Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: jordan83 on March 27, 2010, 02:49:11 AM
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is it normal to see where marks in a cylinder after low runtime on a new topend? just like some vertical glaze lines? thanks
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Can you give us some more details. And if possible, can you post a picture as well.
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sorry cant get a pic. they are vertical lines in the cylinder. just like discoloration. like a glaze. i can still see the hone marks behind the marks. theres some in different spots around the cylinder bore. that help?
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It could mean that dust is getting inside the cylinder.
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so its not normal then?
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I think not. It will reduce the lifetime of your engine. I once had this problem because I was riding in sand a lot (very dusty). I can't tell if it's the same issue in this case, but it sounds similar. Do you clean your air filter, is it installed properly? Maybe somewhere between the filter and the carb there's a hole?
I guess there could be some other things that could cause this, but in my case it was simply dust.
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that sucks man. just had the cylinder replated and shit. damn
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so i should prolly tear it back down again thenand check rings and everything?
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Are they fine scratches or simply bands of discoloration? Do the marks line up with the edges of the port windows?
If they are scratches, then dirt is getting into your engine. If they are bands that line up with the ports, they are just marks caused by the port edges. Chamfering the sides of the ports as well as the tops and bottoms will prevent this.
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couple scratches and some like wider lines. none of them are deep enough to go through the nikasil and i can still see the hone marks. i assume you guys are right and i did suck some dirt. im gona go through everything and try to find a leak.
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Some minor glazed lines are fine. This is because the cylinder DOES move up and down in cylinder. It is just making a pattern in your plating. Normal if you ask me. I wouldn't sweat it. Now, the wall is gouged, that's a different story.
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This is because the cylinder DOES move up and down in cylinder.
I'm sorry???? You must have meant "Piston"... :))
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Depends how you define the cylinder ;D . Yes, I meant piston.
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I have some ring-like horisontal marks in my cylinder. They're shallow, hardly noticeable, but there are too many of them. What should i do?????
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The first thing I would do is crack open the repair manual, get the compression psi range, and rent a compression tester. If it's in the normal range don't worry about it. If it's already off the bike, just have it rehoned and replated. It almost sounds like your getting some sand sucked in the intake somewhere. If you are, The piston ring will thinner on the intake side when removed. Next time when you clean your air filter, take some grease and smear it around the lip of the filter to seal it to the airbox.
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It hasn't been mentioned, but make sure your air filter is cleaned, oiled, and you used grease between the filter and air box. If it is in fact dirt (not saying it is without seeing it) poor filter maintenance is your main cause of it getting in there.
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Thanks man! :) The filter is as moisturized as my girlfriend's p****, so is its inner side also:)))))) , and screwed properly. But - correct me if i'm a fool - the sand particles should scratch marks ALONG the cylinder - not AROUND? And they ain't no along, but around the inner side of the cylinder.
The compression is slightly under stock, cause of a small pisston. It's only 66,32! While my bore is 66.4 and the bike is old.
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The marks you're seeing are called chatter marks. They are caused by too much clearance allowing the piston to rock in the bore. If you're running a cast piston you're lucky it hasn't shed a skirt.
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Wow, that must be correct! I've been used a very small Vertex, so small, that it would swing back and forth when pressed on the skirt by finger! After it finally felt apart i installed a kit of Namura. It doesn't swing, and the clearance seems tiny, but....... It's written 66.32 on the top of it, while my bore is 66.4!!!!! And the cylinder is rather old!!! (The previous owner seems had been using Wiseco, replacement diameter C)
A fella suggested just to ride harder, so the pisston gets hotter and the huge clearance disappears. Says, it's a preferrence;small pistons get skirt falling apart, while big ones make overheat or that kind of thing. What do you think?
How big is the proper clearance???
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The specs on a Wiseco Pro-Lite are .015" if I'm not mistaken. Your OEM specs for a cast piston were probably .002-.003" or somewhere in that range.
Your cylinder is worn out. Buy a new piston and send the piston and cylinder to a re-plater like Milllenium Technologies or Powerseal USA and have it re-plated. It will be better than new.
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The marks you're seeing are called chatter marks. They are caused by too much clearance allowing the piston to rock in the bore. If you're running a cast piston you're lucky it hasn't shed a skirt.
What he said.I think your engine's a ticking time bomb Red. :o
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Holy shit!!! Is there any way without a new cylinder????
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Holy shit!!! Is there any way without a new cylinder????
Why would you need a new cylinder? Just send your cylinder out to be re-plated. $200 and it's better than new. Millenium Technologies and Powerseal USA both use plating compositions and techniques that are superior to OEM.
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You mean, plating some Nikasil onto the cylinder?? But in our country no one does re-plating! The nearest country in Europe doing that is Poland.
Nikasil seems fine. It should be a bit blue inside, shouldn't it?
wHAt about buying a sleeve?
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You mean, plating some Nikasil onto the cylinder?? But in our country no one does re-plating! The nearest country in Europe doing that is Poland.
Nikasil seems fine. It should be a bit blue inside, shouldn't it?
wHAt about buying a sleeve?
Oh I'm sorry, I didn't realize you lived in Europe.
I guess in that case the decision would be based on cost. How much difference in price would there be bewteen installing a sleeve and buying a new cylinder?
While I never recomend a sleeve over a re-plate, if re-plating is not an option and money is an issue then a sleeve is the next best alternative, as long as you can find a GOOD machine shop that can bore it true and match the ports properly. If not, you're better off buying a new cylinder.
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I'd try giving it a light hone(yeah,even though it's plated)see how the marks look and measure it with a bore gauge.If the bores not too bad and not tapered too badly it may survive.Honda typically used A and B cylinders(it's stamped on it)and corresponding A and B pistons.I think the A piston/cyl are smaller so if you have a slightly worn A cyl you can usually fit a B piston-or vice versa.Maybe some Honda types could chime in here......
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Sorry, i can't do re-plating. I live in RUSSIA. No one does re-plating in our country. :( A man that taught me to ride, uses old cylinders as pen stands or keeps small parts in them :((