TE/TC TE 300 Airbox and Carb Vent Tubes

Last weekend my 2016 TE 300 died in relatively shallow water again, it was only about 18" deep, and the bike conked out within about 3 seconds. I used to think this was caused by water getting up the vent tubes into the float bowl, but on closer inspection, I discovered the infamous gap between the airbox and subframe. The gap is where the side stand rubber strap is mounted, and is around 30mm X 2mm. When I got home,I aimed a hose at the gap, and then checked the air filter, and it was soaked.
What is the best and most successful way of sealing this up? I'm guessing silicone sealant, but has anyone fitted any brackets, or self tapping screws to try and keep these 2 parts together, and stop them moving and breaking the silicone joint?

The second point is the pros and cons of routing the upper carb vents into the airbox. I think the theory of running all 5 vents together and down wards (as the bike is delivered), is no water can get up them as the float bowl becomes a sealed system, where the air is trapped above the fuel. So presumably, the deeper the water, the higher the air pressure acting on the fuel, so the richer the mixture. Also when under pressure, no fresh fuel can enter the float valve.
Running the upper vents into the airbox then releases the pressure, so fresh fuel can enter, but presumably then allows water into the float bowl if the carb dips under water?
The way I see it, is the vents pointing down allows for shorter very deep water crossings, and venting the top vents to the airbox allows for medium depth very long water crossings. As my bike will last for around 1/4 mile or more on a float bowl of fuel, I can't see that running out of fuel will ever be an issue.
I have also heard of terminating all the vents into a 35mm film canister, anyone know anything about this?

Discuss.....!

No opinion on air box since I never had an issue...

As for carb vents- any overflow will dump fuel on air filter and wash oil off filter then you have no top end protection

Forgive me if I am wrong but isn't the drain on the air box as low as the gap would be? I am not looking at the bike at the moment but having a hard time figuring how the gap wold get water into the air box faster than the drain vent on the lower rear of the airbox (or is it the front, sorry should probably not be giving opinions if I am too lazy to walk to the shed to look at bike ).

The gap in question is between the left hand subframe and the rear lower mudguard at the position that the side stand rubber strap hangs. This allows the vast amounts of water flung off the back wheel to be rammed into the airbox and directly all over the air filter.

The lower drain has a tab on it to try and stop water entering during forward motion, and also enough water has to enter the drain so as to fill up the lower part of the air box until above the bottom of the filter. This takes a significant time, by which time hopefully the bike is in shallower water.

I rode my old Italian TE450 into some gradually deepening water over around 100 metres. When the water came over the top of the tank I hit the kill button, as the bike was still running! The 450 has a completely open top air box, and a large drain slot in the bottom. So it shows the airbox can cope with a significant dunking in water before filling up.

Yeah if you put flashlight in airbos you will see alot pf light come outa crack in lower left if your facing inside rear fender, terrible subframe design in my opinion. Ive used silicone but it peals off. I coat it with rubber cement a few times a year, little bottle of it that has the brush with it. I think its made by slime. Maybe pvc glue will work, cant see ever needing to seperate that thing anyways. But yes like tge other guy mentioned that water will rush in at bottom vent hole first. I seal fender because tire throws mudd in my box

Take it 100% apart.

Clean everything up including all the mated grooves.

Then black silicone all the grooves and snap everything back together.

Use couple rags and lacquer tig err and removes excess.

That area that comes apart. Get some long aluminum pop rivets and snap couple them in along edge.

Now go back and look at other gaps and run nice bead of silcone to seal those areas up.

I line both edges with making tape to make clean edges.

black gaffa tape its strong and is easy to place over the gap and has some movement, that is enough of a fix to stop your water issue

Gaffa? Local hardware? Whats its designed application for?

gorilla or gaffa tape maybe different name down here, i can tell you its waterproof about 40 mm wide, its also called 100mph tape and gets used to hold together broken fenders/ bumpers in car racing as a stop gap.

it works great, local hardware or motorbike car parts store should have some

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Tetley. My air box came apart as you said. I think it was due to me taking the sub frame on and off while removing and replacing the shock after multiple re valves. I cleaned the locktite off the bolts but I did not clean the locktite out of the frame threads. After cleaning the threads in the frame with a tap, the bolts when in much easier. I think with the locktite in the frame threads I was not getting the sub frame torqued properly so it was flexing due to it being a little lose, causing it to come apart. As Dartyppyt said, I took it all apart and cleaned filled the groves with black silicon. Assembled and pre drilled then screwed it together with some stainless steel screws.

Unfortunately with the sub frame flexing, the seal at the air filter would open up. My engine sucked dirt. At first I thought I was chasing a weird jetting problem but as it turned out it was sand in the reeds. I'm going to rebuild the bottom end, a new con rod and piston. Have not measured the cylinder yet but by eye it looks ok. During winter I'm going to do the rebuild when I get it back together I will be able to see if my theory is correct.

My question to the guys whose bikes air box opened up. Was your bikes sub frame taken on and off before having the problem of the sub frame opened up?

My subframe never comes off because its 1 year old and i have no reason to. But, the gap is a maufacture issue on mine. Its at left side of rear fender top of air box. I own a 16 husq te300, put small flash light inside air box and look through fender, you will see a 2" long gap that muddy water can get in. Is it bad enough to create a serious issue for me? Depends, i dont like muddy water in my box in certain conditions, but not a serious threat. Im kind ocd about my bike on certain things.

The two top tubes wont dump fuel. They just meter atmospheric pressure. Mine are routed to the air box on all my bikes. Never stalled in creeks. The only one that dumps is the one on the float bowl. You want that to stay where it is. I do a loop in mine so it doesn't dump as easily though.