I know that it's a known problem for cylinders like these to seize on the exhaust bridge, the thing im more concerned about are the marks on the intake side of the cylinder. What could've been the thing causing those? Is it just the fact that the engine was running too hot/lean or could there also be a more specific reason? Also, is there something I should do to the cylinder before installing it again? I cant feel the marks with my nail at all so if I've understood correctly the cylinder should still be good to use? All help is appreciated.
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Hi everyone,
As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.
When he passed, I worked with his kids to gather the necessary credentials to keep this site running. Since then (and for however long they worked with Coffee), Woodschick and Dirtdame have been maintaining the site and covering the costs. Without their hard work and financial support, CafeHusky would have been lost.
Over the past couple of weeks, I’ve been working to migrate the site to a free cloud compute instance so that Woodschick and Dirtdame no longer have to fund it. At the same time, I’ve updated the site to a current version of XenForo (the discussion software it runs on). The previous version was outdated and no longer supported.
Unfortunately, the new software version doesn’t support importing the old site’s styles, so for now, you’ll see the XenForo default style. This may change over time.
Coffee didn’t document the work he did on the site, so I’ve been digging through the old setup to understand how everything was running. There may still be things I’ve missed. One known issue is that email functionality is not yet working on the new site, but I hope to resolve this over time.
Thanks for your patience and support!
125-200cc Cylinder Seized, What Caused This And How To Treat The Cylinder?
- Thread starter Aksus
- Start date
I just bought the bike so I'm not sure about the old pistons size but the current piston is a B size. Not sure about the ring gap either but don't think that's the problem either. And yes there were 2 small holes drilled on the piston on the exhaust side. Is the black mark on the cylinder piston coating and if so I've heard that you should ve able to clean it off somehow correct?
The coating doesn't transfer to the cylinder as it wears off. Scotchbrite or a few light passes with an aluminum oxide ball hone should should restore the finish. Just out of curiosity, what brand of piston was in the cylinder? Have you had a chance to mic the piston skirt and the cylinder wall?
Also, on later models (and probably earlier ones too), the base gasket thickness varies. Mine takes a .5 mm base gasket, but there are other thicknesses available. Not sure how that might affect your engine, but pretty sure that if you ran one that was too thin, it would raise compression and make the fuel mix run hotter.
2premo
Husqvarna
Pro Class
there is an entire procedure for setting the "squish" which sets the correct compression, if you raise or lower it, increase or decrease you timing curve, increase or decrease your fuel oil ratio all these things can change the performance as well as heat transfer in your cylinder
since you said you recently acquired it, go stock on all settings then tune from there, baseline is always a good starting point
Thanks for the reply. I'm pretty sure that the piston was one from Vertex. I literally just bought the bike used for cheap and knew that the piston was most likely ready to be changed. That being said, I haven't really had a chance to look at the squish or anything like that. I mainly just wanted the information on how to prevent this happening in the future.
While taking off the cylinder I also noticed that the exhaust metal gasket had a piece broken off of it. Pretty sure the piece would've just flown out of the exhaust, and there shouldn't be a way for it to have ended up in the cylinder though, correct?
Attachments
Thanks for the advice, I'll have to take a look at the whole procedure of measuring the squish as I'm not too familiar with it. I know how to tune a carb tho so that shouldn't be a problem.
Picklito
Husqvarna
Pro Class
Clean the bore with muriatic acid on a paper towel (swimming pool acid). If any aluminum has been transferred from the piston to the bore, this acid will dissolve it out of the bore surface. Muriatic acid dissolves aluminum but not the Nikasil bore surface.
Then clean with soap and water and a green scotchbrite.
Do not hone this cylinder. Nikasil should only be honed professionally with a diamond hone. Clean it with scotchbrite and leave it alone.
Notice how the blowby marks line up with all the port bridges? I've seen this on super high hour bikes when the ring finally starts losing its surface coating. I'd love to get that ring in my hands for inspection.
Then clean with soap and water and a green scotchbrite.
Do not hone this cylinder. Nikasil should only be honed professionally with a diamond hone. Clean it with scotchbrite and leave it alone.
Notice how the blowby marks line up with all the port bridges? I've seen this on super high hour bikes when the ring finally starts losing its surface coating. I'd love to get that ring in my hands for inspection.
I beg to differ. Aluminum oxide ball hones take out a negligible amount of material. I have re-cross hatched all my coated barrels since the first KDX that I owned. Ball hones that are used correctly leave a good finish i n coated barrels. If a coated cylinder wall is being damaged by a ball hone, it may be the wrong diameter hone, or somebody is running the hone at a high speed, wrong stroke and for too long. Several low speed passes will do...maybe 30-45 seconds at the most. I have a stream of solvent running onto the hone as I use it.
Picklito
Husqvarna
Pro Class
OK FINE!! (jk) Technically, yes, you can use an AO ball hone to deglaze Nikasil. But here's why I said don't do it:
Brush Research is where I get all my hones. Unfortunately, I've only seen Brush Research really address this use in NON-ported Nikasil cylinders. If the Nikasil has any thin or potentially damaged spots, an AO hone should not be used. Port edges are the other problem. It is possible to chip the Nikasil from the edges. While Nikasil is "harder" than aluminum oxide, this a bonding problem not a hardness issue. And while deglazing MIGHT be OK, trying to resurface a damaged Nikasil surface is not OK. Sounds like you are doing it correctly for deglazing, using the proper AO material, with slow speeds, and under flow. Otherwise, you wouldn't have had the luck you have.
Brush Research is where I get all my hones. Unfortunately, I've only seen Brush Research really address this use in NON-ported Nikasil cylinders. If the Nikasil has any thin or potentially damaged spots, an AO hone should not be used. Port edges are the other problem. It is possible to chip the Nikasil from the edges. While Nikasil is "harder" than aluminum oxide, this a bonding problem not a hardness issue. And while deglazing MIGHT be OK, trying to resurface a damaged Nikasil surface is not OK. Sounds like you are doing it correctly for deglazing, using the proper AO material, with slow speeds, and under flow. Otherwise, you wouldn't have had the luck you have.
I are a teknishun.
2premo
Husqvarna
Pro Class
setting the squish is actually in the owners manual
A word of caution to anyone using muriatic (hydrochloric) acid or any other dilute acid. Please follow all safety instructions such as wearing acid resistant gloves, eye protection, etc. and use with extreme caution. Anything that can dissolve metal also burns bare skin. Dangerous stuff!