1971 CL70 Project..... engine swap, etc.

[scott s]

I was missing the gas cap and the plug I used allowed some of the cleaner(s) to escape. It was then that I noticed that it was working on the external rust, too!
The marine clean (left over from a POR 15 kit) really did the best. It foamed up like peroxide and baking soda. It's possible I could have left it on there and got even more off, but I was worried that it might start eating away the paint and stripes.

The inside came out nice. There's still a tiny bit of rust at the very bottom, but with fresh fuel lines, a filter, etc., it should be just fine.

 

[scott s]

The bonus is that the tank is much more silver now!

I sprayed underneath with rust converter. I'll go back in a day or two and tape it up and paint the underside with some flat black or something.

 

[scott s]

I'm really happy with the way it turned out!

It gives me just enough patina. I cleared it with some fuel resistant clear coat from the hobby shop. Not as good as the SprayMax 2K or a professional clear, but should be plenty fine for this project. The main thing is that the original paint is protected.

 

[scott s]

I also scrubbed up the seat with some car wash soap and a brush, then treated it with leather/vinyl conditioner.
Not perfect, but perfect for this project.

 

[scott s]

The dog and I finished up by sitting outside Creepy Van, listening to some tunes, having a beer and some pork rinds.

 

[Enginedoctor]

should turn out to be a legit project. some clarification of what i said earlier. Excuse my obscurity lately, i'm in mexico and have internet very infrequently.

Regardless, like raymondguy cleared up, the 50/72 platform can be taken out to 54mm/54mm. the cranks are hard to come by and need to be converted to a 12V system with CDI. I'm planning on buying 2 from japan when i get back to the states. Kitaco and takegawa have a similar setup, if i'm not mistaken, but an aussie guy sent me a link to a clipping point 54mm crank.

To fit a 54mm cylinder in the stock cases, the case halves need to be bored out on this 'egg' style motor. On bigger bikes, there's more holes for cylinders, but on the little mini, alas, only one. to get the skirt on the cylinder to fit in the cases, you need to bore the cases out a tad. this doesn't really affect the rigidity of the aluminum.

Most of us are running 52mm/52mm crank and bore. requires no case mods and only a cut down oil pump driveshaft to clear the bigger crank. At this displacement, a larger oil pump and oil cooler are recommended. This equals about 110cc. give or take 1 or 2. we usually keep the compression between 9-10.5:1. You could go higher if you have no problem running race gas, but keep in mind this bike is intended to be ridden (we hope) and it's a little air cooled unit, so it will probably run on the warmer side of things. As a result, going crazy with compression to make the extra .3 hp might not be worth the gamble. I have a 110 and i know my bike will do 60 all day. probably cruise at 50+ or so, but i don't push it too much. I'd like to have more displacement, but haven't invested the time and money to date. AND, i don't think another 7 cc will make or break me as far as power is concerned, which leads me to our next relevant point…

Heads. The stock head breathes okay from what i hear, but if you crank up the displacement, get a DECENTly sized carb (not a 38mm), and a good head with 25/22mm valves, and a bigger cam, you can spin these little motors pretty quick (10k plus rpm) and even make power in that range, which is your best bet as far as going fast quickly. The chinese knock offs will not be 'built' like this, they're more built as stock knock off reliable, mid range power motors. Fine for cruising, but like raymondguy mentioned above, a chinese 110 vs. a modified 110 is no comparison. Plus your flywheel cover still says 'honda' on it.

When i tear into it again, i'll go 54/54, with the knock off V2 head from Tb parts and big boy cam. That being said, i have a Takegawa 124 superhead sitting in a box in my friend's garage. So for a guy like me, projects line up. If you wanna go hog wild, do the 54/54 with the 12V ignition conversion. it's not for the faint of heart, but it will be reliable, usable power. If you want the easy(er) way out, go chinese. You can still have a great bike that 'looks' stock (to the unsuspecting) and has good, reliable power. OR, as a third option, you could get a 52/52 setup, keep the original harness and a 110cc displacement, probably get the bike to go 65mph Top speed, and tell people in confidence 'it's a honda'… to make it do this, plan on exhaust and carb mods. you could keep the original head and induction/exhaust, but you'd be limiting the ability of the motor by those means.

Thats all. goodnight everyone.

 

[scott s]

Very interesting Enginedoctor. I had no idea that boring/stroking these little engines was even an option.

Do you have links to parts suppliers for all the stuff you talked about? Remember, I'm very new to this particular scene.

How does that route stack up cost wise vs. the China clone?

 

[Enginedoctor]

if you go for the 'clipping point' crank, it's a LOT of money, because it comes from japan and they charge you shipping. i'll be buying 2 when i pop for that reason. Along with it, you'd probably need a good used CDI stator setup from a crf50 or the like.

If you go the 52mm crank (much easier) it's 150 bucks HERE, and you can keep the stock stator/wiring setup. The cylinder is 90 dollars, and the piston another $40 or so. plus incidentals like the gasket set (need it no matter what). So far we're up to $300, assuming you can do all the labor in confidence.

This stuff is HIGHLY RECOMMENDED, but not essential: High volume oil pump with undercut shaft ($50) oil cooler setup and plumbing ($150 +/-) Clutch rebuild with updated plates & springs ($45 in parts) Special tools ($25). Those things are 'piece of mind' add ons, increasing your reliability, and drivability dramatically. If you want to make more power, you'll need a 'race' head of some variety, probably $250 or so (you can run the stock one and the motor turns into a torque monster), and a bigger carb to make it all breathe, assume another $150. As for the heads, i bought a DRatv one that they no longer have. I guess there's a "v2" head out there somewhere that's supposed to be pretty good, i'll probably be getting in the future.

