CB360 smoking badly

look at the black line on the left piston. dammit. the rings are fine, the ring grooves were perfectly clean. Rings were brand new
 

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the passage way is up around a cylinder stud .even if the oring there fails and it leaks all outside it still is impossible for oil to get burned the head gasket has a fire ring the fire ring dooes all the work if it fails you have a really shitty running bike making terrible noises ;D smoke would be the least of your worries :D
 
you must have a really poor condition cylinder wall ? what did you hone it with ? a rock ?
how long did you run it ?
 
ok you see why I'm really getting frustrated with this. Here's the bore and being .005 clearance with new rings really shouldnt make it smoke. This one is really getting under my skin. There must be a crack or something that opens up as it gets hot.

The bike isnt registered yet, so its only been started, idled for a total of maybe 5 minutes... ridden up the street and back once or twice . Thats it.

I took this picture of the left bore specifically after the 2nd time honing it. The hone was just to break the glaze and give it a cross hatch for the new rings. You know standard stuff every builder would do....
 

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lol :-[ i assumed you put break in miles on it :-\ maybe you just used a little extra oil on assembly ? for future reference do not oil rings for assembly/breakin ,you want the cylinder clean and wiped almost completely dry after smearing with oil, no oil on rings, only a couple drops smeared on the skirts
you really should have run it in a bit......... :'(
 
Yep, sounds like it.
You'll be kicking yourself when you eventually see it ;D


jzanutto said:
I'll post this one in the introductions
Click to expand...

Nice pic 8)
 
jzanutto said:
look at the black line on the left piston. dammit. the rings are fine, the ring grooves were perfectly clean. Rings were brand new
Click to expand...
Just noticed the piston closest to camera, oil ring doesn't 'look' right?
I tried downloading from linbk to enlarge it, lks like a piece chipped out?
Was the 'far' piston 'picked up' like that when you assembled it? (partial seizure)
 
I looked at the rings, they are fine.

new 68mm pistons coming. I tried to save some money initially by just doing rings. This time it bit me in the butt. oh well, I'm still ahead on this bike it only cost 100 bucks and I've done everything else pretty cheap. I lace my own wheels.

Those black shouldered rims were on sale for 59 each.
 
I dont think there's any mystery here. Looking at the oil ring there are some spots where it shows no contact with the cylinder wall. Even though it measures concentric, it's obviously not perfectly round down inside and it needs a fresh bore.
 
interesting find on this engine- while waiting on my fresh bore job on my new cylinders I found that this piston was cracked. The cause of the excessive oil smoking. Now that the engine has 2 new pistons and bore, no smoking.
 

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Forgot to ask in last post, is that the piston where I thought oil ring didn't look right?
 
the rings were OK, they had some crud on them that looked like major damage with the closeup focus of the camera.

the main culprit that took a couple years off my life was that cracked piston. It was so bad that oil would come out of the exhaust pipe header joint, and out the back of the pipe too. No oil/ smoke now!!
 
Yep, I realise what happened and it was well spotted. was it the same side as the crud on rings?(no idea why I think it's important, must be lack of sleep again ;D )
 
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