Andy here
I went for a days jaunt with my son-in-law, Mike, a week ago and although it was great fun, Fat Bastard died as soon as I got it into deep water! The design of the Japanese carb allows the fuel drain, in the bottom of the float chamber, to act as an overflow pipe. As soon as the water got to the rubber pipe on the bottom of the float chamber, water got in and stopped the engine! This is not good news as it would only allow me to go through water that was only 12" deep!
The answer was to build a water trap. To do this I got three short lengths of copper brake pipe and a piece of copper I had cut from a copper pipe. I drilled the copper and fitted the pipes through the holes, finally soldering the joints.
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| 100ml bottle and accessories |
Then I used silicone gasket goo (RTV) to stick this to a plastic 100ml bottle so that the pipes penetrated into the bottom of the bottle. This is held in place by a hose clip - which also had to be drilled.
Then I got an old motorcycle tube, removed the valve and drilled out the centre to have a bigger breather. I drilled a hole in the base of the bottle and then I trimmed the valve down until it would pass through the bottle neck and fit in the newly drilled hole. I sealed it all in using RTV and a couple of 'O' rings for good measure.
After inverting the bottle, I attached the two breather pipes and the overflow pipe to the three soldered brake pipes. I used Mikalor 7.35mm-8.3mm spring clips to keep the hoses water tight.
I got a piece of 8mm silicone hose and using a small hose clip to keep it on the 'valve' of the bottle, I threaded the hose up underneath the seat.
I finally sat the bottle in place so the screw-on lid is resting on the front sprocket guard and attached the bottle to the frame using a 'velcro' strap.
Theoretically, this would allow the carb breathers to get air from under the seat via the bottle and if the carb overflowed (usually after dropping the bike) it would be caught in the bottle.
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| The yellow line is the height of the front and rear tyres - 25" |
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| The yellow line is parallel to the ground and is set at 25" |
Last Saturday - 14th April '12 - I took FB to Lopwell Dam at 'nearly' high tide. The water was well over the walkway and nearly at the top of the ramp you can see in the Google StreetView. Normally I would have turned around and ridden away but this was a test of 'water-tightness for FB.
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| The beautiful Lopwell Dam near Plymouth, Devon, UK |
I killed the engine and reversed down the ramp until I was fairly level and the water was halfway between the hub and the top of the wheel. Then I started the engine. It ticked over very sweetly.
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| You can see from these two screen prints from Google Street View that the water does come up level with the end of the wall on the right. |
Then, with the engine still running I backed the bike down the 2nd ramp into the main part of the river current. This is where the River Tavy comes crashing over the weir and flows out to sea. The current was quite strong and the water was about 6" above the walkway. I finally got the bike into the water so the water was above the rear tyre. This is about 25" deep. The bike still ran sweetly and I sat on it and rode it out. No hesitation of any sort.
Arriving home I removed the strap holding the water trap on and inspected it..dry as a bone! Job's a good 'un!
If the water was deeper than 25" then I wouldn't be riding if it was flowing. The amount of air in the rear tyre makes the bike very light on the rear and it tends to move about too much in flowing water.
