Blue smoke coming out of the exhaust

Hello everyone,

I've got my self a '98 VFR this year with 70k km( as my first bike). At the beginning it was running ok then started slowly to burn oil somehow. Blue smoke was coming out of the exhaust at the cold start and especially after it got to temperature or when idling at red light in traffic. Did a second oil change after 2k km , same viscosity 10w40 and nothing much changed. Did a compression test and it wasn't good, 8-8.4 bars (maybe i didn't get the compression test right)
Yesterday got my nose into the pair valves and found the rear one full of fresh oil, it wasn't clogged. The front one had a bit more dirt in it and signs of burned oil. Cleaned everything and blocked the tubes that go into the valves. Started the bike this morning and no more smoke, just a bit of condensation; after a 20 minute ride made a quick stop and shut it down. At the restart it was smoking again but the smoke wasn't that blue like it was before.
Any ideas what else should i check? Could be the valve stems bad or even worse piston rings?
I've looked thru throttle blades inside the engine and valves are all black.
It starts perfectly and the power looks to be there still.

Thank you so much

 

Not sure if there's a such thing as 'worse' when comparing valve guides or piston rings, the engine comes apart either way. If you're in the engine due to burning oil it's probably a good idea to do both.

Low compression is a bad sign, as you mention I'd run that test again as 8.6bar is not where it should be. Coked valves and the coked up reed valve in your picture definitely indicate burning oil.

Looking at the service book (section 1-45 covers the PAIR system), those valves are check valves with a reed on the underside. I've never worked with this system before, but I feel like there shouldn't be any oil there at all, since that system is separate from the crankcase breather and is supplied by filtered intake air. Also, oil in those passages would flow directly into the exhaust when the solenoid valve opened (which seems to be your case).




The reed valves feed air thru passages in the cylinder heads that have O-rings on them. Look at the graphics on 8-33 - 8-35. I tried to attach them but I'm editing so maybe I can't post graphics while editing an existing post.



- Have you looked inside the air intake box?
- Follow the PAIR valve tubes disconnect them and see if you have oil inside them as well.
- Remove the reed valves and inspect to see if they're intact.
- Pull the valve covers to see if you have coking there as well.

 

My fear with piston rings is that I will not be able to find here fitting and quality parts, but will see.

The air intake box is clean and dry, also the tubes that go from the PAIR solenoid valve look dry. The reed valves are all good, nothing broken there.

Will try to remove valve covers to see if the o-rings are bad or the joint collars are missing

 

Honestly I think it's unlikely that those O-rings are the problem, the cam train is at atmospheric pressure as it runs, so if those seals are leaking then oil would somehow have to be sucked past those O-rings all the way up to the reed valves. Aside from that, the odds that all four of those rings would be worn out all at once are also quite low. Since the tubes are dry, I think it's more likely that oil vapor is traveling up those passages thru the exhaust ports as the engine runs, and ending up at the reed valves.

In any case, make sure you have new O-rings before you pull the covers.

On that note, could you possibly rent a borescope from a local shop? If you don't know what that is, a borescope is a hand-held camera but the lens is on a long, flexible line. They're made for exactly this type of inspection, getting into spark plug holes or fluid ports without disassembling the machine. That would save you a lot of potential headache, rather than taking things apart that don't need taking apart.

 

Ok, thanks for the advice

 

Update:
Today I opened the pair valves again and found them full of oil again so I took the head cover off and found a missing o-ring on one of the collars.

 

im not convinced that replacing that o-ring will fix ur problems. look for the missing ring fallen off somewhere. full coolant suggests no headgasket problem.

clean off all the gasket glue, its unnecessary and can fall off and cause problems.

 

I will check again the pair valves after a couple of days, if the oil comes back will dive deeper to look for the problem.
Thanks again.