1974 Honda CL360 barn find

Now that I am a few days into disassembly, I have to say that the 1980 Suzuki GN400 is much easier to work on. It only took me a couple hours to completely strip the Suzuki down to the frame.

Observations:

1. Much simpler design of everything. The Honda parts seem overly complicated in design and fussy in fitment. Good engineering creates simple (cheap) solutions.
2. Much stronger design. The Suzuki has larger diameter tubing in the frame, larger diameter forks, larger diameter shocks, etc. The sheet metal portion of the Honda frame is puzzling.
3. It is easier to work on a bike with less rust. Not a Honda problem.

I find myself wondering if the difference is Suzuki versus Honda or 1974 versus 1980?

What is your experience? Is Suzuki engineering just simpler and stronger than Honda? (I haven't touched Kawasaki or Yamaha for comparison.)
 
So these CB360 pipes should be a direct fit?

CB360 pipes.jpg
 
So, I'm thinking about making an intake manifold and going with a single carb with cone filter for simplicity of tuning. Thoughts? Any specific carb recommendation to feed both cylinders?

Also, been thinking that this motor will likely get a complete rebuild. What performance upgrades are popular?
 
Last night I got deep into an idea of using a Weber DCOE 40. I learned I'm not the first to have this thought (Drixton). The Keihin 747 is a 28mm venturi, and so I should be able to set up the DCOE 40 with 28mm venturis for starters. It sure would be a cool aspect of the build.

Started working on L/R intake plenums in SolidWorks. I know someone who does aluminum sand-casting. I guess it is now possible to lost-PLA casting with 3D printed parts. So I am checking into this feasibility since I can design and print my own parts.

Plenums would have a tapered throat (from 40mm at the carb to 31.5mm at the cylinder). Right now looking at 40mm plenum length with the top of the carb throat equal to the top of the cylinder port. Also a 4 degree tilt at the cylinder flange would level the carb and give a little extra clearance above the carb.

OBA59-Dennehy-Drixton-Honda-8.jpg
 
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So, I'm thinking about making an intake manifold and going with a single carb with cone filter for simplicity of tuning. Thoughts? Any specific carb recommendation to feed both cylinders?

Also, been thinking that this motor will likely get a complete rebuild. What performance upgrades are popular?
Does anyone have engine specs for the 360?

- Bore/Stroke
- CC volume
- quench (do the pistons zero-deck?)
- piston displacement (or flat?)
- Cam timing/lift/duration
- Etc.
 
You've probably read about it already, but one of the mods for the 360 is to bore out and use a pair of pistons from a Suzuki GS850. It's getting so that the 850 pistons are harder to find but it's a mod that offers a relatively significant increase in power. @crazypj is the man who developed it and has done several. He has a thread or two on here that cover it. We (@Hurco550 and I) did it on my 360 and it went very well. The wrist pin diameter and general size, except for the diameter of the bore, are the same as the stock 360 pistons so it's a matter of having the cylinders bored out and having a head gasket made. According to Peter's description, the stock 360 head easily handles the larger volume of intake and exhaust and the percentage of power output increase is greater than the percentage of displacement. As for the Weber DCOE, I believe TJ, @beachcomber on here, has messed with one on a Kawi 750 twin. there may be others as well.

I'm going out to the shop in a few minutes, I'll look to see if I have those specs, or at least some of them, for you.
 
You've probably read about it already, but one of the mods for the 360 is to bore out and use a pair of pistons from a Suzuki GS850. It's getting so that the 850 pistons are harder to find but it's a mod that offers a relatively significant increase in power. @crazypj is the man who developed it and has done several. He has a thread or two on here that cover it. We (@Hurco550 and I) did it on my 360 and it went very well. The wrist pin diameter and general size, except for the diameter of the bore, are the same as the stock 360 pistons so it's a matter of having the cylinders bored out and having a head gasket made. According to Peter's description, the stock 360 head easily handles the larger volume of intake and exhaust and the percentage of power output increase is greater than the percentage of displacement. As for the Weber DCOE, I believe TJ, @beachcomber on here, has messed with one on a Kawi 750 twin. there may be others as well.

I'm going out to the shop in a few minutes, I'll look to see if I have those specs, or at least some of them, for you.
Thanks for the info. I'll look into boring it out.
 
Does anyone have engine specs for the 360?

- Bore/Stroke
- CC volume
- quench (do the pistons zero-deck?)
- piston displacement (or flat?)
- Cam timing/lift/duration
- Etc.
- Bore/Stroke (mm/in) - 67 x 50.6/2.638 x 1.992
- CC volume - 356
- quench - ?
- piston displacement - ?
-Cam timing - ?

