'75 CB360t carburetor question

This is my first post to this site, and I confess I'm perhaps overly proud that I "made it this far" before needing to post.

I have completely rebuilt my carburetors for this bike, which were not at all corroded, but heavily clogged with old fuel deposits (the bike has only 619 miles on it, so has basically sat for more than my lifetime.

Here's the narrative:

1. Reassembled completely, reinstalled carbs, reattached fuel lines, etc.
2. Bike started on FIRST turn-over (full choke, no starter fluid assist)
3. Ran rough for about 10 seconds, both exhaust pipes emitting medium grey exhaust (choke was still on), I had to keep a little bit of tension on the throttle (started to die if I let off), bike ran rough, and stalled out.
4. Hasn't started since, but has had brief ignition randomly while I crank on it.

Relevant observations:

1. I have a normal spark on one cylinder (white, strong, etc), and the other cylinder has a somewhat intermittent, orange spark that doesn't appear to arc from the center node to the side node. I plan to replace both spark plugs tomorrow.
2. I'm unsure if I have the pilot screws set appropriately. Some recommendations are 1 1/2 turns, others 2, and I believe they were about 1/2 when I pulled them off (for cleaning, rubber replacement, etc). The service manual, as far as I can tell, has no listed suggestions.
3. The batter was very low, and soon after went dead. It's brand new, and I wore it down over several recent attempts to start it BEFORE rebuilding the carbs.
4. Batter is currently slow charging.

Any thoughts folks? Battery issue? Mixture issue? Pilot screw issue? If I can get it to a stable idle, I'll adjust to 1,200rpm, etc.

I appreciate the help with this. 'Tis my first bike project.

Make sure you have a strong spark before you continue tinkering with the carbs.
I usually start the mixture screw @ one full turn out and go from there.
If you know your going to be cranking a lot on the starter, hook up a car battery with jumper cables. It won't hurt anything. The bike will only pull as many amps as it needs.
Make sure you have the cables adjusted properly too.
did you install fuel filters? It's cheap insurance that you won't get clogged up again.
Also triple check your float level. I had mine way too lean once and it would barely run.
Did you clean your petcock? are you sure there is enough fuel in the tank? Most times it the stupid little things that get overlooked and cause the biggest head aches.

I haven't disassembled the petcock yet (but do plan to eventually re-seal it), however I can see that fuel flows quite nicely through it - due largely to the fact that there are clear filters on each fuel line. I've also observed that it STOPS fuel flow just fine, too. So, to answer your question, fuel is present, the lines are filtered, and HOPEFULLY I've not picked up any new contaminants.

New observation as of this morning: the bike enjoys fresh starts. This morning, after slow charging the batter all night, the bike was almost able to sustain an idle on the first attempt. Thereafter, it was intermittent, a cough here, a few turns there. Nothing like the first attempt this morning (same as when I first installed it yesterday).

Second new observation: charging the battery does not appear to have solved the weak left spark issue. I'll definitely replace the plugs today, but even with my limited understanding of electronics, this sounds like a broader electrical issue. Aside from the initial "almost-start," the left pipe appears to be emitting less exhaust.

The float levels: I presume you're talking about the 18.5mm measurement, yes? I just wanted to confirm.

Cable adjustments: the throttle cables?

Conclusion:

1. Any suggestions about the spark strength issue?
2. I will re-check floats today, confirming 18.5mm when the valve is seated.
3. Why would the bike be most inclined to start on the first attempt? Am I perhaps flooding it thereafter (which leads me to wonder if the float is set to high, if anything)?

If I may offer a hypothesis (seeing as I know oh-so much): I think I have two issues here: weak/no combustion in one chamber, and an overall bigger issue of too rich a mixture.

I appreciate your help with this, and also generally appreciate that there are forums where info sharing is to generous.

Points are key in a good spark. Dirty, oxidized or pitted points will cause a weak s[ark also.

Check the wiring from the point to the coils, to power. A dirty or weak connection will also cause a weal spark. The bullet connectors are notorious for coming loose, or getting corroded.

Alwys start your troubleshooting with the electrical connections, as it is annoying changing all sorts of parts and find out the wire was loose.

Here's the update:

1. Replaced the plugs
2. Cleaned points
3. Confirmed float level adjustments (had to fiddle with one of them)
4. Re-cleaned fuel lines, in-line filters
5. Tore down, cleaned petcock.

Bike started on the first crank.

New issues:

1. Idle sometimes revs on its own from idle to roughly 4k. Crack it a couple times and it starts to creep back down. When it feels like it.
2. Runs reasonably well (and exhaust feels evenly pressured/colored) until it warms up.
3. When warm, it starts to lose power like it's running out of fuel (it's not, trust me), lags for a bit, then simply dies. Hard to re-start (until cooled down a bit)
4. Right pipe is well blued, feels a little cooler than appropriate right after running. *(by "running," I mean driving 1st to 4th gear for perhaps .8-1.5 miles)
5. At same time, left pipe is not blued at all, extremely hot.

Any thoughts? I think it's fairly obvious I have a carb issue (and perhaps an electrical issue) still, but I'm not entirely sure what to do about it, especially if I can't get at least a consistent idle and it cuts off when hot.

I will be doing the following tomorrow:

1. Replacing carb diaphragms (parts just arrived in the mail)
2. Tearing down both carbs, cleaning everything again (mostly checking for debris in the jets, honestly).
3. Fashioning a voodoo doll in the shape of a motorcycle.

