blow by off back jug on 2007 ultra

[johnarogers]

back cylinder blowing blue smoke happened all at once. think it's rings any other suggestions   

[Scotty]

Rings, valve guides or valve seal
Have to do a leak down test to determine which one it is.

[prodrag1320]

if its smoking all the time,its rings.smokes on start up & de acceleration,its guides/seals.this is not written in stone,but usually holds true

[kd]

    Even dry test compression will cause it to lean more to valves.  If uneven and a "small" squirt of oil in the low cylinder raises it, ring seal is suspect.  That can include anything that is part of the piston or cylinder wall.  If that squirt of oil in both cylinders kinda evens it up it's pretty much nailed as a piston / ring seal issue.

Added later
Don't forget a head gasket can fail on the combustion side but that would usually be accompanied with a change in crankcase pressure. That may manifest as a wet air filter or throttle bore ahead of the throttle plate or if vented to atmosphere as extra discharge.

[FXDBI]

Year? Miles? Modifications ?   Bob

[K4FXD]

Leak down test time.

Harbor freight sells a cheap leak down tester.

[Admiral Akbar]

Leak down and compression tests are a waste of time.  If you are blowing oil out of one cylinder, it needs rebuild. I'd first route the breathers so that they don't feed into the intake. Spray come cleaner into the intake and take the bike out for a good run.  If the smoking still occurs, rebuild the top end.  Disassemble, inspect, repair.

Add:

Try a little seafoam and water in the intake with the engine running. You might get lucky.

[PoorUB]

Leak down test time.

Harbor freight sells a cheap leak down tester.

Cheap is the key word.  I bought one from HF. How could they screw up something so simple?

[jjdalynh]

Leak down test time.

Harbor freight sells a cheap leak down tester.

Cheap is the key word.  I bought one from HF. How could they screw up something so simple?

learned the hard way.  3 different comp testers, 3 different results (all bad).  tried verifying with good gauge, HF gauge was good from 0-100psi, but went off the rails after that.  don't buy anything with gauges from HF.  all my gauge tools are OTC and work.