Wow, good write-up on that. I think I'm going to try that out. None of that work scares me, I need to change my oil anyway, and I am building circuit boards at work right now. Thank you for finding this and pointing it out. It looks like some of the parts have been replaced in Digi-key by more modern parts. I'll let you know how it goes after I've done it if you're still wondering then.

Dan

Edit: I spoke with one of the engineers here at work, and they are baffled that the design even works. They said you can't tie together the outputs of the 7400 series IC's like that. So, he's going to take a look and come up with something a little different.

Along other lines, I think I'm at least going to do the mod to the sensor, cause then I could hook up to a air to fuel ratio meter with the meter being able to graph what's going on for what engine speed, AND what gear it's in. Given that info, I might be able to figure out exactly what the CDI is doing as far as different mappings, which is why I'd guess that the original sensor has contacts other than neutral. With that info, I'd be able to create my own mappings if I wanted to get one of those reprogrammers that are too expensive, or the Dyna ignition and do my own programming to it. Then again, that would be a waste of time and money just so I could be that much of a geek. It would be fun to play with though.

I've always wondered if the gear indicator "puck" from like a '82 Suzi GS450L would fit in the Kat. if i remember right it looks about the same size, and already has all 7 pins wired in place. could just get the gear indicator light setup off the dash of the 450L too and darn hear have "plug and play"

Well, adding the wires and contacts to the sensor doesn't seem that bad to me. Maybe it's just me, but so far, the most difficult part of this job seems to be getting the original silicone off the back of the sensor. That is nice info about the drop in part for the display itself. I'll have to do some research into that.

It does seem a little odd. It was only done when the output from the 7404 was not fanned out, so it may be the case where it works with the particular model of 7404/7432 used. It's supposed to work like an OR gate, so if you wanted to be safe, you'd need a second 7432 so you could replace those junctions with OR gates.

I also don't understand why inputs 2 and 3 don't have pull-up resistors like all the other inputs. The design expects them to float high, but it seems odd.

EDIT: An alternative to two 7432 chips is to switch to 4000 series parts and use a 4075 (triple 3-input OR gate), which would give you exactly what you need.

or just throw on an 80 cent micro :P

Super write up, thanks. Now I have something else to add to the list

I ended up having oil leak issues after some time with my modified sensor, I have since purchased one for an 86 GS that's a perfect fit.

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Are you saying the sensor off an 1986 gs (engine size?) will fit a 1994 750 pre? That would sure save a bunch of time!

See this for sensor:

looking forward to astros!

OK I'll bite.

I copied and pasted this page into google and had them translate it as it's in spanish. I damn near peed my pants laughing. It's a great write-up but the translation is a RIOT!!!!!!!!!

Still anxiously waitin to see the reply about the GS puck fitting a pre 750 kat

I pulled my neutral / gear indicator switch and it has mounting holes 50mm apart and 36mm diameter where it inserts into the case.

There may be many older (early to mid 80's suzuki's) that had gear indicators with interchangeable neutral / gear indicator switches... I'm doing some research now...

It looks like the GS 1100/1150 part will bolt on (thanks Astro) but I'd like to check GS 550/650/750/850 parts too.