88jog
Scoot Junior
Posts: 11 
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Post by 88jog on Jun 16, 2018 20:48:39 GMT -5
I have 1988 Yamaha Jog cg50. It's has the typical speedometer that was on all Jogs and Razz's of the time period. It has an inner half circle of numbers that show kph, and an outer half circle of larger numbers that show mph. For some reason, my speedo indicates kph on the outer ring of numbers. So if I'm going 20mph (verified with GPS) the speedo says I'm doing ~32mph. And if I'm topped out at 43mph, the speedo needle is bottomed out against the bottom edge of the instrument cluster.
I thought that maybe someone had changed the speedo drive gears in the front wheel hub, so I went to a salvage yard and got a different set. I opened up the hub and got ready to put them in, only to discover that the new gears were exactly the same as the old ones. The large plastic gear is 14 teeth, and the small metal gear that the cable plugs into is 8 teeth.
I did repair damage from a crash about 20 years ago, but the instrument cluster is original. I guess it's a possibility that the speedo is faulty, but I have a hard time believing that it broke in such a way that it is perfectly functional, only that it now shows kph.
What the heck is going on?
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Post by 2stroked on Jun 16, 2018 21:21:17 GMT -5
This is new? As in, his hasn't happened before now?
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88jog
Scoot Junior
Posts: 11
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Post by 88jog on Jun 16, 2018 21:44:10 GMT -5
When I was using the scooter in college it did not have this problem. But this problem has been around for quite a while. To the best of my memory, it was probably since the rebuild that the speedo has been misbehaving. The reason I'd like to fix it is that I'm fixing the scooter up for my nephew to use in school, and would like to get everything operating properly.
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Post by 2stroked on Jun 16, 2018 22:15:14 GMT -5
Since its measuring KM not MPH it does seem Luke the gears are off. Its entirely possible that the gears in yours and the junker are both metrics. Do some Googling. See if the metric/standard gears differ....
Edit: when you rebuilt it, did you by chance change the tires? The front tire could be a different size from what is called for.....
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88jog
Scoot Junior
Posts: 11
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Post by 88jog on Jun 16, 2018 22:19:19 GMT -5
I had a local shop look up the speedo gears. 14 tooth and 8 tooth are correct. I can understand if a tire change altered the indicated speed by 10%, but not by a factor of 1.6. Plus, if the tires were oversized, the indicated speed would be lower than actual, not faster.
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Post by 2stroked on Jun 16, 2018 22:21:01 GMT -5
Then its a fundamental error somewhere. If its not the gears, not the tires, and its not normal, then something bad has happened during rebuild......
I know some older scooters speedo is strictly in kph.
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88jog
Scoot Junior
Posts: 11
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Post by 88jog on Jun 17, 2018 0:06:50 GMT -5
I'm thinking maybe I need to crack open the speedo. It works when the scooter is off and I spin the front wheel by hand. I'm thinking its the magnetic type. Maybe theres something in there that is causing the needle wheel to spin faster than it should. Maybe the magnet is too closee to the aluminum pickup or something. Or a cobweb causing drag. There's also a spring that works against the magnet rotation and returns the needle towards 0. If that spring is weak, it would cause a higher indicated speed.
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88jog
Scoot Junior
Posts: 11
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Post by 88jog on Jun 17, 2018 14:12:31 GMT -5
UPDATE:
Well, it turns out that the speedo DID break in exactly the right way that made it display kph. I actually tested the odometer, and it was properly clocking miles. I opened it up and sure enough the clock spring was corroded, and since rust doesn't spring like steel does, the spring was weak and allowing the needle to turn farther than it should.
Now I just need to track down some sort of replacement unit.
Can anyone recommend a slick aftermarket unit that displays speed, odo, turn signal, fuel, high beams, and oil?
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Post by geoffh on Jun 17, 2018 14:51:15 GMT -5
where abouts are you located.Someone may have a used one available.
geoff
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88jog
Scoot Junior
Posts: 11
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Post by 88jog on Jun 17, 2018 15:01:08 GMT -5
I'm in the Madison Wisconsin area, which is fortunate because it's a college town with a large campus and about 45,000 students. Scooters everywhere. But this scooter is old enough that I'm having a lot of trouble, even at the two salvage yards.
A few other parts I need, in case someone sees this.
* Center stand. This seems to be just about unobtainable.
* Headlight. My high beam is burnt out. It's a stupid sealed beam unit, and I refuse to pay over $100 for a NOS unit. Is there a high beam relay or could the switch be bad? I suppose some work with a multimeter is in order.
* Fairing pieces. They are sort of cobbled together now with rivet repairs and such. 30 year old plastic is just not strong anymore.
* Front fork. The current one works, but it was straightened after crash damage, and is still slightly wonky.
* Disc brake conversion. I'd love to find a European spec front end, or something that's compatible that would let me run a front disc brake. The scooter has been modified enough that it now does 43mph and the brakes are lacking.
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Post by geoffh on Jun 17, 2018 15:11:27 GMT -5
1 for sale in the UK £25 2vk-835100-00 it,s on e bay number 263754209771 it,s N O S (new old stock)if they won.t ship to USA
I can help.
geoff
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Post by hamodyjog on Jul 11, 2018 17:20:42 GMT -5
Can i see your bike please?
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Post by geoffh on Jul 12, 2018 15:50:19 GMT -5
I,d love to oblige but windows updated and now my computer will chat to my phone but won,t load photos,it can see them on the computer but they seem to be having "issues" my grandson is due at the weekend to help out.But why an 88 jog is an 88 jog
geoff
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