piston hitting?

[GoingBig]

2001 400ex I tore it down a month ago or so and turned it into a 416 with hotcams stage 1. put it back together it ran strong but started leaking oil from the head gasket after one tank of gas. moose gaskets are junk i have learned. tore it back down and put xr 400 gasket in it. put it back together and it started nocking real bad. i knew something wasnt right so i shut her down right away. pulled her back apart and noticed that the exhaust valves were ever so slightly hitting the piston. is the gasket to thin. i know people use them. was my timing off. woluld that cause it to hit.any info would be helpful. thanks

[greg_gorrell]

timing is off man, sounds like its just a tooth off

[hondajoe05]

hmm mine does that to atleast i think or could it be that my valves are slightly adjusted wrong?? because thats what i thought and if its my timing im screwed cuz i have no idea about how to do that and i got my engine bored about 2 and a half months ago but the knocking didn't start till about a month ago and after adjusting my valves it got better but still makes the ticking nosie? could i possibly have the same problem

[GoingBig]

so if my timing is just slightly off it can cause the valves to hit the piston? i hope that is the case. i would hate to put it back together again and have it be something else and hve to pull it back apart.

[cals400ex]

what kind of piston do you have?

[GoingBig]

JE 10:8 416 bore

[cals400ex]

my ross 426 had the valves ever so lightly nipping the piston. it almost looked like the vavle reliefs were a hair off. i believe it i was my intake valves but i really don't remember.

[GoingBig]

do you think i should just go back to a stock gasket? it didnt do this until i went with the xr gasket.

[Barney]

I had this happen to me.The exhaust are the first to hit. There
is apart to this you can not stop or calculate how much valve
float at high rpm. How i fix my problem was to use my milling
machine and cutt the pockets bigger or deeper.

[nakomis0]

You probably floated a valve. You need stiffer valve springs.... well now actually you probabl need new valves .. and valve springs.

[GoingBig]

the thing is the head is completly brand new all factory honda parts. head,springs,valves everything. it didnt hit with the thicker moose gasket just when i went to the xr gasket. not sure what to think now. maybe go back to the thicker gasket?

[cals400ex]

i would probably cut the valve reliefs bigger and use the thin gasket if it was me.

[wilkin250r]

I thought the JE and Ross pistons were supposed to be top-notch. What's with this problem of hitting the valves?

Crap, this 400EX motor is a nightmare, it seems that nobody makes a proper piston for it. First, there's the deck-height issue and problems meeting compression. If the deck-height issue gets corrected, the valve relief pockets aren't deep or wide enough.

Anybody know if the XR400 has the same problems with valves?

I swear, if I ever DO bust into my girlfriend's 400EX for upgrades, I'm going to design a custom piston.

[Barney]

Ok want happen when you use the thin gasket it moves the valve
so it hits more to the center of the piston if it hits. Just remember
that the valve does not allways follow the profile of the cam at
high rpms. I had 1mm over size valves with kibble white springs
an valves with a thin Gasket With just 1mm bigger it would be close but it didn't hit till you got to the high rpms. this is why you should allways check with the molding clay before you run it hard.
if you check it and you can see how close it is make room of about
.030 to .040 so mash does meet crash.

[GoingBig]

well i guess ill just get the stock gasket back in there. i dont feel like dealing with anymore problems i just want this thing to run again so i can ride.its been apart for to long now.i just hope the stock gasket solves the problem.

[cals400ex]

wilkin, i ran a thin cosmetic head gasket and no base gasket (used hondabonda sealant). this could have been part of my problem. however, it still seemed the reliefs were a bit off. it was only hitting on the back side of either the intake or the exhaust valves. i really don't remember. also, i ran an aftermarket cdi box with stock valve springs. by the way, i reved it well past the stock rev limit too so that could have been part of my problem. i don't know. i still do no feel that the piston was the best made. if i had to do it all over again, i would not have a problem spending $400 on a custom piston that was built more precise and had a few more performance enhancing characteristics. i am not saying that it would cost that much, but i would spend that much if it did.

[eganracing]

i run a wisco piston and i have had no problems.

[JOEX]

Is there a way to tell if the valves are hitting the piston without taking off the head?

[cals400ex]

i had no indications by driving the bike. i just noticed when i swapped heads.