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Bike was running extremely rough (similar to running very lean, lots of backfiring and very loud) when I started it, and billowing white smoke. The oil also smelled of gas, which may be a result of flooding it trying to get it started so many times prior but it could be rings as well.

 

In case it was the coolant causing that white smoke I figured I'd change the headgasket since I needed a project during all this quarantine business, and I found some scoring on the exhaust side of my cylinder (pictured). I can just barely feel the largest score with my finger, the others are smooth to the touch. I included a picture of my piston as well.

 

Should I do anything about this? I don't want to mess up my cylinder if it was just a problem with my carb, etc.

DSCPDC_0001_BURST20200408174044075_COVER.JPG

DSC_0300.JPG

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Honing nikasil is tough, can't just run a ball hone through it. The only thing that can do it is a diamond hone

For significant damage/imperfections it needs replating

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Honing coated cylinders is tough job.. you take away from nikasil coating you should get it recoated since they dont have replaceable cylinder sleeves (wish they had) 

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7 hours ago, Syntax_Erol said:

Honing coated cylinders is tough job.. you take away from nikasil coating you should get it recoated since they dont have replaceable cylinder sleeves (wish they had) 

I'm not so sure I wish they had replaceable sleeves.  I just finished reading a book that details some of the advancements in motorcycle engines. Keeping the engine cool and maintaining the temperature in the exhaust gas is fundamental to making power.  Aluminium does a much better job of heat removal than a cast liner would.

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Take my opinion on this w a grain of salt as others surely have more experience, but I have run plenty of small engines w similar cylinder dmg without issues.  The dmg looks fairly minor imo.  It really depends on your budget, amount of money and time you want to spend rebuilding. I would check ring gaps and specs tho b4 reinstall and replace if necessary as they are fairly cheap.  Good cleaning, New gaskets and make sure valves are within spec and send it. If it still isn't running properly i would guess it's time to overhaul valves, but have a leakdown test done first while the engine is still together to help zero in on the issue.  If it runs fine after just keep a close eye on your oil to make sure you aren't starting to get metalic debris

Edited by RingwoodRaceway
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5 hours ago, roleyrev said:

I'm not so sure I wish they had replaceable sleeves.  I just finished reading a book that details some of the advancements in motorcycle engines. Keeping the engine cool and maintaining the temperature in the exhaust gas is fundamental to making power.  Aluminium does a much better job of heat removal than a cast liner would.

There is often a good reason why old simple techniques die 🙂 

Edited by Atolduso
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8 minutes ago, burntvalves said:

if Nikasil can't be honed, why is it that BRM sells Nikasil dingleberry hones??

 

http://blog.brushresearch.com/engine-hones-for-nikasil-cyllinders

The coating is not that thick and if there is damage beyond LIGHT scratches enough material can not be taken off without the coating flaking and coming off, at that point its ruined and needs a replating. You can put a very light hone on nikasil but thats it. 

Your question is essentially answered in their own wording:

Quote

Because Nikasil coatings are thin, honing stones can remove too much of the cylinder liner. Thank goodness rigid hones aren’t your only option. Does that mean that Flex-Hone® tools are a good choice for every Nikasil cylinder? Maybe! If the Nikasil plating is chipped, nicked, cut-through, has worn spots or is showing signs of wear, do not use Flex-Hone® tools. Instead, strip and re-plate the coating, or replace the cylinder altogether. Again, because Nikasil platings are very thin and very hard, honing will expose any existing damage. If the plating looks to be in good condition but needs a new surface, the Flex-Hone is a great choice.

Honing nikasil is only for giving it crosshatching on brand new coatings. Not for removing fine damage like you can on traditional cylinder liners. At that point the coating has been worn too thin to "hone" out. Your only option is to have it redone or just get a new cylinder. 

Edited by Atolduso

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16 hours ago, roleyrev said:

I'm not so sure I wish they had replaceable sleeves.  I just finished reading a book that details some of the advancements in motorcycle engines. Keeping the engine cool and maintaining the temperature in the exhaust gas is fundamental to making power.  Aluminium does a much better job of heat removal than a cast liner would.

İ havent thinked about thermal conductivity.... mabe aluminium sleeve? having to throw off whole cylinder is realy not cost effective.. also nikasil coating places are not that comon since its mostly a bike thing

Edited by Syntax_Erol

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3 hours ago, ohiodrz400sm said:

De-glaze the cylinder with Scotch-Brite, wash in hot, soapy water, and reassemble.  

Yup. New rings too. Piston is fine.

Was there visible damage that allowed coolant in to cause the smoking?

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