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Fuel tank expansion due to ethanol


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I would like to take the tank off of my 2000 V11 Sport to tidy some things up and replace the plug wires but I'm wary of tank expansion and not being able to get the tank back on properly.  How many folks have had problems with tank expansion and how bad was the expansion/distortion?  

 

TIA  John

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I had an expanded Ducati tank that I put out in our all glass " sun room" this summer..especially on those 100 deg plus days...it is unbearable hot.. I washed it with dish soap first then sat it on a

My experience is to run the tank down as low as possible before removing, and after removing just drain / pour out whatever fuel is left. I think it is better to let the tank sit empty. Also, a number

When this lockdown thing ends and life gets back to normal I'm going to see the guy around the corner thats a retired sheet metal craftsman that used to specialise in remaking and repairing bodywork f

the tank will get longer while it's off. 2-10mm. I had my tank off a couple years ago while doing a lot of work through the winter, maybe 6 months, drained of gas, and it went back on fine, so they do move back some. I had it off this spring for one day and it lengthened about 4mm. Likely depends on regional fuels. I've used wood blocks as leverage, a big phillips to align the bolt hole, it's a pita but has to be done. The po of my parts bike welded the nut mount back further to the rear. Some use a ratchet strap, which I did last time and it worked ok.

All in all I'd say my tank is not as stretched now as it once was. Weird I know, but I can tell from the distance at the seat body front mount. It used to touch there years ago.

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Wow. Is this something that we just learn to live with? I’ve heard the same thing and have avoided removing the tank, which seems lame. Does letting it dry out and coating it help? Will the tank eventually fail, like cracking or what ever could befall it from distortion, or is it just a long-lived irritation?

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Thanks Footgoose.  I have the problem with the resin tank on my MZ.  Draining it and leaving it empty in the garage  over the winter did not help.  I'm glad that the Guzzi tank "shrunk' back for you.  I'll probably take it off right before it goes on the stand for the winter and put the tank in the attic to dry and shrink.

 

Kane:  pretty standard stuff for these plastic tanks of a certain age.  Some of the MZ guys report paint cracking but there are no reports of the actual tank cracking as far as I know.  I just don't bolt the MZ tank down anymore.  :)  

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When planning for a tank-off on the V11, I run the fuel level as low as possible and prepare a place to set the tank (a saw horse works great to keep the pressure off the bottom of the tank which may spread it more). I have also found keeping the tank the same temperature while it is off has introduced less distortion.

I have had consistent results with the ratchet strap, but compress gradually and gently. The various methods to reinstall are detailed here:

 

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My experience is to run the tank down as low as possible before removing, and after removing just drain / pour out whatever fuel is left. I think it is better to let the tank sit empty. Also, a number of people have reported their tanks "shrinking" back to normal size if left to sit empty. As noted by docc, a good idea is to let it sit over a saw horse or other set up that mimics the mounting.

After letting ours sit empty over winter it shrank back to a more normal size. I then used an epoxy tank coating to hopefully better seal it. Time will tell if that works out better or worse.

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It sounds dangerous, but has anyone heated an empty tank to maybe 125º for some time (hours or days) to take advantage of the "plastic memory" effect? If there is a crash-damaged tank out there, it would be interesting to see if this had any effect. 

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5 hours ago, po18guy said:

It sounds dangerous, but has anyone heated an empty tank to maybe 125º for some time (hours or days) to take advantage of the "plastic memory" effect? If there is a crash-damaged tank out there, it would be interesting to see if this had any effect. 

I had an expanded Ducati tank that I put out in our all glass " sun room" this summer..especially on those 100 deg plus days...it is unbearable hot.. I washed it with dish soap first then sat it on a stool for about 2 months during July August turning it over every day..I know it was way over 125 most days. On some  days I even stuck a small hair dryer on low inside the fill hole and let it blow thru to the fuel pump hole for hours ( remember I thoroughly washed it with hot water and soap first and blew it out with the compressor) It  came down nicely..it looks and fits great , like new now..I've done the same with 2 Aprilia tanks in past years.    This time I also put a big sock filled with silica beads inside..not sure if it helped.  I've done about 6 Ducati and Aprilia tanks over the years..some I left off and hung on the garage wall for 3-5 months after washing with dish soap...all shrunk down fine for me.

