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Thread: 1990 R100RT Project Bike

  1. #1
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    1990 R100RT Project Bike

    1990 R100RT, Hooray it runs. The bike was my father's and it has sat since 2000. Had a tranny installed last fall. Rebuilt the carbs, cleaned the gas tank, relined tank, new Spingler brake lines, new battery with home made battery hold-down. Hit the starter briefly to make sure it would turn over, then cranked on it for a second and away it ran. Let it run for 30 seconds to circulate the fresh oil through the new filter then shut it off.
    One thing I noticed was the voltage was 12.1v, 12.2v at idle. At faster idle +3000 RPM it did jump to 12.6, RPM. My question is- should it charge at a little higher voltage? Is there anything else I should be looking for, or doing?
    Now I have to see if I can get the title and have it put in my name and register it.

  2. #2
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    Pretty anemic charging voltages at RPM. Was this a reading from the fairing voltmeter or across the battery posts with a good voltmeter? Until you see what's at the battery, you can't be sure. Did the alternator light come on with the key in, ignition on, but bike not started? If not, then you won't be getting any charging. Beyond that, you could have alternator failure or the brushes could be hanging up. You'll need to systematically step through the troubleshooting.

    Lube on the critical areas could be a consideration...did you lube the tranny input splines last fall? The rear wheel splines could use a check. Tires are probably too old to use. The '85-'95 transmissions will have an internal circlip missing...something to be on the lookout for, especially if more than the usual spooge shows up on the drain plug. Anton has a discussion about the circlip and what could (although not necessarily) happen.
    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!

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    Volt meter on the fairing was not registering correctly. I checked right at the battery and voltage was 12.5 at rest ant 3500rpm was charging 13.47v. That is good for me. Now that things are starting to come together I'm finding small problems. Rear brake switch is not working. Horns won't work.
    I would think that when the tranny was installed that they would have lubed the input splines. In any case I'm going to change the gear case lube just for the piece of mind. Oil is cheap as Dad would say.
    One other BIG problem- When I was checking the Owners Manual for lube content amount I see that Dad made a note that the Rear Swing Arm drain plug is STRIPPED. I now remember him having a fit when he serviced it himself AFTER someone at the dealership had worked on it. I got down to look at the plug and it looks like it was crossed threaded. It's not leaking NOW. What are my options If after I take it out I can't get it back in correctly?

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    Liaison 20774's Avatar
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    Quote Originally Posted by 1der View Post
    I got down to look at the plug and it looks like it was crossed threaded. It's not leaking NOW. What are my options If after I take it out I can't get it back in correctly?
    I would think that helicoiling will be difficult on the bike...mostly likely the FD will need to be removed to get good access to the hole. Also don't know if there's enough internal room to work.

    A couple of options that I might consider before diving in all the way. One would be to find a way to just pull out the oil through the fill plug...various methods can be found to get out probably 95% of the old oil I would think. Second would be to go ahead and removed the drain plug and if it is indeed difficult to fix it the right way for now, get a replacement drain plug and drill/tap it with another bolt. Then epoxy/JBWeld in the regular drain plug. You can then drain it using the secondary plug.
    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!

  5. #5
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    I tried to check the lube in the chamber and it looked clean. I like the first option of removing what I can and refilling. Sometimes it's better not to get to aggressive. Thanks for the info.

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