Has anyone ever seen a piston and head like this?

[Ryah]

I finally had to tear the motor down on my 85 250r. The lower rod bearing went out on it. Anyways, the piston and head both look to have had something sprayed on them to make them very rough (like 80 grit sand paper). Almost as if a piece of metal ran around in there for an extended period of time. But there is no way that that was possible. Just curious as to what it was, is there any benefit to it? Should I just get another stock head for my rebuild? This bike isn't for all out drag racing. That's what the TriZ is for. The 250r is for reliable, relaxed, luggable dune riding.

[Cody]

That should make the bike slower in my opinion. You want the piston and cylinder as clean as possible. I mean, mirror finish. That isnt mirror finish.

[Tri-ZNate]

looks like the top end got water in it, rusted, and then the previous owner tried to polish it up and make it all better. The texture and color are comparable to the screw i did for chriss200x which had rust on it and then i used a wire brush on it.

[Bryan Raffa]

looks like a chunk of your ring broke off by the looks of the gap in the top ring and slamed around in there for a wile, I also notice that your missing some of your piston on the top edge.

[Tri-ZNate]

looks like a chunk of piston broke off by the looks of the one pic.

[Xowner]

too lean did it make noise when it ran?

[Bryan Raffa]

i wouldnt worry about the head that mutch just clean it up a little get a new piston& rings and run it as long as the cyl doesent have to be bored due to scraches there will be no peformance loss with a head like that just hit it with some light sandpaper smooth it out alittle

[Ryah]

Here's a picture of the rest of the piston. Also the piston has some ports on the side. What are they for? There were no parts floating around in it when I took it apart. Anyone got a good head they want to sell? Also what year TRX barrels will fit onto a stock 1985 crank and rod?

[Bryan Raffa]

that 3rd pic was the problem chunk of your ring whats your cyl look like ,Throw that piston right in the garbage. that ring caught a port because of the bern.was shot.

[Ryah]

The inside of the barrel looks good. No scratches and the cross hatch hone is still visible all the way around. I checked both rings and they are both good with no pieces missing. I know I'm always asking questions, it's just that I value the opinions on this board. There are a lot of people on here much more knowledgeable than me. I'm always looking to expand my knowledge base as well as save a buck or two if I can.

[oddball3]

I finally had to tear the motor down on my 85 250r. The lower rod bearing went out on it. Anyways, the piston and head both look to have had something sprayed on them to make them very rough (like 80 grit sand paper). Almost as if a piece of metal ran around in there for an extended period of time. But there is no way that that was possible. Just curious as to what it was, is there any benefit to it? Should I just get another stock head for my rebuild? This bike isn't for all out drag racing. That's what the TriZ is for. The 250r is for reliable, relaxed, luggable dune riding.


That is your lower rod bearing comming apart and pieces came up through the ports into the combustion chamber and beat the piston and the head up.

[brapp]

oddball has the right info here, when the lower rod bearings come apart it causes little bits and pieces of metal floatign around, and it just bounces around hammerign it to hell, the fix for it woudl eb check to se eif the cylender is out of round(oblonged) any good motor or machine shop could do this, if it needs it bore it, and have the head decled and rechambered, i know a great engine builder who has done this for me a few times, and will have to do the same thign with the kids lt80 here in the next few weeks. but have a new rod pressed on the crasnk journals have the cylender bored or at least break the glaze with a hone, and have the head turned down or decked and rechambered and shoudl run liek new. and dont forget to clean otu your exaust you dont wanna suck back in the little pieces of bearing and piston, and also clean out the crankcase and check the main bearings for wear and debris

[dirtybiker71]

I agree with oddball3. I've seen this condition literally hundreds of times at the cycle shop. If your rings are all there and intact, it is coming from the lower end rod bearing. Look CLOSELY at the bearing cage thru the oil slot in the rod. With a little hook made out of soft wire or some type of pick (like a dentists pick) carefully roll the bearing around thru the oil slot by CAREFULLY hooking the rollers. You will probably see a chunk of the cage missing or at least cracked as you cant see all of the cage in the rod. I almost guarantee it is the rod bearing if your rings are still there. Just don't make the mistake many folks do and just shrug your shoulders and put it back together with a new piston. I've seen that many times (even done it myself!) Good luck!

[TimSr]

That is your lower rod bearing comming apart and pieces came up through the ports into the combustion chamber and beat the piston and the head up.


Ive got one like that on my TriZ. I was going to try to pass it off as a performance modification, but now you ruined it!

[TRI Z Racer]

For sure youll have to do something with the head, new, used, rechambered, whatever. When heads get alot of knicks, scratches, dents it creates hotspots during combustion which can lead to detonation.

Now i have never had a rod bearing go on me, but i have blown my snowmobile up enough different ways to have seen alot first hand. I would think if the rod bearing was gone then you would have alot marks in the cylinder, from pieces getting up in behind the rings in between the piston and walls. especially if the head and piston look like that. I would imagine the piston sides would look alot worse too. Shouldnt the bottom side of the piston be all messed up too?, i cant see anything in the pic. Like i said before, i have never had a rod bearing go, so i dont know, i just would imagine more damage. If Someone could clarify this up a litte bit im sure myself and ryah would appreciate it.

What are you running for an airfilter/box. any chance you sucked up anything? Mud, water? Look for missing pieces of your read cage/reeds, check your carb, make sure its all there, just give everything a once over before you tear the crank apart or have someone do it for you. Also like another member pointed out, look over your bearings closely.

[hrc85250r]

i agree with trizracer.... either get the head fixed or dnt use it. and my brothers bike did the same thing, we put 3 differentt top ends in it until we noticed some rollers missing in the lower rod bearing. as for the "ports in the side of the piston, those are areas where material was removed to lighten the piston, the wrist pin "supports" dont need that much beef so they take it out. they dont do anything as far as "ports" go. and when i locked my last motor up it looked like that, but not as severe because when the lower bearing went it locked up almost instantly because of oil starvation heating it up, looks like your rods time was up and it just let go. could have been alot worse. just get a rod kit and a new piston kit/head and your good to go.... dont even think about just putting a new piston in...have it bored next over with a new piston, get a good head and get a GOOD rod kit, not a vesrah or some other junk and have a GOOD shop do it, not the local machine shop.ltr

[Ryah]

Thanks for everyones input. I got a new Wiseco crank, so regardless I'm splitting the bottom end. I'll take some pics when it is apart so everyone can see what the crank looked like. Any thoughts on reusing the crank bearings that are in there. My crank didn't come with new bearings so I'm hoping to just split the cases and put the crank in and go. And I will be replacing the piston. Probably the same size since the cylinder still looks good on the inside. I'm nearing the end of my overbore's I believe. Does anyone know what year trx250r barrels I can use with a stock length 85 crank?

[dirtybiker71]

Often times when the rod bearing starts to go it just looses tiny pieces of the cage material first. This usually travels up through the transfer ports to the combustion chamber area, never reaching the piston/cylinder wall area. The fuel/air charge carries it up there as it is travelling thru the ports at very high velocity when the piston is on the downward stroke. This dumps it right on top of the piston where it is free to bounce around as much as it wants. The rod bearing usually fails rapidly after that and locks up before much more debris makes it out. Remember, the only way out for bearing debris is through the oil slot in the rod, which isn't very big. Therefore large pieces damaging the underside of the piston are pretty unlikely. Sometimes cylinder scoring occurs, but it doesn't have to. Seen it both ways.