Is this Cylinder salvageable ?

[hub97119]

My son managed to do this to my 86. Murphy's law becomes real evident with a 17 year old some times. He had been riding for about 45 min. then boom, tow in time. I would like to keep the cyl. as it has a nice port to it, so my question is 1.) Is this cyl. good for a bore ( at 66.75 now )
2.) Should I take it in and see how far it would have to be bored before buying a piston
3.) Should I just get a piston 1 size up and bore ( or 2 sizes ) I know the machine shop likes to have to new piston in hand before boring
4.) If I had to re-sleeve will that affect the port work at all ?

We are currently stripping the whole bike down and rebuilding for his senior school project

I hope the pics show enough detail for an educated guess....Thanks  Ron   The yellow one is my sphinx ( no one touches that !! )

[Pumashine]

If it was an 86 you would have lots of bores left. You should get one size bigger piston 67mm and get it bored. Re sleeving is way expensive and you don't want to do that as a 310 is the same cost. Yes your sleeve would need to be matched to your port. Try mixing oil in the gas and break in your new piston.

[hub97119]

are you saying this could have been the result of un-mixed gas ?

[Tbone07]

Holy shit! That's quite the damage you've got there

If you have enough bores left in the sleeve i'd say it's definitely salvageable. But it looks like you have a head gasket leak for sure. Which probably created that massive hole. Maybe you can have your head cut for o-rings while it's apart?

If you're riding in the extreme cold, then depending on what type of pre-mix oil and oil/gas ratio you're running, the oil could have separated from the gas.

[bkstoffe]

Once you get all the aluminum off the sleeve from the piston meltdown it probably won't look so bad. I would clean it up, then lightly hone and see how much damage there is, and measure bore.  that will tell you how much / if it needs bored. From tiny pics on phone it looks like aluminum built up on sleeve more than gouges?

[pinned250r]

To answer bluntly, yes it's definitely fixable. Just go .010 bore and you'll be fine.

Also, don't mind tony(pumashine), his mixing oil comment is just his smart alic sense of humor.

[2ndmoto]

I'd second bkstroffe. It needs to have the aluminum removed. I am sure a ball hone will work to remove it. Any motorcycle shop worth their salt can do this. Once cleaned up it can be inspected for gouges, out of round and excessive clearance. At that point you can make a decision on how to proceed.  It might clean up with just a hone, or you might need to have it bored. Going with an 86 style piston will give you more over bores and is a very common setup.

LED is out in Gresham. Arlan has been modifying 250r's since their creation. He is a good guy to meet and will give sound advise on what to do.

Best regards
-Jason

[Pumashine]

are you saying this could have been the result of un-mixed gas ?

 I was just joking as my first motor was run without oil when some one was using it. It proly takes less than 45 minutes to burn one up.

[fearlessfred]

what does bottom end look like,any piston pieces down there

[FerrinMotorsports]

Go to the hardware store and buy some muratic acid...The acid will eat the piston material as it is aluminum and will not damage the sleeve as it issteel...pour the muratic acid into the cylinder.. use an old tooth brush to agitate and clean off the piston residue....rinse the cylinder out with water and dry it ...shoot some WD 40 on the cylinder to prevent rust....then measure the bore to see if it is still within spec ...hopefully you can get away with honing it....

[hub97119]

Nothing in the bottom end that I can see however I will rinse with mix and take another careful look. If I have to split the cases then it's going to be a re-build on the bottom. You had me going there Puma...I wasn't with him, he was over at sand lake with his buddies but he knows better than to run straight gas; he has only owned 2 strokes since he was 12. I will try the muratic acid this weekend. I plan on replacing with a Wossner if all looks good.

[Tbone07]

Nothing in the bottom end that I can see however I will rinse with mix and take another careful look. If I have to split the cases then it's going to be a re-build on the bottom. You had me going there Puma...I wasn't with him, he was over at sand lake with his buddies but he knows better than to run straight gas; he has only owned 2 strokes since he was 12. I will try the muratic acid this weekend. I plan on replacing with a Wossner if all looks good.

From that picture i'd say coolant/water is your main issue. I'd have your head and cylinder checked to be sure their perfectly flat as well

[Jerry Hall]

I'd second bkstroffe. It needs to have the aluminum removed. I am sure a ball hone will work to remove it. Any motorcycle shop worth their salt can do this. Once cleaned up it can be inspected for gouges, out of round and excessive clearance. At that point you can make a decision on how to proceed.  It might clean up with just a hone, or you might need to have it bored. Going with an 86 style piston will give you more over bores and is a very common setup.

LED is out in Gresham. Arlan has been modifying 250r's since their creation. He is a good guy to meet and will give sound advise on what to do.

Best regards
-Jason

This cylinder can be saved!

Check all of the studs for their ability to hold 20 ft-lb of torque.  

Remove the studs and check the head gasket surface for flatness by lapping it on a surface plate or a good piece of thick glass.  If the surface is not flat you may have to machine it.  Also  check the head for flatness on the surface plate

A ball hone will eventually remove the aluminum but will ruin the current bore with the amount of aluminum that has to be removed.  Use acid to remove the aluminum then hone it lightly with a good rigid hone preferably a sunnen mandrel hone.  Now check the bore to see if it is still within spec.  If the bore is out of spec., bore it to the next oversize.