Flush. Water? Not! Gasoline, also maybe not, too flammable. Really light weight oil, diesel or kerosene might be better. Good luck.
The first time I pulled my plug I noticed the stuff hanging around waiting to mess things up. Would not want to have to pull the plug on the trail. Nice to have compressed air or a vacuum handy to clean things up before pulling that plug.

 

But one could assume that numerous people have had a dirty bike, pulled the plug, then dropped crap in their cylinder without even knowing it. Doesn't seem too hard to make that mistake. No catastrophes that I know of

 

For future reference, don't remove the plug when fogging a motor.
Warm up the bike. Remove air filter. Restart bike, giving a little throttle spray the fogging oil into the carb, do not let the bike die. After a little while lots of smoke should come out the exhaust. Now spray a steady stream with part throttle until the bike dies. This will coat all parts with oil, carb, intake track, valves, piston, piston rings, etc.

 

Heck, pull the head - ya got all winter to put it back together...

While in there bolt on a Bill Blue 351 kit... maybe a cam. Then reassemble.

Add a 39 flat slide and a pipe along the way buttoning things up.

Look how much faster it goes when fired up next spring!

 

My vote is for the dan888 vacuum, put the plug back in and don't worry about it. Even if a little pebble fell into the cylinder it probably wouldn't do much before blowing out the exhaust valve and I doubt it would lodge under the valve or scratch the cylinder walls to any extent. Don't stress; I don't think this is any big deal. As far as flushing the combustion chamber with oil, water, gasoline or even compressed air; what flow rate would be required to force a tiny pebble or foreign object out of the plug hole that you have a hose running into? I am not a mechanic but in the opinion of a mechanical engineer I think it is extremely unlikely that flushing will do anything beneficial and will be a waste of time and potentially harmful. If it were me I probably wouldn't even try the vacuum but I'm old and lazy and don't do much other than change the oil and ride... and ride.... and ride.

 

If there was no oil involved, I would poke a vacuum cleaner with a narrow nozzle down the plug hole, then clean the plug hole threads with a cotton bud dampened with iosopropyl alcohol or petrol. Then manually turn the engine until the exhaust valves are open (may need to pop the cam cover off) and repeat.

However the oil may well bind the dirt onto the combustion chamber surfaces, so the vacuum may not be effective. I would not try to use any liquids to flush it out - could cause further problems. I would clean the spark plug hole thread and then check the valve clearances. Then start the engine and give it a few blasts on the throttle. Then recheck the valve clearances, if there are less than before - be concerned!

Other than that, my advice would be to call the local bike shop and ask the mechanic.

BTW there was a program on telly last week with a guy trying to break the record for distance travelled on a motorbike on water. They sunk the bike (Suzuki 4T MX bike) several times including down to 30M for >1/2 hour. After an oil change and a set of new filters the motor seemed to run fine. You probably have nothing to worry about!!!

 

If it's already fogged, frankly, I'd just leave it alone. Make note to work on it when you get ready to ride it again. And what I'd do is this... do the vacuum trick like others suggested. Then, spin the motor over a few dozen times by hand (or with the starter -- disconnect the plug wire so it doesn't start), then change the oil and filter. You'll want to do that anyway after it sits in storage. Then ride it and don't worry about it. Worst-case, you wanted a BB351 kit anyway, right?

Rob

 

Yup , I did not realize that the cylinder had been fogged already.

 

Great suggestions.

To follow up:

Today I attached a narrow hose to my shop vac with duct tape and did my best to remove the dirt from within the plug hole. Due to the minuscule amount of dirt that fell in, plus the 180 decibels of my shop vac, I can neither confirm or deny the presence of particulates in the cylinder. I fished around for a while and didn't feel any rocks, which was my biggest fear.

Upon removing the hose, the end was dirty with some foreign particles, but it wasn't terrible.

It fired right up and after 10 miles or so she's running just fine. Thanks for all the input and suggestions. Happy Spring riding!

 

I don't ride mine off road, at least not in any grimy conditions. But it'd seem to be simple enough to fab something up to keep dirt from going down the spark plug access area and not have to worry about crap falling down in there whenever you pull the plug?

Even some sort of sponge material crammed around that long plug wire cap. Something that engine heat won't destroy.