400ex seapage

[98300exduner]

at the top of my cylinder there is a little bit of seapage.what is causing it. it just started a couple of weeks ago but it isnt bad there is just a little bit but i just want to know what it might be.

[AtvKid4Eva]

probably a blown gasket depending exactly where it is leaking on the cylinder.

[CJM]

The very top by the valve cover? There is a metal gasket there that maybe leaking.

First verify the bolts are properly torqued down, 8 foot pounds is what they should be.

Torque them in a criss cross type pattern and see if it leaks. If it still does you need a new gasket.

Here some mroe torque values FYI: http://www.atvriders.com/articles/torque400ex.html

There is also a gasket where the head meets the cylinder and a gasket where the cylinder meets the bottom end.

[98300exduner]

are those things expensive

[jensenracing77]

can you explain right where it is? like between the cylinder and the head or on top of the head? also on the front or on the side? what side?

it could be the head gasket is blown. also could be the right front bolt is stripped out that goes from the cam cover to the cylinder. (pretty common)
if you are 11:1 or more compression and run pump gas i would bet that it is a bad head gasket but will need more info.

[98300exduner]

it is right next to the bolts on the front right side. it isnt directly on the front part of the cylinder but more to the right.

[hocman123]

is it above wear the pipes go into the engine or bellow it ? then we will know which one it is. but ethor way i would replace both of the seals and maybe the valve cap seals along with it.

and i can't remember but i think the gaskits are like 12 bucks each

[98300exduner]

below

[hocman123]

ok well thats ur cylinder head gaskit it is part # 12251-HN1-A41 from honda 20 bucks at dealler 17 on mrcycles.com

i would also sugest u get the valve cover gaskit Part # 12391-KCY-671 that one is a bit more at 31 online

[98300exduner]

okay thanks man for the help

[jensenracing77]

with it being on the right, it didn't blow from compression. i would say the long bolt is stripped out that i mentioned above. many times this bolt hole has to be fixed when it is apart. i have had engines that have never ben apart in any way have this hole go bad and leak. if that is all it is just keep an eye on it and check your oil and run it. fix it next rebuild.

[rubbersdown]

Originally posted by jensenracing77
with it being on the right, it didn't blow from compression. i would say the long bolt is stripped out that i mentioned above. many times this bolt hole has to be fixed when it is apart. i have had engines that have never ben apart in any way have this hole go bad and leak. if that is all it is just keep an eye on it and check your oil and run it. fix it next rebuild.

hey jensen, I just rebuilt my wifes 400 motor and it went together good and doesnt leak but that bolt did seem a bit "squishy" when torquing it down so im sure it will give me problems in the future. How do you usually fix it? Heli-coil or just a re-tap or what?

[jensenracing77]

Originally posted by rubbersdown
hey jensen, I just rebuilt my wifes 400 motor and it went together good and doesnt leak but that bolt did seem a bit "squishy" when torquing it down so im sure it will give me problems in the future. How do you usually fix it? Heli-coil or just a re-tap or what?
i have got now to where every 400EX engine i have apart, i will heli-coil all 3 6mm holes if they are bad or not. i have never had an issue a single time with a heli-coil in these 3 holes. i did have one time where the bolt was loose in the hole for a long time and a heli coil was not big enough to fix it. in that case we used a insert that was a little bigger than the heli-coil.

[duroc825]

Originally posted by 98300exduner
it is right next to the bolts on the front right side. it isnt directly on the front part of the cylinder but more to the right.
Sounds to me you're describing the "valve cover" bolts. They are the only "head" bolts you see unless you've taken something apart. If it's the long bolt at right front corner then you'll have to disassemble entire head to heli coil it I believe. That one strips out alot like said earlier.

[98300exduner]

thanks everyone for the help really appreciate it