1971 CB350 - slightly obnoxious

Dragonfish

Slightly Obnoxious


After about a year of looking, I finally found the right bike! A running 1971 Honda CB350K3 posted on Craigslist for $750. I offered him $500 and he took it. The bike was downtown Chicago in kind of a sketchy neighborhood. The address he gave me was an old abandoned paint manufacturer and I was getting more apprehensive the closer I got to it. Finally arriving I called the seller and he told me to pull around the one way street and he'd unlock the gate. I pulled in and he closed the gate behind me but I was relieved to see my bike waiting for me. I asked him to start it and he did, but he had to put it on a jump starter as the battery was dead. It ran pretty well! Really loud and I later found a big hole on the bottom of the left muffler. Other issues I have to address not particularly in this order:
  • God awful ape hanger bars.
  • The clutch and brake cables are really stiff and brittle. Will replace.
  • The throttle doesn't snap back to idle when you let it go. Probably also a cable.
  • Right side carb has no choke plate. Looking for a replacement.
  • Rebuild both carbs.
  • Charge the battery and evaluate the charging system.
 

Dale

New Member
Re: 1971 CB350 "Copperhead"

Great little bike. Looks clean.

To be honest I would just replace the battery. Get some carb cleaner and blast it in there and see if its easier to live with.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Seller told me the battery was pratically new, he just let it run down. I'll toss it on the charger and if it doesn't take a charge well I'll replace it. Since it's missing the choke plate on the right side I'm going to have to rebuild it anyway once I find a replacement. Anyone have one lying around? Looks like the entire plate is missing.
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

It's good to see you have a thread going already! However, I think she looks more like a cherry bomb
than a copperhead at this stage! I'm sure there's plenty of things in store I don't know about yet ;D

One thing you'll want to have is a battery tender. They're cheap and pretty much essential to own,
especially when the bike is gonna do some sitting. On any older bike, I always replace acid batteries with
sealed "maintenance-free" batteries. It's just a preference really, but they are safer and much easier to deal with.
The first time that the battery on my KZ overcharged and dripped acid all over my new chain, I said to hell with
them. (Lead acid batteries)
While I'm on THAT subject- The stator and / or regulator and / or rectifier are usual suspects on ANY
old bike. They are now 40 years old, and probably didn't work all that well when they were new. I found a high
output charging setup on ebay, that comes with a new stator, and solid state regulator / rectifier. It's about $200
or so, but that will modernize & boost your charging system, should you continue to have problems. Otherwise, the
battery tender is great for safely charging your battery back up on a regular basis.
As for the carb problem, check out ebay on that as well. You can find parts carburetors for our bikes all day long, and
they aren't expensive. We have a huge advantage here, by owning one of the most popular motorcycles ever built!
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Potentially stupid question:
I've seen several carbs on ebay listed as #2 or #3. I need the right carb for a twin. How do I know it's the correct one? I assume these came off a 4?
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

You are correct, if it says #2 or #3, its going to be from a CB350F, or CB350/4, and will NOT interchange
with the twin. There is not much similarity between anything on these two bikes. The dead giveaway
on the 350 twin carbs is the big round chrome cover on the top, which covers the vacuum diaphragm. The 350F
carbs are mechanical, and have a much smaller cover on top, kind of an oblong cover.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

I let the bike trickle charge overnight and when I got home from work gave it another shot. I kicked the living shit out of it and it won't fire. Interestingly, I hit the start button and I hear the solenoid "click" but the starter motor doesn't budge. I put a volt meter on the battery and it reads over 12v. When I'm kicking it, all I hear is what I can only describe as compression, not combustion. I know I'm getting fuel because there is some dripping out of the float drain. Is it possible the battery is shot even if it shows over 12v?
Okay, here's where I really show my noob colors. Let me just make sure I'm doing this right. Key in ignition, to the first click. I see neutral light and headlap light come on. If I move it to the second click the neutral light turns off. Second, kill switch set to On. Petcock straight down, looks like its set to On. Choke closed. Kick it. Am I missing something obvious?
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

Sounds like you're doing it right... you want the neutral light on, and kill switch to be "on".

It's still possible that the battery is no good. After all, I believe you did say that the guy you bought it from
jump started it? He did use the electric start on the bike, correct?

