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

[scott s]

1971 CL70 Project..... 117cc.

Hey Guys and Gals!
I've been itching to do a small cc bike for a while now and finally found the right bike. I picked up this mostly complete '71 CL70 yesterday. The engine is free and has good compression and it came with a small box of spares.

I plan on polishing up the frame and fenders. I'll clean the inside of the tank, but I want to clear coat it just like it sits. Some fresh rubber, etc.

The big plan is to swap in one of the Honda clone pit bike engines. I'm undecided at this point between the Lifan 125 and one of the Piranha 150-160cc engines. Any advice you can offer I much appreciated.

 

[scott s]

I am missing the air filter/battery cover. If anyone has one in Candy Sapphire Blue, please let me know.

While I know this thing won't be blistering fast, do I need to worry about things like speed rated tires, or will the normal replacement tires be OK? I'm hoping to get an easy 50-55 MPH out of it and possibly more with the bigger engine.

Same question about the drive chain.

Also, there's a complete wiring harness on eBay for about $60. It includes the CDI, rectifier, new ignition switch, etc.

Ct 70 CT70 Harness CDI Rectifier Coil 12V Brake Switch Honda Key Switch Coil | eBay

I can also get a sub-harness that splices into the existing harness, but I'd still need at least the CDI.

ENGINE_SWAP_WIRING INSTALLING_A_CDI ENGINE_IN_POINTS TYPE_BIKE CT70K0_to_76 all_Z50A_MODELs (SUB_W_1)

Opinions?

 

[theraymondguy]

Box up the 70 and save it for a winter project. The Piranha 150 looks to be an absolute bargain,

Piranha YX 150cc Engine

However the bigger they are, the harder they kick, I don't know that I'd want more cc's without a decomp.

Sorting the harness will be the big time consumer, but most worthwhile. Convert to 12V so you'll be seen and heard.

 

[69ST]

Most 10" tires...as used on the CT70...are J-rated (62mph), even the cheapest knockoffs. The the larger diameter tires on the CL70, you've got less than nothing to worry about, in terms of speed rating.

Wiring will likely be the biggest project. Since the CL electrical setup is unique among 6v 72cc bikes, I'd mothball the original harness assembly, complete, with the original engine and just source a correct aftermarket CDI version, with the required modular connectors & reg/rec. The time-consuming part will be lengthening/shortening individual leads to suit your unusual application. In this case, time-consuming doesn't mean complicated.

You'll have to figure out optimal gearing. If you opt for the L125, 7mph/1000rpm in top gear is a good starting point. If you go with the larger Jialing (Piranha, YX, etc), you'll have to consult with a knowledgeable vendor...or do a lot of trial & error testing. With either engine, go with the best quality chain you can find. A legit $45 H.D. chain can outlast 4-5 cheapies as well as extend sprocket life.

 

[scott s]

That is a pretty good deal. T-Bolt USA doesn't show that kick start 150, but they have a 140 that has the CDI, intake, carb, etc., and it looks like a smoking deal, too.

*Piranha 140cc Engine fits Pit Bikes and other Minis - Engines - Piranha Engines - WHS-1143 - TBolt USA, LLC

When we get into 10-20cc differences, will I really be able to tell?

 

[scott s]

Thanks, racerx.
That's all good info. Right I'm leaning towards contacting T-Bolt, simply because they have responded to couple of emails. I don't see wiring harnesses on their site, but I think they all use the same plugs.

I wish they had that kick start Piranha 150 in a kit form.

 

[b52bombardier1]

The larger the engine, the more likely you will need an oil cooler.

And look very carefully at the engine mount bolt pattern here between the motor and the frame. For ease of everything, pick an engine that will not require frame drilling for new mount holes.

Rick

Two CT90 and two ST90 bikes

 

[scott s]

T-Bolt claims that all of their engines bolt right up. Some require some sort of spacer for the foot pegs, but not to the frame. At least that's how I understand it so far.

Rick.... Are the ST90 and CT 90 frames the same as the CL? Would the battery cover for either of them fit my CL? I can find repro covers on eBay for about $25, but I'd really like one in blue if I can find it.

 

[b52bombardier1]

Hello,

The ST90 is a three-bolt motor and the CT90 only uses two bolts. Not sure this helps you very much.

Battery covers? The ST90 battery has no cover because it sits in a battery box under the seat - not so much need for a cover. The CT90 battery sits in a frame cavity but a CT90 battery cover is a completely different shape than your bike needs.

If you can find a repro $25 CL70 battery cover I would buy it if it looks good regardless of the color. As in buy it right now - could be gone tomorrow. I have regretted waiting many times in this hobby on Ebay. With the almost infinite color variety out there in rattle can spray paint, I absolutely guarantee that you / we can find you something close for painting your odd color battery cover. And if that is not good enough, Sherwin Williams Automotive Paint will custom mix you a can of spray paint for another 25 bucks to get it perfect.

Good luck with your project. Looks like a very nice bike.

Rick

 

[Enginedoctor]

Scott:
the cl70 has more in common with the ct70 as far as mounts go. the 90 is a whole different animal, with the ST, SL and CL versions sharing a 3 place frame mount, whereas the ct90, ct110, atc90 and atc110's all had the 2 place frame mounts. You should be shopping for something that would bolt into a 70, not a 90. although they're only 20cc's off, the platform is completely different.

Also, although you're going aftermarket, people are telling you to save that old motor and harness for good reason. that beast has a manual clutch, not often found in either the 70 or 90 platforms, and a 4 speed trans, also somewhat of a rarity. When you can afford to, probably send that motor to be restored or at least rebuilt and cleaned up. keep the flywheel cover close, it's unique (i think) to that model, maybe a few others. Unfortunately, due to what it is, i don't think you'd ever get that motor above 117 cc keeping the original engine cases and look. that being said, lot's of GURUs here running 60mph (approx top speed) and 50mph cruising speed with a 110 setup or similar.

