Planet Minis

yadihonda

I have been restoring a K1 and haven't gotten to refreshing the motor yet. I do have a 1975 K6 motor that is pretty strong. I understand that this should bolt in without a problem and that the stators are different. The K1 has a generator, rectifier and battery that acts as regulator. The K6 uses a lighting stator to power the lights.

My question is could the K6 motor be used in the K1 setup (harness) but by the rectifier? I'm not clear on the output of the K6 DC but was thinking that if it was similar to the K1 rectifier output, I could just utilize the same wiring with battery.

Does this make sense or am I overthinking this?

mexicanyella

I've been wrong about things before, but I thought the stators were the same, and on the K1 the magneto's output was rectified to DC for the battery, whereas on the other lighted 6V versions the lights ran direct off the magneto.

If I'm right, and the plug-ins match, you might not need to do anything. I'll be interested to see what others have to say anyway...

yadihonda

Now thats interesting. I'm hoping someone does confirm - but what you say does make a lot of sense.

dirtbkr188

According to Babbitts Online, the K1 stator (part#31141-045-671)
is unique to that model only, and the K3-K6 models all use the same stator (part#31141-120-005).

mexicanyella

Hmmm. That's a pretty handy link. The diagrams look the same, other than being flipped around on the K6 model from the K1 and K2. Looks like the same three wires going into the square plastic connector, too.

Hmmm.

What's the output connector look like, coming from the stator? And what color wires are going into it?

FastMC

The k1 has 2 AC outputs and the later ones have 3 AC outputs. You may be able to wire the stator in but for plug and play I'd just swap the stator plates.

yadihonda

Swapping stator plates is always an option, but if its as simple as splicing I'm probably going that route. So I guess now that I know all motors have AC output, is there an amperage issue as to why a later K3-K6 motor wouldn't put a charge to a battery in a K1 config? I can't find any Honda specs in my Clymer or online with regards to this.

yadihonda

Another question before I do the swap.....

Will my carb from the K1 work okay with the K6 motor? I can see where over time the carb had changed on later generations, but I'm not sure if the jetting specs really differ so much that I would need to use an entirely different carb. Does that makes sense?

mexicanyella

The carb and manifold should be a straight swap. Jetting should be fine, based on the theory that while there could be differences in backpressure between a hardtail exhaust and a softtail exhaust, you see a lot of little hondas running around missing their baffles and with exhaust leaks and still running pretty much okay, so I don't think it's much to worry about. For all intents and purposes the carbs look different but are both designed to feed the same device, so it should work fine.

The early carbs as found on hardtails are simple caveman devices, but a few things to watch out for are

1) be gentle pushing or pulling on the fuel line where it attaches to the carb nipple; I inadvertently shoved the brass barbed nipple deeper into my carb body once putting the fuel line back on and spent a lot of frustrated time trying to figure out my fuel starvation problem before I realized it. It's not an indestructible press fit by any means.

2) be careful when removing or handling either of the jets; they are tiny, easy to strip and easy to propel into orbit when cleaning them with compressed air. Same goes for the sort of "E"-shaped clip inside the throttle slide, between the return spring and the needle-adjusting circlip. Those can enter orbit on their own springiness.

3) Don't squash or bend the hollow brass float.

4) The pilot jet has a very tiny passage and it doesn't take much crud in it to seriously affect your idle. Similarly, it doesn't take too much of an air leak to affect your idle. It's easy to clean the pilot jet with a torch tip cleaner or similar. It's somewhat harder to repair threads in the intake manifold mounting holes on the cylinder head when you overtighten the manifold bolts trying to fix an air leak. Imagine the parts are made of margarine, use a torque wrench and you should be okay. You'll probably get to install some helicoil thread inserts at some point anyway.

yadihonda

Thanks for the tips Mexicanyella! Here's another question for ya - Is it common for these cylinder heads to have chips around that expansion "V" on the exhaust port? I had the original motor running for about 15 seconds once (before I did a compression check) and the exhaust leaked at the head. It had the two half moon pieces but did not have the donut gasket. I'm wondering if this is motor is a basket case, or at least the top end is worthless. I noticed on my 1975 Honda that there is a chip missing at the exhaust port, but it doesn't affect the exhaust seal.

mexicanyella

Worthless!?!?! Bite your tongue. Tell you what, when you get that inevitable 88cc kit to replace your stock top end, send your worthless original top end parts to me at my top end parts disposal facility here in the sunny midwest. PM me for shipping instructions. I also accept worthless bottom end parts and, especially, 6V points ignitions and parts.

All you need for an exhaust seal is good threads in the mounting bolt holes and an even step inside the port for the gasket and pipe flange to seat together on. If you're talking about the chip that seems missing out of the shrouded area, just downstream of the internal stepped gasket surface, I've never seen a 50 or 70 head that didn't look like that. I think it's just how they're made; with the exit angle of the port and the head's gasket surface being in such close proximity, there wouldn't be enough metal thickness there to last very long anyway I don't think.

Both of my 50 motors that run have the exhaust gaskets fossilized into the ports and despite the exhausts being removed and repaired several times over the years (had to lengthen a softtail headpipe I had laying around to fit on my hardtail when the original rusted out, etc.) I've never had a noticeable exhaust leak.

Do make sure you tighten the two exhaust port bolts down evenly, though. It helps save the margarine (marginal? that too) threads and applies more even pressure to the exhaust gasket. It's a good idea to use antiseize lube on those bolts as well. Also put some on the little tiny bolt that holds the stinger in the muffler, if yours isn't rusted in place forever and you ever happen to have it out. I put a thin layer of antiseize on all the exhaust joints in my hardtail, in case I need to disassemble it again sometime in the future.