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Gas cap seal leaking

8K views 8 replies 2 participants last post by  John Hilmer 
#1 ·
Folks,

I have an '08 690 smc and the gas cap seal is failing, or rather has been leaking for a while now.

I have had it apart all the way to see if there might be a way to replace that seal, and to see what it looks like. From this I see that it would have to be a KTM part, and of course this isn't offered by KTM.

I find this disappointing because only the seal is worn and KTM wants $75.00 + for a new cap where a $3.00 seal would solve the problem.

Is there any way to obtain just this seal that any of you know of?

Yeah, I'm a cheap wrench type and hate spending money for something that is a waste when a simple seal could solve the problem.

I'm an old wrench/guy and though I tried to search for this my feeble ability returned nothing usable.

Thanks for any input on this if you can help.

John
 
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#2 ·
Folks,

OK, I have found that KTM refuses to sell just the seal. They will sell us a cap for about $75.00 to $100.00 depending on the source. This is not acceptable to me.

I'm going to make my own.

If anyone else winds up in this position I can help with the source of the Viton material and probably a drawing of the replacement part after I get mine working properly.

John
 
#3 ·
Two things:

I don't see a 2008 690 SMC in the NorthAmerica parts fiche.

There is a 2009 though.
You are talking about item #16 (16 0770050030 O-RING 50,00X3,00 VITON $3.69) correct?



Chip Munn at Munnracing 888-850-7437 said he could get one on order.

Also McMaster.com has a 2" X .103" (and wider too) Viton o-ring 10 pack for
$10.63 their P/N 9464K133.
 
#4 · (Edited)
Thanks for the reply.

Odd that you don't see the '08 690 SMC, but I've found it on a couple of the typical site like Discounthonda etc.

No, item 16 isn't on the cap but under the mating piece on the tank. That one is fine it is the seal on the cap itself that has failed.

I've ordered a sheet of the proper Viton material and will have it tomorrow.

I won't get around to making the replacement for the cap until next weekend.

If folks here are interested I can take some images and post them here.

John
 
#5 ·
Folks,

I've managed to get it to stop leaking.

I was wrong about the gas cap being the problem, it actually was the flimsy part that the cap engages and is screwed to the tank as others have reported.

I found this by removing it from the tank and placing it on a surface place with back lighting. I could see that it was warped because light was shining through underneath the cap on the bottom side. The warping was significan't, about 1/64th of an inch in three places. These were between the three screws that attach that part to the tank. You can visualize this I'm sure, and it is simple to check.

If you are having the same issue, remove the three screws that attach it to the tank. Be very careful to not drop anything into the tank. Place the part on a flat surface with the "O"Ring removed and with a light from the opposite side from where you are viewing this look to see if light is visible. Rotate it and look for the gap. If yours is like mine there will be three areas where the back light will be seen. These are the leak points. The flimsy ABS part warps from the pressure of the screws that hold it to the tank.

The Solution:

The "O"Ring can't accommodate the created gap produced by the weak part and the screws.

I used "Permatex" Ultra Black sealer, fuel proof, and ran a bead in the caps groove where the "O"Ring fits. I then added a bead of this on top of the "O"Ring and put it in place without any downward pressure using one of the screws to align this assembly, then added the other two screws without tightening any of them at all and lightly pressed it into place. This was in hopes that this blind assembly would create a good seal. It did just that.

I let this cure for two days just because.

Today I torqued the three screw down with heavy finger pressure on the socket wrench and called it good.

Testing so far shows no leak at all.

There wasn't anyone asking for images so I have not taken any.

So, it is in effect glued in place with the Ultra Black.

It has solved the leak problem.

I doubt that it will ever revert to puking fuel because the seal is now a chemical bond between the tank, cap and "O"Ring. If the leak returns I'll report back.

John
 
#6 ·
Good deal a $9 tube of RTV rather than $75.
I'm sure unless the cap has been redesigned,
if you had bought a new one, it would have
leaked eventually also.
 
#7 ·
Back to the drawing board or AutoCad actually

Folks,

That didn't last long!

I suspect that the failure of the sealant is due to the tank being fairly full and the 10% ethanol fuel caused the sealant to nor cure as it should. Much of what I removed after the leak returned was just goo. :001_unsure:

So, the pending solution is tested for theory and the final solution awaits some design time and a bit of CNC machining.

The first step was to get the bottom side of the cap that the "O"Ring is captured in flat again. All three lips where the screws go through and thread into the tank were quite warped. I could have done this on the milling machine but setting that up was going to be too labor intensive. I simply used the surface plate and some 220 grit sand paper to get it flat again. This of course weakened the cap further. Still, by applying very little screw tension, just enough to put some pressure on the "O"Ring it sealed well. We can't leave it like this as it will eventually warp again and the leak will return. Still, this proves that it can be solved. What is needed is a stiff plate to resist the warping tendency, hence the design of a ring to capture the existing tank cap and apply even pressure to the "O"Ring.

I have the basic design done in AutoCad and will be refining it probably today or tomorrow. :) There is just enough room for this plate to fit between the tank cap and the gas cap when assembled. :yes:

Next will be the manufacture of the prototype part on the CNC and hopefully testing by the weekend.

Stay tuned...

John
 
#8 ·
Hopeful @ this point

Folks,

Today, after a bit of corrections in AutoCad, we made the aluminum prototype.

I fitted it to the tank over the factory part and assembled this to the tank, fit the gas cap and did the initial test. This test is to run it up a driveway steep enough to force fuel against the assembly. This held well with no evidence of any leak.

Tomorrow further testing will be done by filling the tank and riding the bike up steep hills and other areas with checking at appropriate times when it has been subjected to steep grades.

I hope to be able to report favorable results tomorrow.

John
 
#9 ·
Folks,

I have not been able to overcome the worn seal on the gas cap itself. I did get the viton "O"Ring leak solved, but the only way that I see to use the factory gas cap is to order a new one. I'm not going there and have ordered the CJ Designs after market set with the screw on cap.

It "MIGHT" be possible to alter the factory gasket by cutting off the worn section and gluing on a mating viton sheet stock piece. I'm done trying on this though.

John
 
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