TW died on water crossing - Carb Vent solution offered

It could be the result of your carb vent line being submerged. This is fairly common problem on KTMs and some folks go as far as to modify their lines to vent up near the headstock.



It sounds like you didn't suck any water through the intake, so that could be the culprit.



Regards,



Mr. BigWheel

EDIT: Vuldub recently pointed out that I never finished posting the carb vent mod. I've redone the entire post and 86'd the old ones as I've revised the mod a couple of times since. I mocked it up on a spare carb for illustration purposes, but you don't need to remove your carb to do the mod. Takes about 10 minutes once you gather all the parts. The same method serves both the old and new style carbs.



The stock setup. In water crossings the end of the vent tube gets submerged and becomes blocked:















Here's what you'll need to fix it:









I used cheap vinyl tubing for the pics. The white "tees" are 3-way 3/16" vacuum fittings, available at any auto parts store. Two weedwacker fuel filters (don't fuss over these, they're pretty generic. They're only there to keep the crud out) and an optional lower vent shutoff made from a drip irrigation valve from the local hardware store.



Cut 2 short pieces of tubing and attach them to the carb. Insert the tees, then either re-attach your existing setup or make up a new one from fresh tubing. Attach your new upper hoses to the tees, making one slightly shorter than the other so they'll line up one behind the other. Insert these into the end of your frame's backbone, just above the carb. Make them long enough to get as high up in the tube as possible. Adjust all your tubing lengths as neccessary to make sure it clears the shock spring on the right side and that the lower vent exits the bottom of the bike as before, but don't re-attach it to the J-tube. The J-tube is just a big crap collector/fire hazard and limits your fording depth even further due to its location.



When you're done it should look something like this:











Without the shutoff valve your fording depth is now the depth of your carb, rather than your swingarm. For really deep water you can close the valve and your fording depth becomes the backbone tube.



Don't ever use the valve without re-opening it after a water crossing. If you dump the bike your lower vent could fill with fuel and cause a bike fire. For the same reason, don't even think of doing away with the lower vents and only running the upper.



Note: If you're not into doing the full vent mod and just want to decrease your risk of stalling on flooded city streets, remove your lower vent hose from the "J" tube. You'll find the J-tube attached to the frame behind the motor. Cut about 2 inches off the tube and let it just dangle behind the motor. That way the end of it will stay out of harm's way and sheltered by the wake of your motor in shallow crossings. I'd highly recomend doing this even on a stock bike.

vuldub said:

Lizrdbrth:

Thanks for taking the time to post the photos, it really helps.



Gerry, where's your innovative missing link award, I think this one deserves it!

...Wes

Click to expand...

Nothing all that innovative, just something that a lot of folks don't seem to know a lot about. The basic principle works for almost any carbed bike. Typically the vents get terminated under the tank or the seat, where they still flood if the water is deep enough or if you drop the bike, and they're constantly exposed to mud and dust. We get a break from that on our Tw's in that we have that open top tube as a sheltered airspace. I'll take credit for exploiting the airspace if it makes me look smarter

I held off on the Lizard Guys 'award' because I needed to figure out where the hell all those tubes went and why he did not buy a new TW so he would have a picture of my carb. I then realized that it all looked my heart valve bypass and since I was still alive, it certainly should work on the TW (just kidding).



Good job lizrdbrth, isn't this your 2ed (3ed?) Missing Link?.... Here is a man that really helps make this a GREAT FORUM.......... I applaud you Sir.. Gerry



to all, feel free to cut and paste the 'Missing Link' anytime you are so inclined.



Lizrdbrth:





Thank You !