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Discussion Starter · #1 · (Edited)
A friend of mine was looking to clear some space out of his garage so I helped him by buying his two 1972 CB350's. These will be the first 350's I have worked on, but I have completely rebuilt a 74 CB750. Looking to keep it mostly stock, but the wife hates the tail light and the blinkers so I will swap those out for her. My friend said he rode it around a couple of years back and parked it when it ran out of gas.

Here is what I am starting with:




Kicking hte bike over it appeared to have compression, I checked the petcock bowl and screen and they were nice and clean. Put some fuel in the tank, took out the float bowl drain screws, and opened the petcock. Fuel started to flow and I let it go until it was clean fuel coming out. Feeling good about what I have seen so far I decided to try and start her up. I jumpered it from my truck, but the only thing that lit up was the tail light and nothing happened when I thumbed the starter. Looked around and found that the 15amp fuse wasn't there and that the wires were just twisted together. I had a single ATC blade fuse holder and fuse in my electrical parts bin so I hooked that up.

Since I wasn't getting anything other than the tail light I decied the jump the starter solenoid. As expected the engine started to turn over, but never even attempted to start. It was getting ready to rain so I packed everything up for the night. I guess today I will try it again with the plugs out to see if they are producing a spark. If they do then I am leaning towards the carbs. They might be getting fuel, but they aren't pulling it through them. What bothers me is that nothing else seems to get power so I will have to break out the multimeter and see where power is going and not going. I am ordering a bettery today so that I won't have to jumper it from the truck.
 

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the bike in the pic is a 1972 CB350K4.

you seem to be poking around at it. I'd suggest a systematic approach. even under ideal circumstances these bikes required a tune up every 2000 miles to run properly.
get a manual and go through the tune up procedures.

compression test
set valves, cam chain tensioner
points, timing
air filters, oil change, carb clean and synch.

I'd invest in some:
spark plugs,
OEM Honda carb rebuild oring kits,
points & Condensers,
air filters.

all are described in the shop manual (which you should also pick up.)

a fully charged battery is critical for these bikes to operate and the charging system is barely adequate when in perfect order. so it's very helpful to go through the harness and take apart and clean all of the terminal connectors and reassemble with dielectric grease. that will also serve as your way of inspecting the harness to see if there are any shorts, problems or things missing. I always keep them on a battery charger
 

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IF ONLY the taillight is getting power, the key switch is in the "two CW click"...Park position......
The center position (one CW click) is "Run"....
 

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Discussion Starter · #4 ·
Outobie...Typically I do have a very systematic approach to things, but knowing the bike ran almost two years ago I decided to just jump into it a bit.

66 Sprint. I figured that out earlier today when I was doing some reading. I didn't notice/feel I was clicking it past the run position into the park position. Still didn't help my no start situation. Everything gets power where it is needed and I have good spark. However looking at the left sparkplug I knew something was wrong. It looked like it has never been used so I knew I had to start looking at the carbs/fuel delivery.

I figured it out. The petcock is broken inside the tank as I don't have the tube sticking up. I only get fuel to come out when it is in the reserve position. Not exactly sure how I got fuel to come out of the left carb drain screw yesterday, but I did. Once I figured that out and turned it to reserve it only took a few seconds of thumbing the starter and she fired right up. However, because of the petcock issue it only runs on one cylinder and does so wonderfully.

Now that I know it runs I can start taking everything apart for the rebuild.

If you are curious or have the time feel free to check out my CB750 build on the SOHC4 forum.
74 CB750 Navy Style
 

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Discussion Starter · #5 ·
the bike in the pic is a 1972 CB350K4.
I had to go back and do some reading and talking to the seller. As far as I can tell this series of bike was sold in 72 and into 73 so it is highly likely or possible that it was originally sold in 73 and as such was titled like that. My title says 73 and the guy I got it from was the second owner and said the guy he bought it from said it was a 73 and was titled as such.

Personally I don't really care. I have a clear title for a bike that was sold across two years so at the end of the day it is all good to me. However, the info could come in very handy later on during the restoration so I thank you for pointing it out.
 

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Discussion Starter · #6 · (Edited)
I know I said that since I had it running I was going to start the tear down, but I wanted to figure out the issue as to why the left side doesn't run first in the hopes it will stave off any issues when I put everything back together. I took the petcock out and found that only one of the tubes was there. The reserve tube/screen was gone but was allowing flow even though there was a lot of crud built up around it. The main tube was clogged which obviously didn't allow fuel to flow. I cleaned everything out, but decided to pull the petcock out of the other bike since I could see it had both tubes. Cleaned that one just to be on the safe side and installed it. I now have fuel flowing evenly through and to both carbs.

Started the bike but the left side still didn't work. Checked for spark again just to make sure nothing strange happened and that was good to go. So I guess tomorrow I will drop the bowl and check to see if I get flwo through the float valve. In the meantime I will be reading up tonight in the manual on how to take apart the carb so I can check and make sure nothing is clogged and that the everything else is working as it should. There were some carb parts (needles, jets, o-rings, etc) in the box of spare parts the PO provided so hopefully I can get away with just using those, but I suspect that I won't be my luck.
 

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Harsh,
I hope those 'spare carb.' brass parts are the OEM Honda parts and are able to install back into your carbs..,that is if the 'replacements' aren't correctly metering the fuel the way Mr. Honda intended them to.I wonder if anyone has re-jetted your carbs.to work with the aftermarket exhaust systems you have on your bike ?
 

