CRF 450 Head Gasket

[400exrider707]

Just wondering if anyone is running this gasket? I've heard that it will shave .020" off for added compression? First of all I've searched and it seems true, now my question is what year should I order? Im assuming for my 05 450R I will just order an 05 head gasket, and secondly will I encounter P/V clearance issues? Im guessing not, but anyways my setup will be - HRC cam, stock valves, JE 11.5:1 piston. I highly highly doubt I will see any issues with this, and I can always clay it to check, but I dont want to order the gasket for nothing, so any input is appreciated. Thanks!

[chad502ex]

the crf head gasket is a two layer head gasket as opposed to 3 layer TRX....

each layer is ~.009"

BTW: the crf head gasket mod only fits 06/07 TRX's

[Rulz]

Just take your head down to a good machine shop and have it milled .020. I just had mine done and it doesn't cost much more than the gasket itself!

[chad502ex]

Originally posted by Rulz
Just take your head down to a good machine shop and have it milled .020. I just had mine done and it doesn't cost much more than the gasket itself!

yup, that's the only option for the 04/05 to bump up compression, unless you go with my 15:1 piston... ;)

i can usually get machining for about $50.

[Sjorge450R]

will this work good on a stock motor with the stock pipe? Im just looking for a little extra umph right now, because when I do the motor, im doing it all at once...lol

[chad502ex]

Originally posted by Sjorge300EX
will this work good on a stock motor with the stock pipe? Im just looking for a little extra umph right now, because when I do the motor, im doing it all at once...lol

IMO you should not be installing a head gasket for added compression or decking a head on a stock engine, unless you've considered porting, or a cam, or a HC piston, pipe or a bolt on mod first.

[400exrider707]

Originally posted by chad502ex
IMO you should not be installing a head gasket for added compression or decking a head on a stock engine, unless you've considered porting, or a cam, or a HC piston, pipe or a bolt on mod first.


Agreed. I guess I should have just gotten a 12:1 compression piston in the first place, but oh well. Thanks for the info chad.

Also why doesn't this work on the 04/05's? Different head gasket design?

Also decking the head and/or thinner head gasket would require to degree the cam differently as well correct?

[chad502ex]

Originally posted by 400exrider707
Agreed. I guess I should have just gotten a 12:1 compression piston in the first place, but oh well. Thanks for the info chad.

Also why doesn't this work on the 04/05's? Different head gasket design?

Also decking the head and/or thinner head gasket would require to degree the cam differently as well correct?

that's good your thinking about the effects of decking a head, as in the cam timing changes associated with it. True, it does, but 0.020" is hardly anything to worry about unless the cam is monsterous and the P-V clearances are small.

06/07 heads mimmick crf where the 04/05 heads are purely TRX.

[Sjorge450R]

Originally posted by chad502ex
IMO you should not be installing a head gasket for added compression or decking a head on a stock engine, unless you've considered porting, or a cam, or a HC piston, pipe or a bolt on mod first.

well i wasnt just gonna open her up without throwing a piston in....lol. I think im going to be running race gas either way.
SInce we are talking about this, i am able to get some 100 octance low lead gas, i ran it in my 300 prior to my second rebuild and it seems to make it run better and i was wondering if it is okay to use in the 450r with say a 14:1 piston? Would i have to run it like 3/1?

[400exrider707]

Originally posted by Sjorge300EX
well i wasnt just gonna open her up without throwing a piston in....lol. I think im going to be running race gas either way.
SInce we are talking about this, i am able to get some 100 octance low lead gas, i ran it in my 300 prior to my second rebuild and it seems to make it run better and i was wondering if it is okay to use in the 450r with say a 14:1 piston? Would i have to run it like 3/1?

Why would you run race gas either way? It is completely useless on a motor with stock compression and/or timing.


Chad - so by decking the head .020, you will in effect ... retard the cam? What power benefits if any will this do for your motor. Also by decking the head .020 on the 04/05 motor about how many degrees would it in fact retard the cam? Thanks. Also is the stock cam chain tensioner able to make up the slack for something like .020"? .040"?

