'96 CR250 top-end...reseat ring ends through intake?

[Jackyl]

Just got my top-end done and I never removed the reed valve. I noticed on one how-to it says to reseat the ring ends through the reed valve / intake opening. I don't know how they would "pop-out" but I figured I'd see what you guys though. Thanks!!!

 

[NO HAND]

Every time I put a piston in a 250 I had to use a screw driver to push the ring back into its groove when the piston was in front of the intake opening. It just wouldn't go any further without doing damage. You were lucky it went in without snaging a ring. Was it hard to push the piston in at some point about half way through?

 

[Jackyl]

Well, it didn't seem too hard...but I did it by hand just to cycle it slowly and I had the plug in the pipe. I sure hope to hell it didn't. I will tear into it again tonight I guess. How does it pop out? What keeps it from popping back out again?

 

[Jackyl]

I also didn't see any markings on the rings that showed whether to install one side up or the other. In my Wiseco papers it said unless otherwise noted, it didn't matter which side went up. Does this sound right?

 

[250aderacer]

you can use the rings either way up,i dont have problems installing my cylinder on piston provided you line it all up properly you shouldnt have problems.

 

[Jackyl]

Thanks man, just called Wiseco and they said either side up. They also said the problem of popping out a ring end is from guys rotating or rocking the cylinder on to the piston. Mine went pretty smooth so maybe I did in fact get lucky. Also, Wiseco rings have a lot less end gap than stock so I'd imagine there's less of a chance for this to happen. I guess I'll pull the plug out of the silencer and cycle it by hand a few times to see if I can tell or not. I'd imagine I'd heard or feel it if a ring end popped out.

 

[250aderacer]

did you end gap the rings with wiseco i always find i have to end gap the rings in the cylinder.

 

[Jackyl]

I checked by dropping a ring in the cylinder and seating it with the piston. The gap was very minimal, so I left it at that. Didn't consider it being too "tight". I also forgot, I cycled the piston a few times before I installed the head back on so I think I would have noticed the ring end pop-out at that time.

 

[James]

The ring doesn't really pop out but if it isn't seated properly around those pins, it will chip off and scar your cylinder (requiring a replate). I just got through rebuilding two engines last week and this little detail nearly drove me crazy...but I feel better after checking each of them 3 times.

One of the tell tales is if it seems like you had to force the cylinder over the piston when installing it.

 

[Jackyl]

Well, it was somewhat of a pain to get it all lined up, but it dropped right in after the rings got passed the first part of the cylinder. Did you have any of them not seated properly? How do you tell?

 

[Jackyl]

Oh I see, so as long as it is seated tightly around the pin, you're good. Problem comes from rotating the cylinder to get the piston in, by forcing the ring to skip over the pin.

 

[Rcannon]

I doubt it would have slid together easily if the ring popped out. I have re-ringed my YZ 250 several times. On 4 occasions the rings stayed put. The last time I had to line it up with the pin.

A person would have had to hit it awfully hard to get the piston to go in with the ring out of place.

 

[James]

Oh I see, so as long as it is seated tightly around the pin, you're good. Problem comes from rotating the cylinder to get the piston in, by forcing the ring to skip over the pin.

Exactly (couldn't have said it better myself).

I agree with Rcannon, if it went together real easy, then you are probably ok. EVERYBODY that I have heard/read talk about this remembers fussing with getting the piston in and/or twisting the cylinder.

May not hurt to pull off the reeds and take a peek but the rings won't come down low enough to see them when assembled anyhow. You might be able to see scarring on the piston. Besides, if you ran it and it was popped out, the damage is already done. I know a friend of mine did this very thing and if I remember correctly, it didn't run well either.

 

[NO HAND]

Don't worry. If it went in easy then it is obvious the ring didn't snag. In the worst case scenario where the ring comes out of the groove and catches the intake, the piston stops to move and it becomes almost impossible to push the piston further. It wouldn't cycle smoothly as you describe either.

 

[Jackyl]

AWESOME!!! Thanks a lot for putting up with my arse. ;)

 

[SULLY]

It is good practice to always 'gap' new rings. Push the rings into the barrell while its off the bike, and use the piston to square it in the bore at point near the top of the bore where there is least wear (this is the narrowest part of the bore so you need to take this measurement here). Now measure the gap between the ends of the ring with a feeler gauge. There is no definite measurement for this, but 0.1mm -0.12mm per inch of bore is a good rule of thumb (e.g a 54mm bore would need 0.2-0.25mm gap). If there is not enough gap then when the rings expand with heat they will touch, forcing the ring out and onto the barrell wall, increasing wear, and possibly ring breakage...you don't want this!. Use a V fine swiss file or whetstone to take material off the end of the ring to achieve the correct gap, and finish off the work with a final slight chamfer (because your removing material has created a sharp edge to the ring end which may dig into the barrell wall or chip off electroplating). Job done :-)