KX Riders

Maintenance & Technical => KX250 / KX125 => Topic started by: Marco810 on January 31, 2011, 09:48:40 AM

Title: Blown headgasket
Post by: Marco810 on January 31, 2011, 09:48:40 AM
was out riding yesterday and my bike went up in a cloud of smoke :-o it was the rad overflow pouring coolant onto the pipe. at first i thought it was the cap but after letting it cool down and starting it with the cap off i could see air bubbles coming out of the hose at the top of the rad. anyways pulled it apart and it defiantly looks like it was burning water. any thoughts on keeping this from happening again?

oh and forgot to add when i was taking the head off the bolts ranges anywhere from 25ft pounds to 35 so hopefully thats the problem
 
some pics cause if your anything like me pictures are very important
(http://img696.imageshack.us/img696/9200/19845131.jpg)
(http://img193.imageshack.us/img193/5953/66247906.jpg)
(http://img7.imageshack.us/img7/8910/26291927.jpg)
(http://img695.imageshack.us/img695/3909/92378646.jpg)
(http://img6.imageshack.us/img6/8378/81388941.jpg)
(http://img84.imageshack.us/img84/3420/89979564.jpg)
Title: Re: Blown headgasket
Post by: stevea100m on January 31, 2011, 10:40:44 AM
I would say that anytime you put a piston in it i would change the head gasket. Ive only ever had major head gasket issues with the 03 kx125 because it uses orings instead of a gasket.
Title: Re: Blown headgasket
Post by: Marco810 on January 31, 2011, 10:48:33 AM
Yeah i ordered a head gasket from ebay. im thinking maybe the guy that did the topend last didnt replace the gasket along with not torquing the head to specs. finding all kind of surprises as im tearing into it
Title: Re: Blown headgasket
Post by: DoldGuy on January 31, 2011, 11:23:27 AM
The 92 Models were pretty good for the Chassis not pulling on the head like the first perimeter frames of 90 & 91, but it still does. Looks like you need to pull the cylinder & hone, & I would recommend to pull the cylinder studs & lap the surface so its flat & then do the cylinder head. Once both surfaces are completly flat you should be able to set them together with a thin film of oil & have a vacumm/suction between the two when you lift the head from the cylinder. The next thing is to loosen the bottomend motor mounts & swingarm pivot & lift  the motor up & while doing so, tighten the mounts.
Hope this info helps!
DoldGuy
Title: Re: Blown headgasket
Post by: Marco810 on January 31, 2011, 12:32:27 PM
some good info doldguy, thanks. think i even have a cylinder hone laying around
not sure what you mean by "lap the surface" though. also how does one pull the head studs?
Title: Re: Blown headgasket
Post by: stevea100m on January 31, 2011, 01:16:17 PM
to pull the head studs you can take 2 nuts and tighten them into eachother on the stud. Take and turn the lower nut and turn it as if ur takein a bolt out and the std should come out
Title: Re: Blown headgasket
Post by: Marco810 on January 31, 2011, 01:46:45 PM
oh ok i see so their just threaded in. thanks
Title: Re: Blown headgasket
Post by: sandblaster on January 31, 2011, 01:58:18 PM
It's probably just my imagination but is the chrome worn through on the left side of that pic?
Title: Re: Blown headgasket
Post by: stevea100m on January 31, 2011, 02:19:53 PM
I was just thinkin the same thing
Title: Re: Blown headgasket
Post by: Marco810 on February 01, 2011, 08:16:10 AM
i think thats just dried rust in the pic, after cleaning the cylinder with oil it doesnt appear to have any defects
Title: Re: Blown headgasket
Post by: Wayfast1500 on February 06, 2011, 04:34:15 PM
If you hone make sure its a stone hone with the 3 long stones and not the stone balls.  The balls will beat the ports.
Title: Re: Blown headgasket
Post by: sandblaster on February 06, 2011, 04:49:07 PM
That's interesting.
I have never had the ball type give me any trouble.
It's possible that you are running the hone to fast or you have the wrong diameter hone.
I'd try slowing it up, using lubrication, and be sure to have the correct size and grit.