Engine freshen up/now need help


7 replies to this topic
  • Big Mac

Posted August 24, 2006 - 05:07 PM

#1

I just performed a top end freshen up on my 426 and I have a couple of problems now. I will take it back apart tomorrow and I am just looking for some suggestions and things to look for before I tear into it again.

I bought a stock cylinder & piston, new rings, valve springs, keepers and valve seals. The valves themselves all seal fine so I just cleaned up the carbon and reused them in in the same locations. I am not able to start it via the kick start, I have to give it a running jump start (leads me to believe timing is off). Also have a knocking noise that seems to be coming from the head and it really has me scared. Only ran it about 1 min with all that noise so I hope I didn't do any damamge.

I also run a 450 cam for the auto decompression but was running that for quite some time before the rebuild.

Anything you guys can suggest would be apprieciated. Thanks in advance.

Chris

  • quailboy

Posted August 24, 2006 - 05:51 PM

#2

sounds like your piston is slapping the cylinder. or your piston is hitting your head. make sure you put your piston on the right way.

  • 642MX

Posted August 24, 2006 - 05:53 PM

#3

Sounds like its out of time to me. The knocking sound was probably a valve kissing the piston. Never try to push start a bike if you can't start it with the kicker. Good luck!

  • Big Mac

Posted August 25, 2006 - 05:11 AM

#4

Thanks guys, I will be checking for both of those senarios.

Chris

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Fastest1

Posted August 25, 2006 - 10:27 AM

#5

What year 426?

  • Big Mac

Posted August 29, 2006 - 08:55 AM

#6

Sorry for the late reply. It was a timing issue. I took the head off and the two outside intake valves were just kissing the piston. I took them out and checked to be sure and they were fine. Not bent or any damage measurable. Recehcked valve lash and timed it again. It started on the second kick and no more piston slap. I was so happy and will be riding this coming weekend again. Thanks for the responses guys

Chris

  • grayracer513

Posted August 29, 2006 - 09:28 AM

#7

I took the head off and the two outside intake valves were just kissing the piston. I took them out and checked to be sure and they were fine. Not bent or any damage measurable. Recehcked valve lash and timed it again. It started on the second kick and no more piston slap.

How does it feel to be the luckiest man in Texas?

  • Big Mac

Posted September 05, 2006 - 06:43 AM

#8

How does it feel to be the luckiest man in Texas?


It feels great. I would rather be lucky than good any day. And I usually am.

It rode great this weekend. No problems or hiccups of any kind. My buddies were quite impressed with the new power as was I . Thanks again Thumper members!!!!!

Chris





Related Content

Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

BIGBORE FOR YZ450F 2006? by Taattie94


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

Should I buy this bike? help....... by Numsa Hul


Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies
Forums
Photo

The "going back to the other darkside" adventure... by Monk


Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  113 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.