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Thread: Compression confusion

  1. #16
    Registered User lkchris's Avatar
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    Reducing compression doesn't really solve the unleaded problem.

    Just run premium ... if it were brand new, you wouldn't notice valve recession problems for 50,000 miles. At 95K miles currently it could need valve work anyway, but it won't fail because of unleaded for some time otherwise.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S

  2. #17
    Nick Kennedy
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    Nov 2011
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    Hey John
    Hope its going well
    Its just me but if that was my bike and it really sat for 35 years, I would get it running and only ride it 1, 2 or3 at the most miles and immediately change the oil and filter again.
    Even thou you borescoped the cylinders there has to be rust in the there
    somewhere and changing the oil and filter very soon after you first ride it might be a very good idea...
    Oil is so cheap compared to a major engine problem due to running with contaminated oil.
    Good Luck
    Nick
    1978 R 80

  3. #18
    Registered User STEVENRANKIN's Avatar
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    Sorry for your problems

    Hey I am sorry for the problems you are having with the blankety blank Philips screws on the carburetor tops. On my last carb rebuild, I ended up drilling and easy outing one of the them. I can say it was a very shaky do not to drill to big a hole to deep and damage the threads or carb.

    On both of my bikes a 78R100RS and a high mileage 84R80RT, the main needles attached to the slides in the carbs had worn to the point of causing poor fuel mileage and rich running. At 95K miles, I myself if your bike was mine, I would change the needles and jets. Of course, this means getting the cab tops off to change the needles. The jets can be reached via the bottom of the carb.

    Sometimes when drilling a bolt or screw out that is frozen or stuck, during the drilling process either heat from the drill or the vibration will free the fastener.

    In my case, I have a matched set of drill bits and corresponding easy out tools. the easy outs I use are spiraled so as you turn them to loosen the bolt the dig into the drill hole tighter. These beat the heck out of the square ones that I found turned in the hole and only made things worse.

    OKAY, I am pretty sure I read the comments on 73bmr's last post. If I have not and this information is nonsense forgive me, I am getting old and goofy. Cheers, St.

  4. #19
    Registered User STEVENRANKIN's Avatar
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    fuel additives

    You really do not need lead or other additives unless you are going to store for the winter. At that point a fuel stabilizer should be added. St.

  5. #20
    Registered User STEVENRANKIN's Avatar
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    Any progress?

    Have you made any further progress? St.

  6. #21
    Curmudgeon nrpetersen's Avatar
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    You maybe can forestall the valve recession problem by sweetening your gas with a few percent with 100LL aviation fuel. Technically according to EPA it is illegal, but I don't think a gallon of it will hurt anybody.
    Use E0 premium fuel if it is available. I have low compression cylinder base gaskets installed on my '75 R90/6 which makes it run almost like a steam engine.
    Retired w 2005 K1200LT, 2000 R1100RT, & 1975 R90/6

  7. #22
    Registered User
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    Update7-5-20

    First: HAPPY JULY 4TH TO ALL!! God bless America!
    Got the Float Needle Seat out using a 7MM tap and 'creative' extracting. Think I'll hold off on removing the left carb seat (which has not been leaking) until I get the new right seat installed, just in case I bung up the new seat and have to use the other from the rebuild kit. OK, so my rebuild confidence only goes so far... Also since the Throttle Slide seems to be working properly, I'll hold off on trying to remove the tops till I fire her up and see how things run. Time to put all the carb 'stuff' together and reinstall. Next, take off the valve covers, remove plugs and turn her over to make sure oil is circulating and oil pressure light goes out. Any suggestions on how to re-install the Float Needle Seat? Anti-Seize compound and wood dowel has been suggested. Careful, careful...

  8. #23
    Registered User STEVENRANKIN's Avatar
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    Thank you

    Thank you for the update, I am glad things are going well for you so far.

    I am afraid I can't say much more about carb rebuilding other than what I have done myself.

    I am not familiar with a wood dowel and never seize method of installing float needle seats?

    There might be something of use in Snowbum's article at https://bmwmotorcycletech.info/earlybingR75CV.htm.

    Good luck with further work. cheers, St.

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