Evo Puking Oil Thru Breathers

[dporto]

I need help from the EVO experts. My neighbor has a 1995 Road King top end rebuild 2 years ago has run about 6k miles till this spring. Motor has .010 over pistons, new s&s heads ev27 cam s&s steel breather. This spring owner change oil and put in Mobil 1 with HD oil filter, got about 10 miles and oil blowing from breathers into carb making lots of smoke. Drained oil and changed filter to kn170 and dino oil 2.5 qts bike ran about 30 miles then started smoking bad again. CCP is 165 PSI front and rear. Could the Mobil 1 screwed something up or is something else failed. I at a loss with this bike.

[Tacocaster]

Your base may be carrying some oil that leaked past the check valve while it sat all winter. Won't show on the dipstick but in effect, you have too much oil with the oil in the tank and the engine base (crankcase).
Just a guess...

[JSD]

With the RC having the sump lower than the check ball I didn't think that would happen. 

[Tacocaster]

Okay,   didn't know that. Thanks JSD.

[wfolarry]

Ride the bike until it starts smoking then turn the engine off. Check the oil. If it's low then you have a return problem. If it's not then you have a breather problem. Should give you some idea where to look next.

[dporto]

Thanks Larry I will perform that test.

[dporto]

Larry we performed the test bike was fine for 10 miles the smoke show started, check oil level was good.
heads, rocker boxes, and cam chest breather device are all s&s and 2 years old. The only change to this motor was the owner putting Mobil 1 oil and it started smoking. Owner wants to try 60 weight oil.
Could you explain further your breather theory ?

[xlfan]

Air filter is oil soaked?

[Dan89flstc]

Playing with different oils is a waste of money and time, the issue is not being caused by the oil.

Don`t let the owner help you diagnose...

[dporto]

Yes air filter element saturated.

[Hossamania]

Clean it, try again

[wfolarry]

Larry we performed the test bike was fine for 10 miles the smoke show started, check oil level was good.
heads, rocker boxes, and cam chest breather device are all s&s and 2 years old. The only change to this motor was the owner putting Mobil 1 oil and it started smoking. Owner wants to try 60 weight oil.
Could you explain further your breather theory ?

Since the oil was returning you need to check the breather. Open up the rocker box & check there first.
If you don't see anything pull the cam cover & check the breather. Verify the timing first. If it's an S&S breather if they get even a small amount of dirt or something in them they'll cause this problem. On big inch motors I would take the screen out of them because they wouldn't work otherwise.

[Deye76]

Is the S&S breather a conventional one, or a reed valve breather? If it's a reed valve type the oil level might be too high. With a reed valve type running the oil a half quart low might help.

[dporto]

Thank You Larry will start invasive investigation, again thanks for the help. Another thought is it possible that the mobil1 being more slippery than mineral oil broke the seal between the oil rings on the pistons and the cylinder wall and fails when hot ? This build only has about 6k miles on it.

[dporto]

Clean it, try again

Did that failed within 10 miles.

[dporto]

Is the S&S breather a conventional one, or a reed valve breather? If it's a reed valve type the oil level might be too high. With a reed valve type running the oil a half quart low might help.

The breather is conventional.

[xlfan]

Too slow oil return from rocker box in combination with cracked or loose valve guide seal on exhaust valve?

[wfolarry]

Thank You Larry will start invasive investigation, again thanks for the help. Another thought is it possible that the mobil1 being more slippery than mineral oil broke the seal between the oil rings on the pistons and the cylinder wall and fails when hot ? This build only has about 6k miles on it.

No. Changing to a different oil won't cause engine damage.
Since you can go 10 or 30 miles before it smokes means there's a restriction somewhere or something fails when it gets hot.

[dporto]

Thank You Larry will start invasive investigation, again thanks for the help. Another thought is it possible that the mobil1 being more slippery than mineral oil broke the seal between the oil rings on the pistons and the cylinder wall and fails when hot ? This build only has about 6k miles on it.

No. Changing to a different oil won't cause engine damage.
Since you can go 10 or 30 miles before it smokes means there's a restriction somewhere or something fails when it gets hot.

Ok tanks again Larry, will start exploratory surgery this week.
 

[dporto]

Opened up both rocker boxes and cam chest with nothing unusual found. Mechanical breather timed correctly and screen was clean.

[xlfan]

Do both cylinders smoke?

[dporto]

Do both cylinders smoke?

Yes both smoke.

[wfolarry]

You'll have to pull the top end.
I just went through something similar with a customer. After checking everything he pulled the cylinders. Rust from top to bottom. Wherever he stored the bike for the winter it wasn't a happy place.
New pistons & rings. Hone the cylinders. Happy camper.
Good Luck.