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Thread: R75/5 Charging issues

  1. #61
    Time to close out this thread I guess! Here the lasts tests I did, since the bike wouldn't take any throttle:

    Condensor wire pinched? no
    Enough fuel flowing from the tank? (Yes, 150 ml in 10 sec)
    Advancer stuck? Don't think so.
    Running on both cylinders? Yes, both hot, but no power.

    At this point I kind of thought it must be the carb(s). I messed around a bit with flow levels, but no improvement. Then I looked over to my (for sale!) toaster, pulled of the carbs, put them on my bike and voila, everything is fine! Put the taoster carbs back on, and put my other carbs on the workbench, for the next rainy day...

    Thanks again for y'all's help! I amy update in a week or so what the issue with the carbs was.
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  2. #62
    B Reams brook.reams's Avatar
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    Quote Originally Posted by anotherbmw View Post
    Time to close out this thread I guess! Here the lasts tests I did, since the bike wouldn't take any throttle:

    Condensor wire pinched? no
    Enough fuel flowing from the tank? (Yes, 150 ml in 10 sec)
    Advancer stuck? Don't think so.
    Running on both cylinders? Yes, both hot, but no power.

    At this point I kind of thought it must be the carb(s). I messed around a bit with flow levels, but no improvement. Then I looked over to my (for sale!) toaster, pulled of the carbs, put them on my bike and voila, everything is fine! Put the taoster carbs back on, and put my other carbs on the workbench, for the next rainy day...

    Thanks again for y'all's help! I amy update in a week or so what the issue with the carbs was.
    Olaf,

    I have seen the slides not move smoothly in the bore. That's easy to verify by taking the air tubes off, running the bike and watching the slides as you rev the motor. That problem can be frustrating to identify if you don't visually inspect the movement.

    I hope that helps.

    Best.
    Brook Reams.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1973 R75/5

  3. #63
    Quote Originally Posted by brook.reams View Post
    Olaf,

    I have seen the slides not move smoothly in the bore. That's easy to verify by taking the air tubes off, running the bike and watching the slides as you rev the motor. That problem can be frustrating to identify if you don't visually inspect the movement.

    I hope that helps.

    Best.
    Brook Reams.
    Good advice, thanks! I decided to disassemble the carbs, I did a quick cleaning job about 2.5 years ago but need to do this right now.
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  4. #64

    Last question, I promise :-)

    I decided to rebuild my carb since it had some issues and was wondering where to shop for a rebuilt kit. I already replaced the floats not to long ago, but now want to do all o-rings, diaphragms, gaskets, etc.

    Brook, I read the thread on your website, and I will be doing something like you did. Do you have any recommendation for a good rebuilt kit? Looks like you used Hucky's?

    Thanks, Olaf
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  5. #65
    Liaison 20774's Avatar
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    I've always bought my kits through Bing in Kansas. I understand that sometimes the kits might be cheaper thru a dealer.
    Kurt -- Forum Liaison ---> 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. #66
    B Reams brook.reams's Avatar
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    Quote Originally Posted by anotherbmw View Post
    I decided to rebuild my carb since it had some issues and was wondering where to shop for a rebuilt kit. I already replaced the floats not to long ago, but now want to do all o-rings, diaphragms, gaskets, etc.

    Brook, I read the thread on your website, and I will be doing something like you did. Do you have any recommendation for a good rebuilt kit? Looks like you used Hucky's?

    Thanks, Olaf
    Olaf,

    Euro Motoelectrics provides kits at a good price. I don't buy rebuild kits from Bing as they are too expensive even compared to what you pay over the counter at a BMW dealer.

    I hope that helps.

    Best.
    Brook Reams.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1973 R75/5

  7. #67
    Thanks Kurt and Brook. I think I am going to only buy the O-rings and gaskets, since my floats are new and the diaphragms actually look pretty good, after I took a second look. That keeps some beer money in my pocket!
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  8. #68
    Just a quick update, and the final one on this thread, I promise!

