My r90 restoration.

Discussion in 'Airheads' started by blaine.hale, Dec 29, 2009.

  1. blaine.hale

    blaine.hale Long timer

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    No gas smell, I'm afraid.
    A weird thing is how hard it hits at idle. You can feel and hear the right exhaust being louder and hitting harder. The left side is just as you'd expect and not too harsh.
    I'll double check my choke but it hasn't changed ever and has replicated all the other carbs I've done. I think there's even a little dot that indicates which way things point.
    I'll switch to normal mixture and lean it a fair amount tonight and report back.

    1 last thing. When playing with mixture screw, as it is now, leaning or richening has zero effect over the idle on the right side. Leaning it all the way in doesn't bog or kill things, same with all the way out.
    The left side is pretty sensitive and bogs and even kills the bike if too rich or too lean (normal behavior.)
  2. onestop

    onestop Been here awhile

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    u dont't need to hook up cables to test if problem moves to the otherside .
    have u checked to see if both header pipes get hot .
  3. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Seems like we've got enough data already to figure this out.

    It's not ignition since the problem didn't migrate swapping plug leads.

    The mixture screw doesn't change idle speed.

    Popping in the exhaust.

    That tells me the right side is running rich. For whatever reason.

    Maybe the butterfly is loose and way off center.

    I was thinking you might have some compromised o-rings, but seems that would make for a lean mixture, not rich. Still, I'd check on that. Those o-rings can get split on the sharp edge of the o-ring groove and it'll be hidden from view. Gotta look close and prod a little to see it.

    The choke is the other possibility. Not too many places where EXTRA gas will come from.

    As difficult as it's been to track this one down, I'd say it will require some close scrutiny to figure out.
  4. blaine.hale

    blaine.hale Long timer

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    I'll take a video of carb disassembly this week. It might drive ya'll as nuts as it has driven me.
    That popping is actually the cylinder dropping. I bumped back to the original pilot/idle jet last night and leaned the mixture screw in as far as possible and still got the same issue. The butterfly valve hasn't changed since day 1 but I went ahead and disassembled it before the carb body went in the carb dip.

    What are the symptoms of piston rings not seating properly or even being broken/blown? Does any of this sound like a valve issue, maybe one is sticking every other cycle or something?
  5. Tin Woodman

    Tin Woodman Mike

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    I'm in the process of completing (29 year process - I don't like to rush into anything) the restoration of a 73 R60/5. Couldn't for the life of me figure out the routing of the wiring harness from mid-frame to the tail lights. Then I saw one of your photos that showed the cable mysteriously emerging from the frame near the tail light - that was the Ah Ha moment. I rushed to the garage and found the two subtle holes in the frame. Don't know why I didn't figure it out myself - too stupid I guess. Photos are excellent! And your restoration is a great read.
  6. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Hey, I was fixing dinner and had an idea what the problem might be, so dropped everything to post this.

    One of my bikes had a problem with a float bowl overflowing and it drove me nuts. The float was set properly and turned off at the correct place, but then one time while taking a closer look, it seemed like the float needle was getting stuck.

    Upon closer inspection, the sharp edge of the float needle had dug a groove in the brass of the float tang, and was hanging up in that. The float would drop, get stuck down and then not stop the flow. Anymore, I chamfer the edges of those needles to prevent that.
  7. blaine.hale

    blaine.hale Long timer

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    I have succeeded in creating a good mystery when I can stop someone in their tracks with an epiphany!
    Funny, I was thinking about that when i pulled the bowl the other night. I cut the fuel the unlatched the bowl and the second I lowered it, fuel dumps all over me and the level of fuel in the bowl was about 3/4 to full. That carb has never leaked but I've almost always noticed the bottom of the bowl having a bit of fuel on the bottom.
    I'm going to check that one tomorrow...even if not the cause, that's not a good thing to keep around.
  8. Wirespokes

    Wirespokes Beemerholics Anonymous

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    For whatever reason, it sure sounds like the fuel level is too high on that side. I'll bet THAT'S the problem! Especially from what you just said!

    Next step is to figure out why.
  9. blaine.hale

    blaine.hale Long timer

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    Been a while...
    I pulled the r90 out yesterday. Cranked right up after not having touched it for 2-3 months, so I figured...why not ride it.
    This time, I left the right side choke up (on). Remember, this is the cylinder that has been dropping within 10 minutes of riding the bike.
    Wouldn't you know it, dang thing ran fine the entire day. Granted, smelled a bit like gas from running rich with the choke open...but that gives me an idea of what's going on.
  10. blaine.hale

    blaine.hale Long timer

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    So after all that and not running for a year...mainly because I've had the r75 to have fun with, the r90 is back to life.
    Turns out it was just a clogged air filter. I rebuilt the bosche starter motor and put the valeo in the r75, put a new filter in, changed all fluids and jetted the mikunis how Rocky Point recommended. Got in a couple hours of riding last night with zero issues. Just doing the fine tuning stuff now. I'm pretty uptight about carb tuning so I'm going to install some vacuum ports on the mikunis. Brad gave me a couple to put in there.
    Brad, if you're reading, what size did you drill and tap for on yours?
  11. hardwaregrrl

    hardwaregrrl ignore list

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    Just saw this.....can't believe you scratched your head and chased your tail over an air filter:huh. Did that piss you off or what???:lol3

    Glad to hear it is something so simple.
  12. blaine.hale

    blaine.hale Long timer

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    I think I fixed and added enough other things in the mean time to make it hurt a little less when I put in the new filter and rode away.
    It's running like a champ now. Mixture is just about dead on but needs some balancing.
    Say, what do you suggest if the brakes are waaaay too tight on the rotors and rotating the cam on the calipers isn't helping it? I would think just rebleed them?
  13. bpeckm

    bpeckm Grin!

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    How would clogged air filter affect just one side?


    Still thinking it was the enrichener/choke... but hey, all's well that ends well!

    :evil
  14. blaine.hale

    blaine.hale Long timer

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    Eh, both sides were effected. Definitely coughing black smoke from both sides. One was fouling and dropping a cylinder, though. That dropping a cylinder side may have been from the recessed valves that are now fixed.
    All I'm battling now is the darn tight brakes. Seems one of those pistons is stuck.
  15. disston

    disston ShadeTreeExpert

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    Bleeding the brakes may help. Can be a plugged return hole in the Master Cylinder or collapsed brake hose, on Stainless Steel lines it can be not visible under the sheathing.
  16. blaine.hale

    blaine.hale Long timer

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    Looks like it was just a stuck piston. I pulled the cap on the MC reservoir and pumped it a few hard times and it freed up. It was pretty damn scary being on the interstate and smelling my own brakes and suddenly realizing they were all but locked up solid!
  17. hardwaregrrl

    hardwaregrrl ignore list

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    Shit! I'm fighting brake problems on my car. new lines having a hard time bleeding them, still a squishy pedal. Glad you got the caliper sorted. Hows the dust cover over the piston?
  18. blaine.hale

    blaine.hale Long timer

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    The dust cover may be questionable. I'm back to squishy brakes now. Does the dust cover need to be perfect to prevent air leaks or something? I know more about drum brakes than disc, so I'm learning a bit.
    My last caliper rebuild went really really well, this one is being stubborn. Should I have polished the piston surface or anything?
    I noticed very very slight pitting in the pistons, dunno how much I can get away with there.
  19. sithndman

    sithndman Been here awhile

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    Squishy could be water in the lines? You blow out all the old brake fluid?
  20. chasbmw

    chasbmw Long timer

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    After you have finished bleeding the brakes, tie back the lever on and leave overnight, most times the brakes will be good.