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TTR gas tank cracks

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Hey all, I've lurked these forums long enough for help that I thought it might be time I create an account and try and contribute something.


I've seen some threads on this topic, and even replied to one with this, but I thought it might benefit some if I just started a new topic to make searching easier. This may or may not be the same for other TTR's, I only have one to verify, my wife's 2001 TTR125L. It had 3 cracks in it, leaking like a sieve, and a new tank is like $300 on average which seems insane. Even used ones are around $200 and I'd hate to have it happen again.  It may be worth noting that Yamaha updated the part number twice for this particular tank, indicating some change was made, maybe to an improved material or design.  I can't be sure. I called them to ask but the representetive wasn't sure either. But if you are interested, the original part number was 5HP-24110-00-00, then there was 5HP-24110-10-00 and the current part number to supersede the others is 5HP-24110-30-00.  Before I invested almost half of what I paid for the bike on a new tank, I ended up deciding to try and repair by plastic welding.  My tank, and I assume the other TTR's are similar has a big "PE" on it visible when  you remove the seat.  This indicates polyethylene, and just PE usually means LDPE or low density polyethylene, not HDPE.  As with anything on the forum, use common sense and don't hurt yourself if you want to try to repair it. Here's what I did:


1. Drained the tank and washed several times with Dawn dish soap and water.  I didn't want to blow myself up or become a burn victim after all.

2. Drilled out the ends of the cracks with a 3/32 drill bit or similar size small bit to stop the crack from propagating.

3. Used a dremel type rotary tool with a tear drop bur to "V" out the crack a little bit.  I didn't go all the way through with that, just a groove along the cracks.  This cleans the plastic to be welded as well as create some room for filler rod.

4. Using a cheap $15 harbor freight plastic welder (like a soldering iron with a triangular tip) I went slowly along the v-groove/crack to melt the crack together somewhat.  Then I applied some LDPE filler I made from a squeeze-it/kool-aid kool burst drink bottle, those are LDPE plastic.  I smoothed over the top several times to get the finish somewhat contoured, but it is a little ugly, I'll admit. You want to lightly go over the edges a little extra to be sure that the filler and base material are melting together.  Constant movement and very light pressure seemed to do the trick.  

5. optionally, you can actually sand or grind smooth the weld and then make a pass over the repair with a heat gun or torch to just smooth the surface.  It looks much better if you do.  I didn't do that yet on this particular job.  I'll wait and see how well it holds up. You can also buy LDPE filler rods on amazon in a color very similar to Yamaha blue.  Since I wasn't too concerned about the appearance, I didn't bother.


I filled it up full with fresh gas (after drying the tank) and rolled it around and no leaks!  It's only been a few days and one test ride around the block, but so far its holding.  I'll try and update after some time to see how it holds.  

Most of the info for this project came from http://www.urethanesupply.com/identify.php and from http://www.urethanesupply.com/step3b.php for those interested.  Mileage may vary with the TTR50, TTR90, TTR110 and TTR230, since I can't be totally sure they are made of the same material, but I would guess they are.  In any case if you can identify the plastic the tank is made from, then you can find a source of the same plastic and the process is the same.  It is worth noting that while the tank on my TTR125L is polyethylene, the fenders, sides, shrouds and other plastics are all polypropylene, so using an old fender for welding rod source wouldn't work in this case.  


Here is a link to a pic of the finished work after I installed it back on the bike, but before I put the shrouds back on: https://drive.google...dGloT09sdjNkdGc


Edited by drdds

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