Couple issues, maybe normal

[hadabadachada]

1978 R100/7 manufactured 10/77
So I’m getting this basket case moving. Getting carbs balanced and what not. Been taking it out on 5-10 mile rides a few times a week. Maybe all these things are normal but,
Still have this rough spot, in the 2500-3000 rev range and a lot of engine noise, kinda clunky. Sounds kinda loud but it could be normal potentially. Let’s see if I can post it.
Also noticed, trying to rule out the clunk as clutch noise, that when I pull the clutch, the revs drop about 100 or 200 rpm causing the charge light to come on. Seems like that’s kinda normal from what I’ve found online, maybe? And the clunk is still there, more than clutch clunk.

I also notice that while riding, coming up to a stop or just slowing, let off the gas and pull the clutch, the revs seem to drop pretty slow. But maybe that’s normal too??

Another thing is electrical. Guess I need to learn about that but, when I turn the ignition from off to park, all the lights come on, when I click it to ignition the headlight, the speedo light and the left turn signal turn off. Gonna have to research I guess. Hard for anyone to give an idea other than, check the wiring.

[melville]

My 1978 R100/7 has some vibes under load under 3K rpm. But I'd also found that it doesn't charge consistently under 3K rpm--when my son was a new rider I was shifting at 3K to keep him in the mirrors. This eventually drained the battery.

So for both those reasons things are much better over 3K rpm. And yes, the charge light should be flickering at idle.

[Kurt in S.A.]

Charge light flickering at idle suggests...to me...that the idle is too low. You might be sacrificing bottom end lubrication at low idle RPMs.

Kurt

[hadabadachada]

I gotta find someone else down here with a similar bike to have a feel.
Ya know, maybe it really is all the fairing. It has a big wind jammer fairing that I can tell is heavy, but maybe it’s amplifying the vibration, and maybe it IS the noise. I’ve tried grabbing and palming all over every part of it to try to silence or stop any noise or vibration, with no noticeable difference.
I’ll have to pay more attention to that.

Was going to open the heads and re adjust rocker play again with a better clamp, maybe that quiets it more. Just sounds more central. To me.

I mean I’ve ridden an r1100s and the r1200r for almost 10 years, obviously they are much newer and smoother than a 78, but it just seems a little extreme the noise and vibes, but maybe normal. I’ll have to upload a clip, I forgot.

What’s the most agreed on idle rev range for an r100/7 with electronic ignition?
Maybe I just up it to 1200, or is that where it SHOULD be? It’s sitting at 1000-1100, so when I pull the clutch and the revs drop to 800-900, the light comes on.
Seems like a lot of people on the net say it’s relatively normal for the revs to drop 100 rpm ish, but that 200 could mean something?
I’m not afraid to ask stupid questions, I just mix it in with a whole story.

[Kurt in S.A.]

I'd run closer to that 1200 IMO. How many miles on the /7 engine? Maybe pulling in the clutch is putting pressure on the end of the crankshaft, causing drag some. Worm out main bearings?

Kurt

[hadabadachada]

That’s the thing, original owner, who I bought it from said he got it new back in 80 from his dealership friend who had it left over still in the crate and that those are original miles, which is 25,000km. So assuming honesty, very low miles.
I don’t have any reason to think he’d lie, and parts of the bike do look pretty “young” so to say, but other things make me question. But then again, it is still 40+ years old regardless of miles.
So I’d like to think it truly has low miles, and he just didn’t treat it well, rather than, “I’m gonna tell this guy it has 25,000 original kilometers even though it’s 125,000, he will never know”
Just have no way to really know if it’s mileage or just bad storage over 40+ years.

[hadabadachada]

AH HA!!
Went for a longer ride today, just feeling and listening, and seeing. I saw something that makes things make sense…
The odometer doesn’t work! So WHO KNOWS how many miles are on it! Wasn’t running when I bought and he kinda pushed that it was, low mileage! And I’d assume if I called and asked when the odometer stopped working, he’d say it worked.
It makes sense some of the things I was seeing, it must be double the mileage I’d say, at least.
So I guess there could be more of a chance of some potential, higher mileage, internal issues that maybe wouldn’t be on a 24,000km bike. Worn bearings or something.

[barryh]

Worn bearings or something.

Assuming the speedo works proving the cable drive is ok, then the usual cause of the odometer not working is a gear wheel slipping on it's shaft. It's a common enough fault and has been discussed on various airhead forums.

Mine only slipped when it got hot due to differential expansion of the pot metal gearwheel and shaft so I caught it at an early stage and managed to fix it by sliding the gear wheel to one side, cleaning the shaft with alcohol, applying some epoxy resin to the shaft and sliding the gear wheel back over the resin

Here's one example of a more involved fix that clearly shows which gear wheel slips.

https://forums.bmwmoa.org/threads/77-r1 ... 552/page-2

[melville]

Yes, I'm at two odometer failures now. I've got a guy who fixes that problem, restores the housing, and recalibrates the speedo so it's within 3% of actual, instead of reading 10% to 15% high. Old stuff doing old stuff things!