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One of thing I've had good fortune is that I've gotten the tank on and off.  The biggest issue is that silly petcock that needed vice clips to shut off.  Since I've lost a lot of gas during the removal process, perhaps that's been my fortune?

I think this ethanol gas stuff is just an excuse instead of admitting to poor quality control.   These tanks are molded in plastic, that's the fact.

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35 minutes ago, LowRyter said:

One of thing I've had good fortune is that I've gotten the tank on and off.  The biggest issue is that silly petcock that needed vice clips to shut off.  Since I've lost a lot of gas during the removal process, perhaps that's been my fortune?

I think this ethanol gas stuff is just an excuse instead of admitting to poor quality control.   These tanks are molded in plastic, that's the fact.

Here's the solution

Ciao

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1 hour ago, LowRyter said:

One of thing I've had good fortune is that I've gotten the tank on and off.  The biggest issue is that silly petcock that needed vice clips to shut off.  Since I've lost a lot of gas during the removal process, perhaps that's been my fortune?

I think this ethanol gas stuff is just an excuse instead of admitting to poor quality control.   These tanks are molded in plastic, that's the fact.

I think they are actually a type of Nylon from all I've read.

 

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No issues getting my '04's tank off/on and aligned independent of fuel level....

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2 hours ago, KINDOY2 said:

I had an expanded Ducati tank that I put out in our all glass " sun room" this summer..especially on those 100 deg plus days...it is unbearable hot.. I washed it with dish soap first then sat it on a stool for about 2 months during July August turning it over every day..I know it was way over 125 most days. On some  days I even stuck a small hair dryer on low inside the fill hole and let it blow thru to the fuel pump hole for hours ( remember I thoroughly wished it with hot water and soap first and blew it out with the compressor) It  came down nicely..it looks and fits great , like new now..I've done the same with 2 Aprilia tanks in past years.    This time I also put a big sock filled with silica beads inside..not sure if it helped.  I've done about 6 Ducati and Aprilia tanks over the years..some I left off and hung on the garage wall for 3-5 months after washing with dish soap...all shrunk down fine for me.

Good information and ery good news. I wondered, since all thermoplastic has a memory effect if deformed. Heat (thermal energy) will aid in the recovery of shape/size. On later tanks with pump in tank, a hair dryer or CPU fan could more easily be used to aid the process.

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3 minutes ago, po18guy said:

Good information and ery good news. I wondered, since all thermoplastic has a memory effect if deformed. Heat (thermal energy) will aid in the recovery of shape/size. On later tanks with pump in tank, a hair dryer or CPU fan could more easily be used to aid the process.

Well that is just my experience..maybe someone else has had a different one..I got the tanks pretty damn hot in the sunroom and with the hair dryer..you could hardly touch them..and they seemed to hold up fine..another tip I've learned is if you have a few little bubbles in your paint you can carefully heat them up with a hair dryer or a heat gun on low, then take a needle and puncture them a time or two and press the  gasses/air out with your thumb and carefully massage them a bit and they will usually lay right down..you can hardly see the needle hole and its sure better than a bubble..I did 2 different Aprilia tanks that were swollen and had mutiple small bubbles and after I dried them out I put a coat of Caswells inside ... that was 7-8 years ago and I see both the bikes around today and the bubbles still haven't returned.

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After I dried out my tank (just letting it sit for maybe a couple weeks with the cap open at room temperature) I've had issues with spooge exiting the overflow/tank vent lines.  I've suspected that something changed with the internal lines that are "somewhat" coated in the tank's Nylon material. I say "somewhat" because I can see some big bulges along their lengths.

Not sure what changed, but it didn't spooge like this before I dried it out.

 

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