Prototype CL350 Build

VintageHondaGarage

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Jul 5, 2020
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Location
Milwaukee, WI USA
Greetings all. I picked up this early 1970 CL350 this past summer with plans to just do a budget build on it.

Well, that is always the initial intention right? Things have quickly spiraled into chaos and it has now become my test bike for a bunch of custom parts that might make their way to market someday.

There is no real “plan” for it, just kind of winging it as I go

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What started off as a basic degrease and clean quickly turned into a full top end tear down.

The head gasket was leaking oil pretty bad and even though this engine was a proven runner, a quick compression test showed both cylinders well under 100psi, so a freshening up on the top end was a no-brainer.

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Welp, there goes the budget portion of this “budget build” CB350. Sometimes you just can’t pass up a good deal. These mikuni VM30’s from sudco should wake this motor up a little bit.

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Im wanting to bring more components of my builds “in house” one could say. Pieced together this little kit from Venhill that should get me started on any CB/CL350 project and then I’ll expand from there. It’s fun making your own stuff.

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Reject tradition. This CB350 drain plug adapter does away with the old and crusty steel ones in favor of a more modern (and cheaper) magnetized aluminum drain plug. It also uses the same tool as the rear wheel retainer ring.

This was a fun one to do with lots of measuring and machine work. Got to do single point threading on the lathe for the first time in about 20 years. Overall super happy with how this came out.

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Why? Because I can. Continuing my goal of making as many parts as I can for this project, I present to you my CB/CL 350 rear wheel spacers. These were designed so that the holes could be seen and not blocked by the chain adjuster/swingarm. Matching front spacer to come.

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Why spend $45 on a single fork bolt when in a few hours you can just make them yourself? This is just an aluminum prototype, the real ones will be made out of stainless when it’s all said and done.

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CB/CL350 battery box prototype. This box is designed to fit the small those guys in Houston MotoBatt AGM battery, provides a new mounting location for the 4into1 regulator/rectifier, and retains the stock mount for the starter solenoid. Still a little bit of tinkering and adjusting to go before it’s ready to be installed, but a great first step nonetheless

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Finally a finished product. These fork bolts are made from 304 stainless steel and are a great replacement for your pitted chrome ones. These bolts replace PN# 90123-292-780 found on the 1970 and 1971 CB350/CL350/CL450.

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You need to pull those Mikuni's apart to check what's inside them.
They are probably still set up for a two stroke but with lean jetting for a four stroke?
The needle jet is most likely a primary choke' instead of an emulsion tube.
I just posted pictures from a 1970~71 carb manual explaining things, post 214

CB350 to cafe' from scratch by a (not so much) teen

Can I grind off the rocker arm instead? Is that something I can do by myself? No, this is a precision adjustment required and the valves are, as you'd expect, hardened steel so it has to be done with the proper equipment to both get the right results and for the modification to be reliable...
www.vintagehondatwins.com www.vintagehondatwins.com
 
crazypj said:
You need to pull those Mikuni's apart to check what's inside them.
They are probably still set up for a two stroke but with lean jetting for a four stroke?
The needle jet is most likely a primary choke' instead of an emulsion tube.
I just posted pictures from a 1970~71 carb manual explaining things, post 214

CB350 to cafe' from scratch by a (not so much) teen

Can I grind off the rocker arm instead? Is that something I can do by myself? No, this is a precision adjustment required and the valves are, as you'd expect, hardened steel so it has to be done with the proper equipment to both get the right results and for the modification to be reliable...
www.vintagehondatwins.com www.vintagehondatwins.com
Click to expand...
They were put together and jetted by Sudco for a CB350, but yes I will double check everything before I fire up the motor
 
SUDCO TELLS LIES, or, they did when I contacted them.
The carbs were jetted for a 1970's 125cc MX bike and every set I saw for 5~6 years were the same.
Main jet was around 185~190, pilots 40~45. I forget the rest (it was about 15~16 years ago)
I still have a new pair of VM's on the shelf in garage, never got around to 'fixing' them.
 
