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Discussion Starter #1 (Edited)
Hi everyone, new to the Forum and MV ownership, so please bear with me.

After nearly 30 yrs of Ducati ownership I decided to jump ship to the MV family by purchasing a 2004 Brutale S 750 with 31000 kms on the clock, cafe racer belly pan and carbon fibre goodies, a lovely looking m/c.
But, (there's always a but) after a couple of weeks she started to run rough and generally misbehave.
This started after I had refilled with fuel from near empty.Thinking the fuel was dodgy I drained the tank and replaced fuel and air filters and added injector cleaner to tank.
When starting, it idles freely at approx 1200 rpm and seems o.k but as you drive away begins to miss, lacks power, occasionally backfires and bogs down. This lasts until temp reaches 90 deg C + (which takes around 15 to 20 mins)and then runs O.K after that, if you stop long enough for it to cool down to say 70 deg c the process starts again.
My first thoughts were to replace the plugs, which i should have done when I had the tank off previously!, but could it be a sensor of some sort i.e air/fuel or Vac.?.
When going well this is a great m/c to ride and this little hick up isn't enough to steer me back to Bologna but before I start throwing the $ around any information would be greatly appreciated.

Apologies in advance if this issue has been covered previously and my slow response to any replies, I work night shift. I'm located in Brisbane, Australia

Regards, Mick
 

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I?

1st Welcome Aboard the Forum......

Now check the SPU .....it's the unified fuse block/ relay POS on the right side of the

bike.......if the back is blue that's a usual problem...... if it's black you're good to go

Now check for air leaks in the small lines coming from the throttlebodies to both sides

of the frame and the clamps on the hoses on the throttlebodies

If it's taking that long to warm up remove the thermostat housing to make sure that the

thermostat is there

Report back.......you've done the fuel/injector stuff.....

Be VERY CAREFUL WITH THE INJECTORS....... THEY ARE FRAGILE!!!!!!!!

and the 750 ones are RARE= EXPENSIVE


:popcorn:
 

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Um, Noel, I do believe you have it backwards. The BLUE backed SPU is the one with all the degradation and faults. The BLACK backed SPU should be better.

Michael, read here: http://www.mvagusta.net/forum/showthread.php?t=41943
BATTERY...check the battery !


Yeah..The blue one caught fire on Cag's bike I seem to recall...


Not wanting to diagnose as such but please check your battery condition and the security of the connections. I had masses of grief with my bike popping and banging and stalling ..It was embarrassing really ! and after the disgrace of having her recovered back to my garage I did a methodical check through and the first thing I checked was the battery..The Ground lead had worked loose.

One simple turn of a wrench and problem evaporated !





joe
 

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Discussion Starter #5
G,day Everyone
Thanks for the prompt replies.I'll check out all your suggestions and the SPU in the next day or two.
Whats thrown me is that it runs fine when the temp is between 90-100 deg c, when I first brought it home it didn't display any hesitation at the lower temperatures. Cheers and thanks again.
Michael
 

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Besides the plugs, you should probably check the idle speed with the diagnostic software (not the tach on the bike!). Low idle speed causes rough, lumpy idle and poor off idle performance. Improves with heat because the fuel mixture is more close to ideal when engine is hot. Maybe a bit rich when cold.

Air leak problems frequently get worse with heat. SPU electrical issues (while numerous) are usually more related to erratic lights, and other relay controlled gremlins than the EFI system.

Remember, it's always something simple. Check your idle speed.

OK, that's my worthless 2 cents worth.


OH! And welcome to the family!
 

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Ed;

It's taking 15-20 minutes to warm up......the thermostat is gone or stuck open...... easy

fix

It's back firing and has no power when cold..... it's lean.....

it's also 12 years old all rubber is suspect by then.....

air leaks are worse on a cold motor because of poor vaporization of fuel.....especially

at low engine speeds, and because the percentage of leaked air is higher making it

worse, than at higher engine speeds where manifold pressure is higher ie less leakage

On the Aprilia Forum people worry about syncing the TBs with the bypass screws....

on a 3mm passage with a M5x 0.8mm screw that's open 1/2 turn VS a 57mm throttle

kind of mental masturbation to say the least......

and Aprilia TBs are almost solvent tight not like the POS Weber Marellis


:)
 

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Discussion Starter #9
Hi Noel,
thanks for the reply. In regards to the thermostat would a clean up normally do the trick or would it be better to replace it ? (remember there are no stupid questions only stupid people!). Also the 2 drain /vent tubes inside the tank that meet at at T on the fuel pump body, do they just drain or are they used in the Vacuum system?there wasn't any pipe attached to this when I removed the tank. cheers

Mick.
 

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Discussion Starter #11
thanks donsy, I thought so.

Just finished removing the tank and having a look at the SPU, which is an all black affair with no obvious markings, checked out all the fuses and connections. Pulled out the no.1 & 4 plugs which are NGK CR9EB with a gap of 1.1 mm, both looked as old as I am with a lot of corrosion, no.4 running lean but no.1 looked ok so I will replace the plugs later in the week, would you go with these or is there a better plug to use ? cheers.
 

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NGK Iridium seem to be a popular choice..do a forum search on " Iridium"

Did you check your battery connections and test the battery voltage drop at start up / generator out put? .Before you start dismantling your bike that is ; ) Many of us have jumped at complex solutions when the problem is as simple as a bad battery.

Good that you have the black backed SPU..That's a relief !

joe
 

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It starts and runs no charging light......forget electrics

1 & 4 plugs are fired by the same coil and same injector driver fires 1 & 4 injector

But they look different???? Air leak?

Plugs should be gapped 0.7-0.8mm that alone can make it run like shit when cold,

Some ignition systems can NOT handle big gaps..... Like.Bosch

Slow to warm? No thermostat or a stuck one

:)
 

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Discussion Starter #15
G'day Noel,
I'm not too worried about the lean plug at the moment as the air filter I replaced was perished and there wasn't any silicone lube around the air intakes, I 'll throw a new set of plugs in tomorrow and fingers crossed she'll be good to go! I will also check the thermostat as it does seem to take a while to reach running temp. cheers, Mick
 

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Mick;
Get 8 M4x 25mm Allen head screws and replace the intake manifold clamp screws

Also get a 3mm ball end Allen screwdriver......

by the time you get the old Phillips out you'll be cussing a blue streak

:naughty:
 

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Discussion Starter #17
G'day Guys,
As it does a lot these days, life got in the way but I've Finally gotten round to fitting the new NGK Iridium plugs, checking the charging system and tightening the intake fittings, etc which has happily erased all of the drama's which caused me to consult the forum in the first place :).
She's now back to normal, which is screaming like a mad woman with a thirst like the town drunk!
Thanks to Donsy and Noel and all who took the time to give advice and share their knowledge.
Cheers,
Michael.:brutale:
 
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