Results 1 to 10 of 10

Thread: R90/6 Base Gaskets

  1. #1
    Macrunch MCrenshaw's Avatar
    Join Date
    Mar 2008
    Location
    Bedford, TX
    Posts
    82

    R90/6 Base Gaskets

    While cleaning the bike yesterday I noticed some oil misting around the base gaskets. Is this an indication that the heads may need to be retorqued? I probably have about 300 miles on the bikes since the last valve adjustment.

  2. #2
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,757
    Unless the torque was down around 15 ft-lbs, I wouldn't think that would be of any consequences. Certainly, the torques need to be more or less correct, but I wouldn't get torque-wrench-happy on doing it every time you check the valves. Typically, once everything is bedded in, it's unlikely you need to check torques all that often unless something changes.

    Remember that the explosions in the combustion chamber is literally trying to blow the heads off the the cylinders, pulling on the head bolts, and possibly very minutely, lifting the cylinder off the base.

    I would think you're slight misting is just due to age and/or an imperfect seal that last time the cylinder was off. How many miles since this was done?

    I'd be inclined to say "they all do that" but some bikes can be made such that the oil stays on the inside.
    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!

  3. #3
    Registered User donbmw's Avatar
    Join Date
    Feb 2004
    Location
    Monroe La.
    Posts
    471
    Look at you push rod seals and the oil press switch. Could also be head gasket leaking around the push rod opening. I have all the above over the last few years on my R90/6.
    1975 R90/6, 1980 and 1982 R65, !959 TR3A Triumph Car

  4. #4
    Macrunch MCrenshaw's Avatar
    Join Date
    Mar 2008
    Location
    Bedford, TX
    Posts
    82
    Oil pressure switch and pushrod seals were replaced about 1,000 miles back. No leaks there. And there are no puddles or oil drips on the underside, only the misting.

  5. #5
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,757
    What was your procedures for sealing the base after the new seals were put on and how have you been checking head bolt torque during the 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!

  6. #6
    Macrunch MCrenshaw's Avatar
    Join Date
    Mar 2008
    Location
    Bedford, TX
    Posts
    82
    The pushrod seals were done by a factory trained BMW mechanic. I can't say how he installed the base gaskets but the quality of his work has always been top notch. I don't think it will hurt anything to go back and torque the heads. These old bikes need the TLC and it isn't difficult. Just need to be careful to know the correct torque settings, back them off, then don't over torque so as not to damage the threads in the aluminum crank case.

  7. #7
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,757
    Sounds like there's been no retorque since the seals were done. Not sure how extensive it was done for you, but I just did a top end on my /7 which included new seals and new head gaskets. According to Oak's manual, he recommends a retorque at 50, 300, and 600 miles, noting changes during each session. Things should settle down pretty quickly. I just did my first retorque at 50 miles...I was somewhat surprised how much I had to retorque...for me it was likely the head gasket compressing which resulted in the undertorque on the bolts.
    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!

  8. #8
    Macrunch MCrenshaw's Avatar
    Join Date
    Mar 2008
    Location
    Bedford, TX
    Posts
    82

    Post

    Kurt you are correct, I have not re-torqued the heads since the push rod seals were replaced. If Bruce told me to do it I completely forgot about it. I'm sure there are less than 1,000 miles on the bike since having it done. My average annual mileage on the R90 is less than 300. Too many other fun bikes to ride, but I plan to give this one some more saddle time when I retire in two weeks.

  9. #9
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    13,757
    Bruce drops in on the list every so often...maybe he'll clear things up. He's a good supporter of Airheads...I did my first tranny spline lube at his shop maybe 10-11 years ago at one of the TxAirheads tech day.
    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!

  10. #10
    Registered User b25bsaboy's Avatar
    Join Date
    Aug 2010
    Location
    Calgary, AB. Canada
    Posts
    423
    Quote Originally Posted by 20774 View Post
    Sounds like there's been no retorque since the seals were done. Not sure how extensive it was done for you, but I just did a top end on my /7 which included new seals and new head gaskets. According to Oak's manual, he recommends a retorque at 50, 300, and 600 miles, noting changes during each session. Things should settle down pretty quickly. I just did my first retorque at 50 miles...I was somewhat surprised how much I had to retorque...for me it was likely the head gasket compressing which resulted in the undertorque on the bolts.
    1+
    Rick MacPherson
    Success is Not a Destination, But a Journey.
    Accredited Motorcycle Appraiser
    1968 BSA Starfire, 1976 BMW R75/6, 2009 R1200RT

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •