CT70 k0 Restoration/Mod

69ST

Well-Known Member
Kitaco is high-end, JDM, product. Their engine parts have been of OEM quality, or better and they're the only one (Takegawa being the other...since Daytona exited the high-end market) that ever offered a 6V-type cam choice. At ~$60 (after paypal fees & the customary double-dip on the currency exchange) delivered, it's not a bad deal. Neither is the cam that OLD CT prefers; cost-wise, it's gonna be close. As I recall, the dratv bumpstick is just an aftermarket reproduction of the NLA Honda "fast road" cam...a good choice, too. IMO, it's "six of one, half-dozen of the other"...

For what you're trying to accomplish, I'd favor the OEM carb or the TB repop of it. There will come a time when you'll need some little chingadera or other and Keihin parts for the stock carb are readily available. The TB repop carb is a faithful enough reproduction to use OEM Keihin parts.
 

whereshaldo

Member
That's the heart of the matter...with 6v heads, there aren't many cam choices.

The non-bearing cam is usually the better choice, for most, especially if you're going to leave the stock carb & exhaust as they are. With an 88cc kit, expect a top speed around 50mph with no real difference in acceleration/pulling power down low. That displacement increase should allow you to upsize the countershaft sprocket by one tooth...not only optimal gearing but where half of the speed gain comes from. Lower revs-per-mile doesn't hurt, either.

I would add that the Long Duration cam does give up some low pulling power but its really only noticeable starting off on steep hills. In Seattle there are hills that you must stop and start on in the 15-19% grade range. With stock cam and gearing I could get going ok, and the new setup is a little too boggy for my taste. I've just learned to take the long way in those instances and avoid the big hills. It all just depends where you are and what you want to do.

H
 

69ST

Well-Known Member
I would add that the Long Duration cam does give up some low pulling power but its really only noticeable starting off on steep hills. In Seattle there are hills that you must stop and start on in the 15-19% grade range. With stock cam and gearing I could get going ok, and the new setup is a little too boggy for my taste. I've just learned to take the long way in those instances and avoid the big hills. It all just depends where you are and what you want to do.

H

Very important point...local topography matters, a lot. Where I live, compared to your neck of the woods, it's pretty flat. There aren't many grades in the 10-20% range and those that do exist, locally, tend to be short. In fact, the steeper the grade the shorter its length. The significant grades I've ridden have virtually all been anywhere from 200-600 miles away...which limits my experience in dealing with them and colors my perspective. For most of us, 20% is pretty steep. AFAIK, 30% is the federal limit for most public roads...FWIW. At 20%, most daily driver/grocery getter cars, trucks & SUVs exhibit noticeable mechanical strain, manifested by holding lower gears longer...or being forced to delay upshifts, if you have a manual tranny. When you're dealing with marginal power (comparatively speaking) things change. You'd never push a car engine to 80-100% of peak output, or it'd have a very short service life. Yet, that's what most of us do with these little bike engines, regularly...and they're built to take it.

Bottom line is that a given power level can only haul bike & rider so many mph and that's it. The best you can do is accept the practical speed capability, for your setup and select the optimal gear for ascending grades. Unlike automotive engines, bikes engines can handle high rpm far better than lugging and that's the key...once the tuning is optimzed.
 

socalbuff

New Member
I have another question. I have started to gather some of the body parts that needed replacing but I am now stumped when it comes to battery and battery box. My bike didn’t have a battery box or battery when I bought it. Since I am looking into using a 12v system. Would a 1990’s battery and battery box work with my k0? My real concern is making sure the battery and seat pan don’t hit.
 

69ST

Well-Known Member
I have another question. I have started to gather some of the body parts that needed replacing but I am now stumped when it comes to battery and battery box. My bike didn’t have a battery box or battery when I bought it. Since I am looking into using a 12v system. Would a 1990’s battery and battery box work with my k0? My real concern is making sure the battery and seat pan don’t hit.

If you're talking about a CT70, the 12v battery setup will require mods to work. Honda changed the seat latch system, completely, with the 12v frames. A threaded boss was added to the middle of the upper shock mount, to accept a third support point for the oversized battery & carrier. Additionally, an extra clearance dimple was added to the rear wheel arch, beginning with the K3 model; I'm unsure how that might affect things.
 

socalbuff

New Member
Hey guys the build is going great but I have couple questions.

1. I made the rookie mistake and forgot to label with axle is which and I now see one is longer than the other. My guess is that the longer one is for the rear.

2. When I pushed the axles through the front hub. The hub does not spin very smoothly. Is it possible to push new bearings to close together. Could it just need some breaking in? Rear spins with almost no resistance. (All new bearing and spacers)

3. The front hub cover seems to tight for the axle after paint. Thinking there is paint in the axle hole. Any ways to get the paint out? I am thinking a light dremal action.

