Might make someone mad if you sell it on a saw but if you're gonna use it, I've seen worse...
Might make someone mad if you sell it on a saw but if you're gonna use it, I've seen worse...
Because you don't want to remove ANY of the nikasil plating.I am curious why nobody mentions using an automotive cylinder hone (also called a glaze breaker)? That is what I use and it will show you the low spots and you can take as little as one or two thousands of the cylinder. I use the hone using a bucket of parts cleaner solvent and dip often to keep the stones clean.
Because you don't want to remove ANY of the nikasil plating.
How thick is the "nikasil" plating?
not much more than “a couple thousandths”
After you remove plating do you do anything with the port edges?From the Forestry Forum:
Nikasil is only about .010 - .012 thick. Chrome is harder and also more difficult to do correctly. Chrome doesn't bond as well as nikasil. If you look at cross sections of cylinders under an electron microscope, chrome has a very defined line where it bonds to the aluminum. A cross section of nikasil blurs the line and, shows the nikasil actually impregnating the aluminum cylinder. This is one of the main reasons why chrome will flake and nikasil won't. Chrome cylinders are more likely to fail with port mods because you expose the edge of the chrome.
Regards
Gregg
A " couple of thousands" is .001o to .002. So it's plenty thick for a light hone job if you start with .010 to .020 thickness. I've done it before and no problems.
thats all good man, but its pretty universally regarded as not a great idea to hone a plated cylinder. not saying it cant be done, its just risky. fwiw, that 066 would have a chrome bore as far as everything ive ever heard (or whatever stihls proprietary plating consists of, not nikasil. plenty of info out there on this topic)From the Forestry Forum:
Nikasil is only about .010 - .012 thick. Chrome is harder and also more difficult to do correctly. Chrome doesn't bond as well as nikasil. If you look at cross sections of cylinders under an electron microscope, chrome has a very defined line where it bonds to the aluminum. A cross section of nikasil blurs the line and, shows the nikasil actually impregnating the aluminum cylinder. This is one of the main reasons why chrome will flake and nikasil won't. Chrome cylinders are more likely to fail with port mods because you expose the edge of the chrome.
Regards
Gregg
A " couple of thousands" is .001o to .002. So it's plenty thick for a light hone job if you start with .010 to .020 thickness. I've done it before and no problems.
After you remove plating do you do anything with the port edges?
The most I would do is run a piece of fine sandpaper around the inside of the cylinder a bit to help in the break-in of new rings. I have a hone but would never use it on a chainsaw engine...
You ever measure the thickness at different spots around a worn in ring? Why do you suppose the end gap measurement is such an important determiner of ring wear as opposed to cylinder diameter? How about piston skirt wear?Hand held sandpaper will not follow the the high or low deflections in the clyinder to even them out. That means the rings will never seat in the clyinder so lower compression and unburned fuel/oil mixture out the exhaust.
Not trying to even out major scrapes and scratches, just a slight roughening so the rings will seat more quickly. If you have a major scratch in a cylinder wall you need to recycle it...Hand held sandpaper will not follow the the high or low deflections in the clyinder to even them out. That means the rings will never seat in the clyinder so lower compression and unburned fuel/oil mixture out the exhaust.
You ever measure the thickness at different spots around a worn in ring? Why do you suppose the end gap measurement is such an important determiner of ring wear as opposed to cylinder diameter? How about piston skirt wear?
Edit: You didn't answer how you address the sharp edges you create around the ports after honing.
There's no chipping at all. Just sanded off platting. I'm going to source another cylinder. I'm thinking if it's questionable I should replace it.
uh oh I started a hone or don't hone thread.
You ever measure the thickness at different spots around a worn in ring? Why do you suppose the end gap measurement is such an important determiner of ring wear as opposed to cylinder diameter? How about piston skirt wear?
Edit: You didn't answer how you address the sharp edges you create around the ports after honing.
As long as @Yotaismygame doesn't mind I'd like to further this discussion and add some pictures. I took measurements around the ring and your eyes aren't lying to you when you look at that pic. My thoughts and opinions on this are just that, based on theories from things I've seen. I believe the rings purpose is partly to make up for the imperfections in the cylinder as well as create the seal for the piston. As the ring wears into the cylinder it creates a better seal around it's circumference, but the gap at the end increases. I've never considered these cylinders to be anywhere near a perfect circle, and I feel like chasing it by removing material on purpose is not the best route. You can see from the piston that even from the factory the seal is imperfect. This unit has around 400 hours of run time, with very little WOT time. Thoughts?
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Mahle recommends a bore brush with impregnated silicon carbide on the bristles to restore cross hatching and remove glaze on Nikasil cylinders.Not trying to even out major scrapes and scratches, just a slight roughening so the rings will seat more quickly. If you have a major scratch in a cylinder wall you need to recycle it...
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