Speedometer

Speedometer won't pass 20mph

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white1j0
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Speedometer

#1

Post by white1j0 » Fri Jun 22, 2018 10:07 pm

Bought an original '47 speedo from a re builder, and it won't go past 20 mph, sent it back and he checked it on his calibration machine, ran it up to 75 mph, he said it worked fine, I have the correct 11 tooth worm gear on the drive, he text me back and asked me to try a different speedo before he disassembles it, the problem is I have another '47 Knuckle and a '52 Pan both have after market speedos with male connections, also the trans is completely rebuilt, So i'm looking for someone in my area Bucks County Pa.that may have any speedo with a female connection that would be willing to rent it for a couple hours, or any other suggestions, You can PM me, Thanks Whitey,



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Re: Speedometer

#2

Post by Andygears » Sat Jun 23, 2018 12:44 am

Maybe the cable? The square worn rounded or shortened where as the resistance increased, it rides over the square. Maybe disconnect the cable at the speedo and tape it to the shift gate, ride it and see or feel if the inner keeps increasing RPM's.

All I got
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white1j0
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Re: Speedometer

#3

Post by white1j0 » Sat Jun 23, 2018 1:08 am

Cable is brand new exact replica of original bought from the same re builder

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Re: Speedometer

#4

Post by RUBONE » Sat Jun 23, 2018 1:37 am

Put the speedo and cable on the '52 and see if it does the same thing. Are you sure the gear in the trans is correct, not just the drive worm, but the spiral gear?

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Re: Speedometer

#5

Post by ozwick86 » Sat Jun 23, 2018 6:16 am

Who rebuilt the your speedometer?

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Re: Speedometer

#6

Post by white1j0 » Sat Jun 23, 2018 1:19 pm

Actually, the speedo is original and was bench tested before I bought it, and didn't need rebuilding, right now I can't exchange it to another one of my bikes for testing, beings it is at the re-builders, also it has the correct worm gear, 11teeth, which if was the wrong spiral in the trans, they wouldn't mesh, I'm going to try to make an adapter to adapt the inner cable to one of the aftermarket speedos, I'll see how that works

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Re: Speedometer

#7

Post by Buddhahoodvatoloco » Sun Jun 24, 2018 7:55 pm

Put a drill to it, and if it spins up past, say 50mph, your challenge is else where.

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Re: Speedometer

#8

Post by white1j0 » Sun Aug 05, 2018 1:42 pm

Still haven't ironed out this speedo problem, still won't go past 20 mph, I was told by the re builder not to put a drill to it, anyone know a reason why, I would like to try using a drill to spin the cable,to see if the speedo registers past 20 mph but I don't want to damage the speedo or new cable

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Re: Speedometer

#9

Post by 1950Panhead » Sun Aug 05, 2018 3:49 pm

Drills spin clockwise, you need counter clockwise, some drills have reverse, 1000 rpm=30 mph on knuckle speedo.

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Re: Speedometer

#10

Post by white1j0 » Sun Aug 05, 2018 9:07 pm

1950Panhead wrote:
Sun Aug 05, 2018 3:49 pm
Drills spin clockwise, you need counter clockwise, some drills have reverse, 1000 rpm=30 mph on knuckle speedo.
Thanks Panhead, speedo is working fine, must be an issue w/ the drive

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Re: Speedometer

#11

Post by white1j0 » Tue Oct 09, 2018 3:22 pm

Speedometer still not working, I came to the conclusion that the drive gear in the trans is wrong, looking down inside the opening where the speedo drive goes it looks to me that it has 7 teeth, which according to Bruce Palmer is correct, but according to the speedo restorer I bought the speedo from, it should be a 4 tooth, I pulled the drive from my '52 Pan and it looks to have 4 teeth on the trans gear, and 11 teeth on the drive gear, and all though it's a repop it's pretty accurate, so who is correct ?

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Re: Speedometer

#12

Post by VPH-D » Tue Oct 09, 2018 6:31 pm

The speedo will work, but read incorrectly, with mismatched drive gears.
VPH-D

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Re: Speedometer

#13

Post by 1950Panhead » Tue Oct 09, 2018 8:18 pm

so who is correct ?
All knuckleheads use 7-tooth drive gear and 11-tooth driven gear
The driven gear can wear in the center and mesh poorly or not at all, post a photo if you can.
Put bike on rear stand, rotate rear wheel ten times, count rotations of driven gear, report back here.

The 4 tooth drive gear was used from 62 to early 69, every speedo rebuilder knows this.
A fine 7 tooth drive gear was used from 69 to 80, the knuckle drive gear is coarse.

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Re: Speedometer

#14

Post by white1j0 » Sat Oct 13, 2018 3:29 am

Pulled the transmission today, removed the top, the drive gear seems to mesh properly with the spiral gear, as far as the teeth on the spiral gear, depending how you count them, it could be 4 teeth or 6 teeth, I turned the gears and the speedo gears seem to work fine, if I grab the female end of the drive gear with a needle nose to keep it from turning, I'm not able to turn the trans gears, also the spiral gear is tight it's not slipping, which is what I expected to see, Also I have an original Knucklehead Service Manual, and they have a picture of the trans. showing the gears and the drive and spiral gears and it looks like 4teeth ? Check the photos out and let me know what you think.
Attachments
speed gear.JPG
speed gear.JPG (225.2 KiB) Viewed 286 times
drive gear.JPG
drive gear.JPG (232.35 KiB) Viewed 286 times

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Re: Speedometer

#15

Post by 1950Panhead » Sat Oct 13, 2018 6:11 pm

Looks like 69 to 80 drive gear.
You need -
7-tooth drive gear #35635-36
11-tooth drive unit #67130-36 (1.57, 2000 rpm)
https://www.ebay.com/p/7-Tooth-Speedome ... /654721423
https://www.ebay.com/itm/SPEEDO-DRIVE-U ... :rk:1:pf:0

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