[ruckusman]

Thanks - probably a rabbit hole that I shouldn't venture down, any idea where I might get some sort of spec for the IC or method/instruction on how to put it into mode 0 and read the contents?

Now that I am wiser, I'll take another look at the TCI and see if there's a signal conditioner leading to that main IC for triggering.

It's all a learning curve...

[JHolland]

The HD6301 datasheet has all the details, the Denso (probably Toshiba made) version there is an extra timer and some more RAM. The same processor was used in the original Goldwing ECU that I did some work on here: https://github.com/RhinomanUK/ECU-Rever ... ain/GL1200
Other variants of these processors were used in many early Japanese ECUs and TCMs.

I have a similar project with an XJ600N TCI but, unfortunately, that has an old NEC processor that, most likely, can't be read so I am just going to replace the processor with a modern item and add a serial port. I will log the advance v RPM and TPS as a starting map but I already know that they respond well to more advance in some areas and transient corrections may be required.

Your connectors look a bit melted, did you heat up the case to get the board out? My board was glued in and wouldn't budge and I got frustrated with it and cut up the case.

[ruckusman]

Thank you for that tip - it took a few iterations of searching but I found some actual info on the HD6301 IC - pretty sure you're right that it's the one used as I did find a rather long thread on a Subaru forum delving into the ECU.

I found the HD6301 handbook - all 1,338 pages of it - that's quite some reading material.

That's not my TCI in the photos, just a picture I snagged from the 2fiftycc.com forum, although I have had mine open to replace capacitors, I used gritted teeth, stern looks and sharp objects to get mine open.

Quite a few of the Yamahas benefit from a wee bit more advance, ~4-5 degree offset woodruff keys are common with the FZR400 - I expect other Yamahas are similar.

When did the XJ600N get a TPS - I've got a '95 YZF600R that doesn't have a TPS, although I belive it was introduced on the '97 model onwards.

[JHolland]

I know its a It is a 6301 because I've worked with them in the past on other projects. Have you got a link to the Subaru thread? it might be of interest to me.
I don't know when they introduced the TPS, my XJ is a 2001 and that TCI (4BR-10) seems to go back a few years. I was a bit surprised that it had one with carbs, but then my 99 Triumph Sprint is full EFI.
There is a 4 deg advance trigger wheel for the XJ600, the reports on it are all fairly positive, which is what makes me think its worth experimenting with. Its no sports bike but if I could make it a little more economical and sort the dreadful on choke behaviour then I would be happy. I'm in the UK and our minimum octane is 95RON, which is way above the 91RON requirement in the owner's manual so I'm not too worried about pre-ignition.
I think I may have a TCI similar to yours, somewhere in my collection.

[ruckusman]

Here's the Subaru thread
https://www.ultimatesubaru.org/forum/to ... rimenting/

The HD6301 handbook
https://www.jaapsch.net/psion/pdffiles/ ... ndbook.pdf

Another HD6301 document
https://www.digchip.com/datasheets/down ... =HD6301V1P

The TPS dependent "3D" ignition advance curve on your XJ600n will be interesting.

Yamaha kept CV carbs for a few years more than some of the other OEM's - I recall seeing the 2003 R6 EFI throttle bodies that were OEM adapted/modified Mikuni CV carbs, with the CV slides, it's an interesting progression as then many of the OEM sportsbikes went to secondary throttle plates.

I don't know yet know the full control methodology of the secondary throttle plates

[JHolland]

That Subaru forum is a good find, the thread faded out without coming to anything but many of these ECUs have chips that don't have the manufacturer's markings on them and the HD46508 isn't a chip that I recall coming across in the past but it looks like a match for a mystery chip in the early Goldwing ECU that I have only partially reverse engineered.
The Subaru ECU uses a standard 6301 so it doesn't haver the extra timer.