DROWNED BIKE: GETTING THE WATER OUT AND RIDING HOME

The Technique

1. The moment the engine stops in water, take your hand off the starter button and keep it off. This is the one rule that matters more than every other step in this lesson. Water does not compress. If the cylinder has taken water in through the intake or the exhaust, the piston has nowhere to put it, and the moment you crank the engine the rod is the softest thing in the path. It bends, and on a four-stroke it can bend far enough to touch a valve or punch a hole in a case. A drowned engine that is never cranked with water in it is almost always a repairable engine. A drowned engine that gets one hopeful jab of the starter button is often a rebuild. Hit the kill switch, turn the ignition off so nobody helpfully tries it for you, and if the bike has a fuel tap, turn it off as well.
2. Get the bike out of the water and onto the bank before you do anything else, and get it out with the engine off and in gear or with the brake on so it cannot roll back in. Once it is on dry ground, drain the water you can see. Tip the bike over so the exhaust points down and hold it there long enough for the muffler and header to empty, and if the muffler has a drain bolt, pull it out and let it run. Then open the airbox. A soaked air filter is the reason a lot of bikes drown twice, because you clear the cylinder, start it, and the engine immediately sucks the water back out of the filter and the airbox boot. Pull the filter, wring it out or bin it, empty the airbox, mop the bottom of it out with a rag or the tail of your shirt, and clear the airbox drain if it has one. Check the intake boot between the airbox and the engine and tip any water out of that too.
3. Now remove the spark plug. Everything else in this procedure depends on that hole being open, because the water in the cylinder needs somewhere to go and the plug hole is the only place it can go. Clean the loose grit and water off the top of the head first so nothing falls into the bore when the plug comes out, pull the plug lead or coil stick off, and wind the plug out with the plug spanner from your toolkit. Keep the plug somewhere clean. On a bike with a coil stick and a fuel injection system, pull the fuel pump fuse or unplug the pump before the next step, because otherwise the pump will prime and the injector will squirt neat petrol into an open cylinder while you are cranking. Either earth the plug against a bare part of the head or unplug the coil entirely, because a loose plug lead sparking next to petrol vapour and a wet engine is a fire you do not need on a riverbank.
4. With the plug out, turn the engine over so the piston pumps the water out through the plug hole. Kick it if it has a kickstarter, or use the electric start in short bursts of two or three seconds with a pause between each burst so you do not cook the starter or flatten the battery. Water will come out fast and hard on the first few turns, so point the plug hole away from your face and away from anyone standing near you, and warn whoever is helping before you turn it. The trick that tells you when you are done is your finger. Rest a finger loosely over the plug hole, not sealing it, and keep turning the engine. At first you feel wet slugs of water and spray. Then you feel a wet mist. Then the puffs change character and become clean dry air pushing against your fingertip, and that change is the signal that the cylinder is clearing. Keep turning it over past that point until you get nothing but air, several turns in a row. If it is a two-stroke, a small squirt of two-stroke oil or a few drops of premix down the plug hole after it runs dry restores the film of lubrication that the water washed off the bore, and one more turn spreads it.
5. Deal with the fuel system next, and this is where carburettor and fuel injection part ways. On a carburettor bike, water gets into the float bowl through the vent hoses and sits in the bottom of the bowl because it is heavier than petrol, which means the engine draws water first when it starts. Undo the drain screw at the base of the bowl, or pull the bowl off if there is no drain, and let it empty until what comes out is clean petrol. While you are there, check the fuel tank by draining a little into a clear container or onto a clean rock and looking for a separate layer sitting under the petrol. On a fuel injected bike the fuel side is sealed and is rarely the problem, so your attention goes to the air side instead: the airbox, the intake boot, the throttle body, and anything water has been drawn through. Dry the throttle body bore and the butterfly with a rag, work the throttle a few times, and check the connectors on the injector and the sensors around the intake for trapped water.
6. Dry the plug and refit it, or better, fit the spare dry plug you carry in your toolkit. Wipe the electrode and the insulator, and if the old plug is still soaked and you have no spare, dry it with heat from a lighter or a stove if you have one, holding it by the metal body. Refit the plug to a sensible tightness, put the lead or the coil stick back on, reconnect the fuel pump if you unplugged it, refit the filter if it is usable or run to the nearest bail-out point without one if it is not, and try to start it. Expect it to run badly at first. It will cough, it will run on and off, it may blow a fine mist out the pipe for a minute, and there may be steam. That is the last of the moisture leaving. Hold a light throttle and let it work through it rather than revving it hard while it is still stumbling.
7. Once it is running cleanly, get it up to full operating temperature and keep it there for a decent stretch of riding. This is the step people skip and it is the one that decides whether the engine is fine in a month. Heat is what drives the residual moisture out of the crankcase, off the crankshaft, out of the bearings and away from the internal surfaces. Water left sitting in the cases at ambient temperature starts rusting bearing races and cylinder walls within a day. This is exactly why riding the bike home warm is better for it than loading it on a trailer and taking it home cold. If the ride home is short, take the long way, or let it idle and ride it gently around the paddock until the engine is properly hot and stays hot for a while.
8. Check the oil as soon as you reasonably can, and check it again at home. Pull the dipstick or the sight glass and look at the colour. Oil that has turned milky, creamy, or grey has water in it, and that oil is no longer lubricating properly. It must come out before the bike does any real work, and on a bike that went fully under it is worth changing it a second time a week later, because water hides in the bottom of the cases and in the oil galleries and keeps working its way back into the fresh oil. On a bike with a separate gearbox oil, which includes most two-strokes and some four-strokes, check and change that as well, because the gearbox breather is a common way for water to get in. Inspect the air filter properly rather than by feel, and re-oil it or replace it. A filter that has been wet and then dried is not a clean filter.
9. Know which engine you are dealing with, because it changes how nervous you should be. A four-stroke has valves and a wet sump full of oil, and both of those make a dunking worse. Water contaminates the sump directly, and hydrolock on a four-stroke does its damage against a closed valve, which is how you end up with a bent rod, a bent valve, and a bill. A two-stroke tolerates a swim far better, has no valves and no sump, and often fires up again after nothing more than a plug pull and a few kicks, but it still must never be cranked with water in the cylinder and its crank bearings are the vulnerable part, because they are roller and ball bearings sitting in the cases with nothing but fuel mix to protect them, and water sitting on them turns into rust and then into a rattle. Either way, a drowned bike deserves a full check-over at home even when it runs fine. Pull and inspect the wheel bearings and the steering head bearings, because grease and water do not mix and a river crossing pushes water past worn seals. Strip and clean the brakes, both the calipers and the pads, and check for grit in the pistons. Open, dry, and grease the electrical connectors, the switchgear and the plug caps. Clean and re-lube the chain, check the linkage and swingarm bearings, and grease anything that takes grease. If in doubt about how deep the water got or how long it sat, have the engine inspected properly rather than assuming a good ride home means no damage.

