Author Topic: Arktasian's 95 K75 on Microsquirt Mod Table  (Read 22190 times)

Offline Arktasian

  • ^ Proficient Motobricker
  • Posts: 116
Re: Arktasian's 95 K75 on Microsquirt Mod Table
« Reply #100 on: April 27, 2020, 01:15:18 PM »
Hello Ben,

Modifying the original Hall sensor cup with extra windows sounds like a marvelous concept. Yes, pretesting with your ecu is a needed step to ensure it will be stable right from cranking to top rpm's.
I don't have any photos here of the cam sensor I've rigged, but can describe it.  I abandoned the idea of adding or machining something to the rear end of one of the cams, and instead have located a VR sensor at the front timing cover that registers with the top cam gear. The timing cover doesn't have a "level playing field" so I fabricated a very small aluminum wedge to allow proper mounting angle and easy "one screw" retention. It isn't registering on the gear as such, but I've fashioned a stainless circular plate that sandwiches behind the retention bolt. I plotted sensor location in advance to jive with the hole circles on that gear and then have two allen bolts affixed to the plate at 180 opposing to maintain balance. One is ferrous (the signal tooth) and the other is 316SS (for balance). That plate is about 18 gauge, and the nylock nuts reside nicely on the back side within any given opposite gear holes. This allows a measure of adjustment on the single tooth which for the MS code choice requires that tooth not line up with any of the 12 crank teeth (the 3 cylinder design adds a level of challenge when you are seeking sequential ignition and injection - which I am). Sounds complex but actually very simple and minimal modifications to original kit and look.
I will post a photo of the set up when I have a chance.

Offline Arktasian

  • ^ Proficient Motobricker
  • Posts: 116
Re: Arktasian's 95 K75 on Microsquirt Mod Table
« Reply #101 on: June 27, 2020, 06:17:10 PM »
Covid driven news flash - placed an order with Motobins subsequent to scoring some funds helping a friend service his MCI motorhome conversion (I repowered it for him with a Cat 3406E "King on the Hill" some 18 years ago now). His rational is to vacation comfortably within BC given travel restrictions.
That effectively thwarts any excuses to "not be tinkering" on the K75  :nono2:

Offline Flatblackdime

  • Curious
  • Posts: 2
Re: Arktasian's 95 K75 on Microsquirt Mod Table
« Reply #102 on: June 30, 2020, 01:49:40 AM »
Why not make a 36-1 wheel at the camshaft location? You already have a sensor there and you won't have high rpm timing drift as it's chain driven. No need for any of the space limited crank sensor with a registered cam position.
  • USA
  • 1990 K75rt

Offline Arktasian

  • ^ Proficient Motobricker
  • Posts: 116
Re: Arktasian's 95 K75 on Microsquirt Mod Table
« Reply #103 on: June 30, 2020, 10:29:09 AM »
Why not make a 36-1 wheel at the camshaft location? You already have a sensor there and you won't have high rpm timing drift as it's chain driven. No need for any of the space limited crank sensor with a registered cam position.

As per Megasquirt recommendations, its best to avoid the jitter that may develop in chain driven cams and such, but more importantly, for a 3 cylinder engine which is a touch uncommon amongst the squirting community, and with a wish for sequential control, wheel and code options seem limited.
There is however a code variation that supports a 12 tooth with one missing on the crank, and a single tooth on the cam. That will allow the highest rpm's I'll be developing on this daily rider type bike.
But that's academic as I have the parts made and they were quite simple and inexpensive. I did a test of the VR sensors I'll be using on my test bench set up, and got the results expected.
Thanks for commenting. Are you an MS participant?
Regards, Lorne

Offline Flatblackdime

  • Curious
  • Posts: 2
Re: Arktasian's 95 K75 on Microsquirt Mod Table
« Reply #104 on: July 03, 2020, 10:41:31 PM »
I didn't know that about MS and chain driven cams! Too bad, that would be a bit easier from a packaging perspective.

I too am working on an efi conversion project using speeduino instead of MS. Going to run fuel only triggered off the CDI box RPM signal and likely just do a straight alpha-n tune with temperature/ baro correction. I'd eventually like to run ignition as well with some GM LS2 coils but will likely just batch fire and run it crank-triggered as half of a 6cyl.
  • USA
  • 1990 K75rt

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