1971 CB350 - slightly obnoxious

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Well, I grabbed it anyway. It looks like it's off a 722A and that carb has the same float height so I bet they are interchangable. I thought $5.99 was a deal :D
 

madmatt1

Been Around the Block
Re: 1971 CB350 "Copperhead"

If you look up the float chambers on a honda parts fiche, there are two different part numbers, depending
on the engine serial number. Hard to say what the difference is!? I guess for 6 bucks, its not too big of a dice roll... ;)
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Actual work being done! The first carb is stripped and is outside boiling in lemon juice. Pics soon!
 

madmatt1

Been Around the Block
Re: 1971 CB350 "Copperhead"

Thats funny, I was just sitting here at work, thinking about all of the work I need to get done on my project.
Then I wondered to myself how your bike was coming. Good luck with the carbs
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

It went great! That was my first experience with rebuilding carbs and it was easier than I was expecting. The first one I did took longer as I had to piece it together from three different carbs and it had a stuck main jet. No major varnish but it had crusty white residue covering everything. I boiled it for 20 minutes in a 30% lemon juice solution. After I rinsed completely in warm water and hit most of it with fine steel wool to restore the shine a bit. Both of the top caps are pitted so some time in the future they'll need more extensive attention but for the time being my main goal is to get it running well. On to pics!
Getting started:
IMG_1966.jpg


In the pot:
IMG_1965.jpg


Before:
IMG_1968.jpg


After:
IMG_1967.jpg

IMG_1969.jpg

IMG_1970.jpg

IMG_1971.jpg
 

madmatt1

Been Around the Block
Re: 1971 CB350 "Copperhead"

Those look good! I've never done the "lemon juice boil" ;D Obviously it works!
So is the mixture just 30% juice and 70% water, or something else?
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Yep, 30% lemon juice, 70% water boiling OUTSIDE. Holy crap did that stink. Rinse it off immediately, if left long enough the lemon juice will pit the metal. I've read others that have tried it ended up with a dull finish which is why I hit them with wool. Look 100% better.
 

WNTITAL

Been Around the Block
Re: 1971 CB350 "Copperhead"

They turned out great. Simple, cheap and effective. What more could you ask for?
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Installed the carbs tonight and set the points. I wanted to check the timing but when I tried to take the cover off I learned why everyone says get an impact driver. Now I own one :)
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Last night I pulled a late night and adjusted the timing, which was way advanced, gapped and installed new plugs, installed the tank and new fuel lines. I will never understand what they were thinking with that fuel level tube! :mad: Today I can put some gas in it and give it a kick! Question: at the top of the valve cover is about a 1/2" ID hose leading to nowhere. Is this some kind of breather tube? It's kind of fugly, what do most people do with it? I don't remember seeing it on other people's bikes.
 

madmatt1

Been Around the Block
Re: 1971 CB350 "Copperhead"

That hose is indeed a breather hose- Positive crankcase ventilation, like you find on most cars. I can't speak from experience on my own CB350- that was all missing...but usually that hose goes to the air box. A lot of times, people will get one of those little breather filters and route it to wherever they want it.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

http://www.youtube.com/watch?v=bPmVhyHBRAM

http://youtu.be/FE2x7mG6n3M

Started on the third kick! Could not have been more excited. I actually got to drive it around a bit. Two issues still at hand; the right carb drips gas out of the overflow hose. I'm pretty sure thats from the tube in the float bowl. It was cracked and I hoped it was small enough to not leak but looks like I was wrong. I'll pull it off and put some JB on it tomorrow. Second as you can probably hear it has a pretty loud clattering sound. I did not get to adjust the lifters and I hope thats all it is. Other than that it pulled really nice! I can't believe the PO managed to get it started when I first looked at it. The timing was off, the points were off and the air screw was turned out 1.5 times on one side and 2 on the other! I set it all to stock which is out 3/4. Next steps are bars and cables and some exhaust. I kind of like how loud and throaty it is now with the hole in the exhaust but I can't run open pipes here. Any recomendations?
 

madmatt1

Been Around the Block
Re: 1971 CB350 "Copperhead"

Congrats man, glad to see the update! So is the one float bowl itself cracked? I don't know how long JB weld will hold up to gasoline-
guess it's worth a try though. Did you also set the floats to the specified height? That's always important to do as well. The engine sounds healthy to me- the valvetrain clatter is perfectly normal. There's an old saying that goes "it's better to hear them than to smell them." Just set the clearances to spec, and you shouldn't have anything to worry about. As for the exhaust, the best thing I would recommend is to replace it / them with factory style. If you go with something less restrictive, you'll most likely be fiddling with the carb jetting way more than you want to. That's just my 2 cents. Some bikes are easy to dial in...my experience with twin cylinder bikes that have CV carbs have not been great. It's sooo much easier to go stock and just enjoy the easy upkeep. You can always buy a 2nd bike for the "experimenting" 8)
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

No the float bowl is fine but there is a tube in it that acts as an overflow with a hole near the top. That tube split up the middle so it will let the bowl drain overflow much lower than it should. I set both floats to 26mm per the manual.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

I need some advice. It was running pretty great a few weeks ago, then it sat until today. I got it to start but it was hard! Then it really just won't stay running. I could feather the throttle to keep it running but it would eventually die. I pulled the plugs and this is what I found:
preview_image_0_9943942x.jpg

The left plug came out of the left cylinder. That side's muffler is basically gone, so it's got wide open air flow. The right plug looks much better, just a tad wet. I cleaned them up and it fired right up! For about 2 minutes. Pulled them again and the left plug looked totally sooty again. Any suggestions? From what I read that should mean the cylinder is running rich but I would think that with the hole in the exhaust it would be lean. Help?
 

Nasty N8

New Member
Re: 1971 CB350 "Copperhead"

Looks like a float needle sticking and flooding that cyl. while it sits. Need to shut off the fuel when it's parked. Can clean the needle and seat with Simichrome polish and Qtip.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

I always shut off the gas when it's parked. I recently rebuilt the carbs and the float needle looks great. I'm pretty sure the culprit was me installing the air filter on that side. It's the one that came with the bike and it's in pretty bad shape. Looks like it's bad enough to have made that cylinder run really rich. When I pulled the plugs, the left was WAY hotter than the right. I'm going to rebuild the filters, replace the plugs and try again and see how the plugs look after that.
 

interceptor

Coast to Coast
Re: 1971 CB350 "Copperhead"

Looking good! It's a learning process, isn't it ;) My overflow tubes were cracked all the way up, too. I went to the hobby store and bought some 1/8" copper tube and cut it to exact length as the stock one. It comes out of the bowl with pliers and the new one goes in with a little force. No more leaking :) $1.50 fix. Can't buy just those stinking tubes at the dealer.
 

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