Valves hitting the piston ..help

[nakomis0]

Ok on the top of 400ex pistons they have notches for the valves. Well I was looking at my old piston and I noticed marks where the valves hit the top of the piston. They are about an 1/8" deep.

On the exhaust side you can see the valves hit about 1/4"-1/2" towards the OUTSIDE of the piston.

On the intake side you can see the valves hit about 1/8"-1/4" towards the INSIDE of the piston.

Any thoughts on this?

I'm taking it to my engine guy tomarrow so he can get the cylinder bored and im going to ask what my problem is but hopefully you guys can give me some clues.

I hope my valves arent bent. I'm taking that also to him to inspect. Can I inspect the valves myself? I looked on the outside and they look good.

:scary: :confused2 :huh

[RED121572]

Was your piston installed backwards? Are you valves too loose? :confused:

Let us know what you find out.:D

[nakomis0]

My first thought when looking at it was 'did i put the piston in backwards?'

And I can't remember.. even when I took it apart I didnt pay attention enought to notice. I wanna say that I had the 'arrow' on the piston pointing towards the exaust. but like I said I can't remember.:(

As far as the valves I don't know if they are loose they dont really look or feel loose. Those where done by a professional.

[nakomis0]

The more I think about it, the more I think I did put the piston in backwards.

There are no marks on the valves at all. Those must be pretty strong compared to the piston.

Wow I can't believe I did that... if thats what I did. It ran like that for a yr and a half.:eek:

I can't think of any other conclusion. Valves seem tight and they still 'look' straight.

[jerry-89-250R]

by any chance did you check the timing as you were tearing it down? was there lot's of slack in the timing chain, sounds like you caught it just in time, did you get the 450f chain?

[honda350r]

I have seen the piston in backwards twice and the piston hits the valves !

[nakomis0]

Originally posted by jerry-89-250R
by any chance did you check the timing as you were tearing it down? was there lot's of slack in the timing chain, sounds like you caught it just in time, did you get the 450f chain?

Didnt check the timing and my crf450 timing chain is something new that im putting in with this rebuild. So I havent had a chance to ride on it.

I think i did catch it in time. It still somewhat unreal to me that I could make that mistake but i guess it can be easy to do.

I just hope my valves are straight. They look straight to me.:confused2 ..lol .. welp guess im just gonna put it back together and run it.

I did get pretty lucky i think.

[jerry-89-250R]

spray some carb cleaner or even wd-40 in the intake and exhaust ports on the head, look under at the valves too see if any seeps out around them before you put it back together, and if you would let me know about the 450f cam chain after you get it together, i almost ready too put my 440 back together

[Guy400]

Wow, you're lucky that you didn't have any catastrophic failure from that! If I were you I'd just buy new valves. While they may appear to be straight there's no telling how much damage may have been incurred internally. It would really suck to rebuild the motor again and fix the original problem only to have a valve break off and dance around inside your brand new motor this time damaging the piston, head and cylinder. Spend the extra +/- $110 and get the peace of mind.

[nakomis0]

Jerry thanks for that wd-40 tip. I'll let you know about that timing chain. But even without installing it It looks like there will be zero problems. Its the same lenght but almost twice as wide.

..And Guy. I wish I could, I dont know how much my aftermarket o/s valves cost, but I don't know enought to replace them myselfs so I job like that would probably cost me more like $200+.. and I'm broke like no other right now. Had to take back bottles just so I could party this weekend.:ermm: So I'm gonna try good old fashion prayer.

[Geoff Thomas]

Good ol' fashioned prayer isn't goin to help if you have a bent or bad valve. More than likely if you spray some contact clener in the ports and watch for seepage past the valve if there is none it will be OK. If there seepage or if it dumps out fast then you have a problem and need to change the valves. $200 now is way cheaper than paying $200 for it later + new pistion, head, and possibly cylender. Make sure you put it back together right the first time and save some money in the long run. Also if there isn't clearence between the valves and piston with the piston in backward then it would have done it right away. It wouldn't have lasted a year before this happening. It could have been caused by either overreving it if you have the rev limiter set higher with a rev box or weak springs/ not strong enought springs for the cam you are running or by a cam chain that has jumped a tooth or two.

[Ketch]

Nakomiso, I just went down this road my self but i was not so lucky. I had all the right set up too. over size valves with stronger springs and a ross piston and the thin head gasket too. i now have it fixed and this time i did the molding clay on the piston for a
test to see how much clearance there was and it was a eye opener wow no room for valve floating at all. i even talked to Honda Jim at ross and he said you allways run a test to check for
clearance
ss and this was with a Hot Cam stage2
and your cam has a lot more lift than my did. If you want more PM me. Jimmy:macho :

[chad502ex]

checking for clearances is a great idea!! As a matter of fact, I have a "Tech Talk" article on my site to tell ya how to check for valve-piston clearances. I always spend the time and check before final assembly cause when your squeezing for every 0.001" in your cylinder you better be sure before it's too late. Anyway,... http://www.chad502ex under "Tech Talk" might help.

just my .02
;)

Chad502EX.com

[nakomis0]

Originally posted by Geoff Thomas
Also if there isn't clearence between the valves and piston with the piston in backward then it would have done it right away. It wouldn't have lasted a year before this happening. [/QUOTE

Ya i think its just pounded its own notch into the piston head. And then I rode it like that for a yr.


[QUOTE]Originally posted by Geoff Thomas
It could have been caused by either overreving it if you have the rev limiter set higher with a rev box or weak springs/ not strong enought springs for the cam you are running or by a cam chain that has jumped a tooth or two.

I used a caliper to kinda compare the notches and it did look like if the piston was in the correct direction it would of been ok. I over rev all day long I gotta admit. But I think if i did float a valve, it would of made the dent in the piston in the correct spot.... just deeper.

This dent looks the correct deepness, just its off center a little bit .

And I will be checking for clearences before I close up this time.

Oh ya and I also sprayed PB spray and no leaks, and the valves look in perfect condition still.

This bike will be back together this weekend, and will most likely be going through the breakin process on Sunday.. so If anything goes wrong i'll be sure to post. But Im pretty confident its gonna be just like lasttime a fast mo' fo.... except this time the piston will be in the right direction... :huh .. lol

[cals400ex]

how do you know what way is the right direction? doesn't it say in the manual?

[nakomis0]

Ya theres an arrow which points to the exahaust.

I still can't believe I did that.

"Exhaust is in the rear.... arrow points to the rear" Must of been what I was thinking. .. yup prurty dumb on my part, lets let this tread die so peeps might forget im a moron. :p

[cals400ex]

Originally posted by nakomis0
Ya theres an arrow which points to the exahaust.

I still can't believe I did that.

"Exhaust is in the rear.... arrow points to the rear" Must of been what I was thinking. .. yup prurty dumb on my part, lets let this tread die so peeps might forget im a moron. :p


i thought that the arrows pointed to the exhaust ports? they are towards the front of the bike correct???

[jerry-89-250R]

arrow points to the exhaust