head bolts

[tigerdog]

hey guys,
my 11:1 piston will be in today and ive read in the tech section
how upping the comp.ratio will make the bike stronger all around.
so here is my question
when i up the compression will i have to do any modifications to head bolts?
i seem to remember reading something about it but not sure what.
any feedback would be appreciated, thanks

[cals400ex]

it is possible that the head studs may pull out. however, they could pull out at less than 11:1, but the higher the compression the more likely they will pull. the question is, are you running a true 11:1 or a rated 11:1? i personally don't think you would notice 2 or 3 tenths difference in compression.

[gojk]

I would change them to the FDO studs if I had the engine apart. They will make the enigine a ton more reliable. Mine lasted about 6 months, then it started blowing head gaskets left and right until I replaced the studs.

[tigerdog]

i baught i wiseco piston thats rated at 11:1 and am planning to use the xr400 head gasket and remove the cylender base gasket
thaught that would be close enough ,still good boost over stock compression. where would i get the studs and do the holes need to be retapped ? i dont want any reliability issues. and i wouldnt want to have to do the same job twice. i would rather do it once and have it work right, thats why i felt it was important to ask those that have allready done it.

[TC426EX]

I would leave your base gasket alone if I was you... The XR head gasket is a good mod, but I would personally feel iffy running my bike with no base gasket. Im sure it doesnt add very much to the compression ratio anyway, and with the XR head gasket you should be right at the 11:1 that its rated for since they rate them for the XR and not the TRX...

[cals400ex]

i think the XR head AND base gaskets are different from the EX, but i am not positive. i thought both were thinner on the XR, but it may only be the head gaskets that differs. however, the small difference in compression shouldn't make much if any difference. i just put my buddies bike back together and he only had a 10:1 piston, so we ran no base gasket. let me tell you, that hondabond is better stuff than the RTV. the hondabond goes on smoother. we haven't had any problems with no base gasket. however, with only running 1 layer of the head gasket we periodically have a leak. the key is to clean the heck out of the gasket and then paint it with high-temp paint.

also, a cam will really help the bike out. the piston itself won't do a ton.

[tigerdog]

well i was going by what i read in the tech forum, but them both being rated for the xr400 makes sense. the piston and gasket tha is

do you think the 400ex builds enough base pressure to have to have a gasket? or are you thinking about the oil passages leaking?

my 400 has a breather that goes directly to my intake tube with no valve so i assumed there would be minimal base pressure.

one other question is the honda bond that white stuff you find here and there in place of gaskets?

[INFANTRY RACING]

ok
run a base gasket (Cometic make a thin one)
run the xr head gasket
forget about the head studs you won't need them
have fun

[lilpoppy]

I don't know what mods you have but with my mods my head studs pulled out and it was a headache. If all you are doing is putting in a new piston then I wouldn't worry about it but if you do much more and you don't feel like breaking into it again I would put the FDO studs in now. When my head studs pulled it also pulled some other bolts and I had to Heli coil a few bolts on top of replacing the stock studs with the FDO studs, and yes the cylinder does have to be tapped for the new studs but the head doesn't need any modification at all.

[cals400ex]

hondabond is a honda sealing product that can withstand high temps. you should be able to pick it up or order from your local honda dealership. by the way, it is white.

[tigerdog]

thanks guys i appreciate the advice

[cals400ex]

not that i think of it, the EX and XR base gaskets may be the same. i really don't know. i thought they were different, but they may be the same. i know the head gaskets are different though.

[lilpoppy]

Personally I did the no base gasket mod and I am running faster now and havn't had a problem yet.

[tigerdog]

how long ago did you do this mod?
and what type of sealant did you use on the cylender base?
just curious:)

[cals400ex]

my buddy ran high temp rtv sealant with no base gasket on his bike with great success for about 6 months. however, i heard that the oil in the bike may actually be able to break the rtv down so we switched to hondabond and haven't had a problem. the honda bond seems to go on smoother and easier too.