02 MM Headgasket questions

N

nst115

VIP Lfietime Member
Joined
Dec 9, 2010
Messages
228
Age
35
Location
Hardin, MT
So the last time I rode my sled it kept blowing the coolant bottle lid off and eventually started boiling some coolant in the bottle. I never saw a temp light come on and I shut it down and let it cool on the way back to the truck several times.
Anyway I got to checking stuff last night and noticed at idle it bubbled quite a bit in the coolant bottle. I found several posts on here that suggest this is likely a headgasket issue.

Pulled the plugs and the clutch side had a slight but of milky on it just from idling it a few minutes in the shop.
Borrowed a compression tester and all cylinders read 124 cold.
Pulled the head off, Looks like I have a single layer head gasket. Pictures coming in a few minutes from my phone.
 
Picture are clutch side first on plugs I think.

Do you see an obvious headgasket problem? Do I need to find something else wrong that caused it to go? How do I check head flatness?
Should I pull jugs and look at the bottom?
Based off of the compression should I consider new rings or is that not really a concern. I have only put a couple hundred miles on this sled since I bought it, history is unknown.
 
The bubbling was probably air escaping and not boiling. Hard to tell from the picture but it looks like the pto piston is clean around the edge which would suggest that coolant was in it. Is that the milky stuff on the head? You can check straightness of the head with a good straight edge across it. I am guessing you cant see anywhere it is obvious it was leaking. If it was mine I would pull jugs and put a new base gasket on and if it has quite a few miles I would also check piston specs and change rings. Again that is if it was mine as I am pretty ocd and like to know for sure when the last time that stuff was checked.
 
That is milky on the head in clutch side. I guess that's PTO?
I couldn't see anything super obvious wrong with the gasket. I may as well pull the jugs I guess just cause the history is unknown. Where to find piston specs and how to check em? Rings from Yamaha?

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The service manual would have the specs and you are vip so if you don't have it you can get it free from here. If it were mine I would use oem parts but that is up to you.
 
Looks like where the protective coating is wherein off or someone used a marker to mark the pistons to make sure they put pistons back in the same spot.
 
Definitely pumping coolant, replace the head gaskets and base gaskets. If you run a single layer head gasket make sure to spray it with gasket sealant. You could just try the head gaskets but not knowing exactly where it is coming from, might as well replace the base gasket too....................SRXtreme

Did all the head bolts feel about the same torque?
 
Is the motor ported? Looks like the ports are marking the skirt. Can the marks be felt with your fingernail? or is it more of a visual thing?...................SRXtreme
 
I can feel them on the back side with my nail but not with my fingertip. Can't feel the front either way. I don't know what to look for for porting.

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Pistons are cheap, replace them all with rings. If it is ported the easiest way to tell is if the exhaust pipe flange is the same diameter as the exhaust port in the head. Stock you will see the cylinder protrude out from the exhaust flange. You should make sure all ports have a nice chamfer to them, no sharp edges................SRXtreme
 
I don't have the stock exhaust to compare to but compared to my pipe flanges the port is about 1/16 smaller most of the way around.
 
Who is it on here that does porting? I was thinking of having a mild port done sometime, no better time than when I have to have it apart anyway. But I suppose they are too busy this time of year to get them back to me in less than 2 weeks....
 
Well I reckon I don't have the money for a port now either. Ordered new pistons, rings, clips, pins, and gaskets. reckon I'll save my old ones for emergency spares.

Should I peel layers on my brand new head gasket? Not sure I really like that idea but I don't want less power than I had either...
 
I wouldn't peel it yet, put it on and run it if everything works like it should then peel the gasket and spray with copper gasket spray.
 
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