Am I a victim of tank suck?

[wheelsucker]

I changed out the exhaust on my 2003 LM, Mistral x-over and FBF carbon pipes, installed the PC USB3 and map from Guzzi Tech. Ran fine in the morning at about 65F, it got up to about 80 today and on my ride home about 6 hours later my engine started sputtering and I had to keep revving the throttle to keep it running. Thought I might be running out of gas but filled up in 4 gallons. After filling up, bike didn't start for a few minutes then started up but sputtered for about 5 minutes as I rode on before returning to perfect/normal.

 

Anyone with any ideas???

[jtucker]

When you opened the cap to put gas in, did you notice any "woosh" of air rushing in? That would be a pretty good indicator of tank suck.

 

__Jason

[Ryland3210]

When you opened the cap to put gas in, did you notice any "woosh" of air rushing in? That would be a pretty good indicator of tank suck.

 

__Jason

 

If it is, there's a thread in the FAQ section on the subject and the tipover valve orientation required to prevent it. There is only one right way to connect and orient it, and it's not the way my bike came.

[stormsedge]

Directly after similar installs on my bike, which included an open airbox kit, I had similar problems. During the hot-rodding test phase, the open air box sucked the aluminum insulation panel from the bottom of the gas tank, effectively blocking airflow at certain rpm ranges. I check it and reglue once a year now. If it idles pretty well and starts cutting out above 3500 rpm or so, I'd suspect this as part of the problem. k

[dlaing]

I changed out the exhaust on my 2003 LM, Mistral x-over and FBF carbon pipes, installed the PC USB3 and map from Guzzi Tech. Ran fine in the morning at about 65F, it got up to about 80 today and on my ride home about 6 hours later my engine started sputtering and I had to keep revving the throttle to keep it running. Thought I might be running out of gas but filled up in 4 gallons. After filling up, bike didn't start for a few minutes then started up but sputtered for about 5 minutes as I rode on before returning to perfect/normal.

 

Anyone with any ideas???

Tank suck is obvious when you hear the whoosh of air that Jason mentioned, and the tank visibly gets wider as the air rushes in.

It would not have caused those symptoms that could have been caused by many things.

Could be vapor lock, although your aren't experiencing classic symptoms.

Make sure fuel lines don't touch hot engine.

Or maybe tight valves???? But that would probably have trouble idling.

Or a bad relay???? Or other electrical connection.

Maybe a bad ignition coil???

Or bad electric petcock, but I think your bike has the manual petcock.

[Ryland3210]

Directly after similar installs on my bike, which included an open airbox kit, I had similar problems. During the hot-rodding test phase, the open air box sucked the aluminum insulation panel from the bottom of the gas tank, effectively blocking airflow at certain rpm ranges. I check it and reglue once a year now. If it idles pretty well and starts cutting out above 3500 rpm or so, I'd suspect this as part of the problem. k

 

Holy smoke!

 

I'd better check mine. I recently eliminated the airbox cover and installed Staintunes without baffles.

 

Thanks for the heads up.

[toknee]

Yeah,

 

Just did similar mods:

 

Staintunes

Stucchi Crossover

FBF Airbox Eliminator

 

During the testing phase:

 

Day1 bike ran like a champ

Day 2 Ditto

Day 3, starts sputtering, kinda like not enough air, very rich exhaust smell, seems like it's runng rich.

 

Bike is ok to about 4000m then when I peg it WOT, it starts sputtering.

 

I need to take a look at this also, as this seems like the cause. I will pull the tank, and take a look at the padding attached to the bas tank.

 

 

 

 

Holy smoke!

 

I'd better check mine. I recently eliminated the airbox cover and installed Staintunes without baffles.

 

Thanks for the heads up.

[wheelsucker]

stormsedge,

 

what did you guys use to reglue the shielding on the underside of the tank?? I lifted my tank and the shielding was all bunched up in front of the air box just like you said.

[Skeeve]

stormsedge,

 

what did you guys use to reglue the shielding on the underside of the tank?? I lifted my tank and the shielding was all bunched up in front of the air box just like you said.

 

3M Super77 spray adhesive. The reason the Guzzi oem adhesive fails w/ regularity is probably due to their not choosing the 3M product...

 

Minnesota Mining & Materials' products are invariably pricey, but in my experience, invariably work as advertised.

[Guest ratchethack]

Holy smoke!

 

I'd better check mine. I recently eliminated the airbox cover and installed Staintunes without baffles.

 

Thanks for the heads up.

FWIW, during the short time I ran the "open top" filter bracket (before the horrendous intake honk started to make my ears bleed in earnest) I considered fixing an "arch" of heavy screen to the bracket just short of touching the insulation, to obviate any attempt of the aforementioned to disattach and strangle off air flow, as had been posted here by Stormsedge way back when.

 

Just an idea.

[quazi-moto]

I'm running Staintunes, FBF cross-over and FBF intake along with a My15M ECU. A while back I was getting severe tank suck and if I opened the filler cap I not only got a huge "woosh" but I could visibly see the tank go back to its normal shape. I took a rubber bulb type syringe and blew out the little doo-dad inside the filler neck and haven't had a problem since. FWIW I'm not bothered by the additional intake noise from the lidless filter kit, just don't put me on a Harley with open pipes.

[Ryland3210]

FWIW, during the short time I ran the "open top" filter bracket (before the horrendous intake honk started to make my ears bleed in earnest) I considered fixing an "arch" of heavy screen to the bracket just short of touching the insulation, to obviate any attempt of the aforementioned to disattach and strangle off air flow, as had been posted here by Stormsedge way back when.

 

Just an idea.

 

Thanks, Ratch. I wish I had known about this potential problem a while back, but I guess maybe my '04 used better adhesive, since I haven't noticed any problem when hot-rodding. Nevertheless, I'm going to pull the tank off to make sure.

 

I wonder what difference there may be between our bikes, because I haven't noticed any intake noise! I actually like to hear some moaning from intakes when I gun it. It reminds me of another pleasurable activity.

[Guest ratchethack]

I wonder what difference there may be between our bikes, because I haven't noticed any intake noise! I actually like to hear some moaning from intakes when I gun it. It reminds me of another pleasurable activity.

Probably aren't any differences in the bikes, but individual hearing sensitivties to certain frequencies and sound pressures are another thing altogether. When opened up anything over about half throttle over 6K RPM, it was frickin' excruciating in my case , whilst other guys seem to have no prob wotso??

[dlaing]

Probably aren't any differences in the bikes, but individual hearing sensitivties to certain frequencies and sound pressures are another thing altogether. When opened up anything over about half throttle over 6K RPM, it was frickin' excruciating in my case , whilst other guys seem to have no prob wotso??

Although my pain level was more annoying than excruciating, when you consider that hearing damage occurs below the threshold of light pain, earplugs and or airbox lids are a good thing.

I like the added power of no airbox lid, so I continue to annoy the world triggering car alarms while wearing earplugs.

The muffers sound sweeter with the airbox lid on, but the bike sounds and runs meaner with it off.

A better airbox could certainly be made.

[Ryland3210]

I find myself wearing earplugs primarily because of wind noise. I find the high frequency of that at 65+ annoying. Perhaps that's why the high frequency content of the intake noise isn't perceived. I also run the Staintunes without baffles.