Forums
 FAQHelp  LinksLinks    SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Fuel tank cracked - twice

 
Post new topic   Reply to topic    Forums » General Discussion Previous topic :: Next topic  
Author Message
Christophers
Member


Joined: 14 Oct 2010
Posts: 602
Location: Los Angeles, CA
Psycho

PostPosted: Mon Nov 18, 2013 8:30 pm    Post subject: Fuel tank cracked - twice Reply with quote

I was riding my Blackjack this Saturday up in the canyons, and over the course of about 5 minutes my fuel level went from just below half a tank to stone cold empty (needle on the pin). At first I thought I must have mis-read the gauge when I last looked at it. We were riding very hard and at altitude, and perhaps I was burning fuel significantly faster than I anticipated

I slowed the scoot down to 50 bmph and let the lead group pull away in front and babied the scoot for the next 4-5 miles (luckily, just recently turned to a downhill grade) to a stopping point where the lead rider had pulled over to wait for the rest of our group to catch up. While we were waiting I decided to refuel with the extra fuel I was carrying. Immediately, as I poured in my spare fuel, it started to leak profusely out of the bottom of the tank. The tank had cracked in a circumference around the weld of petcock where the autotap attaches to the tank.

Interestingly enough, this was not the first time that this had happened. The exact same thing happened about 2 months ago on the original tank, again after riding the scoot hard, for about 30 miles on the freeway this time. (Although the first time that this happened we were not riding quite as fast or quite as hard as when it happened the second time). The tank that broke this weekend was a new replacement tank.

Has anyone ever heard of this happening before? Or does anyone have any possible solutions to prevent it from happening again? Clearly something is going on that is causing this to happen. It would be too coincidental that I just happened to buy the one bike in the world with a defective tank and then the second tank in the world that has the exact same defect.

If Eric can help me out I would like to post a short 7 sec video of the fuel leak (from the first time it happened).


Last edited by Christophers on Mon Nov 18, 2013 9:08 pm; edited 1 time in total
Back to top
View user's profile Send private message  
BeefSupreme
Member


Joined: 25 Oct 2011
Posts: 306
Location: Mobile, AL
'12 Kymco Like 163, '12 Burgman 400, '09 Buddy 125

PostPosted: Mon Nov 18, 2013 9:07 pm    Post subject: Reply with quote

Did you replace the tank yourself or did you take it in. Any chance it was just poorly repaired and not replaced?
_________________
"Knees to the Breeze"
https://www.facebook.com/groups/GulfCoastScooterRiders/
GCSR Banner
Back to top
View user's profile Send private message   Visit poster's website
Tocsik
Member


Joined: 02 Jun 2008
Posts: 1938
Location: Denver
'08 Pamplona (sold) : '08 Suzuki S40 : : RIP: '75 Yamaha RD200 : '77 Yamaha XS400

PostPosted: Mon Nov 18, 2013 9:35 pm    Post subject: Reply with quote

I wonder if something is mis-aligned with your tank and it's getting some sort of shear stress from the frame or body parts. I haven't heard of any other Buddy tanks cracking; certainly not 2 on the same bike!
Hope you get it sorted out.

_________________
.::I know the voices in my head aren't real, but man do they come up with some great ideas::.
Back to top
View user's profile Send private message  
ericalm
Site Admin


Joined: 10 Jun 2006
Posts: 17637
Location: Los Angeles, CA
STELLA FOUR STROKE FURY! + Vespa LX 150/190 + '87 Honda Helix CN250

PostPosted: Mon Nov 18, 2013 9:51 pm    Post subject: Reply with quote

Odd. I've never heard of this happening before. Did it crack/break in the same place both times?

Worth mentioning that this scoot is HEAVILY modified. Is there anything that might be adding weight or pushing against it?

As for video, best thing to do would be upload to YouTube or Vimeo and we can grab the embed link!

_________________
Eric // Flickr group // LA Scooter Meetup Group // twitter: @scooterism // ScooterFile
Back to top
View user's profile Send private message [ Hidden ] Visit poster's website
Christophers
Member


Joined: 14 Oct 2010
Posts: 602
Location: Los Angeles, CA
Psycho

PostPosted: Mon Nov 18, 2013 10:09 pm    Post subject: Reply with quote

Oh, yes. Thanks Eric - I should have mentioned that the scooter is set up with a 177cc BBK, stroker crank, 30mm carburetor, 30mm intake manifold and a pod air filter (also running 11g Dr. Pulley Sliders). So when I say I was pushing it hard, I was really pushing it hard.

The tank cracked in the same place both times - circumferentially outside of the petcock weld.

