Topic: Smoke from breather filter

[mgilvary]

A few months back, I installed pods on my 75 550, along with a small filter on the breather cover to take the place of the hose that ran to the now-non-existent airbox. A couple weeks ago I noticed that the filter seemed a little oily. And now I'm noticing a slight amount of smoke emanating from the filter. I don't know how long it's been doing this, but I never noticed it before.

Last week, I rebuilt the carbs with a K&L kit. I didn't change jet sizes, but the engine runs a lot leaner anyway (I suspect because the main jet o-rings are no longer decrepit). Could this smoke be an indication of overheating? My guess is no, because it starts soon after warm-up and does not appear to get any worse during a 20-minute stop-and-go ride. Still, I want to be sure.

My amateur guess is that perhaps the piston rings are gummed up with carbon (the bike ran pretty rich for a long time). Any opinions?

[n9viw]

It's possible, but not likely. Smoke and oil from the breather is usually an indicator of bad rings. If you were running rich, you could have been washing down the cylinder walls with unburned fuel, which would accelerate the wear on the rings.
Run a pint of carburetor cleaner thru the gas tank to rid you of any built-up carbon (you might also try Seafoam, I've had good luck with that but never tried it on a bike), and then do a compression test. Remember to have the engine warm and the slides wide open when you do it, otherwise you'll get false readings. Use that to judge the condition of your rings, and go from there.

[MRieck]

It's blowby. It happens more when the engine is hot.