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Discussion Starter · #1 ·
Hey everyone, I have recently aquired a cb350 that had been sitting for around 20 years. The bike had a small electrical meltdown before it was put away (part of wiring harness was melted) I put new wires, and soldered them all up. The bike runs and idles great, running on both cylinders. My problem is it has a really uneven rev and when the rev drops down after reving, the bike pretty much just trys to stall. I was able to ride it flawlessly a few times without this problem before. But it keeps reoccuring. I have cleaned out the carbs almot 4 times, i have cleaned the points and stuff, but really right now im not sure what to do. Sometimes the bike looks like its running good, but then it runs like crap. Both cylinders have good compression, (the motor is in very good shape). What i really dont like is that the right cylinder spark plug hole is stripped, the spark plug goes in but rough, i have to re-thread it. :( Il post a vid along with this so you can get a good look at whats happeneing.
Here's the video of the bike when i first got it:

And here's the update video with the problems with the bike:

thanks for your help everyone
 

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Welcome to the site.

Good video. First thing I'd do is to check all the regular things to make sure they are in spec. You mentioned compression was good, so I'd also check and adjust valve clearances, ignition timing, carb float levels and also fix the throttle cables to they work the same on both sides. At least with all these things done and in spec, you can then rule them out as possible causes.

It seems like when you put it in gear and tried to take off it wasn't getting enough gas, could be float levels or even just the gas tank vent being clogged which will starve the carbs of fuel. Is the petcock on and functioning correctly? New gas?

Also, you mentioned charging issues and other electrical gremlins, wondering if they are robbing power for the coils. Spark my not be good enough.

When you get a chance, check out the NEW MEMBERS PLEASE READ post and update your profile. It helps everyone out.
 

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Re: the brake light, my first guess would be the rear brake light switch. Test this by disconnecting the wires for the front brake light switch and see what happens. The rear switches are fairly cheap and available from Honda. With the rear switch disconnected, you can check the continuity between the two wires. Pull down the plunger and see if it works. If the rear switch is good then check the the adjustment of the rear switch and make sure it's not too tight and holding the switch on all the time.

The fact that the bike starts right up and idles well initially is a good clue. It sounds to me like it was running out of gas. If it sits for a while and starts right back up then I'd say you've got a fuel delivery problem. Either the floats are set low, the petcock is plugged inside the tank or the float is sticking closed.

You can pop the fuel cap open and trying running it as well. When you open the tank can you here it go "wosh" like there was a vacuum in there?

You mention in the video that you checked and cleaned the points. That is not going to cut it. You need set the points as outlined in the manual. Gap the left first, then the right then check the timing, first the left then the right. Again, as outlined in the manual.

I don't think you have a serious problem or a problem that is going to be expensive unless the tank is full of junk and plugging up the petcock.
 

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Discussion Starter · #4 ·
Thanks for the help, im going to mess around with the brake switch later, see what happens. But the petcock works good, but the fuel lines dont look full of gas, only the part that connects into the carbs are full, there is some sort of vaccum in the lines, even with the gas cap open. Il make anopther video and show you guys, il post it soon. But what is weird is I let it sit for 4 hours and i was able to take it out and ride it and then i parked it and it does the same thing all over again. I've watched videos on how to gap the points but i still have no idea, because the guy in the video shows you how to "check" the points instead of just gap them, I downloaded the manual from this website and it doesn't show how to gap it or anything, just how to re-assemble the engine and stuff. The battery has enough power to start the bike with the electric start so it should be enough to allow the bike to rev. I unhooked the battery while it was idling and the lights stayed on which means the charging system is working good. Im not to farmiliar with how to adjust the valves, can you just unscrew the tappet and work on them? or do you have to remove the head all together. Anyways I still think its a carburator problem. Im still learning how to do stuff with these twin motors, ive worked on singles and they are much easier ;) But anyways thanks, il take another look at everything and get back to you guys asap!
 

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Discussion Starter · #5 ·
Sorry, i just realized that I actually did check the timing,i used a blinker to see if the points and all are aligned :mrgreen: they were aligned properly, the light came on at the right intervals.
 