As always, I sincerely appreciate the help.

Check your carb intake boots. They may be worn and sucking in too much air. Check it by spraying carb cleaner or something safe over the carb boot seal and see if it sucks in the fluid like a vacume!

I checked the boots as you suggested, and there was no spike (or drop) in rpm/function.

Current condition:

1. Starts, runs roughly.
2. When I disconnect the right plug wire, it runs reasonably well after I adjust the screw.
3. Periodically, when the rpms are around 2k, will rev up and hover at about 4k. If I crack it a few times, it slowly goes back down.
4. Doesn't like to run hot.
5. Invariably stalls out when I disconnect one plug wire or the other.

Notes: set screws are started at 1.5 turns.

Thanks for the help!

Stock air filters and air boxes?
Blue pipes means you have serious overheating, they are double skinned and shouldn't get hot enough to blue
You should open choke as soon as possible after it fires, there is a detent position about 10degrees from full closed (lever pointing to 9:00 O'clock position)

Correct; stock air filters, boxes, everything. Nor have I run it with the choke on in the slightest. Always choke OFF.

While I confess that this is my first project bike and I'm learning as I go (it's an ugly, steep curve), I think that I have multiple issues here.

1. Inspecting one of the throttle plates (right side), I can see that it's bent in on the bottom just enough that the bypass ports are BOTH on the engine side of the carb. This, I think, explains why the bike hits about 2k rpm and then steadily climbs to 4-5k. This is also the overly-blued pipe side. Perhaps that problem is explained. This would certainly help account for the fact that I can twirl the mix set screw as much as I want without appreciable changes in that cylinder's idle.

*I would absolutely LOVE suggestions for a part number on this, and a place to buy a replacement (or a pair...whatever). I cannot find a part number for the throttle valve ANYWHERE.

2. I do think there's an electrical issue somewhere, but I'm not sure how to more accurately diagnose it (I'm thinking weak spark, causing incomplete combustion in the left chamber). What currents/charges am I looking for, and where precisely? I'm considering replacing the points just for good measure, but that could be $40 spent just to say, "no, well, I guess that's not it." I'd like to check the coils, condenser, etc for full function, but this is - at present - slightly beyond my expertise.

Any suggestions? I definitely appreciate the assistance.

You shouldn't need points at the low mileage you have, even if springs are weak it will still run and idle OK. (may miss-fire after 4K or so?)
If you haven't done it already, download service manual and do a full service.
Bent throttle plate is real unusual but does happen.
Sounds like carbs are out of sync as well?
You need special adapters to do carb sync with vacuum gauges (manometer)
As far as I know I'm the only person making them?
You can do a basic check of ignition timing by turning motor over with a wrench (plugs out, fitted back into plug caps & grounded)
You should hear 'click' as plug fires, timing marks under left cover, LF & RF
Lean bike to right before removing cover and you loose less oil.

Try running it without the points cover installed. Its possible for connectors to short to the wall of the cover. Causing bad spark to one or both of the plugs.
also,
I have a list of things to do before starting carb tuning on the 360.

http://www.hondabrat.com/2012/06/before-list-of-things-you-need-to-do.html

crazypj:

- Thanks for the insight on the points. This thing has never been rained on (save for this week, unfortunately), so there's NO rust or other water-related deterioration on anything.

- I have the full manual, and a few of the supplementals, too

- Full service: once I get a halfway stable idle, I do intend to calibrate the carbs more precisely. I've already replaced the oil, cleaned the screen (it was spotless, so "checked" is more accurate), replaced the plugs, etc. I'd like to replace the wires, however, since I get a minimal buzz when I put a hand on it (left side) while running.

- I'll check the timing using your suggestion; sounds simple enough.

- On throttle plates: I will get you a photograph in short order. You gotta see this thing. I'll also take a photo of the overly-blued pipe. I think this may have either been installed incorrectly from day one, or some idiot somewhere along the way managed to bend it.

On that note, do you have a suggestion where I might find a part number for a replacement plate? To my total surprise, the service manual's exploded view of the carbs completely lacks throttle plates/valves. Any suggestions?

trek97:

Thanks for the information. I'll try running it at night and see if there's any arcing. As far as your to-do list on your website, I have done virtually everything you suggested (some aren't necessary, like filing new parts. There aren't any new metal parts at the moment. A good cleaning got rid of all the shellac on the old components).

A coupe of thought to add to the mix.

Fuel:
Is the throttle plate actually bent or is that side just further open than the other? The position of one relative to the other can be adjusted.
Are the air filters clean and in good condition?
Cold starting without choke suggests it's rich
When you adjusted the float level did you do it with the carbs upside down or at a 45 degree angle? Upside down gives a false setting.

Ignition:
Weak spark could be a bad plug cap, dirty points or bad ground lead. Try to clean the points again by pulling a business card between them. Grab a replacement plug cap and snip 1/4" off the plug wire to get a good connection.

You can't buy a throttle plate, you have to buy a carb (it's easier to remove it and straighten it out)
They have angle on edge so only fit one way.
Do plug caps have metal covers?
If they are originals, you almost certainly need new ones

+1 on the points cover. Mine was grounding out one set of points when installed. A little grinding with the dremel, and all was well.