compression

[missouritrailrider]

are you able to obtail higher compression using stock piston, just a smaller base gasket? would it be worth it? mine is leaking and needs replaced anyways...

 

[courchaine]

Yes it's possible just look into cometic gasket they can make you one with your specs....or you could even just use some sealant to replace the gasket like 1104 or something like that.

 

[missouritrailrider]

ok has anybody seen this or what info do i need for cometic? i emailed them with no response yet, it is all I need to finish up my motor with cam, stage 2 port polish, and 5-angle valve job, also i need to send my flywheel in to get lightened

 

[missouritrailrider]

anybody else?

 

[ogener]

you could get the head milled a bit to up the compression but it does cost come money.

 

[2kwarrior]

I did this on my Suzuki before I went all out on the engine. I made my own gasket. I just went to the auto parts store with my base gasket and compared it to the rolls of gasket material they sell. Its the cheapest way to gain like a point of compression. Easy to do and cheap.

 

[paulie1959]

On the warrior and raptor 350, the factory head gasket consist of 3 thin gaskets, take them apart, clean it up and use just one of them, I did this on my stock raptor 350 and work good, if you want even more don't use a base gasket use RTV form a gasket, but make shore you have enough piston to head clearance, back in the '70s the 2 stroke MX bikes were air cooled, we used lapping compound to seat the head to the cylinder and used no head gasket, just copper coat sealant to get more power, maybe you can try that, but make shore you check piston to head clearance

 

[griff]

*Call* Cometic, its a lot faster...

 

[jasonp]

all you need to tell them is what kind of bike you have year and engine. Also how big of bore. Stock is 83mm.
They have several type of gaskets and I sugest you go to there web site and check it out. You must maintain at least .035" of deck clearance. With the stock piston you should be ok but I would for sure measure what you got when you take the head off and that will tell you what thickness gaskets you are going to need.

 

[jasonp]

You go under that deck clearance you will have problems with the piston making "friends" with the head or valves.

 

[missouritrailrider]

thanks jason, also do you know what these other guys were referring to as being 3 base gaskets? would i be safe removing one of them?

 

[jasonp]

yes. the stock head gasket is a muli-layer type and basically it is the best gasket to use for sealing the head to cylinder.
I read people that have done this and removed a couple layers to get there deck and used a copper coat spray to get it to seal. After a while they tend to leak or blow out because the heat from expanding and contracting will cause it to break eventually. I would much rather see if you had to a copper gasket to get your clearance rather then trying this method but it still may work for you if done correctly.
Just to give you an idea.
Stock head gasket thickness is .043"
Base gasket is .020"
All you have to do is measure the piston at TDC, figure how far down in the bore it is then find what you need in gasket thickness to make your .035 to .040" and you are good to go.
If you have a look at cometic web site they go into detail asbout all there gaskets and help you to choose the type you want.
I recomend a EST type head gasket though.

 

[missouritrailrider]

est type? is this what the cometic ones are?

 

[jasonp]

est type? is this what the cometic ones are?

if you go to there web site you will find that they offer a wide section of gaskets and materials. I was just recomending the EST as it is like stock but thinner (well can be any thickness you want with in reason) and doesn't need to be re-torqued and can be used again.

 

[jasonp]

Personally though if I was this deep into a engine I would spent the money and get a wiseco piston of like .020" over. They can be had for pretty reasonable price and you can even end up with a really strong running engine with bringing the deck height with in spec. A bigger bore is also a good way to add a little more compression as well.

 

[missouritrailrider]

ya i would but i have been spending too much money on it lately, i just want the extra little boost to get through the summer and it needs a base gasket anyways, i am getting a port/polish and a .415 web camas well as KW springs and valves, ill wait to get the piston done i want a 400 kit next winter i already have it all stripped down so the base gasket wont be tough lol