    I disassembled the carbs, but the new o-rings in, cleaned everything, blew through every opening with compressed air, and put it all back together. I didn't find anything that was wrong, except that some of the o-rings looked a bit "swollen". Bike runs great in mid range and WOT, however I cannot seem to get the idle lower than 1,500 though. It does not seem to be one of the obvious things. I made sure I have lots of slack in the cables, completely turned out the idle screw, but that's not it. I also tested for air leaks by spraying starting fluid around the carbs when the engine was running.

    I was pretty busy, it's raining like crazy and I sold my other /5 last week, so haven't investigated any further. I'll start a new thread if I can't figure it out :-) Hang in there everyone and stay healthy!
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  9. #69
    Liaison 20774's Avatar
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    I think you should start over on a carb sync. The mixture probably is not right.
    Kurt -- Forum Liaison ---> 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. #70
    Registered User Guenther's Avatar
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    The idle screw should only be out ~ 3/4 turn. Other check points for idle RPMs: check the timing for the 'S' mark on the fly wheel.

    Check the seat of the diaphragms by checking that the pistons are in the correct direction looking into the input side of the carb.

    Check that the enrichers do close completely.

    /Guenther
    2017 F700GS

  11. #71
    Thanks, I know I need to check some more basic stuff, just got it back together and then I was sidetracked. Hopefully I'll have some good news ion a couple days!
    Olaf - Austin, TX MOA #200565
    Current bikes: 2016 R1200GS, 2 x1973 R75/5 www.R75slash5.com, the Toaster is for sale!

  12. #72
    Registered User STEVENRANKIN's Avatar
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    Points

    My R75/7 used to give me fits in that I was forever adjusting points on it, It would go from them opening to closing. Of course, this changes the timing.

    As you say, the basics; valves, points/timing, carbs. in that order.

    Oh yes, check for a vacuum leak, could be a loose rubber sleeve between the carb and head.

    It will be something simple, just frustrating. cheers St.

  13. #73
    Beemermark
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    Quote Originally Posted by ebeeby View Post
    Just me and YMMV, but my first rule of trouble shooting on an airhead is to throw the battery in the Mississippi River and start with a new battery.
    Truer words never spoken. A few years ago I had to replace the wiring harness on my R100RS. Typical project, probably took a year. Bike had a newish battery when I started. After everything was hooked up and bike wouldn't start. Not even try to turn over, just click, click. Battery was kept on charger and measured a good 13.5 vdc. Clock, voltmeter, lights, all worked. Hit the starter button and click, click. Spent the next 2 or 3 months troubleshooting. Battery always read 13.5 vdc.

    Finally got smart. Put the multimeter on the battery terminals and hit the start button. Voltage instantly went from 13.5 to 0.0 vdc.

  14. #74
    Quote Originally Posted by beemermark View Post
    Truer words never spoken. A few years ago I had to replace the wiring harness on my R100RS. Typical project, probably took a year. Bike had a newish battery when I started. After everything was hooked up and bike wouldn't start. Not even try to turn over, just click, click. Battery was kept on charger and measured a good 13.5 vdc. Clock, voltmeter, lights, all worked. Hit the starter button and click, click. Spent the next 2 or 3 months troubleshooting. Battery always read 13.5 vdc.

    Finally got smart. Put the multimeter on the battery terminals and hit the start button. Voltage instantly went from 13.5 to 0.0 vdc.
    Starters need amps, not just volts.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  15. #75

    re: charging issues

    Wouldn't be the first time someone mixed up the Df and D- brush connections or did not install the insulating washers correctly, etc.
    If the D- and Df wires from the harness are not connected, and a the brushes are insulated by an added piece of paper at the two brushes....then there must not be 1 ohm between Df and case ground. The reading should be approx. infinity.
    BTW....there are two types of brush-holders and brush holder mounts. On one type the D- is case grounded directly by the design of the mounting post.
    Snowbum

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