
Top