Hi Neville, the hole goes through to the outside, so if you spray something in it it might help. I remember the first time i unscrew it, i made this kind of like round movement of the knob, small circles with out turning it actually, left turns and right and then it to let go. The small round part in the housing its made out of rubber.
Thanks! - I have sprayed some WD40 into the hole to try and ease the thread contact - good suggestion also to try and move the knob around in circles without turning it to also ease the thread - will try that as well.
Damn thing will still not unscrew - I tried heat, WD40, moving the knob around in circles but it still just "clicks" at the same point each revolution. I spent 45 minutes trying to work it loose with no progress whatsoever. I am increasingly worried that the original owner (pre 1985) might have removed the instrument cover when he fitted a badge to the forward face of the housing and may have damaged the original knob internals, so in some way bodged a repair by gluing the knob back onto the threaded shaft on the trip dial. This would fit with a few other bodges I found and had to repair.
I am increasingly thinking about the "nuclear" solution which is to buy a new reset knob and cut away the original in the safest way I can to avoid damaging the speedometer. I need to get a new knob first so I can measure it to work out the best way to remove it with my Dremel tools.
It would be really helpful if anyone has a photo of the internals of the speedometer - I can't find anything online?
Hi, if you've no options left than its better to cut it than break something inside while trying to unscrew it. Whatever happens just take you time you still got some options. Here is the knob (instruments section), and couple of pictures i got, nothing much usable but it will give you some idea. If you need than I'm willing to dismantle my tacho and make photos as guidance.
Thanks Daro, really helpful - yes, my main focus will be to cut away the end of the knob as gently as possible so I can extract the instruments from their housing. I have not quite worked out whether it would be best to clamp the knob in a makeshift vice whilst also supporting the housing and gradually drill away at the centre hole - using progressively larger drills to only take a small amount of material at a time - or to use a small Dremel high speed cutter and gradually nibble away at the centre.
I also saw that MCG sell a replacement knob so that was my first target purchase - I might also get the needles just in case as mine look a little frazzled.
I was interested in a picture so I could work out if it would be possible to remove the remainder of the knob once the speedo had been removed - I eventually found a picture on this site that looks helpful but appreciate your offer to explore further - I would not want to burden you with any dismantling of your own meter!
From the pic below it looks like a) the threaded part of the trip shaft is exposed sufficiently to remove any remnants of the knob and b) should be possible to grip the other end of the trip shaft to apply more torque to remove the remaining parts of the knob.
I also found a picture of a Suzuki GT750 speedo that looks very similar - maybe the same manufacturer?
Cut up a cereal box for a suitable size piece of cardboard, cut a slot and slip it over the reset shaft. It will act as a heat shield. Then - carefully - heat the knob with a hair dryer. The expansion should allow removal.
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !