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Discussion Starter · #1 ·
Hey All,

Working on a 1976 CB360T with the 754A carbs. I'm following the service manual and have removed the carbs and completed the disassembly as far as the process goes in the manual (page 66). I have the gallon can of GUNK Carb Cleaner.

Draining the fuel. Yikes! With all that sediment I can't believe it ran at all. No wonder it didn't run well.
IMG_0246.jpg

Before I go any further, I want to confirm a few things.

The float valve seat is really stuck in there. How hard do I pull on that to get it out? Or what other method should I try?

Second, do I break the carb down any further before putting it in the cleaner dip? The manual didn't say anything about parts like the idle screw or butterfly valves.

Finally, is that little plastic plug (yellow/tan circle on the output side of the carb) ok to go in the dip? Don't want to melt that thing.


Thanks
 

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Yeah goes to show how clean you need the carbs to be, but also shows that the bike will try to run anyway!

For the float valve seat, I was planning to replace it with a new one from a rebuild kit (one of the few replacement brass parts I think are OK to swap with the originals), so I just used a set of needlenose pliers to pull it out like a bad tooth!

Did you punch out the secondary emulsifier tube (it is pressed into the body of the carb, I used a metal punch to LIGHTLY tap it out)? Mine was FILTHY and had to be cleaned up with some scotchbrite pad rubbing and carb cleaner spray. I don't recall if your upper jets are removable or pressed in, but I cleaned mine up. They looked spotless, but I figured I would clean them anyway. Other than that, I think you would be OK to just plop that sucker into the carb dip.

For the plastic plug, I had mine in Berryman Carb Dip for an hour or two and it was fine. Take this as anecdotal evidence only...
 

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Generally, you don't want to soak any rubber or plastic parts in carb cleaner. It depends on the cleaner used and what the plastic/rubber parts are actually made of, though.
 

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Discussion Starter · #6 ·
So, got 1 cleaned up. 20 minute soak of the body and then the loose parts. The carb wasn't in terrible shape to begin with. Mostly just the gunk on the outside. And it came out pretty good IMO. Just had a little pick of picking and scraping to get the last of the gasket sealant out of the float bowl groove. And that little plastic plug looks no worse for the wear.

Still waiting for the rebuild kits to arrive, so I can reassemble this one before I tear apart the other. Don't want to get ahead of myself.

Before pics. Forgot to take the after. I'll upload later.
IMG_0275.jpg IMG_0294.jpg IMG_0293.jpg

A separate question. Both carbs are missing the little plugs that cover the end of the butterfly valve shafts. CMC has replacements for $18. Has anyone found adequate substitutes? I get the feeling they're more than a suggestion given all the stuff I've read about eliminating air leaks and tuning the carbs.

Thanks!
 

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Hmm... my last post disappeared. Here it is again:

I was also missing the shaft plugs. I ended up ordering the plugs from CMC and felt the sting of buyers remorse. Nearly $20 for little machined metal disks? Come on! I am sure you can find something equivalent at an Ace Hardware, and then seal up the gaps (and to keep them from falling out) with some gasket sealer. I also recall seeing somewhere that HondaTwins member crazypj makes them too, probably for a lot less than CMC.
 

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Discussion Starter · #11 ·
After waiting for the parts & supplies to arrive, I finished the carb cleaning & rebuild. Took lots of pictures before I tore into the left one. All those attachments looked pretty intimidating but ended up not being too bad. I think the previous owner (or whomever she hired) didn't clean the left one as recently as the right. There was significantly more gunk & residue in this one than the first. Even with that, it took only 20 minutes in the chem dip to clean it just fine.


Anyway, I followed the manual and the videos as best I could to reassemble. I went with the 100 jet (removed the 107.5 that was already in there) and 18mm float height. I'm not after performance, just simple reliability. I don't do high-rev riding so I decided to start with the factory recommendations.


Being the optimist (and relatively inexperienced and niaive) I put everything back together on the bike. I was hoping to get to ride a little on this beautiful Sunday afternoon. But it was not to be. It took some time to cut and install the fuel supply and carb drain tubes (no drain tubes on the bike when I bought it. more on this later). It took a while to get the replacement regulator/rectifier mounted and connected. Took a longer while to get the carb boots connected. Took a while to get the airboxes and filters mounted. And what a special tortuous device from Satan are those little snorkel/screen tubes up from the airbox!

Finally got that done and mounted the gas tank. Connected the supply hoses and watched the fuel start to flow through one of the in-line filters but not the other. Hmmm... Oh well, maybe it just needs a little suction to start the flow so I turned the key on but set the kill switch to off. Pushed the starter button for a few seconds but no luck. So I decided to go ahead and start it, it just needs a little more encouragement, right?

