What causes a cylinder to wear like this???

[Honda 250r 001]

i broke it in good, and the jetting was perfect maybe a little rich. What caused this?!?! It was always warmed up before every ride also.

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture3.png

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture2.png

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture3-1.png

[Burns310r]

Hard to see in the picture, but it looks like the wearing is above the exhaust bridge.

Did you releve the bridge when you built the motor.

After honing the cylinder, you have to take a file and grind down the bridge like .002 to allow for expansion. Other wise it expands into the cylinder.

Im not sure exactly what the clearance is supposed to be.

[Honda 250r 001]

Originally posted by Burns310r
Hard to see in the picture, but it looks like the wearing is above the exhaust bridge.

Did you releve the bridge when you built the motor.

After honing the cylinder, you have to take a file and grind down the bridge like .002 to allow for expansion. Other wise it expands into the cylinder.

Im not sure exactly what the clearance is supposed to be.

no i did not relieve the bridge unless the machine shop did. But it has two wear pillars on each side of the exhaust bridge to?? what caused that???

[fearlessfred]

it looks like it started to cold seize , but that is usually 4 corners

[jcs003]

x2 on the hard to see well.

from what i can see, it looks like glazing on the exhaust side. what kind of piston are you using. i know wiesco like a long break in period. my 2c

[Honda 250r 001]

Originally posted by fearlessfred
it looks like it started to cold seize , but that is usually 4 corners

well it kinda has the 4-corner cold seizure look to it. because there are 5 spots total that are worn, exhaust bridge, left and right of the exhaust bridge, and on the intake side of the cylinder it also has the same thing but not near as bad as the exhaust side...

[fearlessfred]

yea it looks like it started to cold seize. is the piston messed up . normaly the person who bores it relieves the exhaust bridge

[Honda 250r 001]

Originally posted by fearlessfred
yea it looks like it started to cold seize. is the piston messed up . normaly the person who bores it relieves the exhaust bridge

na piston is good and the rings are good to not stuck to the piston. Im gonna keep running it like this after i pull the top end off and clean the bore up a little bit and clean the piston up. im also going to relieve the exhaust bridge and see what happens.

[fearlessfred]

u might wanna concider honing and fresh rings

[Honda 250r 001]

Originally posted by fearlessfred
u might wanna concider honing and fresh rings

rings are perfect it had perfect compression. And i have a dune trip in like 10 days so i dont have enough time haha

[fearlessfred]

sounds good what dunes are u headen to

[Honda 250r 001]

Originally posted by fearlessfred
sounds good what dunes are u headen to

waynoka oklahoma. i cant freggin wait

[cdrookie]

with that kind of wear something isn't perfect, whether it's rings or piston, or a bad bore job, something is wrong.

it sure would suck to get a few miles out in the dunes and have it lock up. you can get parts in a couple days, even next day, so fix it now.

[Honda 250r 001]

Originally posted by cdrookie
with that kind of wear something isn't perfect, whether it's rings or piston, or a bad bore job, something is wrong.

it sure would suck to get a few miles out in the dunes and have it lock up. you can get parts in a couple days, even next day, so fix it now.

Ive had it running like this for over 5 hours. Ive raced mx with it like this, ive messed around at my house. I dont think shes gonna lock up. I appreciate the suggestion though! Unless my rents would help me out, i dont haev enough money to get a new piston, because i have to use all my money to get to the dunes, and for food at the dunes.

[Honda 250r 001]

Originally posted by cdrookie
with that kind of wear something isn't perfect, whether it's rings or piston, or a bad bore job, something is wrong.

it sure would suck to get a few miles out in the dunes and have it lock up. you can get parts in a couple days, even next day, so fix it now.

Ive had it running like this for over 5 hours. Ive raced mx with it like this, ive messed around at my house. I dont think shes gonna lock up. I appreciate the suggestion though! Unless my rents would help me out, i dont haev enough money to get a new piston, because i have to use all my money to get to the dunes, and for food at the dunes.

[Ruf Racing]

Originally posted by Honda 250r 001
i broke it in good, and the jetting was perfect maybe a little rich. What caused this?!?! It was always warmed up before every ride also.

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture3.png

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture2.png

http://s804.photobucket.com/albums/yy330/hedberg345/?action=view&current=Picture3-1.png

You should shoot Neil a PM. Ask his opinion. He's pretty sharp on diagnosing pictures. Good luck! :macho

[86 Quad R]

X's 2 on the pics and exhaust bridge......

it also appears that the ports werent chamfered either. it also looks like it may have tried to cold seize at some point. did you check the piston to bore clearance prior to assembly? if so, what was it?

[C-LEIGH RACING]

I couldnt see the pics in the PM, but I did on here.

Looks like the bridge area got tight & maybe partly stuck & then everything went crazy after that.

