OP
UTC

Enthusiast
PX Vespa 125
Joined: UTC
Posts: 70
Location: Moira
 
Enthusiast
PX Vespa 125
Joined: UTC
Posts: 70
Location: Moira
UTC quote
Why does my Speedo only Go as far as 37mph while my GPS is saying 45mph or more ?? I have changed out most parts clean and clean again ! But Hay it just doesn't work over 37ish mph New PX vespa with only 2000 miles on clock!! Any advice most welcome!! Best foot forward soulboy74 🇬🇧
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Addicted
PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
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Posts: 616
Location: UK
 
Addicted
PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
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Location: UK
UTC quote
it could be the incorrect number of teeth on the speedo drive worm but this would mean the speedo would under/overread and not stop at 37mph.

Or it could be something out of alignment in the speedo itself.

The speedo works with a magnet spinning against a springloaded metal disk that is attached to the needle. If the metal disk (or shaft its on) is out of true, it could be binding.

The other thought is that the spring pressure it too strong because the speedo has been apart and incorrectly put back together.
OP
UTC

Enthusiast
PX Vespa 125
Joined: UTC
Posts: 70
Location: Moira
 
Enthusiast
PX Vespa 125
Joined: UTC
Posts: 70
Location: Moira
UTC quote
Thanks for the heads up I think it most likely the second one you spoke about because that was something I was wondering about!! You see it took a nock in a previous life !! and the spring balance looking about right ! Thanks can it be repaired?? Or just keep it as ever think alse is working just fine !! I have started using GPS now and it's not too bad !! Best regards soulboy74
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PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
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Location: UK
 
Addicted
PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
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UTC quote
You'll probably destroy the bezel if you take it apart but you can get replacements.

Once the bezel if off you can take the screws out the back to get the case off and see the workings of the speedo.

Then its a case of manually pushing the needle/metal disk up to 37mph and seeing where its sticking. Then tweaking it so it doesnt stick.

So............... Probably more hassle than its worth if you are using gps.
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Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
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Posts: 1558
Location: Tucson, AZ
 
Molto Verboso
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71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1558
Location: Tucson, AZ
UTC quote
I had that issue on my P200E. It was my inner speedometer cable that was frayed. The speedometer use to work then use to stop whole you were still picking up speed then resume. Change the inner cable and put a new outer as well. You might want to look at the plastic gear at the hub as well.

I mean, it could also be a faulty speedo but I think nk the cable would be the culprit.
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Location: Planet Earth
UTC quote
Get drive worm, inner and outer cable (if yours is a disc brake you need the plastic clip in type for the speedo unit). Should be able to get the lot for less than 20 quid and easy to fit too. My px2003 speedo didnt work at all when i got it and it had 7000km on clock. Even when they are working, they dont read too great. The higher the speed, the more the reading is out, often overread by 10% when you get past 100kmh. Mine was showing 110kmh last friday, the GPS said it was 101, which is what, 60+ MPH.
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