Well, it started just fine but I could tell it wasn't right. Only running on one cylinder and no fuel being pulled through that second hose. Turned it off after about 30 seconds and started checking around. Looked under the bike and see a steady stream of fuel coming out of one of my shiny new drain tubes. Yikes! Shut off the petcock, get a pan under there, open the garage door, turn on the fan!!!

Anyway, I was instantly exhausted and frustrated so I drained the tank and the one carb that had fuel; dried up, cleaned up, and went inside for the night.

I guess even though I carefully measured 18mm float height, it's not enough. I had originally aimed for 16mm the way it's described in the CMC carb rebuild videos but that bottomed-out the float so I moved to 18mm. I'll have to figure out the fuel supply problem that is preventing flow from the other tube but I won't be surprised if that carb overflows too. For float height, I'll reset for 20mm and see how that works. Maybe it's just a difference in the way I'm measuring.

Onward through the fog!
 

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The floats could be set incorrectly, but it's also possible the float valve isn't shutting off due to a defect or some trash hanging it up.
 

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You said that there was a lot of sediment when you began the carb project, which would mean that your petcock would have been subjected to that same amount of sediment. That's where I would guess your fuel flow problem is to one of your carbs.

The other carb (the one that is overflowing) . . . you said you set float height to 18mm but, if my thinking is correct, because you're measuring that float height with the carb upside down, that means the smaller the measurement, the higher the fuel level in the bowl (right?)

So setting to 16mm or 18mm is giving you a lot more fuel in the bowl than if your floats were set to 20mm.

Clean your petcock and set your floats to 20mm and see what happens. Good Luck!
 

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Discussion Starter · #14 ·
I suspect you're right on the sediment. I cleaned the petcock but I think there's still junk on the bottom of the tank that will keep causing this.

What do people use for cleaning tanks? There's not really any rust that I can see. I think it's just dirt and grime.

And what do y'all do with the dirty, gunky fuel? I've already collected about a pint and I don't really have a good place to dispose of it.

For cleaning the tank, I found an article that goes through using vinegar, then acid & water, then baking soda, then gas. Maybe I'll give that a try. Removing rust from a gas tank - Moped Wiki

As for the float height, I think you're spot on there, too. I watched a MotorcycleMD video last night on this exact topic and he showed how much variance there was measuring upside down versus tilted. I forgot the exact amount he had but it was several millimeters, easily enough to cause a problem.

I've just been putting it off for a few days because I was disappointed that I was going to have to tear it all apart again. Oh well, like I tell my boys, "Do it right or do it again."

Cheers!
 

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Hmm... my last post disappeared. Here it is again:

I was also missing the shaft plugs. I ended up ordering the plugs from CMC and felt the sting of buyers remorse. Nearly $20 for little machined metal disks? Come on! I am sure you can find something equivalent at an Ace Hardware, and then seal up the gaps (and to keep them from falling out) with some gasket sealer. I also recall seeing somewhere that HondaTwins member crazypj makes them too, probably for a lot less than CMC.
Without the shaft plugs bike runs like ****e, there is a hole directly into intake. Honda doesn't list them, you have to buy a complete carb body
I make the plugs for CMC, don't charge him that much but he stocks them and has to make a profit. (and it isn't a whole lot)
They need to be specific thickness as well as diameter plus have relief machined into reverse side, I designed them to have a flush surface and look better than stock
Plugs are also an 'odd' size, I haven't found a standard size that works (it's Imperial not metric, 1/2" plug will most likely split body :()
Oh, stock float level no longer works with modern fuel, you need a minimum of 1mm higher and 21mm if you can only get E10
There are two filters stock, one inside tank, one on sediment bowl of fuel tap. CB uses brass mesh filter on 'standpipe', CJ should have a nylon micro-mesh in tank. Never found a way to remove CJ filters without damaging them and the brass ones are often damaged.
 

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Discussion Starter · #16 ·
Thanks, PJ. I went ahead and ordered some of the plugs along with the carb vacuum nipples. Figured it can't hurt to give a little support back to the crew on here. And given how much effort I'm putting into these carbs, I really don't want to end up with poor performance, so the plugs can't hurt.

Also ordered a petcock rebuild kit from 4into1. Theirs includes the sediment bowl filter and is a little less $ than CMC.

AND... discovered there are no mesh filters on the in-tank petcock supply tubes. Makes it really easy to understand how the sediment keeps appearing in the fuel that I drain from the carbs...

I took the carbs off this morning and reset the float height to 20mm (measured with the carbs tilted to the point where the floats are just fully seated).

Thanks again everyone for the help.

Cheers
 
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