Here are a couple links to a good site. He has good explanations for things you are not all that clear on.

http://www.dansmc.com/batteries.htm

http://www.dansmc.com/electric_starters.htm

I was going to give you a paragraph on starters, but lets start with the battery, and go from there.
If you have jumper cables, you can give it a go that way, if it works, obviously you aren't getting enough
power with the bike's battery.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

No, he kicked it. I tried to jump it off my car and that didn't help.

I'm going to spend some time tonight going over the basics. Check for spark, pull off the bowls and have a look at the carbs.
Thanks for the links! I'll read it on break at work :)
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

I would think your engine has to be in at least pretty decent running order, considering that the guy
was able to start it with the kicker.....as long as it didn't take all afternoon! ;)

Anyhow, sounds like you know where to start. If you have fuel overflowing from the carbs, something is wrong.
There's a good chance that they're gunked up inside, making the float valves stick open. Or the floats might be
set to the wrong height. Too much gas dumping in the motor will give you a flooded condition, which usually makes
it impossible to start....and can contaminate your motor oil as well. You don't want to run it with gas in the oil!
The carbs are easy to remove, and to overhaul. Let me know what you find out!
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

Cool, glad you can make use of it. I don't know if you found it, but the page labeled
"Dan's Online Motorcycle Repair Course" covers it ALL. Gotta say, it was real nice of him
to put all that info out there!

http://www.dansmc.com/mc_repaircourse.htm
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

A little progress tonight. I pulled the battery and jumped it off my car. Still didn't start so I jumped it right across the starter solenoid and still nada. Lastly I jumped it right to the terminal on the starter and it's dead. So chalk up a replacement starter to the list. Next I pulled the plugs and found them totally black. Checked for spark and both sides are firing. I cleaned them up a little, dropped 1ml fresh gas into each cylinder and gave it a kick. This time it clearly caught! I gave it another kick and it popped a little but did not start all the way. I put 1.5ml gas into each cylinder and gave it another kick and same result. Definately better but still no joy. The PO must have sprayed the shit out of it with starter fluid before I got there to start it up. So my next plan of attack is to replace the plugs and check the points and timing. It's pretty clear I need to pull the carbs and clean them. Also looking for a parts carb, mine is stamped 3D.
 

madmatt1

New Member
Re: 1971 CB350 "Copperhead"

One little tidbit I'd like to mention to your carb cleaning.... How's the inside of the tank? If it's nice and sparkly,
and the gas is fresh, I wouldn't worry too much. If it isn't, you should think about cleaning it out. The tank
will have to come off anyways, so it won't be much extra effort. More importantly, you'll want to replace
(or add) inline fuel filters. Visu-filter makes nice, inexpensive little clear filters...they work great. I say this
because fuel filters get overlooked way too often. Hell, I don't remember any of my old bikes having fuel filters
when I bought them. But anyhow, if you don't have them, all it takes is a little bit of crud to get in
your carb(s) and then you're doing it all over again!
 

707racing

New Member
Re: 1971 CB350 "Copperhead"

I have this identical bike sitting in my shop. I picked it up a few years ago, and still haven't started on it! I'm planning on putting a digital electronic magneto ignition in it. That will get rid of the battery, and any ignition problems. The only down side is that they are $660 on eBay!

My 350 is in pretty rough shape, but I can see if I can locate the carbs for you. I always convert to Mikuni VM's, or flatslides so I won't be needing them.
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

That would be a total lifesaver 707! Thanks! PM me when you dig them up?

Interesting thing I found about the bike. The fuel lines are really ugly green lines and there are filters in-line, but the PO didn't find he needed any clamps on the fuel line so every time I bump a hose gas leaks all over! I was planning on replacing all the lines anyway but while I'm at it I'll drain the tank and peek inside. Thanks for the advice Matt!
 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

Many thanks to Bobdot! Progress will resume, new pics in a couple days.

 

Dragonfish

Slightly Obnoxious
Re: 1971 CB350 "Copperhead"

This carburetor is the bane of my existance :mad:



I finally made some progress today, got the tank off and pulled the right side carb. Float bowl looks like shit, and PO did a half ass repair job. On the plus side, the inside is surprisingly clean! I'm going to JB weld this up a bit and spray it silver for now while I look for a replacement. I also was happily surprised to find that the tank is very clean inside, and already has some kind of liner! I'm going to go through the carbs tomorrow night.



Oh, and the obligatory vintage bike shot.

 
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