Blew plug out of head????


13 replies to this topic
  • speddie3

Posted April 17, 2006 - 09:39 AM

#1

So I went out ridding for the first real time this year, about 5+ hrs of hard ridding. When I was loading back up after, i noticed that I have a small hole that is open on the kick starter side of the motor, on the head. I know it was never *open* before, it is on the side bottom of the head, and i think it is one of those wholes that are plugged with a small steal ball, but I have no idea why it is gone. Any and all help would be great. The bike still runs fine and there is just a small amout of oil that leaked out. Looking inside it almost looks like a valve is visable. Thanks guys!!

  • grayracer513

Posted April 17, 2006 - 10:14 AM

#2

It's gone for one or both of two reasons:

1> The plug that went there is a cheap, inadequate rubber coated plastic thing, and

2> your breather hose is pinched at one of the metal clips that hold it to the frame, or something else.

You can prevent a recurrence This Way or by inserting an 18mm steel or brass cup plug.

  • FFRacing79

Posted April 17, 2006 - 04:10 PM

#3

There is a reason these plugs "blow" out. Contrary to popular belief, they do NOT fall out. The most believable reason as grayracer stated is for a short time the vent tube got pinched one way or the other. The crankcase pressure has got to find somewhere to go. I have had the cam cover gasket blow out on the left side when my rider thought it best to zip-ty the breather hose a little too tight. Things just don't happen without a reason...find the cause. tdub

  • Butta

Posted April 18, 2006 - 06:38 AM

#4

So I went out ridding for the first real time this year, about 5+ hrs of hard ridding. When I was loading back up after, i noticed that I have a small hole that is open on the kick starter side of the motor, on the head. I know it was never *open* before, it is on the side bottom of the head, and i think it is one of those wholes that are plugged with a small steal ball, but I have no idea why it is gone. Any and all help would be great. The bike still runs fine and there is just a small amout of oil that leaked out. Looking inside it almost looks like a valve is visable. Thanks guys!!



If what you are explaining is what I'm thinking, then this is NOT the decompression plug blowing out. The decomp plug is on the front of the motor, right portion above the exhaust and just under the valve cover. If your "hole" is on the right side of the motor (not the front) then we have an entirely different issue. A picture would be great here.

  • eazrider

Posted April 18, 2006 - 07:07 AM

#5

Is that the drain port for the spark plug cavity? To let water, etc, out?

  • Zique

Posted April 18, 2006 - 07:45 AM

#6

A picture would be great here.


That would be best before we start throwing assumptions out here.

  • speddie3

Posted April 18, 2006 - 11:40 AM

#7

thanks guys, the pic will be up tonight. and it is on the right lower side of the head. its not the decomp plug, because i still have my decomp system on the bike. it is a small hole, like a 1/8 of a inch and I would bet it use to have one of those steel balls in it. I will def check out the breather tube when i get the pic. thanks

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

Posted April 18, 2006 - 12:11 PM

#8

I'll bet you $100 that he's looking at the port that drains the spark plug cavity to the atmosphere. If so, it's suppose to have nothing in it and your a goober for not noticing this earlier. You've been ridin' the darn 3 wheelers too much Bro...

  • grayracer513

Posted April 18, 2006 - 12:27 PM

#9

thanks guys, the pic will be up tonight. and it is on the right lower side of the head. its not the decomp plug, because i still have my decomp system on the bike. it is a small hole, like a 1/8 of a inch and I would bet it use to have one of those steel balls in it. I will def check out the breather tube when i get the pic. thanks

The roughly 5mm hole that is located about 3/4" above the lower edge of the head, on the right side, centered between the head bolts, is the spark plug well drain port, as eazrider and PK have suggested. It was never plugged with anything, and should not be. Its purpose is to allow the escape of any combustion gases that might leak past the plug threads, as well as to drain away any oil leaking from the cam cover, or water that entered by whatever means.

The decomp bore is about penny-sized, and is in the front of the head, on the right side just above the exhaust port, facing forward.

  • Butta

Posted April 18, 2006 - 01:14 PM

#10

Its purpose is to allow the escape of any combustion gases that might leak past the plug threads, as well as to drain away any oil leaking from the cam cover, or water that entered by whatever means.


I also use it to blow out any debris (with an air compressor, low pressure) that might be in there after pulling the spark plug cap and prior to pulling the spark plug so it doesn't go into the cylinder when you pull the plug. Works good!

  • PK

Posted April 18, 2006 - 06:26 PM

#11

Butta, we are going to CycleRanch on Saturday if you wanna go. It's our last ride here before we move to Hawaii...

Pat

  • speddie3

Posted April 19, 2006 - 07:02 AM

#12

Well I feel kinda dumb now. I guess you guys are right, it is a drain for the plug. I don't know why i never noticed it was open before. It just struck me funny because I could see a little oil comming out and when I looked inside I saw nice shinny parts, Ha. Guess its time for some more wheelin, thanks

  • speddie3

Posted April 19, 2006 - 07:03 AM

#13

Oh and sorry about the pics, my bro ran off with my camera!!

  • grayracer513

Posted April 19, 2006 - 07:07 AM

#14

It just struck me funny because I could see a little oil comming out ...

The most common cause of that is that oil is spilled into the hole while the cam cover is off. If you haven't done that in a while, check that your spark plug is tight, and then have a look at the cover gasket.





Related Content

Forums
Photo

Should I buy this bike? help....... by Numsa Hul


Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies
Forums
Photo

BIGBORE FOR YZ450F 2006? by Taattie94


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
 
x

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.