Water on spark plug

11 replies to this topic
  • mikandrews

Posted November 10, 2007 - 03:26 PM


I have a 99 yz400f pulled out plug to change and noticed water on plug. Kicked it over with the plug out and water shot out of the engine. Never over heated or run without water. Ran before I changed oil, changed plug assembly and plug, will not start.
Any ideas before I have Yamaha look at it$$$?

  • grayracer513

Posted November 10, 2007 - 04:40 PM


Did you wash the bike before all this happened?

  • nap__kxf

Posted November 10, 2007 - 05:15 PM


has it been sitting for a while? like sitting outside, or in your garage and your garage is leaky?

  • mikandrews

Posted November 10, 2007 - 06:08 PM


I washed the bike two weeks ago after riding. When riding the bike had to be pull started and ran bad. Found the plug assembly was off the plug and broken. Replaced with new assembly and plug. Bike does not sit outside or in leaky garage.

  • grayracer513

Posted November 10, 2007 - 07:14 PM


On the right side of the cylinder head is a small (5 or 6 mm) hole. This is the drain port for the plug well. If it gets clogged, whatever gets into the plug well, be it water, oil, combustion "smooge", whatever, will build up instead of draining away. Sometimes water trapped there will boil and the steam will pop the plug boot off.

If there was water there, and you unscrewed the plug, the water would have drained into the cylinder oer the tip of the plug and given you all of your list of symptoms.

Put a plug back in to protect the engine and rod the hole through with a wire, and/or compressed air.

  • mikandrews

Posted November 10, 2007 - 07:57 PM


I will check the drain hole. As for starting the bike again, is there a way to drain the water out of the engine? Would there be enough water to damage the engine? Should I wait to restart?
Thank you for the information grayracer!

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted November 10, 2007 - 08:02 PM


If the water got in through the plug hole when you pulled the plug, there wouldn't have been much there to start with. When you then kicked the engine over, you would have blown 85% of that out the top again.

Spray some carb cleaner in the plug hole, kick it a few times, then put in 3-4 drops of oil and kick a couple more. Then put it together and don't worry about it again unless it shows signs of having a bad head gasket.

  • sirthumpalot

Posted November 11, 2007 - 10:08 AM


To add to the above; change the oil and look for water. If there's no water in the oil the you didn't get much in there. Also check your radiator level. If it's not down significantly then it's probably not leaking into the motor, but if it's way down then start looking at things closer (leak down or compression test).

  • mikandrews

Posted November 11, 2007 - 03:56 PM


I did notice when I checked the water level was low. When I drained the water from the system, I thought I smelled gas. I left the water sytem empty overnight. Went to put on gas tank and notice when I turn on the gas from the tank it leaks/runs out the tube from the bottom of carb. Any ideas?
thanks for all the info.

  • Yamahafan

Posted November 11, 2007 - 07:27 PM


What about your oil? Did you check yet to see if it was milky white? Gas running out the carb overflow can be from a worn out o-ring in the gas tank petcock, and possibly the float getting stuck in the carb.

  • mikandrews

Posted November 11, 2007 - 08:08 PM


Will the oil be milky without the bike being started? I have not been able to start it since I changed the oil, plug and assembly. When I changed the oil it was not mikly, it looked normal. I have a new petcock, so i will change it>
Thanks for the info

  • mikandrews

Posted November 12, 2007 - 08:41 AM


tTried to statr the bike today, no luck. took out plug and it had gray water mixed with gas on it. Drained the oil and it was milky. Guess I'm headed to the shop.

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.