Are those ports champhers real good, cause in the pic the exhaust dont look like its been worked enough & has an edge to it.
If the exhaust bridge not been relived like its suppose to then it will stick in that area for sure &looks like that is the case.
Once the bridge sticks, the piston swells & then you end up with a 4 corner seize.

I'm not a fan of reusing a seized piston, but in a money pinch & if the rings not stuck in their grooves, you could clean that piston up in the seized areas with like some real fine sand paper, take a fine ball hone & ball hone the cylinder bore lightly & put in a new set of rings & go again. Just be sure to get all the aluminum off the cylinder walls.

Keep in mind though, there is no such thing as a free no worrie seize deal.
If a piston seizes, even just a lite small amount, it has some damaging effects on the bottom end.
Every time the piston goes up & down, some of that aluminum from the piston is scraped off & right down in the bottom end it goes as fine dust like junk, no way around it.

This is why some are telling you to take care of it & do it before its to late.
At the least clean the aluminum off the cylinder walls.

Keep this in mind as well, if that bore shop you used didnt releive that exhaust bridge or knew it would swell once hot & touch the piston, how many other things do they not know about on a 2 stroke engine.
Neil

[Honda 250r 001]

Originally posted by C-LEIGH RACING
I couldnt see the pics in the PM, but I did on here.

Looks like the bridge area got tight & maybe partly stuck & then everything went crazy after that.

Are those ports champhers real good, cause in the pic the exhaust dont look like its been worked enough & has an edge to it.
If the exhaust bridge not been relived like its suppose to then it will stick in that area for sure &looks like that is the case.
Once the bridge sticks, the piston swells & then you end up with a 4 corner seize.

I'm not a fan of reusing a seized piston, but in a money pinch & if the rings not stuck in their grooves, you could clean that piston up in the seized areas with like some real fine sand paper, take a fine ball hone & ball hone the cylinder bore lightly & put in a new set of rings & go again. Just be sure to get all the aluminum off the cylinder walls.

Keep in mind though, there is no such thing as a free no worrie seize deal.
If a piston seizes, even just a lite small amount, it has some damaging effects on the bottom end.
Every time the piston goes up & down, some of that aluminum from the piston is scraped off & right down in the bottom end it goes as fine dust like junk, no way around it.

This is why some are telling you to take care of it & do it before its to late.
At the least clean the aluminum off the cylinder walls.

Keep this in mind as well, if that bore shop you used didnt releive that exhaust bridge or knew it would swell once hot & touch the piston, how many other things do they not know about on a 2 stroke engine.
Neil

There is no aluminum stuck to the cylinder walls and the piston only has minor pillars of scratches. Im going to pull the cylinder off, clean the piston and hone the bore, relieve the bridge, chamfer the ports a little more, and throw it together. We will see what happens, right now its my only option.

Do you think this sounds reasonable neil?

[C-LEIGH RACING]

Ok, I understand, I've been there myself before & got to do what you got to do.

Dont hone the bore to much, just enough to tell how deep the scars are, but clean that piston real good & if you can, somehow flush that bottom end out, dont want any of that fine junk hiding down there to do anymore damage, just to be safe.

Lot of people frown on trying to use that piston again, but hey, when you clean it up, you dont have to worrie bout it sticking in those same place again.

Neil

[Honda 250r 001]

Originally posted by C-LEIGH RACING
Ok, I understand, I've been there myself before & got to do what you got to do.

Dont hone the bore to much, just enough to tell how deep the scars are, but clean that piston real good & if you can, somehow flush that bottom end out, dont want any of that fine junk hiding down there to do anymore damage, just to be safe.

Lot of people frown on trying to use that piston again, but hey, when you clean it up, you dont have to worrie bout it sticking in those same place again.

Neil

Am i just doomed for a blown top end when i get to the dunes? Or what do you think here. Do you think this sounds like it would help the situation here? the piston is still tight in the bore and the rings are good and not stuck to the piston...
Thanks

[rablack21]

Just so you know, the exact same thing just happened to me. My cylinder looks just like yours. I did have a seizure, a light one. I shut it off, it was running fine. I tried to kick start it 5 minutes later and the piston got stuck. I had to take the top end off to look at it. It pulled free without much difficulty though. I called my engine builder and asked him about the streaks on the cylinder. He said it sounded like a light seizure. So I am in the process of sending him my cylinder and piston to check it out. Hope this helps.

[Ruf Racing]

Originally posted by rablack21
Just so you know, the exact same thing just happened to me. My cylinder looks just like yours. I did have a seizure, a light one. I shut it off, it was running fine. I tried to kick start it 5 minutes later and the piston got stuck. I had to take the top end off to look at it. It pulled free without much difficulty though. I called my engine builder and asked him about the streaks on the cylinder. He said it sounded like a light seizure. So I am in the process of sending him my cylinder and piston to check it out. Hope this helps.