Either way, should be a sweet bike when you get it done the way you want. i think you would notice a SLIGHT difference between a 140 and 150cc. Look for one that bolts into a 70 frame, not a 90.

 

[scott s]

Thanks, everyone, for all the replies. This is precisely the kind of information I was hoping to find. I was also told to check into the Firepower minis because of their customer service. See, this is where your experiences can help save me time and money!

I'm admittedly dumb about the pit bike swaps. The info I have about them fitting the CL70 frame comes from here:

Engines - TBolt USA, LLC

You'll see they list the CL70 as bolting right in. Who knows?

I'll have to look into the old motor and rebuilding it, maybe. Is it really worth having if I'm not doing a concourse restoration?
Enginedoctor, when you say "taking it out to 117cc" and "plenty of people running 60 mph with a 110", are you talking about the stock engine bored out? Or an aftermarket 110?

Lastly, if you can do 60 mph with a 110, what are the 140-150's capable of?! I guess they're clutchless manuals?

 

[scott s]

I see this kit to take it out to 88cc, but how are you getting 110cc?

52mm 88cc Big Bore High Compression Cylinder Kit All SL70 XL70 CL70 ATC 70 SL XL | eBay

 

[theraymondguy]

Gear RPM & MPH Calculators

This gearing calculator has been very accurate for me. The rear sprocket looks hopefully similar to the CT70, and if so you're in good shape for rear sprocket selection (I had to guess at a couple of variables, but 13 front, 35 rear = ~ 65 MPH top speed).

 

[theraymondguy]

I see this kit to take it out to 88cc, but how are you getting 110cc?

52mm 88cc Big Bore High Compression Cylinder Kit All SL70 XL70 CL70 ATC 70 SL XL | eBay

The original 72cc engine can go up to 117cc. The cases will have to be bored to accept a larger cylinder, the crankshaft replaced to provide more stroke. This is a moderately expensive, it requires as much work as a complete overhaul and assumes the transmission in your engine is in good shape (which is not always the case by any means).

This 'kit' lists at $550, but plan at least an additional $200 to 250 for carburetor and shift forks/incidentals.

The 'china' horizontal engines are commonly based on the z50/ct/cl/sl/atc70 engines. If it has 2 mounts it will bolt in to a CL70. The only concern is, as the cc's go up, the length of the cylinder increases, there are limitations for certain Honda frames as to what will fit.

China small blocks are anything less than 110cc. China mid blocks are 125 to 160. Beyond is big block and not for the uninitiated.

Displacement is no guarantee of comparative horsepower. A 110cc China engine will not hold it's own with a TB Parts 108cc kit. One could list comparisons all day, suffice it to say that a 150 will produce ~ 10 - 12HP. More than enough for a first timer.

 

[scott s]

Here are some pics I just snapped of the engine and mounts. It's raining out and the bike is still strapped down in the van, awaiting a trip to the DMV.

It appears that I have a 2 bolt engine and the Piranha engines look to be 2 bolt....at least in the pics. Or, am I not picking up what ya'll are laying down?

 

[scott s]

The original 72cc engine can go up to 117cc. The cases will have to be bored to accept a larger cylinder, the crankshaft replaced to provide more stroke. This is a moderately expensive, it requires as much work as a complete overhaul and assumes the transmission in your engine is in good shape (which is not always the case by any means).

This 'kit' lists at $550, but plan at least an additional $200 to 250 for carburetor and shift forks/incidentals.

The 'china' horizontal engines are commonly based on the z50/ct/cl/sl/atc70 engines. If it has 2 mounts it will bolt in to a CL70. The only concern is, as the cc's go up, the length of the cylinder increases, there are limitations for certain Honda frames as to what will fit.

China small blocks are anything less than 110cc. China mid blocks are 125 to 160. Beyond is big block and not for the uninitiated.

Displacement is no guarantee of comparative horsepower. A 110cc China engine will not hold it's own with a TB Parts 108cc kit. One could list comparisons all day, suffice it to say that a 150 will produce ~ 10 - 12HP. More than enough for a first timer.

Thank you. Please keep the info coming.

BTW, this is my first bike with this type engine, but I have several CB550's, some stock, some warmed over, as well as some DOHC '80's Yamahas, so I'm an experienced rider. I just think the idea of a small cc bike is very appealing.
I built a KZ250 café racer a few years ago. There's something about being able to ride a bike at 9/10ths or 10/10ths.

 

[theraymondguy]

You've got it. One mount over top of the cases, one down the back.

Passing other vehicles on a secondary highway with a mini Never gets old

 

[scott s]

Gear RPM & MPH Calculators

This gearing calculator has been very accurate for me. The rear sprocket looks hopefully similar to the CT70, and if so you're in good shape for rear sprocket selection (I had to guess at a couple of variables, but 13 front, 35 rear = ~ 65 MPH top speed).

It looks like there's a HUGE selection of sprockets to choose from, front and rear, for this bike, so I'll definitely have to play with the calculator a bit.

 

[scott s]

One thing that concerned me is that the box 'o' spares included a shift shaft and some sort of selector(?).
I straightened the bent shift lever and attached it and found all four gears, and the clutch works, but now I can't get it back in neutral.

 

[scott s]

The plan all along was to keep the patina. The tank had some varnish and minor rust inside, so I started to clean it using my tried and true methods.
Here are all the fluids I needed.