250-500cc New piston, scratched. Cylinder also.

God damn it, didnt expect this.
While im waiting for a new tiretupe i tought i could check the piston and cylinder. That was suposed to be new, maybe it is.Think the piston is, but....
It has allot of scratches, and it looks like the cylinder does to..
The compression is nice, and it runs nice and starts on the first kick 99% of the time. So it was just free time that made me look at it.

This is what it looked like.


Is this engine ready to blow up, or can i ride it? Cant afford a new piston right now... Hope the cylinder isnt to damage, i dont like the look. But again, I know that it can look worse that it is on a cylinder.

To sum it up.
The rings on the piston looks undamage.
I could feel the biggest scratch on the piston with my nail..
Compression is good, havent messured it tho.
Engine turns smooth.

Can i ride it, or is this a disaster waiting to happens?
What could have done this?
I havent ridden it hard, oilmix is good.

I doubt i can return the damn thing, and i bet my balls that the seller would blame me because i had it for some weeks anyways.
Feel like the luckyest man alive!

If the engine runs smooth and ticks over fine if there was debris its gone now, how scratched is the piston when you run a nail over it is it grooved or just polished? As for cylinder you can see marks have you had the head off? Pics would help.

Personally i would just ride it, order a piston to suit look out for a second hand cylinder get that matched to the piston when youve got the funds.

Havent had the head off yet, i dont have headgasket.. So i only saw what i filmed.
The biggest scratch is grooved, could feel it. The other smaller scratches wasnt that bad. Wasent easy to feel , not sure if i did.
I have pics, but the blitz makes them bad quality. Tried my best, but they all sucked.
Here are the best..

So you think its dirt\debris that is behind this?


Thanks for reply, and help\advice for this shitty situation..

Could be result of a cold seize during running in period, its a wr250 ? They have o rings as gaskets so whip the head off for a proper nosey.
Is she a good runner? If so i would stuff an hour meter on it and see how many hours you get before noticable decline in performance.

Keep an eyeout for another jug n piston when you have the money.

Yea. Its a wr 250 1999. She runs good. Havent noticed change in performance, but agin. I havent pushed the eninge. So the way it is now compared to 100%, i dont know..
Havent started it in couple of days, first kick it started couple hours ago. No enginenoise, runs fine. Im gonna take it easy, not push it to hard...
The compression went litle lover last week or so, not much, so apart from free time. This is one reason i tought i have a look. Someone that dosent know about motors would not noticed it. And friend that tried it havent noticed it. I think its still in the ok range, and havent changed since i noticed it...

I dont really know where to look for new cylinder, e-bay has nothing and dealers take 50% what i gave for the bike. They cost a small fortune here, 1\6-7 of a new bike...
God must hate me. Haha... I can see its a new piston\sleeve and the cylinder is new, and the seller havent done anything wrong. Was 100% before this shit happened. Cry now, lol later in life i guess.... Not sure yet...
I havent run the bike hard cold, have used it to work (heavy sleeper) havent varmed it up. But have been carefull because of cold sezure. Are these bikes really so sensetive that you cant put it in gear before this can happen?
I runed a 50cc with a bad piston for a long time, pistonring made a nasty groove in the cylinder. It's still going strong. Is it possible for this kind of bike to last some time with a bad scare in the cylinder? If that the case. Or is it to much forces involved in these engines?
I had problems with clutch, but changed oil etc so its ok, for now. Use that money on piston, pray to god the cylinder is useable for some time and dont have to much damage..

Is it possible to hone the cylinder, if it has scrathes?
Is there any tell tell sign i should be aware of if it performe ok. Noise, etc before it dies?
With the state the piston etc is in now, what is best. Lower rpm but higher gear, or ligher load\gear but higher rpm? Know its not quite that easy, but my english limits my typing without help from firefox-plugins... :P

And again. Tnx for your input juicy. Even tho my questions may be stupid.
Im a noob when it comes to these kind of bikes and this brand, and i just got it. Want it to last for some time, so i'll get the time to learn how these engines perform and so on...

Ok right no honing a nicasil cylinder with scores is futile if its broken the nicasil it needs a new coat, millenium coatings, if youve got the horn for a liner check out kustom kraft, ive got a 360 cylinger done by them there works good but tidy up the verticals and chamfer the ports.

