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Discussion Starter #1 (Edited)
Hey Everyone! New here but wanted to start my build thread, I get a lot out of following these builds, so I am hoping to contribute by sharing my projects and process with ya'll.

Bike is a '71 CB350 - first time working on a vintage bike. I also have an '83 Virago 750 I've been working on. The Honda stole my heart a long time ago, this thing is amazing. I love that everything is analog/mechanically controlled.

Short timeline on the bike - Purchased last summer for my girlfriend to ride. I shattered my left thumb right after we bought it, and 7 months post-op I am back in the garage and riding again. I drove the bike right to a local mechanic who did a basic run through, cleaned carbs, new plugs, valve timing, oil change... oh yeah, and heli-coiled the stripped spark plug (yeah, yikes) Took the bike out on the road recently and she hits a wall at 42mph.

So far I have -

New handlebars
New grips
New pod filters (replaced old foam pods)
Fixed all wiring issues - lights, blinkers, starter and control switches (there were a lot)
Cleaned all major electrical connections, frame grounds etc
Cleaned gas tank
Rebuilt Petcock
New fuel lines/filters
Valve timing
Ignition timing
New side cover gasket
CM Rectifier/Regulator
Yellow/White wire mod

Need to -
Rebuild/Recheck carbs
Change fork oil
Clean the chain
Check Cam timing, then valves, then ignition
Replace points/hardware

Even with all the pampering and parts - the bike still hits a wall at 40-42mph. I live at 6000ft elevation -
Plugs are black as night, bike starts and runs without the choke - dies with the choke - she's rich on both sides. Ill start with the idle air adjust and see if I can get a little leaner low end...

I haven't ridden with the Rectifier yet, we'll see if that helps.

@ancientdad and @alan F suggested checking the centrifugal advancer, and carbs - An old thread on here suggested a stuck slide. I will check into these ASAP - and am open to suggestions!
 

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Discussion Starter #2 (Edited)
Got the Common Motor Rectifier/Regulator upgrade installed tonight!

I pulled off the old mounting brackets for the outdated rectifier, regulator, and cross over tube.. after some examination - I found a neat way to mount the Rectifier, using the old regulator mount, I flattened it, and the spot weld holes just happened to line up nicely with the spot welds for the old rectifier mount. Reuse recycle I guess. I like keeping things hidden and clean, happy with how it came out. The wires clear the seat, with a passenger seated.

She started right up, with more gusto than I've heard before!
 

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Hey Everyone! New here but wanted to start my build thread, I get a lot out of following these builds, so I am hoping to contribute by sharing my projects and process with ya'll.

Bike is a '71 CB350 - first time working on a vintage bike. I also have an '83 Virago 750 I've been working on. The Honda stole my heart a long time ago, this thing is amazing. I love that everything is analog/mechanically controlled.

Short timeline on the bike - Purchased last summer for my girlfriend to ride. I shattered my left thumb right after we bought it, and 7 months post-op I am back in the garage and riding again. I drove the bike right to a local mechanic who did a basic run through, cleaned carbs, new plugs, valve timing, oil change... oh yeah, and heli-coiled the stripped spark plug (yeah, yikes) Took the bike out on the road recently and she hits a wall at 42mph.

So far I have -

New handlebars
New grips
New pod filters (replaced old foam pods)
Fixed all wiring issues - lights, blinkers, starter and control switches (there were a lot)
Cleaned all major electrical connections, frame grounds etc
Cleaned gas tank
Rebuilt Petcock
New fuel lines/filters
Valve timing
Ignition timing
New side cover gasket
CM Rectifier/Regulator
Yellow/White wire mod

Need to -
Rebuild/Recheck carbs
Change fork oil
Clean the chain
Check Cam timing, then valves, then ignition
Replace points/hardware

Even with all the pampering and parts - the bike still hits a wall at 40-42mph. I live at 6000ft elevation -
Plugs are black as night, bike starts and runs without the choke - dies with the choke - she's rich on both sides. Ill start with the idle air adjust and see if I can get a little leaner low end...

I haven't ridden with the Rectifier yet, we'll see if that helps.

@ancientdad and @alan F suggested checking the centrifugal advancer, and carbs - An old thread on here suggested a stuck slide. I will check into these ASAP - and am open to suggestions!
Hi Juniper, My name is George but I use cycledr on this site. I have over 50 years experience working on Hondas and in looking at the pics of your bike I see what look like VW muffler tips from an old VW. I would simply try taking those off and take it for a ride. Easy solutions are always better and it sounds like you have already addressed the tuning side of things. If that helps it will tell you you have too much restriction in the exhaust and it is time to rethink your options. The air filters are less likely but you cold pull those just as easily but do them seperately as a good diagnostic habit of mine. One thing at a time.
I am almost done with my 68 CB350 but am still working on dialing the carbs in. Mine runs rich too but hard to tell what PO has done. Early 68 carbs are different from late 68 and later and mine is a very early 68.
Let me know how you make out as I am following several different threads!
 

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Bike looks very sharp, that's a great color on the tank. I don't think the idle air adjuster will do much to help with the carbs at speed. Do you know what sizes jets are in the carbs? Like suggested above it will probably be easiest to get a baseline with stock intake / exhaust and then go from there
 

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Are pod filters where they attach to the carb face the same ID as the OD of the carb? The laminar air flow to the carb and the small ports is critical, the ports cannot have any form of airflow interference.
At 6000' if you were running stock jets you would need to go 1-2 sizes smaller since the air is thinner at that elevation.
 

