messed up Tomos speedometer

the speedometer on my tomos gold bullet TTLX is messed up, up until about 30mph it reads fine, then when i get around 35, it DROPS down to about 20-25 suddenly and sits there wiggling around. ive replaced the cable and drive unit, so i know its gotta be somthin with the guage itself, is somthin worn out in there? the bike only has 1887Km on it, so i find this hard to believe. by the way, the speeds are in MPH, but the odometer on tomos bikes reads in Kilometers. unless these speedometers are total crap (which wouldnt surprise me) what the F*$& is wrong with it?

-Garret

Re: messed up Tomos speedometer

chuck russo va /

i had an a3 golden bullet lx that did the same thing, the whole thing itself was a trud so i sold the bike on ebay it was a strait up lemon

Re: messed up Tomos speedometer

Kate Kleiter /

Hi Garrett.

I have a Tomos 2000 Targa and the speedometer just broke a couple of weeks ago. I didnt know that the odometer was km. I took it apart and it worked for one run, then it broke again. I am going to buy a new speedometer, then Im going to cut open the housing to see why it broke. Let me know what you do. Thanks.

Kate

Re: messed up Tomos speedometer

Ron Brown /

Kate,

You say you "took it apart" and it worked for one run. I assume you mean disconnecting the cable.

Before replacing the head, disconnect the cable at the head and spin the speedo shaft wit a small screwdrive. If the pointer moves, check the cable and drive unit on the wheel. Sometimes, as simple as a rounded, or too short cable end will stop the speedo.

Ron

Re: messed up Tomos speedometer

Hi Ron,

Yes, thats about all I did was disconnect the cable. Also, took the whole thing off the bike and tried to pry open the housing but couldnt do it. I will try to do what you suggest and see how that works. Do you know where I can read up on how the speedometer works. Maybe I need a new drive unit because it is making this clicking noise.

Thanks. Kate

Re: messed up Tomos speedometer

Ron Brown /

Kate,

Which end makes the clicking noise? If it is the wheel, your drive is probably frozen. The unit on the whhel contains a "worm" drive. One gear rotates with the wheel and is keyed to it by two thin metal tabs. This gear drives another, in line with the speedo cable. Often, these gears freeze from lack of lube and the key tabs that drive it bend, slip and make a clicking noise. You can often just clean, lube and staraighten them.

Take of the front wheel, making sure you keep track of all the spacers washers and any seals. If it is bad, the problem will be obvious. While you are in there, check the front wheel bearings, they like to be lubed too.

Ron

Re: messed up Tomos speedometer

i noticed today that when the speedo needle starts looking like it has parkinsons syndrome, i feel an odd vibration in my handlebars, im gonna try to test the speedo and cable with a power drill, im thinking the cable may actually be too LONG, even tho the guy at the shop said it was the same for all tomos 'peds, regardless of year. im thinkin it might be that its length is makin it curve too much and making the cable rub against its housing, and thus twisting and giving me that odd vibration. if anyone has an a3 with its original speedo cable, PLEASE measure it for me, im almost sure mines too long.

why im so sure, is that ive replaced the drive unit, and cable, when i got the bike the original cable had snapped. and ive tested the speedo with a small square drive (roberts head) bit in a power drill, so i know its ok, and that damn drive unit is BRAND new, its gotta be that bastard cable.

-Garret

Re: messed up Tomos speedometer

Ron Brown /

Garret,

Don't discount engine vibration from your equation. I have a motorcycle with a speedo and tach that do strange things at certain engine rpm. Try using you left hand on the speedo to damp out the vibration and see if it improves.

Ron

Re: messed up Tomos speedometer

david f martin /

Wow. Makes perfect sense, but I wouldn't have thought about it before... I've worked on VW speedos and have a pretty good idea how they work, but they aren't subject to the kind of vibration a moped has, and that might definitely have an effect on them.. Good thread.

david

Re: messed up Tomos speedometer

today i went and took out that cable, and FLIPPED it around, and VOILA, it works ok, not GREAT like my neighbors Tomos A3's speedo does, but decent enough, still does the weird thing at high speed tho, & it aint vibration it actually happens when the bike vibrates the LEAST, oh well, ill keep working on it. ripped one of the spade lug terminals from my left front blinker wire while tryin 2 re run the cable back in, gotta go2 the auto parts store and get some more tomorrow. when i rebuild that engine, im gonna put a brand NEW 0 mile speedo on that bike, im starting to suspect the actual guage itself is shot, CEV isnt known for quality manufacturing.

-Garret

Re: messed up Tomos speedometer

Ron Brown /

Garret,

If your neighbor has a ped with the same speedo set-up, Swap cables as a test.

Btw, "& it aint vibration it actually happens when the bike vibrates the LEAST", this is a dumb statement. Vibrations often affect things based on frequency, not amplitude. If you have done the "damp it with your hand test" and nothing happened, then you are right, but for the wrong reason.

Ron

Re: Who needs a speedometer

You're going a little faster than the Bicycle you just passed, but not as fast as the SUV on your ass.

I have one moped qt-50 with a working speedo and one with no speedo.

Although I know exactly how fast I am going, I still look at the broken speedo.....

Yes--- my cable makes a clicking sound just about the wheel... I think the cable snapped and the two ends are attacking each other.... so to speak.

This is a Yamaha, not a Tomos, but the principles must be similar.

When and if i sell one of my bikes.... Make sure you buy the one with the low mileage (only 171 miles) and I'll throw in a bridge/w tollbooths!

Re: Who needs a speedometer

david f martin /

The speedo on my QT read high, til it started bouncing around and finally quit... I never got a chance to fix it before it got stolen, though... The speedo on my Elite seems to be fairly accurate.

I'm not sure how the speedo works on a moped, but on a VW, the cable turns a magnet which moves the speedo needle. If the cable gets in a bind and moves in a jerky fashion, this will wreak havoc with the needle. Either it will read high, low, or jerk the needle around. The kind of resonant frequency Ron is talking about is when engine vibration frequency and cable jerking frequency start affecting each other.

I'm thinking about mounting the headlight and speedo from a PA50I to my Elite, and I'll have to figure out how to recalibrate the speedo for the smaller front tire...

david

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