Excess smoke coming from breather hose


New Member
Hi, I am in the process of doing a full motor rebuild on a 1976 CJ360T, actually the rebuild is complete just a few niggly things that i am trying to sort through.
When the motor is up to operating temperature, i am getting a lot of oil smoke i guess is the best way to explain it coming from the breather hose that connects to the head of the motor.
It is not that black smoke, just sort of a vapor smoke.
As i am new to these bikes and motors, is this normal or do i need to go back and strip it down some to find out what is going on?
The motor was in pretty bad shape when i got it, Hadn't had the internal oil filter cleaned out, both cam chain guides were gone, fairly bad condition.

Any advice would be appreciated.


New Member
How many miles have you had on the bike since the engine rebuild? Much highway riding?

Are you sure it’s not just condensation? Put a catch can on it to inspect the vapor residue.

Too much engine can sometimes be a culprit. Keep your bike upright and check the level.

How were the cylinders? Were they honed and properly cross-hatched? New rings? Valve seals replaced and valve seat adequately lapped?

Have you checked compression?

Some blow-by is common on engine rebuilds, but it should dissipate after some riding. The smoke shouldn’t be too excessive coming out of the breather hose. If it is as excessive as it seems as though you are concerned with, you may have to check the cylinders again, maybe even inspect the grooves where the piston rings go, and if you’re at it anyway, make sure to clear out all of the carbon buildup where the rings go as they may get stuck, which is sometimes the cause of some blow-by.

Sent from my iPhone using Tapatalk


New Member
Thanks for the reply.
No miles on it yet since the rebuild, maybe 1 mile at the most to adjust some carburetor settings that is about all.
Yes everything was lapped in correctly, good cross hatch in the bores with new standard size rings as the others weren't worn much at all.

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