The tank was professionally replaced, and neither the first time nor the second time did anything look like it was remotely close to touching either the bottom of the tank near the petcock nor the autotap itself. My current hypothesis is that the autotap is cracking the tank by shaking back and forth when running hard. One approach that I am considering to avoid having this happen again is to offset the autotap with a short piece of hose and mount it to the frame with some sort of bracket - possibly designed in CAD and 3D printed. Does anyone have the experience and/or equipment to assist in designing something?
Back to top
View user's profile Send private message  
ericalm
Site Admin


Joined: 10 Jun 2006
Posts: 17637
Location: Los Angeles, CA
STELLA FOUR STROKE FURY! + Vespa LX 150/190 + '87 Honda Helix CN250

PostPosted: Tue Nov 19, 2013 6:21 am    Post subject: Reply with quote

How do the hoses and clips look?

Wish I still had a Buddy to peer into!

_________________
Eric // Flickr group // LA Scooter Meetup Group // twitter: @scooterism // ScooterFile
Back to top
View user's profile Send private message [ Hidden ] Visit poster's website
Syd
Member


Joined: 18 Jul 2007
Posts: 4710
Location: Tempe
'09 GTS250

PostPosted: Tue Nov 19, 2013 6:48 am    Post subject: Reply with quote

Is all the smog stuff removed and the cop unvented? Could the fuel be building up excessive pressure in the tank?
_________________
The majority is always sane - Nessus
Back to top
View user's profile Send private message  
Christophers
Member


Joined: 14 Oct 2010
Posts: 602
Location: Los Angeles, CA
Psycho

PostPosted: Tue Nov 19, 2013 8:09 am    Post subject: Reply with quote

A couple of short videos of the leak from the first time.



Back to top
View user's profile Send private message  
lascooterservice
Member


Joined: 19 Nov 2013
Posts: 12
Location: Los Angeles, CA

PostPosted: Wed Nov 20, 2013 12:56 am    Post subject: Reply with quote

neither the fuel line nor the vacuum line are putting any undue stress on the tap-- both are lengthened and zip tied up and out of the way.

fwiw, the first tank cracked next to the tap in a small crescent shape that was not visible until removing the tank and holding it up to the light.

this time was a total failure-- the threaded bung where the tap attaches is entirely detached from the tank.

-g
Back to top
View user's profile Send private message  
Christophers
Member


Joined: 14 Oct 2010
Posts: 602
Location: Los Angeles, CA
Psycho

PostPosted: Wed Nov 20, 2013 1:06 am    Post subject: Reply with quote

lascooterservice wrote:
neither the fuel line nor the vacuum line are putting any undue stress on the tap-- both are lengthened and zip tied up and out of the way.

fwiw, the first tank cracked next to the tap in a small crescent shape that was not visible until removing the tank and holding it up to the light.

this time was a total failure-- the threaded bung where the tap attaches is entirely detached from the tank.

-g


[lascooterservice currently has the scooter in his shop, and this is a firsthand description of the failure.]

Also worth noting that the rate of leakage was accordingly greater the second time that the tank cracked than the first time. The rate of leakage for the first time the tank failed is shown in the two videos linked to in my earlier post.
Back to top
View user's profile Send private message  
ohiotj
Member


Joined: 21 May 2009
Posts: 82

2006 Buddy 125, 1989 Honda Elite E, 2006 Honda Big Ruckus

PostPosted: Wed Nov 20, 2013 1:52 am    Post subject: Reply with quote

It's been a long time since my engineering classes, but my first thought based on the description is fatigue due to excessive vibration. Reinforcing the area where the tap meets the tank is my first thought, probably TIG welding a bit more material in place if its a metal tank, or adding some JB Weld around it if its a plastic tank.

I've not pulled a tank, so I don't know how it mounts to the bike, but adding some rubber washers to where it bolts to the bike might also damp the vibrations a bit, too, but I'm guessing most of the vibration is coming from the engine through the fuel line.
Back to top
View user's profile Send private message  
OldGuy
Member


Joined: 18 Mar 2013
Posts: 250
Location: Everett, WA
Roughhouse R50, Vespa LX50

PostPosted: Wed Nov 20, 2013 5:31 am    Post subject: Reply with quote

With all the mods on the scooter, is it possible that the engine is surpassing the tank's ability to breathe? In other words, might there be a slight vacuum on the tank, that the tank vent has trouble keeping up with when allowing air in? This, over time, might be hard on things. Adding more venting to the cap could help. Just a guess.

But, as ohiotj said, seems like mechanical vibration is the more likely culprit. I can't recommend a fix though.

