HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
J-Dawg

bad head

12 posts in this topic

has anyone broke an exhaust valve before and what do you think caused it ? Possibly is someone wanting to get rid of a head ? When my valve broke it screwed up my valve bucket guide.

Share this post


Link to post
Share on other sites

I broke ex valves. It also shattered the valve buckets, and the cams drove the bucket parts into the soft aluminum head. It took a while, but I finally found someone here on TT selling a used head. I believe nine was caused by overrev when I missed shifts during a race. I also found a bent shift fork (cause of missed shifts).

Share this post


Link to post
Share on other sites

Floating exhaust valves is what causes contact between valves and heads. The intakes dont get smacked because they are closed when the piston comes up, but the exhaust valve is hanging open, and when floating because of over rev or weak springs, some times gets tagged and tagged good. If your a racer that has a deep relationship with your rev limiter, ya know Im talkin about, the kind of relationship with lots and lots of contact, you should change out your valve springs at least once a season, maybe twice depending on how much you race.

Share this post


Link to post
Share on other sites

As a moderator............... I have to say this title caught my eye :):D

Bill :D

Share this post


Link to post
Share on other sites

The speed at which the valves are traveling allows them to lose contact with the cam momentarily. So therefore it is referred to as float.

Share this post


Link to post
Share on other sites

Valve float is what happens when the valve springs are not able to close the valves hard or fast enough, and with the exhaust valves, they are open when the piston comes back up and wham - a collision at about 25m per second or 90kmh... not sure of the mass of the piston, but that is a lot of force...

As for a having a bad head, well, don't drink so much the night before... :):D

David

[ June 19, 2002: Message edited by: yamaha. dude ]

Share this post


Link to post
Share on other sites

When I broke the valve I was doing a wheelie up a hill at Pismo , so I think it could have just been a weak spring . Luckily it did not happen earlier when I was jumping a 90 foot double or I could have been on my head . On that same double I overjumped and broke my Shoei on my bars and pushed my goggles up and scraped up my foreherad . You know what they say , go big , crash big !

Share this post


Link to post
Share on other sites

Quote: Bill As a moderator............... I have to say this title caught my eye

Bill

I was gonna add.... is there such a thing?

Share this post


Link to post
Share on other sites

BAD HEAD????

(confused look)

thats like saying ''BAD RIDE''

OH,,,errrrr,,,,, hang on,,,,,,,,,

[ June 21, 2002: Message edited by: Mark_UK ]

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0