Have you checked the sender unit on the disc brake side of the front wheel? They can jam up, or the lugs can bend. This will then cause the sender unit not to rotate in unison with the wheel (if at all) giving a false reading. A pre-cursor to this is the needle bobbing about as opposed to maintaining a steady speed.

Not that I am aware of, will contact my local garage and see if they know anyone , failing that I will try and source a second hand one cheap.
Thanks for all the help,
if I ever track down the cause I will update.
:thumbup:Cheers Ian

A quick update, I decided to go the path of least resistance and try a new cable in case I was wrong. Sadly the speedo is just the same with the new cable. One of those occasions I would like to have been proved wrong.
As they say back to the drawing board. I will probably end up replacing the whole unit as I am not sure even with locating a source of the problem in the unit whether or not I could replace individual parts.
Ian

As far as i know you cant dismantle the speedo head. Looks to be a sealed unit ian. Someone on here will know for sure.

Bill

Hi Bill, someone before me has had the unit apart so I can separate had a mph face put on it, maybe that's what's caused the problem. I have had the bike for 6 months with no issues so seems unlikely, I have managed to source a second hand unit for £30 which seems reasonable so might just replace it.
Ian

I think that's easiest and most logical solution, fit the replacement and delve into the workings of the old one. You might be able to fix it and have a spare then. Did you manage to get one in mph?

Hi Bill, unfortunately not, this one doesn't sound like it's been tampered with has the stickers on the dial to show mph, not ideal, from past experience impossible to see in the dark, I will just have to learn the mental conversion again.
Unfortunately for me where I live we are inundated with speed cameras so I've become paranoid. I already have a good estimate of mph for gear and rpm.
Just one more thing to concentrate on. Hopefully as you say I may be able to repair the current one and refit.
Ian

Got this one, if you have one with km/h we can swap, i just like to have one for spare.



http://s21.postimg.org/5c65sshyf/DSC_0800.jpg
foto upload

I was keeping an eye out for one in mph's for you, no joy , (couple of kph ones.) it seems theyre as rare as hens teeth. And dont get me started on speed cameras!i

Or buy one of these, i can recomend its good quality.

Koso DB 01R Multi Function Electronic Speedometer | eBay

Hi xtrock definitely interested, I will need to get the replacement first, check it works , I assume it's the speedo that's at fault. Once sorted I will look at shipping costs and pm you if that is ok.
Ian

Shipping is insane here, checked and its 27pound...

Does the previous fit?

1984 Yamaha XT600 XT 600 Speedometer Odometer Assembly with Cable 84 - 89 | eBay

93 YAMAHA XT600 ENDURO 91? 92? 94? 95? 96? 97? SPEEDOMETER GAUGE GAUGES CLUSTER | eBay

And what about the DT speedo, looks like same size.

http://www.ebay.co.uk/itm/Yamaha-dt1...item4621e53aff

Maybe 350 speedo fits?

1993 YAMAHA XT350E XT 350 E XT350 SPEEDO SPEEDOMETER | eBay

When I got my bike it was already fitted with a Facomsa eSpirit digital speedmeter, I gather the original drive failed.

Facomsa

I highly recommend this unit, it's backlit, has warnings for high beam, neutral, indicators etc and is easily set up. I have a friend with a Koso, it even has a tacho built in, another excellent piece of kit. Sometimes it's better/cheaper to go for a new solution that is proven than keep replacing old parts in my opinion. I know this doesn't 'help' but maybe an option?