08 yz450 timing question after valve shim


2 replies to this topic
  • yzrider487

Posted September 18, 2015 - 01:40 PM

#1

I just shimmed the valves on my 2008 YZ450F for the first time. The bike started and ran good after finishing but it was backfiring bad and seems to be running hot. I removed the 45 pilot and installed a 48 from the jd jet kit with the screw open 2 turns. Still backfiring very pronounced on decelleration. I removed the spark arrestor and found what appeared to be fiberglass packing. After running without spark arrestor it almost seems to be slightly backfiring at idle?? I can't imagine the bike would be running lean/backfiring with the 48.

 

-I checked TDC with screwdriver thru spark plug hole and it was true with the I mark after H mark thru inspection port. I got my exhaust cam mark as close to 9 oclock and intake cam mark as to 3oclock as I thought possible. Pin count was 13 between the two top marks on intake and exhaust cams. I lubed cams with bel ray assembly lube. Pics are below, sorry the pic quality is pitiful but it's all I've got.

 

-Is my timing off or are there any other beginner mistakes I could've made to cause this? Thanks

 

 

IMG_05511.JPG IMG_05522.JPG



Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted September 18, 2015 - 03:39 PM

#2

Be sure the exhaust is sealed up well.  Could be n air leak there.  Also be sure that the pilot screw O-ring is in place and intact.  If you had the slide out of the carb, you may have installed the vacuum release plate upside down.  The square end with the hole near the edge goes down.  



  • yzrider487

Posted September 18, 2015 - 06:17 PM

#3

Thanks for the help, I'll check those points out!





Related Content

Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
Forums
Photo

Michigan Motocross Tires by 288yz450


Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply
Reviews

Yamaha YZ450F 2017 by Chris.GVS


Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 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.