HELP 99' YZ400 motor probs.


2 replies to this topic
  • jimbob69

Posted April 30, 2006 - 08:32 AM

#1

Heres the deal.
I got the bike about 2 weeks ago for a killer deal.
The bike had oil leakin at the head, base and right side cover gaskets.
So i got a complete gasket set and replaced them all, no external leaks.
So i go for a little ride and i see some coolant dripping from the over flow, i didnt think too much of it, but i topped it off and just took a bottle of water with me for a little ride to make sure all was good.
The leak out the over flow got worse and worse, until it came to the point that it would lose about half a quart every 10 minutes.

So i figured the head gasket was blown, forcing pressure in the system.
So i take it all back apart, and it was obvious that was the problem, so i lapped the crap outa the head on slab of glass and some 400 grit paper.
I used the gasket that i took out of the bike the first time i took it apart, put a glaze of high temp silicon on it (i know ur not sposta do this and that the silicon is not meant for head gaskets, but ive done it in a crunch many times on my 2 strokes) put the head on, waited an hour, then torqued all the bolts in a crisscross pattern, put the cams in, but when i turn it over with the kickstart its not right, i can get it past the compression stroke with my hand.

I KNOW the cams are in right, i probably checked it about 10 times, but the valves must not be seating right or somthing, Im STUMPED, please, anyone have any ideas??

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jimbob69

Posted April 30, 2006 - 11:44 AM

#2

bump...

  • 1rkcooper

Posted April 30, 2006 - 12:50 PM

#3

If you can turn it over by hand you are probably right. If the cams are in correctly, check again for the 11th time just to be sure, then you probably have a valve that is not sealing. You could do a leak down test. The other way you can find out which valve isn't sealing is to take the head off and fill the intake chamber with clean solvent, if it leaks through a valve you have found the problem, do the same on the exhaust chamber. OR, perhaps there is something stuck n the valve holding it open a tiny bit. Check your compression release cable first to be sure it works correctly.

Good luck





Related Content

Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
Forums
Photo

Megabomb Fitment by 288yz450


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

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo
Supercross

Wilson the Blue Privateer by jetfuel


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 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.