78 kz650 SR BURNING OIL

Hey all this is my first post here. So bear with me!

I've got a 78 kz650 SR model with 10,000 original miles that seems to be burning oil and I cant figure out why.

Motor mods:
MAC 4-1 no baffle
Dyna electronic ignition
Pod filters with crank vent ran to behind the swingarm

Ive checked all 4 plugs and they are all perfect tan color which makes sense because the carbs have been jetted and synched darn near perfect. The oil level is dead center between the marks on the window. The bike still pulls hard and has no issues running whatsoever. I also just ran a compression test and came up right at 155 psi in all cylinders. I have correct timing etc.

On to the symptoms:
ive been riding the bike for about a week now with no problems or blue smoke. However, today I noticed at a red light that there was blue smoke steadily coming from the pipe, not like a two stroke but enough you can see it, it puffs more every time I goose the throttle and a friendly driver caught me and said he could smell something burning behind me.

My question is, if I have solid compression on all cylinders and the plugs look fine, what would make me burn oil while riding? normally i would think valve seals if it just smoked on startup but it worries me that it smokes after its warmed and all. partially blown head gasket maybe?
sorry for the book guys but I would like to get to the bottom of this quickly

Check that vent tube to make sure it is not crimped or blocked in any way.

Hmm now that you mention that, it seems to me that the smoking problem started the day after i ran a piece of hose from the crank vent to down over the swingarm. But from what i can tell its not crimped or restricted in any way. Also, i can feel a small amount of air coming out with the bike idling. What could this vent have to do with it burning oil? My understanding is that vent only lets excess pressure out of the crankcases.

Kawilk01 wrote: Hmm now that you mention that, it seems to me that the smoking problem started the day after i ran a piece of hose from the crank vent to down over the swingarm. But from what i can tell its not crimped or restricted in any way. Also, i can feel a small amount of air coming out with the bike idling. What could this vent have to do with it burning oil? My understanding is that vent only lets excess pressure out of the crankcases.

Good Fortune!

Kawilk01 wrote: ...78 kz650 SR model with 10,000 original miles that seems to be burning oil...4 plugs and they are all perfect tan color... oil level is dead center between the marks on the window. The bike still pulls hard and has no issues running whatsoever. I also just ran a compression test and came up right at 155 psi in all cylinders. I have correct timing etc.

On to the symptoms:
ive been riding the bike for about a week now with no problems or blue smoke. However, today I noticed at a red light that there was blue smoke steadily coming from the pipe, not like a two stroke but enough you can see it, it puffs more every time I goose the throttle and a friendly driver caught me and said he could smell something burning behind me.

My question is, if I have solid compression on all cylinders and the plugs look fine, what would make me burn oil while riding? normally i would think valve seals if it just smoked on startup but it worries me that it smokes after its warmed and all. partially blown head gasket maybe?....

Would examine and sniff-test the crankcase oil for possible gasoline contamination. Which might maintain the "level" while reducing burnt-oil residue on the spark plugs.

As known, blue smoke from the exhaust comes from oil being burned in the combustion chamber, which is inconsistent with perfectly tan spark plugs. And if burning oil -- as opposed to leaking oil -- the spark plugs won't remain perfectly tan for long.

If chrome exhaust headers are fitted, is there excessive bluing?

Good Fortune!

Forgive me if this question sounds insulting; I'm not trying to be a smartass. When you check the oil level do you have the bike on the centerstand or side stand? If it's on the sidestand the crankcase is overfilled with oil. I have read that some have done this without realizing the problem it causes. Ed

[/quote]

Would examine and sniff-test the crankcase oil for possible gasoline contamination. Which might maintain the "level" while reducing burnt-oil residue on the spark plugs.

As known, blue smoke from the exhaust comes from oil being burned in the combustion chamber, which is inconsistent with perfectly tan spark plugs. And if burning oil -- as opposed to leaking oil -- the spark plugs won't remain perfectly tan for long.

If chrome exhaust headers are fitted, is there excessive bluing?

Good Fortune! [/quote]

Sniff test on oil passed with flying colors I don't smell any fuel! As for the headers, yes they are chrome but there is no bluing. Only a slight change to a golden color

650ed wrote: Forgive me if this question sounds insulting; I'm not trying to be a smartass. When you check the oil level do you have the bike on the centerstand or side stand? If it's on the sidestand the crankcase is overfilled with oil. I have read that some have done this without realizing the problem it causes. Ed

650ed - I have removed the center stand on the bike but I did have a friend hold it perfectly vertical while checking the oil level. PO had about 1/3 quart too much in there so I drained it and refilled to proper level

Just because there's good comp.
does not mean the oil ring's are good.
If the bike sat for a long time then some surfaces
rust on the cylinder can wipe out the oil ring's
and not hurt the comp. ring's.

zukdave wrote: Just because there's good comp.
does not mean the oil ring's are good.
If the bike sat for a long time then some surfaces
rust on the cylinder can wipe out the oil ring's
and not hurt the comp. ring's.

The bike sat for about 6 years before being cleaned out and ran and basically all maintainence done by me and the guy I bought it from. I hope I don't have to put new rings in it after riding it only a week I mainy work on dirtbikes so street motors are somewhat new to me. How hard would it be to put new rings in it?

Ring's would be a basic top end rebuild
on four dirt bike motor's line'd up.
If you can do a four stroke single you could do this motor.

Hmm. Anything important i should know like special torque specs or a common mistake people make that i should avoid? Id really rather not tear into this thing it runs too good and is in too good of shape to need a top end already. Anyone else have any ideas what the smoke could be?