water proofing CR250R

Never had any problems, even when I went off a jump and landed in an 18 inch deep pond that I didn't see. Everything stays pretty water tight until the water level gets up to the intakes on the air box. Most of the stuff you hit on the trail is going to be 6 inches max, this won't harm the bike at all. The 18 inch puddle put me about 1/4 below the air intake. The water was loaded with silt so I could see a perfect waterline on the bike. I got a significant amount of water in the airbox, but if the airbox drains are clear and the filter well oiled, it should keep the engine sufficiently protected.

Now, the bike can take it, but some of its accessories can't. O-ring chains are a must. If you select the wrong brake pad compound, your brakes will eat themselves alive if you use them while wet. Either that or they just wont work at all like my last set. Expect many of the brake parts like the pins to wear at an accelerated rate. One great thing about the Nissen brakes is that all of that is replaceable so you don't have to buy whole calipers. Stay on top of the maintenance of your hubs and swingarm/linkage bearings. Make sure your carb vents and crankcase vent hose stay clear. Seal up the air boot to airbox connection. Corrosion will become an issue. Make sure you anti-seize everything, especially the chain tensioner bolts and spoke nipples. It may be wise to pack all of the electrical connections with silicone grease or dielectric grease. Watch out for rim rot.

Just disassemble the bearings periodically and grease them up. I don't know why your bike would be stalling. When I hit that 18 inch deep pond, I made the decision of fill my boots with water and shut the bike down or pin it and hope for the best. I had that motor turning faster than it had ever gone and it pulled me out, but it never stalled. A little bit of water through a motor wont actually shut it down. In fact, it's a great way to remove carbon from the combustion chamber.

not that you would recommend putting water in the combustion chamber. ;)

water in the combustion chamber for any length of time will kill your engine

(so If you let it sit in there for a couple minutes, or you put too much in, then kick it over)

Ya....water doesnt compress very well..... bad experiences.

76GMC1500 said:

A little bit of water through a motor wont actually shut it down. In fact, it's a great way to remove carbon from the combustion chamber.

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It has to be very tiny amount or it can cause major damage!

A 250cc engine with a 12:1 compression ratio leaves only 20.8 cc's of space above the piston at top dead center. If you get 0.7 ounces of water into that cylinder it will completely fill that space and there will be no possible way to turn the engine over. If it happens to be turning 15,000 RPM when that happens you have the "irresistible force vs. the immovable object" problem, something's going to give!

In practice it takes considerably less water to increase the compression ratio to the point that resulting pressure will bend rods, cave the piston in, or crack the head.

Sucking water into the intake can be very, very bad!

Surprisingly, engines seem to survive it much more often than the doom and gloom suggests. In my experience, getting a four stroke going again is a lot easier than getting a two stroke going. On a four stroke you pull the plug and pump the water out of the cylinder. Change the oil. Dry out the ignition and you are good to go.

On a two stroke it is much harder to get all the water out of the crankcase. I have been told that if you turn the bike upside down you can get the water to drain out via the carburetor and/or pump it out the cylinder.

I haven't had the need to do this on a dirt bike yet. I have had to do it on a Jet Ski, and didn't have the capability of turning it upside down.

Getting back to Keith's original question: Trying to set your bike up to run deeper than the 18 inches that 76 talked about is going to be very difficult. I suspect that you would find that going any deeper than that, even if you modified the bike, would be very difficult to ride due to the resistance of the water, the loss of traction and buoyancy issues.

In addition to the water ingestion problem there is also the wet ignition problem. A quick splash through a puddle and you are probably okay. Making a long run up the creek bed will get everything soaked, and even a medium run in water deep enough to cover the engine side plate could allow water into the magneto system.

If you want to avoid ignition problems keeping water out of the wiring is essential. Good gaskets/seals on the flywheel cover. Waterproof connections to the kill switch and coil. A little grease on the spark plug wire rubber boot will seal the spark plug.

It is like a chain, it will only be as strong as the weakest link.

Rod

Good point about the wet ignition. I took some waterproof grease and greased up all of the rubber seals around the ignition cover to help seal it.

As I said, it doesn't hurt an engine to suck a little water through. That's what water injection is. On a large engine runinng at full power, water can be fed in at the rate your windhsield washers spray with good benefits. Of course the dirt bike will not be able to handle as much, but it can still take some. The trouble with water is, as it moves through the air filter, it pulls dirt through. Keep that filter as clean as possible to minimize the chance of dirt passing through.