K2 ATC 90 Barn find

[wellys88]

stumbled accross this, one tire is perfecrt and tank has no holes or rot, motor turns over and has compression, the carb is seized, the man told me his father bought it new and its been sitting in a shed on there pea farm now for almost 30 years, one owner, His father passed away recently and they where clearing out his stuff and they found this under a cover in a barn, I plan on a full restore,

[HairyJR]

Looks to have all be there, a great beginning to a great project.

"HJ"

[wellys88]

yes all there except pull start, the reason they eventually parked it

[Joseph Farrow]

74 is one of my favorites.
Keep us posted on the resto!

[81ATC185S]

Pretty good, can't wait to big bore my 90. Good luck on this build.

[1979atc]

Nice find! Love this style of the US 90s

[wellys88]

Finally back on here and getting back to this project. Having problems with stator. Are there and alternative to original equipment. Some type of conversion. Don't really want to spend 350$ for a stator

[shortline10]

Not for the 90 , did you check eBay for a good used one ?

[wellys88]

One on there for 150 with broken wires

[ps2fixer]

I'd have to do some digging, but I might have a US90 stator (81 if I recall correctly). I also parted out a 76 ATC90 that I have just a few parts left on. I have the OEM 76 seat in fairly good shape, the seams have stitching pulling apart, someone with some time and effort could make it back to OEM good maybe great shape. If I recall correctly there's no rips or tears in it. Currently still mounted on the rear fenders, I think they had the typical small cracks at the corners of the seat, other than that good. Shipping is probably killer on fenders though (mine are a nice color and such yet). Also have a nice tank externally, but inside is rusty or something, full of a bunch of brown crap. Maybe it's old dried up pre-ethanol gas?

The ATC90 was a whole machine in good shape, no one locally would buy it, so it got shipped all over the country as parts. The US90 came in horrible shape with a ton of missing parts.

Do you have a way to make accurate measurements? If I don't have the US90 stator, I know I have an early version of the ATC110 stator. I'd have to double check, but pretty sure it was also 6v as well. It might put out more wattage though so a headlight bulb might have to be upgraded to a higher wattage unit to eat the excess power.

I found the ATC110 one. I'll get some measurements for it and double check the service manuals to note differences in power and such.

Can't find hard numbers on the ATC90, so I'll have to base it on total load (all light bulb wattages added up).

ATC90 - Uses 6V 15W headlight + 6V 3W tail light
79 ATC110 - 43w (Uses 6V 25W headlight + 6V 3W tail light)

Sounds like for power difference, you'd just have to run a 25w 6v headlight bulb instead of the 15w. ATC90 Spec should be roughly 33W (atc110's 43w - 10w smaller bulb). Also appears the connectors are a match. Hopefully it's physically the same size.

I'll use mm for the measurements since it's likely what it was designed with.

Overall diameter - 130mm
Mounting bolt pattern has 6 holes, the ATC110 used 3 of them. Measuring straight across center to center it's 114mm, going from one bolt to another how it was mounted on the 110, it's about 98.8mm.
Hole for the rotor is roughly 80.65mm
Thickness where the bolts go though - 18mm
Bolt hole size - 6.55mm
Wire length - about 6in from the grommet (152mm)

Markings of interest: 37000, 0950 9H

Wire connectors
Yellow - 3.5mm Bullet Female
Black - 3.5mm Bullet Double Female

The wiring on this is pretty stiff, I could include new wire if you wanted to replace it. I'm unsure if the grommet will be easy to get off though. The insulation is broken in a couple spots, pretty typical for old harnesses. The pig tails I'd throw in free if you wanted the part. I would hate for you to use it and have a wire break and fail and have no way to repair it.

[shortline10]

69-1980 should all be the same stator .

[ps2fixer]

Update, I've found the US90 engine, I have it labeled as 1970-1971. Stator and rotor both missing so I probably don't have them. The side cover was already loose, so I took it inside and test fitted the ATC110 stator in the side cover. Fits like a glove. The only thing I'd be unsure of is rotor size, but I'd assume they would be similar/same sized, worst case I have the ATC110 Rotor too.

I couldn't find any ohm specs for the stator for either year. For the newer completely different designed stator for a 81 ATC110, the exciter coil wire doesn't spec as good. I kind of hate this service manual because it lacks the details for what the specs are for the older machines. Here's my measurements vs specs of the 81 (it's from a 79 though)

My measurements:
Yellow to Ground - 0.3ohm
Black to Ground - 3.7ohm

81 ATC110 Specs:
Yellow to Ground - 0.4-1.2ohm
Black to Ground - 100-400ohm

Also it's worth noting the 79 was a points based ignition while 81 was CDI based.

Really hard finding specs on other points based engines, I found the alternator specs for an 1985 ATC70 though. Black to ground is 2.43-2.97ohm, seems very similar to the ATC110 stator I have. I'm pretty sure this should be a good part based on this research.

[wellys88]

Will that work. How much you want for it

[big specht]

this one has the same story as yours I got it after there dad passed. His wife learned to ride on it when she was a kid and there kids rode it for a little. Then it was shoved in the back farm shed for years until he passed then I got it.

[wellys88]

Nice. I took balloon tires off swapped over too steel rims. One of the balloon tires is like brand new. Is yours running.