Newbie with a 1979 CT70

Talonfcc566

Talonfcc566

Member
Hello forum. Let me start by saying I have already learned so much from you guys, thanks. I just bought a 1979 CT70 50 cc.
The guy who had it blasted most of it and painted it John Deere green. He wired it to run without a battery which I sort of like. No battery to mess with. The kill switch is the blinker switch. It runs a little rough and or oddly but he said its do to the wrong intake manifold .. and a carb which is on an odd angle. The carb was a leftover from spare parts he had with no markings.
I started reading posts trying to put together a plan. First things is a fuel tank. He mentioned someone seal coated it, but forgot to mention it's like a loose glove in there with fuel in behind the sealant.
I think after the tank arrives and I change it, I will check and or replace the points. Then look over the carb for tank sealant debris.I want the correct manifold and carb but since most of you suggest an 88 cc upgrade kit that would nip it all ... more power, new carb and manifold .. and oil pump upgrade to do it right. The first thought was change out the motor but from what you've all said, that starts a mess of changes including changing from 6v to 12 v system and then a battery.
I don't mind dropping some cash on it, but I do want to ride it for a few weeks and enjoy it.
If anyone has a better idea, please pass on your thoughts.
20190407_134052.jpg

I call her the Green Weenie. Not very original but I like it.
Thanks in advance.
 
OLD CT

OLD CT

Well-Known Member
The carb that is on it is a new aftermarket knockoff of the original, nothing wrong with it.
You do want to get rid of the adapter '' they are known to leak'' pick up a stock style intake manifold/gasket and a stock airbox/filter setup. Previous owner lost the plastic spacer that goes in between the intake and carb,BTW. Post some pics of the under the seat battery wiring, if you want
the headlight/taillight bulbs to last, you need a battery. Bulbs will blow out. There are some good inexpensive sealed battery's now that last around 4 years or so and won't leak. If you don't care about lights/ blown bulbs, leave it as is.I bet you have a intake leak going on.
 
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Talonfcc566

Talonfcc566

Member
Adam-NLV
That was my first thought as mentioned, but changing over to 12v when I don't have a battery box or battery at this point sounds worst than just changing upper end only plus oil pump and maybe sprocket. The wiring is also a mess. The current motor has 1450 miles on it if seller was correctly stating it. I can get her up to 20 -25 mph running poorly so not too bad .. is it? I'm 185 lbs.
The tank is on the way .. stuck with metal only cuz it was and I plan on only running regular ethanol free.
I'd like to put most things back to original but I dig my handle bars.
 
Talonfcc566

Talonfcc566

Member
Old CT,
Thanks for the clarification on the carb. I thought it might be okay if it was correct. The intake manifold seems like another story. Nobody seems to have one. I only see Chinese manifolds coming from China on EBay. Makes me nervous.
I too felt like I should get rid of that converscon plate and put on a normal air box.
The space you mentioned that is missing .. didn't know that. Thanks.
I'll send a wiring pic but it's a mess. Didn't know that I would have issues but I ride it after work behind a park on some trails. It's not titled so I just want to enjoy it like that to start. Kind of a stress reliever. Would the old WD-40 trick also work to check for air leaks?
Thanks again for the information and suggestions.
 
OLD CT

OLD CT

Well-Known Member
Get yourself familiar with what you need at dratv. Check out ct70 parts by diagram. 79 to 82 intake/carb pics. You have the older version knockoff carb, but should work fine. The 79's had a round bowl I think. You may have an aftermarket head also. Some pics of that would help. The wiring does not look terrible, that's a plus. That grounded blue wire is odd.:confused: It might be the ground for the battery. Not needed if you ain't running one.. LOL. The key switch, coil and taillight gets grounded. A 88 kit would be good. I use carb cleaner for checking leaks. WD might work, never tried it.
 
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Talonfcc566

Talonfcc566

Member
I actually have some Ethier that would work better for finding leaks too. So I got the head numbers. I'm pretty sure the paint on the head and jug doesn't help much with cooling. Need to blast those some day.
I have hit a lot of sights for parts. I need to call some. I don't see a "want to buy" section here. My AMC forum has both "sell" and "wanted" section. Is that correct?
Again, I appreciate you knowledge and experience mix in with the help. Thanks OLD CT.
 
kirrbby

kirrbby

Well-Known Member
I'd try mounting the intake manifold directly to the head, like OLD CT said...get rid of the adapter. That might level out your carb a bit. Used stock CT70 intakes should be cheap and plentiful. Good aftermarket too. Your carb might be a little too big for 50cc tho. Consider a smaller carb, or a bigger cylinder.
 
Talonfcc566

Talonfcc566

Member
Kirrbby,
I believe I read you recommending the 88 cc idea on a post I read. That when I changed my thinking cuz it made good since.
I will do what you and OLD CT mentioned ... look for leaks, and remove adapter. I'll have to research this space at the carb and keep looking for a used stock intake manifold. If that doesn't work well, I'll research the 88 cc idea.
I'll get it start this weekend maybe and update how it goes.
Thanks for the ideas and suggestions.
 
OLD CT

OLD CT

Well-Known Member
That is a Honda head. Good news. When you do take the intake off I want to see if it is a 50cc head by looking at the port size. If you go with a 88 kit you want a 70cc head on there.
 
kirrbby

kirrbby

Well-Known Member
There is a lot to be said for a bike that runs and rides. 20-25 is slow for a CT70, a bit slow even for a Z50. But...at least it goes.