Common Mistakes

Trying one quick start attempt to see if it is alright. Fix: treat the starter as off limits until the plug is out and the cylinder is clear. There is no version of this where a test crank tells you something useful.

• Clearing the cylinder but leaving a soaked air filter and a wet airbox. Fix: empty and dry the airbox and remove the wet filter before you refit the plug, otherwise the engine simply drinks it again.
• Cranking on the electric start in one long grind. Fix: short bursts of two or three seconds with a pause between them, so the starter and the battery survive the job.
• Leaving the plug lead connected with the plug lying loose on the head. Fix: earth the plug against bare metal or unplug the coil, so you are not making sparks over petrol vapour.
• Trailering a freshly drowned bike home cold and parking it. Fix: ride it home warm, or if it has to be trailered, run it to full temperature before it goes in the ute and again when it comes out.
• Changing the oil once and calling it done. Fix: change it, ride it briefly, then change it again, because water keeps coming out of the cases for days.

The Drill

Practise the plug pull in the driveway with the engine cold and the bike on a stand. Time yourself from bike on its side to plug out, and find out whether your plug spanner actually reaches your plug, whether you need to move a tank shroud, a coil stick or a subframe bolt to get to it, and whether you own the tool for that. Then audit your pack against the job: plug spanner that fits, one spare plug in a padded tube, a small adjustable or the right spanner for the float bowl drain, a length of clear hose, a rag, cable ties, and a way to make heat. Do the whole sequence dry, out loud, once, so on the day it is muscle memory and not a debate on a riverbank.

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