Head Gasket

[Ruby Soho]

I blew the head gasket on my 99 400ex. Im replacing it, but ive read some people dont trust after market ones, and like honda's better. but the 400 has a wiseco .040 over piston, so that means i would have to buy the wiseco big bore replacement gasket right? what do guys recomend?

[exrider008]

do u have HD head Studs? if you dont then that is prob why u blew your head gasket.

[Ruby Soho]

HD head studs?

please tell me about them.

[exrider23]

There heavy duty head studs, Once you bore out your motor its a good idea to put these heavy duty studs in because the motor is under more stress with the big bore. You will blow gaskets like crazy if you dont put the HD head studs in.

Contact Colby over at C&D racing (site sponsor) and he will set you up.

[Ruby Soho]

thanks for telling me this!

im going to start taking it apart friday, so how do i know if i have HD studs?

[2004exrider]

You can use a standard head gasket, it will work fine. You can replace the head studs if you want, but they usually dont need replaced unless you're running a bigger bore and 12:1 compression or higher.

Jimmy

[Ruby Soho]

well its .040 over, so does that count?

[400eXr1d3rZ]

Originally posted by Ruby Soho
well its .040 over, so does that count?

That would make your quad a....440? Yes it's a good idea to get HD Studs.

[2004exrider]

Originally posted by 400eXr1d3rZ
That would make your quad a....440? Yes it's a good idea to get HD Studs.

Nope that makes it a 406. I would just put in a new gasket.

Jimmy

[tooanxiousii]

Go with the stock bore gaskets ... They only make to different gasket sizes (85mm stock, 89mm 440 big bore) and you are only 86mm with you being only 1mm over stock bored the big bored gasket would be to big ...

What compression do you have ?

[Ruby Soho]

how do you check compression?

[GPracer2500]

Originally posted by Ruby Soho
how do you check compression?

You check compression with a compression tester. It's basically a pressure guage that screws into the spark plug hole. You'll get a figure measured in PSI. But I think tooanxiousii is asking what the static compression ratio is for the piston. That figure is not a measured with a tool, it's calculated using combustion chamber volumes. The manufacture of the piston will assign a static compression ratio for the piston (e.g. 10:1, 10.5:1, 12:1, etc).

[Ruby Soho]

well we took the top end off today. when we were finished taking the cams out we started unbolting the head. and come to find out the bottom of the 4 bolts was loose. one crank with the ratchet and it loosened. we knew that wasn't good, and later to find out the gasket blew right where the stud for the loose nut was. we checked to see if it was warped at all and nothing. so hopefully a new gasket will be all

[Ruby Soho]

hey guys, whats a good way to clean the surfaces on the cylinder? what should we use?

[exrider008]

u need to get it honed.

[christophere251]

Then clean it with warm soapy water and coat it lightly with oil!

[Ruby Soho]

Originally posted by exrider008
u need to get it honed.

honed for what?

[250X_project]

He was talking about the cylinder walls, where I think you mean where the head gasket lies on the jug. This will clean up well with a "wiz wheel" air tool. Or just a razor blade if you are CAREFUL. When done blow out the cylinder with air. Do not move the piston until you have blown it out.

[Ruby Soho]

yeah i thats what i meant. thanks for the input

[christophere251]

They also make gasket strippers that are kinda like liquid paint stripper and it just melts it off. aLL u need is a plastic scraper and the stripper it will come right off!

[250X_project]

sweet

[XR650]

have the cyl. jug o-ringed, $30.00, problem solved, and use a copper gasket from copper gaskets unlimited or cometic, stock studs for yur applic. are fine, after you o-ring it you will not have any more problems.

[250X_project]

$30 for an O-ring? Besides what does the O-ring on the bottom of the jug have to do with the head gasket?

[Ruby Soho]

heres a pic of her torn apart for your viewing pleasure :)

http://myspace-362.vo.llnwd.net/01482/26/39/1482709362_l.jpg

[exrider008]

WOW!:eek2: a little dirtty. make sure u dont get dirt in the engine.

where did i get the black sprockets? sidewinder?

[GPracer2500]

Originally posted by 250X_project
$30 for an O-ring? Besides what does the O-ring on the bottom of the jug have to do with the head gasket?

That's not what he's talking about.