No the bikes not bad but it comes from italy and its hot i seized my 250 did heat cycles and rode to mates place had cuppa tea n ciggy rode back 5 mins on idle getting to robots(lights) thought shes warm opened her up know the road no gatso's over took two cars and as i nipped infront the engine seized! Spanking coating new wossner piston conrod etc....
The cooling on these bikes is second to none! Warm that morher up!!!
I would take a look under the head see if its eaten rings at some point.

Dont worry too much about scars in the piston as long as the cylinders good and it souvnds good run it.
If the cylinder has minor scaring then keep an eye out for peeling/ flaking.

Like i said run it as all sounds sweet.
Dont look under the head if ignorance is bliss.
Look out for another cylinder, pm me if you need me to look here/ bounce to you, (Any one on here this also applies)

Ignorance is bliss, intil the point where ignorance blows up in your face.
Will take the top op this tomorrow or sunday.

Tnx.

Ride it,save some dough and get your jug replated.

Ok.
Here is my plan.
I hope to finally ride in the woods tomorrow, maybe sunday. If the engine fine, like now.
Check the top tomorrow or sunday, depends on the engine. If its running fine, il probably take the top off on sunday. Will take off the pipe tomorrow to check. Not ideal, but the pic and video suck compared to the human eye...
Sunday... Check if there is any changes, check how bad the cylinder is. I will order new piston asap because it dosent hurt anyway, if the cylinder feels fine (feel for grooves with nail and so on) ill keep it and use it normal if the new piston dosent scare up, etc. I will check this when the time comes.
If the cylinder have grooves, change piston anyways. Keep a eye out for blow out or piston damage, if this happens over a short time. Dont use the bike, intil i fix or get a new cylinder and new piston..
...This is my plan.
Will update the thread when i check it or i gett the piston up my ass. :P
I have have used a bad cylinder for some time on a old moped, just changed the piston. I still have this old thing. Still runs fine after use and 2 years stoned cold. But not sure if this can be compared to a wr 250cc . Hehe.

And again. Tnx for your input and help.

Shoot,back in '78 I stuck the ring on my 250 Husky out in the desert: popped the cylinder off, unstuck the ring with a razor blade and sanded the scoring on the cylinder with REGULAR sand-paper (not even fine grit). Ran just fine after that so I didn't even bother replacing it..........

Haha, not bad.
Here is a video of the engine running. Had the time, so tought why not record it and hope for fame and glory when i put it on the big web.

Dosen't sound bad....has a nice "crackle" to it.

I'd pull the head and check the cylinder bore. The piston is the easy part, if the nikasil is compromised it gets a little more spendy.

Having gone thru this I'd pull the head, see if you can clean up the bore with a scotch brite and wd 40. If it's gouged you should send it out to be replated with a new piston for them to match to the bore. Or buy a new cylinder. It kinda sucks but the plus side is you get in there and make everything 100%.

Have checked now, top was off. Did have a hell on getting the inner O-ring back on,but i think its gonna work for now..
I took some pics, and i think it looked like crap..
I also checked compression before i opened it up, was arround 175psi, do not thrust the messure. Used some cheap tester where air can escape. But its something. If im not wrong, its not hight. But its not that bad compared to what chape the cyl\piston is in.

Here are the pics.
First one 0079 and 0081) is before i wiped it.

Could only feel one groove, right over the port.

Other pics.

The head looks like there has been a war inside. Maybe overheated sometime in its lifetime, if this hasent happen since i got it...
The powervalve has a small bit missing. Not sure if its new or old damage. Could explain it all, i think this sucker is behind this.

All in all, i think it looks like shit, even tho most grooves shown on pics. wasent that bad. Could feel one groove. Looks like spekks of metal or something on the cyl. wall, not sure. Looks like that on the pic. didnt feel them with my finger.. Is this something scoth brite maybe can remove, considering i cant hone it?
What are your tought about the head?
And, i know i'm runing the bike rich at the moment. But isnt there a litle much oil in the exaust. Can this be comming from powervalve?

Thanks.

The head has been dinged up by some trash bouncing around in there. It looks typical of most blow ups. You are probably right in thinking it was caused by a broken spec of the power valve.

So you think i can continue using the cylinder.