Pix of the info I have:

Hondaspecs04.jpeg


Hondaspecs03.jpeg


Hondaspecs02.jpeg


Hondaspecs01.jpeg
 
Its interesting that you critique Honda parts as over complicated while also contemplating a Weber DCOE swap.

Honda ran stamped frames on some bikes through the 80s, but not all. A CB450 didn’t have a stamped frame, while a CB500 did. CM400s and 450s had stamped, stress member frames.
 
Its interesting that you critique Honda parts as over complicated while also contemplating a Weber DCOE swap.

Honda ran stamped frames on some bikes through the 80s, but not all. A CB450 didn’t have a stamped frame, while a CB500 did. CM400s and 450s had stamped, stress member frames.
LOL... yeah, but the Webers are complicated in such a sexy way. :)

When I look at Honda's engineering from an engineering perspective, I see decisions stacked on top of decisions. Almost sedimentary. Rather than designing a new part to update an old one, they just add another modification to the old part. So you end up with more pieces/bends/welds than is necessary if you just started over from scratch. This is what I mean by "complicated" - from a manufacturing standpoint it seems like there is a lot of lost efficiency.
 
This is what I mean by "complicated" - from a manufacturing standpoint it seems like there is a lot of lost efficiency.
I can't disagree w/ you, but I'll bet the Japanese would. :)
 
Here are some renderings of the plenums to adapt to the DCOE40. Larger side (closer together) is the carb side. 4 Degrees of downward tilt at the engine-side flange.

Think I might include a boss in the casting to drill and add a port for taking vacuum measurements.

Plenum1.jpg


Plenum3.jpg


Plenum2.jpg
 
I can't disagree w/ you, but I'll bet the Japanese would. :)
I owned a Honda, Toyota, and Subaru at the same time. I do all of my own wrenching. The Subaru was junk. Wasn't designed to be repaired... a disposable car (so I got rid of it). The Honda is mostly reliable, works well for what it does, but lacks the refinement and efficiency of the Toyota. And working on the Honda is complicated - nothing is as easy as it should be (or is on other vehicles). Toyota, by far, has better engineering. Their engineering obviously takes future maintenance and repairs into consideration, and their designs are very efficient.

This is what has me wondering if there is a corporate cultural difference between Honda and Suzuki that makes the Suzuki so much simpler and easier to work on... or between 1974 and 1980 had manufacturing efficiency just progressed that much?
 
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I can't disagree w/ you. One of the best vehicles I've ever owned was the Tundra pickup I just got rid of. (One of my brothers told me I sound like our dad who always maintained that the best vehicle he ever owned was the one he just traded off and the worst one is the one he has right now.) I will say, though, if you want complicated, try changing out the starter on a 5.7L Tundra! I'm a halfway decent wrench and it took me two days! And, yes, I have often wondered what a Toyota motorcycle would be like.
 
Here is a mockup of the plenums with a Weber DCOE. I added ports for 1/4in hose barb fittings - primarily for measuring vacuum, but secondarily for running a balance tube to soften the intake pulses.

For the plenum lengths (50mm + 7mm per flange) I sorta licked my finger and stuck it in the air. Ideally, I think the intake runners should be tuned for the 5k-6k RPM range, but there are so many variables it is dizzying trying to calculate the ideal length. If I can find a good way to get me close on calculations I might stretch them (don't really want them shorter) because I have a feeling longer plenums might benefit drivability. However, the factory Keihin carbs are mounted pretty close to the engine.

Carb Mockup.jpg


Carb Mockup 2.jpg


Carb Mockup 3.jpg
 
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I think I can work with this plenum length:


1701708020456.png


I am assuming the GS850 pistons and using the shorter calculated length (294mm). I measure 84mm from the flange to the valve seat, 64.5mm for the plenum (centerline), and 118 for the carb body. This leaves 27.5mm for the air horn throat length (not counting inlet radius) I might be able to print these to get a more generous intake radius and a consistent throat diameter.

(I chose a target RPM of 8650 because this lined up with what I measure for the intake port diameter - 30.5mm.)
 
I've heard of lost PLA casting but I've always wondered why people bother when there are filaments available that are made specifically for sand casting? Sure PLA is dirt cheap but if you're putting the time into designing the part to begin with, is $50 for filament really a big deal? For example:

https://machinablewax.com/wax-filament/

I've considered casting parts for a few vintage Ducatis but so far haven't taken the plunge. Mostly because I don't have the resources to do the actual casting, but the number of possible projects that could use it are growing. There is a makerspace type of place around here that could probably help but dag nab the membership is expensive. Those costs would go a long way towards buying the equipment needed to do it myself.

