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Thread: How much oil should mist from the crankcase vent?

  1. #1
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    How much oil should mist from the crankcase vent?

    1963 r69s. Rebuilt top end of the motor due to a meltdown, new pistons, last overbore, etc. The story has been told here before. The bike seems (knock wood) to be ok now, have about 250 to 350 miles since I did the work. Compression is over 160 each can, exhaust isn't blue or smoky.

    I've got to tighten things again, but I still have some misting out of the breather. Maybe I notice it more because the bike is white, but I'm not lugging the motor. Thoughts?

  2. #2
    Cam Killer marchyman's Avatar
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    Enough to keep the oil pan from rusting and the center stand pivots well lubricated is normal on my bike. Not enough to actually drip on the ground.

    The center stand pivots are actually an issue. Even with blue loctite they loosen up every so often.

  3. #3
    Administrator 20774's Avatar
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    Oil mist coming out the breather suggests high internal pressures. You could still be experiencing some blowby given that you're only 300 miles into the break-in. When the rings seat, that should be minimized. Hopefully the break-in process is being done correctly.

    You could consider running slightly lower on the oil level...try not to keep it right at the top mark all the time. If the level drops, let it go, but watch it. Even mid way on the dipstick is probably not time to immediately fill up. As you approach the quarter mark...probably time. Lowering the oil volume will give more internal air volume and maybe cut down on the amount going out the breather.

    I forget when the breather assembly was redesigned. IIRC up to some point, it was possible to put the breather in 180 degrees out. Not saying that's what's going on here, but stuff does happen.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Proper break in process

    What is your suggestion for proper break in? Always open to ideas. Thanks!

  5. #5
    Administrator 20774's Avatar
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    There is a link in the Resources and Links thread to a break-in procedure.

    http://www.mototuneusa.com/break_in_secrets.htm

    I feel the first 60 seconds is the most critical to break-in. That is when you get the most abrasion to form the rings before the engine begins to glaze the cylinder walls which begins to reduce the friction. I get the bike started right after engine build and hold the RPMs up to around 3K for 45-60 seconds. Then I come back to idle and hop on for my first ride. During that ride, I try not to idle if possible and continually accelerate to about 80% of speed in each gear and find places where I can chop the throttle and let engine pressure push the rings back up against the cylinder. The action of acceleration and deceleration pushes the rings tigher to promote wear.

    I do this sort of thing for the next 300-500 miles, changing oil multiple times during this period and checking the head torque and valve clearances. I just did a top end on my /7 and ran the valve clearances quite wide, like 0.25mm on exhaust and 0.20mm on intake. This promotes valve cooling.

    Since you're 250-300 miles in, you should continue to accel/decel wherever possible. I would hold off on speeds to the 80% level until you at least reach the 500 mile point. Probably check things one more time at 1000 miles.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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