lowering compression

[440ex78]

i have an 02 440ex with a 12:5:1 compresion and it keeps on blowing head gaskets is there a way to lower the compression

[enduro400rider]

put a different piston in it, do you have HD head studs? that will help keep it from blowing gakets, what kind of gas are you running?

[underpowered]

if you get the right gasket it wont blow. a Comet Flexsteel gasket will not blow, and is about the same price as normal gaskets

[2004exrider]

Did you put in bigger head studs, if not that's why its blowing gaskets.

Jimmy

[440ex78]

i have the commetic gasket and the oversize head studs and i just blew it the other day it makes kind of a chipiring type noise

[enduro400rider]

the chirping is because of the gas your running, you need to run race gas with that kind of compression. your denoting and probably running too hot because your using pump gas(i hope at least premium), when you run too hot for too long you will break things and its not good for the head gaskets, put a good gasket in it and run race gas and you should be ok. when i say race gas i mean race gas you cant buy it at most gas stations, you might have to go to a race shop or a dealer to find it, its expensive so be ready to spend money

[440ex78]

do i have to run straight race gas or can i mix it with 93 to bring it up to a certain octoane level

[underpowered]

for 12.5:1 i would go straight. you may be able to do a 50/50 mix with 93 depending on what race fuel you get. if ou get 110 and mix it with 93, you will still be at about 100 or so.

[plkmonster2]

A 50/50 mix is the minimum, or get 100 fuel if you can find it. A liquid cooled at 12.5 : 1 is pushing it. You should not run premium in a air cooled at that compression. Check your spark plug to make sure there is no aluminum specks on it. It is a sign of permanent spark knock damage.

[Eddiesanders250]

I was told by professional engine builders to use honda gaskets and not after market companies.

[1fst400]

its possible that your head is warped. Mabie it is time to have them trued.

[enduro400rider]

Originally posted by Eddiesanders250
I was told by professional engine builders to use honda gaskets and not after market companies.

no dont use the junky stock OEM honda gakets get some good cometics or something. aftermarket is usally better than stock. for 440ex78 what kind of ridding do you do? if you just do regular trail ridding change that piston out you dont want that kind of compression in the woods, your just asking to over heat it, now if your on the track keep that ratio, but for regular riding use a 11:1 or something near that compression.

[400exrider707]

Originally posted by Eddiesanders250
I was told by professional engine builders to use honda gaskets and not after market companies.

Yeah but honda doesn't make head gaskets for a 440 engine.....;)

[wilkin250r]

Originally posted by enduro400rider
aftermarket is usally better than stock.

The key word here is "usually".

Honda makes good stuff. Now, I'll admit, I haven't played with the 400EX all that much, but I know that the stock OEM Honda 250r crank is better than aftermarket, the stock Honda clutch disks are better than aftermarket, and I know lots of people that swear by the stock 250r Honda head gasket as well.

I don't have any direct experience, but I've also heard the same on the stock 400EX gasket. Better than aftermarket.

Not all aftermarket is better than stock, especially where Honda is concerned.

[440ex78]

i do mostly trial riding so if i use the 11:1 will i still have to use race fuel or can i use the 93 octane

[EXevan91]

you can run 93 with 11:1