Good pics so far, the more you show us, the more we'll have a chance to help you figure out what you have there. Show us the other side of the bike. Tell or show us the stampings on the cylinder...many are stamped 49cc when they are actually bigger. Did the PO say it was 50cc? If it's a Honda part, we'll recognize the stamped number/letters.

It looks like there could be a heat spacer...or something, between the intake and head. There could be some funny business in that area. I'm wondering why it was assembled the way that it is. Maybe it's the only angle that works..? Maybe it was the first and only way he even tried..? Maybe it's all just glued together and will fall apart if you touch it..? Funny business is common in that area.

How does it shift? If it's shifting well, a new top end isn't a bad job. If the exhaust is adequate for 88cc, a complete kit with the head, carb, and air cleaner...$350-400 will take you from 20-25, to 45-50...and zippy, for only a couple days work. A kit, correct for your engine, is tried and true, proven, works as advertised, everything works together...fits correctly.

Same with the electrical. You can buy everything you need to get it wired, with HL, TL, keyswitch, and battery...basic 6v lighting, except you'd need a used battery box.

Tell us the number on your engine case too. Down near the gearshift...ct70xxx or z50xxx...??
 
kirrbby

kirrbby

Well-Known Member
It's a good lookin bike...nice green weenie. lol
And it's early April. Maybe take the plunge...new top end, installed. We can help and hopefully your bike would only be down for a week. Then it'll be fun all summer. By October, you'll know what else YOU want to do for it.
 
6

69ST

Well-Known Member
Nice looking bike with good & not-so-good signs of PO changes. The engine is a head-scratcher. All that silver paint, weird intake + turning plate and those dents near the cam cover...real "wtf" material. What's the SN of the engine? A stock 72cc CT70 motor should be able to take you into the low 40s, if it's reasonably healthy. 25mph is very weak.

Nothing wrong with an earlier style, rectangular bowl, carb. But, that intake has to go; the mounting angle is too far off. You'll never be able to get the float adjusted to compensate.

Even if that's a Z50 motor, the lower end is virtually the same as a 72cc version. The entire top end (head assembly, cylinder & piston) can be replaced, to easily build this into an 88cc motor. Let's figure out what you have, first.

Contrary to popular lore, there's nothing wrong with the steel tank. It's larger filler neck also fits the mounting bracket properly, no mods required. The biggest single mistake I see being made...repeatedly...is inadequate prep for sealer. You may be able to remove the failed sealer using acetone, MEK, or both (in sequence). Once that's gone, the interior must be completely cleaned of all petroleum residue; then, the rust can be chemically removed, using phosphoric acid. These days, I seal brand new tanks; the prep is dead-easy. Non-oxygenated fuel has all but vanished. So unless you're going to source all of your fuel from a specialty supply, such as VP, or buy only "True fuel", imho it's best to deal with the reality of 2019 pump gas. POR15 sells a very good tank sealer kit. I've used KREEM however, it's very temperamental and will fail unless applied perfectly...not what I'd call "DIY-friendly".

As for the electrical system, if this were my bike, I'd pull the wire harness, unwrap it, and make any repairs necessary to return to original configuration. I'd also source a battery carrier, rectifier and SLA battery, regardless of whether you run turn signals or not. The battery is the voltage regulator and, though crude, works well enough to keep bulbs from turning into flash bulbs.
 
OLD CT

OLD CT

Well-Known Member
I found a intake and manifold to carb spacer off a 1970 K0 CT70, if you are interested. Let's see what you have for a intake port, when you get a chance.
 
Talonfcc566

Talonfcc566

Member
OLD CT,
You got me thinking, the seller told me 50cc but I looked back at the message and what he said was, the carb was from a 50cc. You are probably right, it's not a 50cc. I never throught about it. I never really ask cuz I didn't care. I never see CT's around here and I just bought it. I figured I would learn a lot about them soon enough. So you are correct, as the pic shows, she is a 72cc.
20190411_164024.jpg

Did the markings on the head mean anything?
I need to get a manual next.
Fuel tank made it so I might knock that out tonight.
Yes OLD CT, I am interested in the manifold and spacer. I imagine the other issue is a 50cc carb on a 72cc motor right?
Did I mention how great you all have been and understanding on my rookie mistakes.
Thanks
 
OLD CT

OLD CT

Well-Known Member
The tires look like they will last a long time. I would gently ''pressure wash'' all the ''sand'' of the intake, cylinder and head ''before'' working on it. After you do that pull the intake. There are some real funky bolts on the intake, so I hope it will be ok ''as is''. If the threads are wonked, you can heli coil em or farm it out to a machine shop to do it if you never heli coiled before. then use the correct size/lenth intake bolts.

The cylinder says 72 ''cm'' instead of ''CC'' telling you that it is a ''china replacement'' not OEM Honda. Not really a big deal for a cylinder only. They either work properly or they don't. I never hear bad reviews about the cylinders.
The ''head'' on the other hand should preferably be OEM Honda, like you have! Ebay China replacement heads are garbage. I have a friend that had a failure where the intake valve seat came out and destroyed the piston/ head when it let go on a stroker 110. Not good. I installed a OEM head and new piston and it runs great now.

One more suggestion.... Go over the whole bike to make sure all the nuts and bolts are tight.
Start with the rims and hub bolts! Pics of the intake port and the carb inlet size is next. Getting the port sizes sorted out and re checking the ''point gap'' will most likely get you doing 40+ mph, in no time.
 
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