crazypj said:
SUDCO TELLS LIES, or, they did when I contacted them.
The carbs were jetted for a 1970's 125cc MX bike and every set I saw for 5~6 years were the same.
Main jet was around 185~190, pilots 40~45. I forget the rest (it was about 15~16 years ago)
I still have a new pair of VM's on the shelf in garage, never got around to 'fixing' them.
Click to expand...
I have some saved data from a few racers in my area that run the Mikunis. I’m confident I’ll be able to get it sorted out
 
Racers are usually concerned with top end more than idle and low throttle opening, even the $25,000 Tod Henning's bikes used 'primary choke' though.
They can be made to work well enough for most people, I just like things 'right' so I modify stock carbs to work with K&N filters.
 
crazypj said:
SUDCO TELLS LIES, or, they did when I contacted them.
The carbs were jetted for a 1970's 125cc MX bike and every set I saw for 5~6 years were the same.
Main jet was around 185~190, pilots 40~45. I forget the rest (it was about 15~16 years ago)
I still have a new pair of VM's on the shelf in garage, never got around to 'fixing' them.
Click to expand...
Want to sell them?

If I can afford them.
 
VintageHondaGarage said:
Reject tradition. This CB350 drain plug adapter does away with the old and crusty steel ones in favor of a more modern (and cheaper) magnetized aluminum drain plug. It also uses the same tool as the rear wheel retainer ring.

This was a fun one to do with lots of measuring and machine work. Got to do single point threading on the lathe for the first time in about 20 years. Overall super happy with how this came out.

View attachment 54322View attachment 54323
Click to expand...
My reservation about this would be that those later small drain plugs are generally from engines that come with an oil filter, so hopefully there wouldn't be too much crud floating about in the oil. I'd guess that with the large original drain plug there'd be a better chance of getting all the muck drained out. Agreed, your solution does look neat.
 
VintageHondaGarage said:
CB/CL350 battery box prototype. This box is designed to fit the small those guys in Houston MotoBatt AGM battery, provides a new mounting location for the 4into1 regulator/rectifier, and retains the stock mount for the starter solenoid. Still a little bit of tinkering and adjusting to go before it’s ready to be installed, but a great first step nonetheless

View attachment 54331
Click to expand...
Question, why does Common Moter (misspelled on purpose) get filtered to “those guys in Houston”?
 
VintageHondaGarage said:
Question, why does Common Moter (misspelled on purpose) get filtered to “those guys in Houston”?
Click to expand...
Because the internet is flooded with their BS, backyard repair videos and way overpriced parts already. They're doing just fine with their own SEO, they don't need or deserve any exposure from here.
 
As things move along with the build, I’m always looking for new things to create to make the bike more “mine”. Today’s example is something that most people wouldn’t even realize is there, the steering lock cover. Now I can color match to whatever color I end up painting the tins. IMG_0702.jpegIMG_0703.jpegIMG_0704.jpeg
 
VintageHondaGarage said:
As things move along with the build, I’m always looking for new things to create to make the bike more “mine”. Today’s example is something that most people wouldn’t even realize is there, the steering lock cover. Now I can color match to whatever color I end up painting the tins.
Click to expand...
Pretty cool - if only you could make the little cover as well and have it pivot on a shouldered version of that allen screw.
 
ancientdad said:
Pretty cool - if only you could make the little cover as well and have it pivot on a shouldered version of that allen screw.
Click to expand...
I thought about it, but ultimately decided to just go with the exposed version. This bike (and most these days) don’t see the kind of weather that the little flip was designed to keep out anyways
 
Sometimes mixing parts from different models and years doesn’t always work out the way you’d hope, so
you gotta improvise.

The fork lower is off of an earlier CL350 and the fork cover is off of a 71 CB350. Since the CL350 lower is larger in diameter, the little chrome cover piece that comes one the CB350 doesn’t fit, leaving a small section of spring exposed.

Solution: a simple piece of round aluminum machined to the proper size. Now it looks like it was meant to go together.


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