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Not convinced it’s running right…

The place to discuss the R 90 S as well as the R90S Worldnet archives!
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schrader7032
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Re: Not convinced it’s running right…

Post by schrader7032 »

Until you have located the problem, don't run the speedometer with the needle flopping around. You'll do more damage and the costs go up dramatically.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

Thanks, Kurt. I think I read that somewhere on another thread also. My intention is to ride it once more, if it EVER stops raining, and see what happens. I’m still kinda baffled as to why it works great hooked up to my drill and flops all over the place when riding. I’m thinking it MUST be something in the transmission, and I REALLY don’t want to pull that thing apart if I don’t have to.

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

I can tell you now from experience your speedometer problem is NOT a transmission problem. There is nothing in the transmission that will cause your problem unless your transmission is total trash, then you would not be able to ride the bike.

Everything inside the transmission that runs the speedometer is bullet proof. LOL, of course you could have a one and a million bike.

Seat the cables, try it, if not, put a new cable on, then if all else fails repair the speedometer.

FYI, I had a long argument with a fellow who ran his speedometer on a drill a long time ago, it worked fine until he rode the bike. in his case, the speedometer was fine, the cable was not. Remember when you have the cable off and hooked up to a drill, there is a chance you have taken one of the bends out of the path it follows and now the cable is not rubbing on the inside of the sheathing.

Yeah, I can't stand it when it rains and I need to check out a repair. I have that going on here today, I haven't ridden in two weeks due to a wiring problem on both of my bikes, now I have one sorted, it is raining. St.
Owner of a 84, R80RT and 78, R100RS

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

To add, the insides of the speedometer is two parts, the odometer which is all gears and interlocked and the speedometer which is part gear drive and magnetic drive. The needle itself is not connected to anything except a hair spring that returns it to zero when the magnetic disk is not spinning. From what I gather, the tension on this bloody hair spring is what determines the speed calibration, and in my past experience the steadiness of the needle at speed.

It is possible to have a properly calibrated speedometer for speed have a needle bounce plus or minus a few mph. I had been in a long email debate with two of the repair shops as to why it is from the factory the needle is steady and why after sending it in for repair and calibration it bounces plus or minus five mph. I never got a satisfactory answer. Experiments on a 85mph BMW speedometer I had in my tool box in my mind points to the hair spring on the needle being the problem. Too tight and speed is off when riding, too loose, the needle bounces.

The last guy to repair a speedometer for me claimed his bench test after repair showed a steady proper calibrated unit. I was going to send him a video of my needle after he did the repair bouncing at 60mph. I never got a camera mounted to record and found a new old stock speedometer at Bob's for sale. Rather than shipping a unit back and forth and messing about, I installed the nos unit when I rolled over another 100K and the odometer was all at zero. I have been happy since.

St.
Owner of a 84, R80RT and 78, R100RS

Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

I’ve seen the speedos jump 5-10 MPH, on YouTube videos, and that is annoying enough, but mine was like I say, from 30 to 120. I do see what you mean about the spring being weak though. I’ve noticed that just running it in the garage if I rev it up the needle jumps a little bit. Like maybe a VERY weak spring.
Maybe playing with the cable made a difference… one can only hope something would be so easy!

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

LOL, sorry I am such a pain, but go with the easy cheap stuff first.

LOL, I sacrificed that BMW 85mph speedometer for answers. I never did get it to work right and further experimentation has left it a collection of parts in my tool box.

I did forget to mention aside from the gear drive for the odometer part, there is a worm gear in the speed part that spins on of the magnetized discs. It could be the lubrication in it is dry, I strongly advise not trying to take it apart your self.

They can be repaired. I wish I could be more help. St.
Owner of a 84, R80RT and 78, R100RS

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Re: Not convinced it’s running right…

Post by Workinman »

You’ve been a big help! Another thing I was curious about is the fact that I think I read somewhere that these bikes came with the dreaded 85MPH speedometer. I actually thought that happened later in the 70’s, as my 77 Wing has a 140-150 MPH speedo, and my 1980 CB750F has the 85. Did these bikes, in fact, come with an 85 and mine has been replaced? Just curious.
Thanks.

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Re: Not convinced it’s running right…

Post by Workinman »

I’m also thinking that if I can’t get this speedo to act right, and it turns out that a new cable doesn’t help, I’m considering mounting a small aftermarket GPS speedometer somewhere up there that doesn’t cause any damage to the bike, such as drilling any holes, and that can be easily removed should the need be. I won’t be setting any land speed records on this bike, so the speedo isn’t really that crucial, but it IS nice to know what ballpark you’re in.

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

LOL, your R90S never was equipped with the dreaded 85mph speedometer. To be honest, I can't even recall how it was I came to have one myself? It may be possible that it came on a 79RT I bought for a parts bike years ago.

As for what years they were installed, well it would be the time of the country wide 55mph speed limit. My teflon memory has lost the dates.

They work the same as their bigger number brothers and I have no desire to have one on a bike I own, so, it made the sacrifice in the name of learning.

There are all kinds of GPS speedometers in the aftermarket, if you choose that path. Hopefully, you don't. St.
Owner of a 84, R80RT and 78, R100RS

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schrader7032
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Re: Not convinced it’s running right…

Post by schrader7032 »

I had heard that the 85 mph speedometers were actually more accurate.

Anton posted on ADV that 85 mph speedometers were US law from September 1979 to October 1982.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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