Thanks guys

Will post some photos tomorrow
 

69ST

Well-Known Member
You're absolutely right choosing to take the binding seriously. It could be something inconsequential, like paint where it shouldn't be. I would NOT bet on that, bearings a primary safety issue. First thing that comes to mind is the internal spacer, a.k.a. the "distance collar". Is it installed? It's an easy item to overlook, for a first-timer. Without it, rapid bearing failure is guaranteed.

That having been said, the most common rookie mistake involves the speedo ring gear and you'll be able to inspect that before you can look for the distance collar. The drive tangs/ears, fit into two recessed pockets in the hub nose. If you miss, they'll get crushed and that might be the issue here. The easiest way to get them indexed is to install the gear on the hub, then slide the brake hub asm. over it.

FYI, not only should the wheel assembly rotate freely with the axle nut torqued...full torque is needed for structural strength.
 

socalbuff

New Member
Yes the collar is installed. I haven’t installed the speedo gear yet so the issue shouldn’t be coming from that. The hub cover was a paint issue as I was able to fix that this morning. But the bearing within the hub is still and issue. It rotates but not very well.
 

69ST

Well-Known Member
With both bearings & collar properly installed, you should see both bearings spin...and smoothly...when one is rotated by hand.

Seems that you may have a damaged bearing.
 

ctbale

Member
I think the distance collars are different. Like 1 or 2 mm variations. Not sure if the parts book says there length. I remember running into this. could have been when I was doing CT90s though.
 

socalbuff

New Member
Hey guys thanks for the help on the wheels. In the end I got it figured out and the wheels are rotating smoothly.

My next questions now is with the Engine gaskets. I am starting to put the engine back together and so far has been fairly painless (knock on wood) and the gaskets are sticking out above the metal in certain spots. Is this normal? Is it best to just cut of the peices that are sticking out once assembled?
 

cjpayne

Well-Known Member
Its normal for them to stick out a little and follow the contours of the engine, but if they're lumpy looking, they may have shifted outta place during assembly. Post a pic(s).
 

69ST

Well-Known Member
When in doubt, it's best to at least partially disassemble the parts that sandwich the gasket(s) in question. Some aftermarket gaskets are cut way oversized; they'll seal just fine but need to be trimmed to look right. If that's what you're dealing with, a few minutes with a single-edge blade can set things right.

OTOH, if a gasket...especially the center crankcase or/and cylinder base gaskets.... has shifted, going back to remediate the resulting oil leak, once the engine has been running for a while, can be a demoralizing chore. Mo`better to do whatever it takes to sort this now, imho.
 

69ST

Well-Known Member
Those appear to be one of the slightly oversized flavors, to which I alluded in #33. No biggie...as long as you verify the center gasket has remained in place, end-to-end, especially along the bottom edge. FYI, once the temporary support piece has been removed from across the bore opening, these like to walk out of place along the lower edge and at the cylinder end of the upper edge, ask me how I know this.

Note: do remember to trim any excess left protruding into the bore opening. You don't want anything, not even a little bit of excess gasket, pressing against the spigot end of the cylinder.

BTW, nice cleaning & cosmetic work!(y)
 

Tripod

Well-Known Member
I use the motor stand from trail buddy to build my engines. The one drawback is trying to assemble the cases. Initially, i did two things wrong:
1). I cut the portion of the gasket that runs through the bore before I had the case halves assembled.
2). I assembled the cases with the motor standing up, like it goes in the bike.

The end result was a leak, teardown, and frustration.

On my next build I left the gasket portion at the cylinder bore together until i was ready.

One trick I used was prior to starting the rebuild, I put together a USPS box (free), took one case half and drew circles for where the crankshaft, countershaft, and kickstarter stick out and cut holes in the box. Same thing with the other half. I then was able to place the motor on its side, flat, and was able to get the center case gasket sitting just right before placing the screws into the case halves.
 

dirtbkr188

Active Member
Many years ago, I put together a wooden box made of scrap 2 x 4 pieces set on end, and it has worked well for me

MaQQpW.jpg


BTW, the pic was taken 12 years AFTER I put it together, and it ain't pretty, but it works for me...
 

cjpayne

Well-Known Member
I made one of those boxes from the dimensions that kirrbby gave me out of 2x6's. Be sure to drill small holes and then put 4in long wood screws in it or it will pull apart when using a hand held impact.
 

socalbuff

New Member
Hey the bike is really coming along right now. Started the engine for the first time it runs great. I have run into an electrical issue. The highlight works perfectly and switch as well. The worm only works intermittently. The tail light doesn’t not work at all. The biggest issue issue is that the key does not turn off the bike.

Any obvious reason why I would have these issues? Second the ignition switch has a green wire but the wire diagram from DrATV shows no green wire is this wire important. Does the k0 have no ground wire?

I got a new wiring harness from DrATV. I also got the connection between sator and wiring harness from mini trail part 449.

I plan to check the voltages this week when I get more time.
 
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