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Discussion Starter #6 (Edited)
I would simply try taking those off and take it for a ride. Easy solutions are always better and it sounds like you have already addressed the tuning side of things. If that helps it will tell you you have too much restriction in the exhaust and it is time to rethink your options. The air filters are less likely but you cold pull those just as easily but do them seperately as a good diagnostic habit of mine.
Hey George! Thats a great idea! She'll be louder than heck haha! Will report back after the rain clears out!

Have the carbs ripped apart in front of me now and found a ton of crap in the secondary emulsion tube on the Left side carb, I'm excited to see what a good carb clean/rebuild does for me!

Bike looks very sharp, that's a great color on the tank. I don't think the idle air adjuster will do much to help with the carbs at speed. Do you know what sizes jets are in the carbs? Like suggested above it will probably be easiest to get a baseline with stock intake / exhaust and then go from there
Thanks! Idle air didn't do much for me, its fine at 7/8th out... Jets are 115/72 on both sides. I did grab a jet kit from Common Motor that has the 110 main and 70, 68 secondary options.

I just dissassembled both carbs and left side secondary emulsifier was all clogged with goop. That should help things along as well.

Wish all the oem intake/exhaust parts came with the bike, going to see what I can do with the current situation.
 

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Discussion Starter #7
Are pod filters where they attach to the carb face the same ID as the OD of the carb? The laminar air flow to the carb and the small ports is critical, the ports cannot have any form of airflow interference.
At 6000' if you were running stock jets you would need to go 1-2 sizes smaller since the air is thinner at that elevation.
Simple answer yes, its set of the Common Motor pods.. ill try and drop down a size this week when the jet kit arrives and see what happens!
 

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Discussion Starter #8
Had some time this week to check in - The centrifugal advancer seems to be in good working order, all the parts in the right places, expanding and contracting properly. Lubricated all necessary parts.

Replaced the points hardware with some new SS Allen heads - I love Ace Hardware!
Rechecked the ignition timing - its dead on.

Its raining this week so I pulled apart the carbs - They're in decent shape but not amazing. Currently both have 115 Main and 72 Secondary jets. Right side float has fuel in it, I ordered a replacement float. As I mentioned above, I found a lot of crap in the Left Side Secondary Emulsifier tube, that could definitely contribute to the loss of power. Both secondary emulsifier tubes were broken like someone tried to un screw them instead of pressing them out. One of the little black caps is in bad shape. Both Idle mixture screws are missing o-rings and washers.

All of those small issues could certainly contribute to 'the wall,' there was plenty of ethanol oxidation crap inside as well.

Ordered some parts from CM including the carb rebuild kit & jet kit, new carb boots and some other bits and pieces - in hindsight I should have grabbed a kit with smaller Main Jet options, but I can drop down to 110 main, and/or drop the secondaries to 68/70. Can anyone explain in more detail how and why to choose the secondary size?
 

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Primary jets are the smaller size.
Air density decreases with altitude, fewer air molecules. So less air with jets for sea level to 3000' will make the overall mixture too rich. Although with pod filters there's more air passing thru so it's possible that the jetting could end up too lean. But you always want to establish a base line setting before modifications are done.
 

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Discussion Starter #10
Carb rebuild report -

The Main Needle was shimmed & one of the slide "top hats" was cracked, the emulsifier tubes were gunked up and damaged from someone attempting to unscrew them, those tiny black plugs were missing... probably some other things too.

Haven't got the carbs back on the bike yet but I am excited to see what all those small changes amount to. I left the jets the same, assuming that shim was way too much fuel up here. I'll get a baseline and I can swap jets from there.

Adjusted Cam Chain, re-checked all valve gaps and timing as per the recommended process.

Bought a KLR650 last week so I've been getting to know that bike as well :cool:
 

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Discussion Starter #11
Hey friends - long time no post, but I need some advice :)

I rebuilt both carbs, followed Common Motor's guide/kit the whole way through just in case I forgot about something. All went well, I removed the shims on the main needle and reassembled both carbs... put them on the bike andddd only the bike is only running on the left side cylinder.

I double checked everything on the right side carb, disassemble, reassemble, nothing. Still on one cylinder.

If I spray starter fluid and hold the throttle open a bit the right side will snap crackle and pop to life, but its weird and inconsistent, won't stay running on both.

My initial thought was that it wasn't getting gas, but when I pull the carb after its been running (on one cylinder) the intake port is wet with fuel. Spark is also good... so why does it need starter fluid...?

My hunch is a timing issue? Maybe I set the timing wrong at some point while the carbs were off?

Open to suggestions, I would like to ride this thing again before winter sets in.
 

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Discussion Starter #13
So its not the carbs - I splurged and grabbed a set of Mikuni's, figured I'd like to keep the bike for a while and it's an upgrade I read about constantly. Bike fired up first try, clearly needs some tuning.... but the same out-of-sync can't-rev hot-mess thing is happening. Clearly I did something wrong somewhere and need to go back through the timing process.

Yep, check your timing. Preferably with a timing light.
You mean with a timing gun? Could you provide any other resources/info on this method?
Ive been going off Common Motor with the test light on the notch deal

Thanks!
 
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