[Sjorge450R]

Originally posted by 400exrider707
Why would you run race gas either way? It is completely useless on a motor with stock compression and/or timing.


Chad - so by decking the head .020, you will in effect ... retard the cam? What power benefits if any will this do for your motor. Also by decking the head .020 on the 04/05 motor about how many degrees would it in fact retard the cam? Thanks. Also is the stock cam chain tensioner able to make up the slack for something like .020"? .040"?

when i said either way, i was refereing to no matter what, once i open the motor, its going to be built for race gas.

[400exrider707]

Originally posted by Sjorge300EX
when i said either way, i was refereing to no matter what, once i open the motor, its going to be built for race gas.

ahhh gotcha:cool:

[DirtDevilBT]

who makes a 2 layer gasket for the 04/05? I heard that Gosmetic makes head gaskets and they will make one with 2 layers. But when I emailed them, they didn't know what I was talking about and said all they sell are stock replacement or over bores.

Would it be ok to simply remove the center layer of the stock 3 layer gasket?

[GPracer2500]

Originally posted by DirtDevilBT
who makes a 2 layer gasket for the 04/05? I heard that Gosmetic makes head gaskets and they will make one with 2 layers. But when I emailed them, they didn't know what I was talking about and said all they sell are stock replacement or over bores.

Would it be ok to simply remove the center layer of the stock 3 layer gasket?

That's strange. Must not have been talking to the right person, I guess. This is right off the Cometic website:

Can I order a head gasket with a different thickness than you have in your catalog?
Yes. Call Cometic with the engine type or Cometic standard part number (search online or in our catalog) along with the thickness you would prefer and we will create your custom gasket. (800-752-9850 or 440-354-0777)

[400exrider707]

Originally posted by DirtDevilBT
who makes a 2 layer gasket for the 04/05? I heard that Gosmetic makes head gaskets and they will make one with 2 layers. But when I emailed them, they didn't know what I was talking about and said all they sell are stock replacement or over bores.

Would it be ok to simply remove the center layer of the stock 3 layer gasket?

Removing the center layer would not work at all. Their 3 and 2 piece gaskets are held together with a rivet of sorts. I know some people remove the center layer and use that alone, but using more than one layer after disassembling it would probably not work.

[chad502ex]

no, i would not just remove a layer.. they are folded together and crimped.. but cometic will make a two layer, but the time for delivery and cost is up for those 'custom' gaskets...

[400exrider707]

Originally posted by chad502ex
no, i would not just remove a layer.. they are folded together and crimped.. but cometic will make a two layer, but the time for delivery and cost is up for those 'custom' gaskets...


I've seen it done where people are prying the crimped part away and using just the middle layer, it is very thin and if done correctly would not damage the middle layer. It probably isn't the best idea, but its cheap power. I tried it on my 400ex before and could never get the gasket to stop leaking. The less layers it seems the less forgiving the gasket is. I boughta cometic thin gasket and never looked back...

[speedfreaksguy]

Try the EST gaskets from Cometic.

[sandmanblue]

BTW - this mod only adds about 0.5 - 0.6 points compression to the motor. If you are at under 14:1 or so, and if you're tearing it apart and can't get the compression you want with just the piston, then the 2 layer gasket is an easy way to decrease the head gasket thickness by 0.009 inches. Milling the head is usually a last resort.

The Cometic gasket is a shelf item for the 06/07 TRX motors - they had it designated as a CRF-X gasket. You'll have to custom order for the 04/05.

The change in head position only makes about a 1 degree cam timing change. Not enough to do a heck of a lot of anything, unless as chad said, your piston to valve clearance is on the edge .

The compression increase will, however, add approximately 0.5 - 0.7 hp. For $35, it's one of the cheapest mods you can make.

[chad502ex]

running a 14:1 with decked head 0.020" and 2 layer crf and a 208 camshaft makes P-V real tight on Baldwin.....

[DirtDevilBT]

When I tear my 12.25 equiped engine down for ring change and cleaning, or when I thow my new crank in... I'm thowing this gasket in for the hell of it.