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Discussion Starter #1 (Edited)
Hey guys, Derrick here. I typically don't post but, rather spend my time lurking and gathering info. :) Anyway I come to you guys with a problem that I haven't been able to figure out thus far. I have a 2012 F4 RR Corsacorta that's running like shit below 4500 rpms. The only engine mods at the moment are exhaust flapper valve disconnected and Bodis slip-on. Below 4500 rpms it backfires pops and sputters and idles really low. Feels like its misfiring or running on less than 4 cylinders lol. Above 4500 it feels like the shower injectors kick in or something and the bike rips. I did some research on this forum and found a few really old posts that i'm not convinced relate to my F4. To date I've ruled out the ECU, bad fuel, fuel pump, fuel filter, fuel lines and the fuel injectors and fuel rail as well. I'm fortunate enough to have a second working track F4. So I swapped these working items to my street F4 and it ran just as poorly. Last night I pulled the plugs and inspected them and all look normal. Meaning, they don't look wet or fouled. Regardless I'm going to replace them with fresh plugs this evening. However, if it runs the same that would only leave coils and or the TPS correct? Any ideas would be greatly appreciated. Thx guys!
 

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I'd be looking for vacuum leaks. Did you swap ECUs also?
 

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Discussion Starter #3
yes I did. I swapped in two actually. I have a OEM MV "Race" ECU on stand by as well as the ecu from my track F4. Both had the same results.
 

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Discussion Starter #4 (Edited)

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Since the problem exists outside of the ECU, then you have to check downstream things.

It is Fuel, Vacuum or Spark.

How did you eliminate the fuel system?
 

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Discussion Starter #6
Since the problem exists outside of the ECU, then you have to check downstream things.

It is Fuel, Vacuum or Spark.

How did you eliminate the fuel system?
I swapped the entire tank from my F4 track bike. it has fresh fuel just added this past weekend. I also swapped the entire fuel rail with injectors.
 

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Alrighty then! It is either spark or vacuum....you said spark plugs look good and not fouled, so I would be looking for vacuum leaks.
 

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Discussion Starter #8
Alrighty then! It is either spark or vacuum....you said spark plugs look good and not fouled, so I would be looking for vacuum leaks.
Now that I that you mentioned vacuum and I think about it a bit. The bike does lope at bit at idle which makes perfect sense for a vacuum leak. Thank you sir! I'll start checking the vacuum lines when I get home tonight. :)
 

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What was the last thing you did with this bike immediately prior to it starting to run poorly at low rpm?
 

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Discussion Starter #10
What was the last thing you did with this bike immediately prior to it starting to run poorly at low rpm?
That's a very good question. This bike has a history and not all of it good. But the short version is, it was being painted. The slightly longer version is, the last time the bike ran properly or ran at all was approx 8 months ago. Since then it's been with my painter. Don't get me started on why he had the bike that long, as that's another topic of conversation :| However, my feeling is that, in the time he had the bike, the vacuum line(s) developed a leak or cracked or who knows while sitting, or that happened during reassembly? So the bike hasn't run in nearly 8 months until recently. So I've gone through the bike (for a second time) and did all the things you should be before firing up a bike that's been sitting for a long time. Anyway, it started fine but as I mentioned before, runs like crap at low rpms.
 

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...and it ran fine when you dropped it off?
 

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Discussion Starter #13
I just realized you're in Duxbury. I grew up in Stoneham. In fact, in a week or so i'll be in Haverhill for the summer :)
 

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I just realized you're in Duxbury. I grew up in Stoneham. In fact, in a week or so i'll be in Haverhill for the summer :)

Well, taking all of that into consideration, it seems that something is probably not plugged into where it should be.

If the painter took the bike apart, as you imply, then I'd be checking all of the work that he did.

If you'd like to pop down to Duxbury for a visit, I am retired and can host whenever you have time.
 

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Discussion Starter #15
If you'd like to pop down to Duxbury for a visit, I am retired and can host whenever you have time.
I might take you up on that, thx for the offer! I'll know more once I get home
 
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Discussion Starter #16
***Update***
I checked for vacuum leaks but didn't find any. I don't have a smoker so I removed each line and inspected them. I did replace a few just because I had already purchased a few feet of vacuum hose. I also replaced the spark plugs with the standard NGK CR9EB's. While I was in there I tested the resistance on each coil. I don't know what the primary and secondary resistance specs are but, all were reading pretty much identical except for the #2 coil. So I pulled one from my track bike and replaced the #2 coil. Now the bike is running much better, which is to say it runs like a typical poorly tuned italian superbike bike hahaha! Now I can move forward with my performance mods and tuning! Thx @silentservice703 for your assistance.

BTW, if anyone has the coil primary and secondary resistance specs please post them or direct me to where I might find them. I can't seem to find them in my service manual.
 

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?

Air leak.......
Go to the hardware store and store and buy 8, M4x25 Allen head screws and a 3mm ball end Allen screwdriver
Now replace the Phillips head screws on the intake manifold hose clamps.......you'll thank me later

Stop at the auto parts store and get some flammable brake cleaner
Have a CO2 fire extinguisher handy

Lift and support the fuel tank
1st do a visual of all the vacuum lines and caps, don't forget the EBS hose on #2

Start the motor and go exploring with the plastic tube in the spray nozzle of the brake cleaner:wink2:
When you find the leak, engine speed will immediately rise
 

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Discussion Starter #18
Air leak.......
Go to the hardware store and store and buy 8, M4x25 Allen head screws and a 3mm ball end Allen screwdriver
Now replace the Phillips head screws on the intake manifold hose clamps.......you'll thank me later

Stop at the auto parts store and get some flammable brake cleaner
Have a CO2 fire extinguisher handy

Lift and support the fuel tank
1st do a visual of all the vacuum lines and caps, don't forget the EBS hose on #2

Start the motor and go exploring with the plastic tube in the spray nozzle of the brake cleaner:wink2:
When you find the leak, engine speed will immediately rise
I thought about the brake cleaner method and decided against it. I'm going on vacation in 2 days and don't want any trips to the ER before hand LOL! And yes my bike already has those screws replaced with allen head screws. Although one is kinda stripped and needs to be replaced. I'll get to that next :grin2:
 

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Thanks Knurl for the tip! Putting back together my bike AND removing those silly Philips head screws were a bi#$%! Can't imagine putting them back in!
 

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I just searched my resources and could not find the coil resistance spec.

There is no primary coil as the Plug Top Coils are driven by a low voltage signal from the ECU.
 
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