Did your cylinder have the bridge port relieved?

[wild250rman]

Has the cylinder actually been bored to size or was it just honed out to fit the next size piston, has the cylinder been checked for out of round. were the rings sized to the new bore and was the piston sized before the cylinder was bored. what condition is the writ pin and bearing in. were there any air leaks around any gaskets? what condition is the crank, crank bearings and seals

[Honda 250r 001]

Originally posted by wild250rman
Has the cylinder actually been bored to size or was it just honed out to fit the next size piston, has the cylinder been checked for out of round. were the rings sized to the new bore and was the piston sized before the cylinder was bored. what condition is the writ pin and bearing in. were there any air leaks around any gaskets? what condition is the crank, crank bearings and seals

Cylinder was bored perfectly strait, rings were new and i checked the end gap before installation, crank was like new, wrist pin bearing was new, as far as i know, no leaks, or bad seals.

[All250R]

Originally posted by Honda 250r 001
Am i just doomed for a blown top end when i get to the dunes? Or what do you think here. Do you think this sounds like it would help the situation here? the piston is still tight in the bore and the rings are good and not stuck to the piston...
Thanks
That's going to depend on if you discover the problem that caused it in the first place. The symptom/scoring is just the symptom. The cause is what you need to address and it's not really solid to say it won't happen again just because the piston has potentially worn in the tighter tolerance areas...

When you say "tight in the bore", how are you determining that? I have a feeling you're not using a bore gauge and micrometer. If you are, what is the clearance? 2stroke engines let you get a way with a lot of fuzzy logic, but doing it right is not really a speculative art. Your problem could be as simple as not enough warm-up time, or a problem in the cooling system, to improper machining in a variety of areas.

[Honda 250r 001]

Originally posted by All250R
That's going to depend on if you discover the problem that caused it in the first place. The symptom/scoring is just the symptom. The cause is what you need to address and it's not really solid to say it won't happen again just because the piston has potentially worn in the tighter tolerance areas...

When you say "tight in the bore", how are you determining that? I have a feeling you're not using a bore gauge and micrometer. If you are, what is the clearance? 2stroke engines let you get a way with a lot of fuzzy logic, but doing it right is not really a speculative art. Your problem could be as simple as not enough warm-up time, or a problem in the cooling system, to improper machining in a variety of areas.

I did not have time to check the clearence yet, but the bore looks perfect in places where its not scarred, and the piston looks perfect in the places where its not scarred. STill has cross hatch on bore, and still has rings running around the piston. so i dont see how it could be very worn. Ill measure when ig et the top end off. I let my engines warm up PLENTY long i wait till it gets to 180 to fully open it up. And it has only been up to around 225 when i wasnt moving very fast. I cant verify that the exhaust bridge was relieved, thats why im going to do that my self. Im hoping thats what caused the whole situation here.

[Ruf Racing]

Good luck. Keep us informed.

[86honda250]

what is the minimum temp on the water temp gage you should have it at before starting to drive it?

[All250R]

Originally posted by Honda 250r 001
I did not have time to check the clearence yet, but the bore looks perfect in places where its not scarred, and the piston looks perfect in the places where its not scarred. STill has cross hatch on bore, and still has rings running around the piston. so i dont see how it could be very worn. Ill measure when ig et the top end off. I let my engines warm up PLENTY long i wait till it gets to 180 to fully open it up. And it has only been up to around 225 when i wasnt moving very fast. I cant verify that the exhaust bridge was relieved, thats why im going to do that my self. Im hoping thats what caused the whole situation here.
I suggested you check the clearance to make sure the machining was done correctly, not to assess the damage.

225 is pretty high. Oil probably isn't going to like that temperature for very long. If it flashes, you will experience metal to metal contact.

I doubt the ex bridge is causing the accelerated wear around the bore you're seeing. if it's not clearanced, it's probably one problem to solve, but not all of the problems.

From experience I know that a lot of machinists don't spend the time chamfering that they could to minimize oil loss on the piston skirt and rings. But you're having relatively symmetrical problems, so I'd guess the problem is heat in the piston, not necessarily chamfering.

[Honda 250r 001]

Originally posted by All250R
I suggested you check the clearance to make sure the machining was done correctly, not to assess the damage.

225 is pretty high. Oil probably isn't going to like that temperature for very long. If it flashes, you will experience metal to metal contact.

I doubt the ex bridge is causing the accelerated wear around the bore you're seeing. if it's not clearanced, it's probably one problem to solve, but not all of the problems.

From experience I know that a lot of machinists don't spend the time chamfering that they could to minimize oil loss on the piston skirt and rings. But you're having relatively symmetrical problems, so I'd guess the problem is heat in the piston, not necessarily chamfering.

Maybe ill install my new waterpump bearing, mechanical seal and waterpump impellar with a brand new one before i go to the dunes.