For now my 3D printed stuff has been limited to ASA and some PETG parts, but casting aluminum was one of the reasons I got a 3D printer to begin with. I really should get more serious about it. Especially since there's this tail light I've been working on that would be so much cooler cast than printed/painted...

In other news, as a retired development engineer (automotive exhaust mainly) I applaud your enthusiasm on the bikes you're working on, but as someone who's been riding for 30+ years I've been biting my tongue when I read your threads. Don't get too hung up on the theoretical part of what's "ideal". The details that make that intake runner ideal at 8650rpm will hurt it at 5800rpm or where ever. In your other thread, those angles you've calculated so precisely will change as soon as you sit on the bike or hit the brakes. I get the interest in it, and do not mean any of this as any type of flame, but keep the big picture in mind as you do all of this. Yeah you need a starting point so why not try to make it good, but the reality is a heck of a lot of engineering decisions in vehicle development are based on making it fit the space or using readily available parts, and the end result is perfectly fine for bikes that don't get judged by lap times in the hands of alien riders.

I know it's a cliche, but the idea of not letting perfect get in the way of good enough is SO true... don't fall into the trap that some engineering "ideal" is the best answer and you're somehow taking a short cut if you don't use it. A bike out there being ridden with less than ideal intake runners is a lot more impressive/fun than the one that has all the ideal numbers in it's CAD model but hasn't been built yet because you haven't quite worked out the ideal shape of the velocity stack or where to source 34.7mm diameter tubing or whatever.

Again, I don't mean any of this as a flame. These threads are much more refreshing than the typical "I got this Japanese cruiser free because it sat at the bottm of a lake for 20 years, where can I buy the kit to make it into a cafe racer OH LOOK A SQUIRREL!" threads.
 
I've heard of lost PLA casting but I've always wondered why people bother when there are filaments available that are made specifically for sand casting? Sure PLA is dirt cheap but if you're putting the time into designing the part to begin with, is $50 for filament really a big deal? For example:

https://machinablewax.com/wax-filament/

I've considered casting parts for a few vintage Ducatis but so far haven't taken the plunge. Mostly because I don't have the resources to do the actual casting, but the number of possible projects that could use it are growing. There is a makerspace type of place around here that could probably help but dag nab the membership is expensive. Those costs would go a long way towards buying the equipment needed to do it myself.

For now my 3D printed stuff has been limited to ASA and some PETG parts, but casting aluminum was one of the reasons I got a 3D printer to begin with. I really should get more serious about it. Especially since there's this tail light I've been working on that would be so much cooler cast than printed/painted...

In other news, as a retired development engineer (automotive exhaust mainly) I applaud your enthusiasm on the bikes you're working on, but as someone who's been riding for 30+ years I've been biting my tongue when I read your threads. Don't get too hung up on the theoretical part of what's "ideal". The details that make that intake runner ideal at 8650rpm will hurt it at 5800rpm or where ever. In your other thread, those angles you've calculated so precisely will change as soon as you sit on the bike or hit the brakes. I get the interest in it, and do not mean any of this as any type of flame, but keep the big picture in mind as you do all of this. Yeah you need a starting point so why not try to make it good, but the reality is a heck of a lot of engineering decisions in vehicle development are based on making it fit the space or using readily available parts, and the end result is perfectly fine for bikes that don't get judged by lap times in the hands of alien riders.

I know it's a cliche, but the idea of not letting perfect get in the way of good enough is SO true... don't fall into the trap that some engineering "ideal" is the best answer and you're somehow taking a short cut if you don't use it. A bike out there being ridden with less than ideal intake runners is a lot more impressive/fun than the one that has all the ideal numbers in it's CAD model but hasn't been built yet because you haven't quite worked out the ideal shape of the velocity stack or where to source 34.7mm diameter tubing or whatever.

Again, I don't mean any of this as a flame. These threads are much more refreshing than the typical "I got this Japanese cruiser free because it sat at the bottm of a lake for 20 years, where can I buy the kit to make it into a cafe racer OH LOOK A SQUIRREL!" threads.
Great advice on using wax filament for investment casting, but just want to point out that it's not always so cut and dry. In many cases, print nozzles need to be altered or swapped out, so a little bit of research is necessary to determine compatibility for your printer. Personally, I would go with PolyCast. It's more compatible across the spectrum.
 
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