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I had to go back and do some reading and talking to the seller. As far as I can tell this series of bike was sold in 72 and into 73 so it is highly likely or possible that it was originally sold in 73 and as such was titled like that. My title says 73 and the guy I got it from was the second owner and said the guy he bought it from said it was a 73 and was titled as such.

Personally I don't really care. I have a clear title for a bike that was sold across two years so at the end of the day it is all good to me. However, the info could come in very handy later on during the restoration so I thank you for pointing it out.
back then bikes were titled based on the year they were first sold. If a bike sat on a dealers floor it could very easily have been made in 69 and sold in 72 (which would have meant it was titled as a 72) to make things even more confusing Honda began production of the following year models in the fall of the prior year so a your 72 k4, titled as a 73, could very well have been made in 71 ...when acquiring parts you will need to know the correct model, (1972, CB350K4). many things are interchangeable between years but not all of them :)

I'm still sticking to my original suggestion of going through it systematically. it may seem like too much work and overkill now however, with the amount of time you've already spent chasing things down you could be half way through the tune up list and know that it's done properly and can be eliminated.

I do this to every bike that comes into my garage that someone besides me has worked on it.
 

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Discussion Starter · #9 ·
Both of mine were made in 71 according to the date on the VIN tag. The one I am currently working on was Aug and the other was Dec. I definatley appreciate the info.
 

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on the vin numbers I forgot to mention one thing....the definitive answer is found in the first of the serialized numbers.
so your Bike is a CB350 4XXXXXXX
if it still has the correct engine then the engine will be CB350E 4XXXXXXX

That corresponds to me telling you your bike is a 72 CB350 K4

A bike made in 71 could be a K3 or a K4 check that number location to see if it's a 4 or 3 to be certain.
 

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Discussion Starter · #12 ·
Yep both start with a 4. Oh yah, all of the spare carb parts are in OEM Honda bags. Hopefully today I will be able to get it running on both cylinders.
 

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Discussion Starter · #13 ·
So I dropped the bowl on the left side then turned on the petcock. Fuel flowed out of the float valve, but it wasn't as fast as I thought it should have. However, unsure as to how fast it should flow I thought it was good. At first fuel was very limited coming out so thought that maybe it was just a little clogged and that everything would be good do go so I put the bowl back on. I took off the bowl drain screw so I could visually see if the bowl was filling up. Cracked open the petcock and nothing. A big fat plate of nothing.

I took the bowl back off and took a good look at the float valve and float level tang. There wasn't very much movement of the valve from fully open to fully closed. Just a tiny bit of movement of the float caused the flow to stop. I decided to adjust the tang a little bit to see if that made a difference. Well it made a world of difference. Flow increased a lot and it took a bit more movement of the float before fuel stopped flowing. I buttoned everything up and gave it another whirl. When I opened the petcock I could hear the fuel flowing into the bowl.

I decided to see what happened when I started it. The bike roared to life and I could see some white smoke coming out of the left tailpipe. The exhaust gasses were warm and the header pipe started to heat up nicely. So I think I have that part semi licked. the carb will obviously need to come back off so I can go through it and replace/adjust what is necessary.

So I guess NOW I can start the tear down. I will say it may be a bit slow since I have a lot of things to do at the house. My daughter graduates high school in a couple of weeks. As such there will be a number of people at the house so I have a pretty good hunny do list.
 

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Discussion Starter · #15 ·
Yah it was pretty nice. Since I can't really work on it for a bit I can at least start ordering some parts. I know where to go for CB750 parts, but is there a place for 350 stuff? Right now I am looking for a full gasket and seal kit(s). I have read some on the chain roller tensioner which will I be replacing. I have seen a few different types, but I am not sure which one I need. I am not looking for overkill and the bike will be treated fairly gently so I hope that helps in recommending which one to get.
 

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Bore-tech will have everything you need for the 350 motors and bill there is a nice guy to deal with.
there are other places as well but that's the first place I'd go.
as for the cam chain stuff, the KA slipper one is good for race and street bikes alike and cheaper and heartier than OEM
 

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Discussion Starter · #17 ·
Thanks for the Bore-Tech info. I actually have them bookmarked, but haven't gone through their site thoroughly yet. I have been collecting links like crazy that look promising.
The KA is the one that requires some machining to the engine because of the rivets, correct?
 

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I used a set of new aftermarket cam chain rollers made from a tough plastic product called PA6,bought them from a guy in Poland about 2 years ago off of Ebay,I don't know what happened to the guy though..? I just use the stock cam chain tensioner system w/ those new rollers.Did you pull the motor yet ?
 

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that polish guy has gone silent for about 6 months
yes, the KA requires some mild machining...nothing much though...you can actually do it with an aluminum file in about 20 min
 

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Discussion Starter · #20 ·
I have seen the guy from Poland mentioned alot, but like has been said has gone silent. I just read something about a steel upper roller on the ohio cafe racers site. They had an email link to ask about inquiring one, but I didn't click on it. I might when I get home, but I will more than likely go with the KA. I appreciate all of the info. My Dad will be coming to town next week and is a mold maker/machinist so he will probably be able to give me some pointers on setting up something to machine the area needed. I like the simplicity of using a file, but I also like the look of clean machined surfaces. Who knows. The engine is still in and probably will be until after the weekend of the 20th. There is just too much to do around the house. Right now I am just gathering info to make a coordinated attack. I try to plan everything I do well in advance to help keep from making mistakes that will cost me money.
 
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