Polaris xplorer 250 head gasket leak

18 years old.
2 stroke 250cc
Air cooled
Still runs just fine but oozes oil from head gasket onto exhaust pipe
Oil injection system still works based on the amount of oil leaking.

So does a head gasket just go bad?

The gas tank is draining as I type, and I hope to have the head off tonight if the head bolts don't fight me.

Besides cylinder scoring, what should I be looking for to determine the cause and solution needed?

Thanks in advance

 

Is it the head or cylinder base gasket that leaks? They do blow out sometimes...often from improper assembly, or sometimes things just loosened enough to let it leak...you don't want to let it go, it can make a cylinder air leak...not good.
But are you sure its not just the exhaust pipe gasket/joint leaking? Those are notorious for leaking on most 2 stroke bikes...and it blows up on the cylinder, looks like something else is leaking sometimes...makes a mess for sure

 

Pic.

 

Yeah that pipe ain't leaking is it?!
Looks like you could get away with just a head gasket then...potentially a 15 minute repair.
Is it running ok otherwise? If so there is no reason to go any deeper than just taking off the head (unless you wanna freshen up the top end)...probably just 5-6 12mm nuts to remove, bam, you're in.
Clean up both gasket surfaces real well...scotch brite works gooder...clean off with brake cleaner, assemble dry, no sealer. (put a new/clean rag on piston to keep any/all dirt outta the cylinder while you work) (good time to check the cylinder walls for scoring too, obviously)

 

Finally got gas tank off. Head bolts sprayed with a liberal coating of pb blaster. Gonna let it sit overnight and soak I think. I'm impatient, but I can't afford a trip to the machine shop if a stud pulls out of whatever happens when this doesn't go as planned.

Yes It runs just fine. Fires Up easy, Etc.

 

Can't say I recall ever having issues getting those particular nuts off...you could always heat 'em a little if they don't want come...if the stud does screw out of the cylinder, no big deal, double nut it and thread it back in later...if the threads strip, a thread insert works real well there...might hafta pull the cylinder to install though...still pretty easy, not expensive either.
Just FYI, it is very common for those nuts to not want to budge, than when you lean on 'em a little they pop loose suddenly with a load crack...sometimes makes you think something snapped, unless you are expecting it.
Use 6 point sockets if you have them!

 

Impact gun or by hand?

 

I've done both...impact is quicker, but sometimes the nut and socket go flying off and hide too!
(I never use impact for assembly though!)
They are not very tight (although could be "stuck" as I said, come loose with a snap) if they are 12mm nuts (socket size) then those are 8mm studs...they should only be torqued to 18 lb ft (that's dry, or 14 lb ft for lubed threads)

 

Brendy, many thanks my friend. I owe you a beer or 12 at Dennis'

I'm in no rush, so I'm gonna let it soak overnight. My lasagna is about to come out of the oven, and I won't wanna fight that with a bloated belly. I eat lasagna like Garfield

 

Yeah that really only looks like a head gasket failure. You might find a loose head bolt or 3. If you do, then that's a real good reason why a head gasket would fail. Should be a really simple repair, especially if the head unbolts with no drama. Being an air cooled 2 stroke they are about as simple as can be.

 

......

 

Head came right off. The area where the leak is had loose head bolts.

Any chance I can clean this up and retorque without replacing the gasket or is that foolish having it apart already? brenndatomu Horkn

Edit To Add: Nevermind guys. Gasket only $20 so its already been ordered.

 

Nice. Glad they came off with limited persuasion.

 

If it is a fiber gasket no, one time use. A metal gasket can be painted with aluminum paint and put back on if it is in good condition and there no issues otherwise.
The cylinder looks good I assume?

 

Little bit of exhaust side scoring. Visible but you can't feel it with fingernail. Almost guaranteed to be from when the oil line melted off of it last summer. Funding not available for any work to be done to cylinder, so it gets a gasket and reassembled.

 

I wouldn't worry about that. Just put on the new gasket and run it till it pukes.

 

Yup, if it starts and runs good...run it!

 

I had an old 2-stroke dirt bike that got a jug gasket leak. Every once in a while it would spool up like a run-away diesel and the only thing you could do was choke it to death and/or hit the petcock and cut fuel. That was exciting if it happened while riding a tight trail.

When I finally got the $ to fix it (high school kid, broke), I pulled the jug and it looked pretty rough, but if you closed your eyes and ran your finger across it you'd never know anything was wrong. I rode the pizz out of that bike for another couple years before I sold it.

 

Yup, same here...was my first rebuild. A 197X Yamaha MX100...ran the PIZZ outta that thing...one day it went ker chunk! Piston broke...a new Wiseco piston and ring...back in bidness