So, it can get pricey. I think pound for pound, china might have this setup beat. What i did, however, was do the crank and the cylinder/piston, kept the stock head, got a better carb, then 1.5 years later, got the better head, and a bigger exhaust pipe. I might have had the pipe originally i can't remember. This way, i didn't have to remove the motor to update the add ons i got.

In the future i do plan on going hog wild with a 54/54, CDI updated ignition, and a roller head. but i plan on this costing close to a G. the other stuff (exhaust etc) i pretty much already have. probably a carb upgrade for me at that point

 

[scott s]

I talked to the guy at FirePower mini's today and after a lengthy discussion, I've decided to go with the 117cc using the stock engine.
One of the biggest factors is that I would have lost the CL exhaust with the clone engine. The exhaust is part of what MAKES the bike, to me.

He believes that with the low miles, better Honda clutch and transmission, etc., that I'll get a good compromise of power and longevity. Plus, it'll be a Honda, too.


Oh....and here's why there's a shift shaft in the box of parts:



The splines are broken off right where the pinch bolt goes.

 

[scott s]

Took it outside and gave it a good scrubbing. Polished the chrome and waxed the paint.

 

[scott s]

Pulled the wheels for new tires. I'll be pulling the forks soon to change the oil and install the new gaitors that came with the bike.

 

[Tripod]

The paint looks really good. You are starting from a very good point.

 

[scott s]

I got bored so I dropped the engine. I can honestly say I've never pulled an engine single handedly before!
It looks like someone has been in there before. The wiring harness is spliced. I'll solder it back together and shrink wrap the wires before installing the rebuilt engine.

 

[Enginedoctor]

yeah agreed on tripod. that paint is mint. And yes, i agree with you that the bike is very sleek and unique looking. So firepower has a complete 117 kit huh? thats billy(badass). I'll have to look into that, as i'll be tearing into mine probably this winter. There's only an ST90 in line before it but it's sold when it's done. The ct70 is for me.

As for the engine, you need a special tool to remove the flywheel easily. there's a hacker way to do it that i know, but i won't tell you in fear that you might try it then mushroom the shaft. Clean the threads in the flywheel (they're super fine thread reverse ID not OD) with a wire brush and some WD40, then maybe hit it with compressed air and brakleen to get it down to clean steel. id recommend a tad of lube on the puller itself as well, thread it into the flywheel, then tighten the center bolt and it will push on the flywheel positively. i've used an impact wrench (small one) with success in the past. Also, there's a 4 recess nut under the clutch that requires a sort of special tool as well. i've used needlenose pliers after removing the lock and been successful, but again, hacker move. When you get the clutch and flywheels off, then remove the primary drive transmission input (this assuming you have everything else apart) and of course the countershaft sprocket, then you're ready to split the cases carefully. keep the stock cases in a safe place. clean without abrasives. it has an 'as cast' finish that's a one time only deal, as far as originality is concerned. the rest can be painted or polished to suit.

When you do get in there check the shift forks for wear where the forks contact the transmission gears themselves. This is a common area for wear, and from what i understand, the forks are still available. So probably a good time to replace, as these parts are becoming relics as we speak. Otherwise, look for obvious damage, keep everything organized and you'll do fine.

 

[scott s]

I'm going to let Terry at FPM assemble it for me. His labor charges are VERY reasonable and, since he's taken the time to talk to me about my options and walk me through the process, I don't mind sending him some business. If I were to do it myself I'd have to pay to have the case machined and, in the end, the final cost difference is minimal.

He said he'll change out a couple of parts specific to the 70 engine for my build, but this is essentially the kit.



And I decided to give this oil cooler a try. Terry says Honda did a nice job on the Scrambler exhaust and it should work fine with the 117cc kit. An oil cooler is never a bad idea, and I'm in South Carolina, where it gets very hot and humid in the Summer.

 

[scott s]

Changed the fork oil (95cc of 20W) and installed new gaitors.

 

[scott s]

So, I got the new sprocket, dampers and chain adjusters. The new snubbers are a TIGHT fit and, after much beating, banging, WD40, heat and cussing, got them installed.



It was then that I noticed the castle nut seemed to thread on very deeply; the cotter pin wouldn't really do anything to hold it.




I referred to the parts diagram to make sure I wasn't doing something wrong and only then did I notice that I'm missing the damper cover, part #7 in the diagram.



It wasn't on my bike when I took the old sprocket off. The dampers are IN THERE....I mean a TIGHT fit. I could remove them, but I sure don't think they'll be coming out on their own, especially if the old ones didn't. The old ones literally fell out of the hub when I removed the old sprocket.
Think I'll be OK?

 

[MiniBike Mike’s Garage]

You mention not going with the aftermarket motor because you wouldn't be able to use the original exhaust. I have a CL70 with a Lifan 125 and I used the original exhaust.

 

[scott s]

Really? Terry at FirePower told me the exhaust port was ~15mm forward on the Chinese engines. Now, I was asking about 150-160 cc stuff.
Does it clear the shock properly?

 

[MiniBike Mike’s Garage]

He would be correct, it is a little forward. But....not enough that the stock exhaust won't work. The only thing you'll notice is that the bracket that the exhaust hangs from in the rear is no longer parallel with the shock, the bottom of the bracket is slightly forward. Its one of those things that if you didn't know, you'd never notice it.