You can have a very small groove machined around the top of the sleeve. In this groove you place a stainless steel wire that's sized to exactly fit the groove. Half the thickness of the wire sits up above the top of the sleeve. The head gasket goes on top of this and when it's all bolted together there's a little bit of extra compressive force where the wire "o-ring" is.

It's a little tricky installing the wire. It's stiff and hard to put a nice even radius in it AND keep it perfectly flat when laid on a flat surface. And then you've got to get the end-gap to zero. I used little dabs of superglue to keep the wire from popping out of the groove while I installed the gasket and head.

When I built my old 416 I installed HD studs and o-ringed the sleeve. Overkill? Perhaps--but I ran her hard and didn't want any problems.

[Ruby Soho]

Originally posted by exrider008
WOW!:eek2: a little dirtty. make sure u dont get dirt in the engine.

where did i get the black sprockets? sidewinder?

haha the picture makes it look worse than it really is. but yea we have the piston etc.. covered and we cleaned it all off and everything

gaskets should be here in a day or 2. cant wait!

[2004exrider]

If your ever thinking of investing more money into it down the road, deffinitely different tires. Bandits are good because they take FOREVER to wear down but they dont hook up worth a crap wet, dry, snow, etc. Just a tip :blah:

Jimmy

[250X_project]

Oh okay I have never heard of that. I was wondering what that rubber piece around the sleeve at the jug bottom would help. :rolleyes: Thanks man.

[Ruby Soho]

Originally posted by 2004exrider
If your ever thinking of investing more money into it down the road, deffinitely different tires. Bandits are good because they take FOREVER to wear down but they dont hook up worth a crap wet, dry, snow, etc. Just a tip :blah:

Jimmy

thanks for the heads up. only question is, i heard its REALLY hard to remove tires and put them on existing rims. the rims i have are great, and i dont need new ones so idk any suggestions?

[250X_project]

Yeah, wheeler tires suck, They are 100x worse than car tires. If you can break the bead your 1/2 way there. We used a portable tire changer where after the bead is broke (By tool made for just that using compressed air) you put the bar in the bead and walk it out by going around the center post......Other wise any tire place can do it.

[2004exrider]

I was lazy and just bought new tires and rims:o , i wasnt going to even attempt removing them. But when i did call around about having them removed $20 a wheel was a pretty average price.

Jimmy

[F-16Guy]

Originally posted by Ruby Soho
well we took the top end off today. when we were finished taking the cams out we started unbolting the head. and come to find out the bottom of the 4 bolts was loose. one crank with the ratchet and it loosened. we knew that wasn't good, and later to find out the gasket blew right where the stud for the loose nut was. we checked to see if it was warped at all and nothing. so hopefully a new gasket will be all
I had the same problem and tried a new gasket with no success. The reason the stud was loose is because it's pulling the threads out. You might be able to get a good torque, but it probably won't last. I would just do it right the first time and be done with it. I'm guessing it was the stud by the exhaust ports. That's where the most heat accumulates, and it causes the aluminum to break down and weaken. You can try the new gasket, but if it doesn't work, you just added another $30 to your repair bill.

[Unverfehrt400ex]

Quick question. how do you know when your gasket is blown. I have a small amount of oil leaking out of the top of my head everytime a go for a good ride and dont know if a gasket would have caused this or what it could be.

[Ruby Soho]

Originally posted by F-16Guy
I had the same problem and tried a new gasket with no success. The reason the stud was loose is because it's pulling the threads out. You might be able to get a good torque, but it probably won't last. I would just do it right the first time and be done with it. I'm guessing it was the stud by the exhaust ports. That's where the most heat accumulates, and it causes the aluminum to break down and weaken. You can try the new gasket, but if it doesn't work, you just added another $30 to your repair bill.

it worked fine for me, i think it was just the guy i bought it from though. he did it himself, and didnt do a good job. he tourqed some and just hand tightened others. there were missing bolts holding down the tank etc.. so he wasnt to good with the bolts. ill see how it goes for the next couple of rides.

and the way i found out about my gasket is it makes a ticking noise, and put your hand around the cylinder and topend and feel for air comming out of it

[dariusld]

Originally posted by Unverfehrt400ex
Quick question. how do you know when your gasket is blown. I have a small amount of oil leaking out of the top of my head everytime a go for a good ride and dont know if a gasket would have caused this or what it could be.

Mine sounded funny when I was going up hills or when I was really on the throttle on the top end.