Results 1 to 14 of 14

Thread: cam timing

  1. #1
    jimmy armour
    Join Date
    Jul 2009
    Location
    Lucknow ontario canada
    Posts
    134

    cam timing

    hi guys I guess its my turn to ask for input,I have a 1977 r100s and am about to replace the timing chain,the third one in 340,000kms,and am thinking of installing an offset woodruff key to advance the valve timing as per the 1978 on bikes ,has anyone done this and what was the result?thanks in advance Jimmy

  2. #2
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    12,403
    Hmmm...why would you want to do that? The '77 models have some of the highest power of the Airheads. The began the detuning process with the '78 models....this was aimed more at satisfying EPA requirements than anything else. I've heard it started with the January 1978 bikes but it could be all of them.
    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
    Join Date
    Sep 2007
    Posts
    1,248
    There is a increase in torque with the advance in valve timing. I have altered valve timing with sport cams and aftermarket performance cams and have had no problems with key failure. I add a bit of Loctite RC609 when doing this. The latest offset key from San Jose BMW is a nice, if expensive piece.

  4. #4
    jimmy armour
    Join Date
    Jul 2009
    Location
    Lucknow ontario canada
    Posts
    134

    cam timing

    hi guys thanks for replying ,I was aware of the differences in cams and why, way back when my bike was sporty and so was I, I too had made a lot of mods sports cam etc,but over the years have detuned ,std cam and lowered compression,what I was wondering was how my bike would run,with the san jose off set key ,much more torque or some ? my exaust has always been black never grey like my riding buddies,off coarse i have rebuilt the carbs many times over the years,and changed float needles ,twin bing float kit,needle jets, mainjets and needle positons ,but exaust remained slightly black sootie (rich)I put it down to the dirty cam and pistons,since then I have had her rebored and new 1978 on type pistons installed, so did anyone note an improvement in tractability ? thanks again Jimmy

  5. #5
    No longer a member here
    Join Date
    Apr 2006
    Posts
    1,432
    Quote Originally Posted by 20774 View Post
    Hmmm...why would you want to do that? The '77 models have some of the highest power of the Airheads. The began the detuning process with the '78 models....this was aimed more at satisfying EPA requirements than anything else. I've heard it started with the January 1978 bikes but it could be all of them.
    I am confused!!! I always thought that BMW upped the horses of the 1000cc in 1978 from 65 or so to 70. What do I have wrong??

  6. #6
    Sir Darby Darryl Cainey's Avatar
    Join Date
    Mar 2003
    Location
    Fenwick, Ontario Canada
    Posts
    2,076
    How are you taking your plug readings Jimmy?

    Back in the day when I was setting up my racebike we ran it very hard and shut it off, then checked the plugs.
    If you are just running easy on idle you won't get the plug reading you want.

    Ride it like you stole it!
    Ambassador BMW MOA Ontario Canada
    President Niagara BMW Riders #298
    Knights of the Roundel #333
    1977 R100RS, (Retired) 1993 R100GS (just getting started)

  7. #7
    Registered User
    Join Date
    May 2008
    Location
    B.P., MN
    Posts
    683
    Opinion, if engine runs black at tailpipe, might be burning oil? Way back in old clymer book, the only mention of using offset key on cam is to degree a new cam when installed, if needed. Don't really know why airhead would need, or could use more advance in timing than is available? Depending on year of manufacture, which is around 27 degrees. With the low octanes available today as opposed to what was available, would advanced timing increase ping?

    Much has been posted about cams, as stated before, I run 336 in 90S, don't find it racy or peaky, just breathes real good, timed at TDC with dual ignition, pulls real good from 4K on up. Always thought airheads love to spin, hate to putt putt.

  8. #8
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    12,403
    Quote Originally Posted by EMSimon View Post
    I am confused!!! I always thought that BMW upped the horses of the 1000cc in 1978 from 65 or so to 70. What do I have wrong??
    My '78 R100/7 is shown as only 60Hp but the same year R100RS or RT was 70 Hp. That's probably in the difference in compression ratio 9:0 to 9.5.

    I don't imagine the EPA requirements they had to comply with did any good to total performance. Hp is only one measure of performance.

    I've always had it in my mind that the pinnacle of the total Airhead package (in terms of engine performance) was the 1977 bikes.
    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!

  9. #9
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Location
    Albuquerque, NM
    Posts
    4,600
    Quote Originally Posted by 20774 View Post
    My '78 R100/7 is shown as only 60Hp but the same year R100RS or RT was 70 Hp. That's probably in the difference in compression ratio 9:0 to 9.5.
    And in the larger valves and 40 mm carbs.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  10. #10
    Sir Darby Darryl Cainey's Avatar
    Join Date
    Mar 2003
    Location
    Fenwick, Ontario Canada
    Posts
    2,076
    The 70 HP was from the 77RS with 40mm exhaust, yes?
    Ambassador BMW MOA Ontario Canada
    President Niagara BMW Riders #298
    Knights of the Roundel #333
    1977 R100RS, (Retired) 1993 R100GS (just getting started)

  11. #11
    jimmy armour
    Join Date
    Jul 2009
    Location
    Lucknow ontario canada
    Posts
    134

    plug readings

    hey!Darryl !,well just like you said,do what we called a plug chop, but thats not what I am interested in I will be installing a cam chain, and due to the mileage a new cam flange bearing ,as it would be better to remove the cam complete,so gearbox clutch, flywheel comes off,which I have to do anyway, as the last time I had the flywheel off (lightened no ot or or other tdc marks only full advance dot),anyway some dummy installed the flywheel in the wrong position,crank must have moved, so am interested to know if anyone has installed the cam key to advance the cam ?

  12. #12
    jimmy armour
    Join Date
    Jul 2009
    Location
    Lucknow ontario canada
    Posts
    134

    cam timing

    Hi once again, before the thread falls off the bottom of the page,I have decided to leave the timing chain and related work until next year!,and save my old back not to mention my knees ,so thanks to those who tried to help,but I would like to check the ignition timing,it has a lightened flywheel and has no top dead mark just a full advance dot,could someone with a 1977 r100,(I belive the 1978 and later are different) count the gear teeth on the flywheel from tdc, to full advance,that way I can mark my flywheel and check the timing,until I remove and replace it correctly sorry for being long winded ,thanks in advance Jimmy

  13. #13
    Administrator 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    12,403
    You should be able to find TDC just by rotating the engine and watching when the piston stops moving out and then starts moving in...half way between those two points is TDC.

    On the flywheel, 2mm is 1 degree.

    The S-mark for the '77 /7 should be 6 degrees BTDC. The F-mark is 31 degrees BTDC.
    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!

  14. #14
    jimmy armour
    Join Date
    Jul 2009
    Location
    Lucknow ontario canada
    Posts
    134

    thanks

    Hi , Kurt thanks for the info,I know how to find top dead,had the flywheel lightened way back in 1984,and has been off many times since, just when reinstalling the flywheel last time must have moved the crank so timing marks didnt line up with my strobe ,so I will do as you say and mark the flywheel 62 mm for full advance,that will allow me to check, the timing has never altered (dyna 111) in 150,000 km, but would like to check it,many thanks again,keep up the good work,Jimmy

Posting Permissions

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