Motorcycle Repair: CB160 drips oil from the right exhaust flange, exhaust flange, oil drip

Question
Hello Mr Silver,

CB160 with about 9,000 miles.

It has happened again...An old Honda has "followed me home" :^)   I have been very lucky in the past.  Drag an old bike home, lubricate, clean carbs, do a little cleanup and adjusting, maybe replace a few parts, and go for a ride.  This time, not so lucky.   When I got this one started, I noticed oil smoke coming from the right exhaust.  After a few laps around the block, a slow oil drip appeared on the right exhaust flange.   Rats!  I have never done more than general service work, but assume that this one needs new rings.  What other possible sources are there for this oil?
     
I have a Honda Shop manual.  What is the best manual to use for working on this engine?

Any guidance will be greatly appreciated.

My 13 yo daughter is excited about this bike. Looks like a miniature of my superhawk.  

Thank you,
John Janosik
VJMC 703
ICOA 4247
S.E. Iowa  

Answer
Aloha, John....  Could have been seized or maybe just stuck rings from sitting. I had a bike like this and didn't even remove the motor from the chassis. Just pulled the exhaust system, loosened the motor and tipped it forward on the back mount bolts, popped off the top end, installed new rings, honed the cylinders and put all back again.. ran fine! You must clean the piston ring lands real well, if you are going to reuse them. If the cylinders/pistons were seized, then you will have to rebore and o/s pistons/rings.

You shouldn't have any oil leaking from the exhaust flange!
The gaskets compress, but the flange should hold a pretty tight fit. Check the flange stud nuts for being tight. Check the spark plug... if it is loaded with oil then there is a problem in the cylinder. If it is dry and smoking, there could have been some kind of leftover oil residue in the cyl, perhaps someone wanted to try to protect the cyls from seizing. I'm sure you can tell after about 15 minutes if it is getting better or worse.

The heads don't have any valve stem seals, but unless a valve was seized in a guide, that isn't much of a normal source of oil/smoke. External oil leaks can come from the valve cover caps or the cylinder head side cover gaskets.

The factory shop manual should be okay. Most of the aftermarket ones are just reprints/reorganization of the factory books. There is a lot of simiarily between the 160 and 175 series engines, just a change in orientation of the cylinders, other than the CL175K0 series.

Worst part of working on ones that haven't been apart is the gaskets sticking to the parts. Otherwise, they are pretty straight forward in the Honda mode of design of their little twins. Get two small pieces of wire to keep the ends of the camchain from falling inside the cases, once you separate the camchain master link. Stuff rags and/or paper towels down in the cases to keep dirt and gasket bits from going down inside, too.

You may be more comfortable with the motor out of the chassis for repair.

Bill Silver