Bursting valves, please, please help
Posted November 07, 2001 - 05:09 PM
Posted November 08, 2001 - 04:09 AM
Posted November 15, 2001 - 06:29 PM
Posted November 15, 2001 - 07:06 PM
Can you give us a little more info on motor?
How many miles on it? How many times had your valves been adjusted and how many miles ago was your last adjustment?
What type of riding do you do and what kind rpm's do you put the motor through?
Posted November 16, 2001 - 06:11 AM
You could get a 400 head for a 426 and visa-versa.
If you are going to throw your old head into the garbage I would like to see it.
Posted November 16, 2001 - 07:40 PM
When this happened to my 400, the valve that broke turned over and punched a bunch of holes in the piston. The result was a wasted rod as the aluminum went through the oil holes in the top of the rod, and impregnated between the rod and piston pin. Luckily 400/426 rods are pretty cheap, but tearing down the bottom end will suck.
After much searching for a used head, all I found was a complete engine for $2000.00 brand new in the crate. Thr repairs would be $1000.00 for just parts, $1700.00 if I used 2001 426 parts. I still owed $1000.00 on the bike and was so disgusted I never fixed it. Most of my disgust came when talking to folks at Montclair Yamaha (Ty Davis's bike builders and sponser), Factory Yamaha (the famous BK), and notebles such as stroker. They all said catastrophic failure was very common in 400's. Major changes were made to the 426. Head, rod and carb changes were the biggest. BK told me to scrap all the 400 stuff and go 426 if I ever wanted it to be reliable. It was at that point I bought the coolest motorcycle ever made. The KTM 520 EXC. The blue beast still sits, broken and battered.
Posted November 16, 2001 - 07:43 PM
Posted November 17, 2001 - 07:54 AM
BTW as I had expierienced catastrophic engine failure with this bike once before (broken con rod),I had a valve adjustment done the week before the race.