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By good compression you mean 170 PSI RIGHT?.....Less than 153 is BAD....
Air leaking in the stripped spark plug threads could be the overall culprit...
Point timing must be EXACT on BOTH sets.........
 

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Discussion Starter · #7 ·
yeh i checked both left and right cylinders but maybe they weren't dead on I can't remember, but i remember they lid up at the two ""lines, the spark plug is still in there good and tight so i dought thats the problem. Also its the same in both cylinders. This is drivin me nuts, im thinking of just selling the bike LOL.
 

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Discussion Starter · #8 ·
The timing from what i remember seemed to be dead on. Before when i used wire extensions, the wire i used was smaller gage than it was supposed to be, so i suspected that coulod be problematic. So today I replace the wire with the proper size gage wire and its running the same. I have the carburators apart right now (well partially), iVE corrected the throttle sync with both. Now i am stumped, I don't know what i should do next. the bike runs like its being starved of fuel. Im suspecting it could be the jets. I tried removing them already (on both carbs) and only 2(the smaller jets) could come out. The larger one in the right carb was seized and the one in the left carb would just spin (but could be tightend, just not removed) So really, rite now i dont know where to start. let me know what you guys think.
 

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Discussion Starter · #10 ·
Re: 1971 Cb 350 Not running right still!

Alright, so carbs are all opened up, take a look. Also i had to bend the thing that the jets hold onto inwords because it was hitting the top of the carb, and when i would screw everything back together it would leak gas because of the pressure. You can see it in the pictures. I think the floats are fine, i checked the levelk and if i bend it anymore, the floats will always be letting gas in and it will leak all over the place.
 

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With regard to the float, you really need to set them a specific height. You can use a cut up credit card to help with this. There are some posts here on the site about doing this (e.g. Carb float heights for measurement?). Also, here is a good thread documenting the different float heights of the 350 carbs. You'll need to find out which particular model yours is, and set the height accordingly: 350 Carb Types
 

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Discussion Starter · #12 ·
alright, il check it out, thanks so much!
 

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If I understand you correctly you say the jet holder was touching the "top of the carb". That's the bottom of the bowl actually 'cuz you got it upside down. right? Anyhow, it' supposed to be like that so the jets are held firm in their sockets. While you are at it look at the carb casting surface of the little sockets that the jets go in. If it's pitted or rotten the the "O" rings around the jets won't seal good. I had that problem. Consider new carb bodies. They are available. Again if I understand, you had leaking at the bowl gasket when the jet holder was pushing on the bowl. Thats a bowl gasket issue. You need a new one. Save yourself a lot of headaches and get a 4 pack of KZ750 gaskets. I know that's a Kawasaki part but the bowls are the same and these gaskets are nice 5 sided ones not round ones that will drive you nuts.

I have a similiar bike and it took 4 sets of carbs to find ones that worked well. All of them had been "cleaned" and were supposedly good. With all the time I put into it, I would have been better off buying a guaranteed, rebuilt pair. There are outlets for these now. That way if they are bad, you just sent them back. After a couple of tries, I would say that it's not the carbs then but about 90 percent of getting these bikes running is the carbs.

Good luck,
Edy, whose CL350KO is now a daily driver
 

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Discussion Starter · #15 ·
the reason why the carb leaked was because te metal hanger that the jets connect to was hitting the top of the carb and it was putting pressure between the boal and the top of carb. i fixed that by bending the hanger back a bit so it doesn't leak now. im going to try measuring the floats with a credit card.
 

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Discussion Starter · #17 ·
:lol: :lol: Sounds like a plan! Im going to post a vid soon, right now its processing on youtube, when its finised il post it. You guys can see first hand whats going on.
 

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" because te metal hanger that the jets connect to was hitting the top of the carb and it was putting pressure between the boal and the top of carb."

Its supposed to do that. Push down hard and send the screws in. It keeps the jet O rings snug.
If it leaks, your gasket is bad or the screws are stripped.

Edy
 

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Discussion Starter · #20 ·
It was weird with the one carb, like the jets wouldn't go in far enough so it pushed the metal hanger onto the top of the carb, it was leaking from the seal. but when i bent the hanger a bit it was fine. Here's the video:
 
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