_________________
1971 Hodaka Ace 100
1977 Suzuki GT250 is now sold... Good bike!
1980 Yamaha IT125
Honda: '66 CT90 KO; '83 CT110; '92 CT70; 2001 XR250
and 1 or 2 others... I need to sell some bikes!
Back to top
View user's profile Send private message  
TVB
Member


Joined: 21 Feb 2009
Posts: 4961
Location: Grand Rapids MI
1999 Trek 7300 (Jim); 2009 Buddy 125 (Flash)

PostPosted: Wed Nov 20, 2013 2:25 pm    Post subject: Reply with quote

OldGuy wrote:
With all the mods on the scooter, is it possible that the engine is surpassing the tank's ability to breathe? In other words, might there be a slight vacuum on the tank, that the tank vent has trouble keeping up with when allowing air in? This, over time, might be hard on things. Adding more venting to the cap could help. Just a guess.

I think that's pretty unlikely. The flow of gas out of the tank is slow enough that if there's any vent at all, air will get sucked in fast enough to prevent a vacuum from forming. The only way you can get a vacuum is if the tank is totally sealed.

_________________
"Keep smelling the flowers, Todd" - Philip McCaleb
Back to top
View user's profile Send private message  
Syd
Member


Joined: 18 Jul 2007
Posts: 4710
Location: Tempe
'09 GTS250

PostPosted: Wed Nov 20, 2013 6:02 pm    Post subject: Reply with quote

Will the earlier, plastic tanks fit in the newer models? Maybe you could locate a plastic tank and see if that works.
_________________
The majority is always sane - Nessus
Back to top
View user's profile Send private message  
bikebuda
Member


Joined: 03 Sep 2007
Posts: 113
Location: WILMINGTON ILLINOIS
over 15 machines

PostPosted: Wed Dec 04, 2013 2:03 am    Post subject: Reply with quote

make sure the suspension bushings are good and the rear shock is not blown if not the rear fender can hit the fuel petcock under full compression , and it only takes a few times to crack the bung on the tank. i just noticed by your photo your shock is set at the lowest possible height setting i am pretty sure this is your problem.
Back to top
View user's profile Send private message  
Christophers
Member


Joined: 14 Oct 2010
Posts: 602
Location: Los Angeles, CA
Psycho

PostPosted: Wed Dec 04, 2013 3:22 am    Post subject: Reply with quote

bikebuda wrote:
make sure the suspension bushings are good and the rear shock is not blown if not the rear fender can hit the fuel petcock under full compression , and it only takes a few times to crack the bung on the tank. i just noticed by your photo your shock is set at the lowest possible height setting i am pretty sure this is your problem.


Very impressive! Good eye. We eventually came up with the same hypothesis. The rear shock was functioning intermittently, and I replaced it when we installed the third fuel tank. Over here, we also felt like the malfunctioning shock was also the culprit, although we didn't specifically consider that the fender might be hitting the fuel tap. I was going to report the success of our efforts later after we had a better idea if we had solved the problem with the new tank and shock.

We also considered substituting the plastic tank for the metal one. The plastic tank appears to have a larger capacity than the metal tank (which may, in part, account for the different numbers that have been floated for fuel tank capacity in other threads on this forum), and it has a very nice molded in place brass bung. However, it is not a direct swap for the metal tank. In order to mount the plastic tank we would have had to have cut off two mounting tabs from the frame in front of the tank and possibly ground back two of the flanges on the back of the frame in order for the plastic tank to fit. The tabs and flanges that we would have removed are used for mounting the metal tank, so it would have been a dedicated modification to use a plastic tank.

I'll report back to this thread with the success and durability of the new metal tank and shock after I put a couple thousand miles on the scooter.
Back to top
View user's profile Send private message  
ericalm
Site Admin


Joined: 10 Jun 2006
Posts: 17637
Location: Los Angeles, CA
STELLA FOUR STROKE FURY! + Vespa LX 150/190 + '87 Honda Helix CN250

PostPosted: Wed Dec 04, 2013 6:29 pm    Post subject: Reply with quote

Good call! Were you running the NCY shock on the rear?
_________________
Eric // Flickr group // LA Scooter Meetup Group // twitter: @scooterism // ScooterFile
Back to top
View user's profile Send private message [ Hidden ] Visit poster's website
Cheshire
Member


Joined: 28 Jun 2008
Posts: 1995
Location: near Asheville, NC
2013 Vespa GTS 300ie

PostPosted: Wed Dec 04, 2013 7:45 pm    Post subject: Reply with quote

Excessive vibration was my downfall. Regularly traveling a multi-mile stretch of fire road on one of my commute routes cracked the tank on a B125 at the fuel tap. New tank never had he issue repeat: I also found an alternate route that was all pavement. I figure the washboard parts were also bottoming out the suspension.

Hope you found your solution! Smile
Back to top
View user's profile Send private message  
Display posts from previous:   
Post new topic   Reply to topic    Forums » General Discussion Previous topic :: Next topic  Time: GMT

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

  Scootergear designed by riders for riders


Powered by phpBB © 2001, 2005 phpBB Group
All Content Copyright 2007-2011 by Modern Buddy. All Rights Reserved.