1975 Honda CB360 only idles on one cylinder - Motorcycle Forum
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Old 02-26-2010, 06:32 PM   #1
roehlerich
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Default 1975 Honda CB360 only idles on one cylinder

I just posted this under the vintage forum and then found this one. Sorry for the repeat.

On my CB360 twin only the left pipe gets hot under idle. I have the rev the engine above 3000 rpm for the right side to kick in and get hot.

Just cleaned the carbs (could this still be the idle jet?)
Replaced the coil
I have spark, even at idle, blue too

No idea what this could be. You can even tell she idles on one cylinder only. But when you pull the spark plug connector on the right side, nothing happens, when you pull the left one, she dies.

I did check the gap on the points but did not play with the timing.

I did not check compression yet either.

Any thoughts?
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Old 02-26-2010, 07:01 PM   #2
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Just checked compression:

150 on the right side (the one that does not get hot under idle)
100 on the left side

Still no clue on what it could be.
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Old 02-26-2010, 11:04 PM   #3
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If the right side does get hot at high RPM, you should have spark so I would look to the carbs.

"Cleaned the carbs" means different things to different people. Did you remove the pilot adjustment screw and the pilot jet and soak both in cleaner? Did you run some fishing line through the pilot jet and "floss" it?

Also, Have you verified that the float level is correct on the right side bowl?
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Old 02-27-2010, 07:16 AM   #4
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I did not remove the pilot adjustment screw since it has a stop built in and can;t be turned further. I should have done that. I did remove all jets and blew them out with carb cleaner. They were really clean. I checked all the holes and I use wire brush wire to poke the holes clean when they are plugged. I will shoot some starter fluid into the right carb under idle and see if she fires. That should tell me if it is the carb. I did not check the float level, but the carbs do "leak" out when sitting with the pet **** open, so I know they are getting fuel. Not sure if the float valve closes all the way. Had that same problem with 2 sets of carbs on this bike and also my cb 350 four with professionally rebuilt carbs. They all leak a little fuel when you try to start them.

I will post an update later when I spray the right carb.
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Old 02-27-2010, 09:02 AM   #5
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OK. Call me s-pid. I just took the air adjuctment screw out and sprayed carb cleaner i nthere. Reved right up.

Also sprayed starter fluid into the air intake. Same thing.
So I think I have a blocked idle jet, right? That would be the little jet under the cap. I did take it out and blow it out, but might have some blockage in the cab housing itself.
I am running seafoam through the carb to see if I can break things up. These carbs were not completely dried up, just some gummed ags in the bowls.

This will be my 4th attempt to get a good set of carbs on this bike. But now I have it narrowed down.
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Old 02-27-2010, 11:26 AM   #6
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Quote:
Originally Posted by roehlerich View Post
but might have some blockage in the cab housing itself.
Yeah it sounds like you did a good job on the jets, but a piece of gum is probably lodged somewhere in the carb's passageway from the pilot jet to the intake -- possibly near the screw that you can't remove. If fuel is not passing through this area then Seafoam will have a hard time getting through, too. Perhaps you can use the carb cleaner straw to shoot cleaner down the passage from the pilot jet side, and dissolve/force whatever it is past the pilot screw.
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Old 02-27-2010, 03:03 PM   #7
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Another twist:
I kept playing with the idle and the choke. Bike starts only without choke (Butterfly open) on left cylinder.
Bike idles at 2000 rpm. Then, when I close the choke almost all the way the right cylinder kicks in but runs rough and backfires. I must be creating some kind of vacuum somewhere. When I take the idle adjustment screw all the way out on the right cylinder, the carb gets too much air and the right cylinder stops running again. I put the screw back, and it starts up again.
Weird...
So I definitaly have a timing issue with the right cylinder. It should not stutter and backfire at 2000 rpm with the choke closed 80%.
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Old 02-27-2010, 03:10 PM   #8
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It could be backfiring because it's running lean, and it could be lean because the pilot fuel passage is restricted.
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Old 05-13-2010, 12:23 AM   #9
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Default pilot screw

hey, I dont know if you have it worked out yet I sure hope so. This is identical to mine but opposite. I just traded for a 360 that was cool on left but the right side blistered my finger. I was getting spark and there was gas to the carb but none to the cylinder. I unplugged the left plug and nothing happened. I unplugged the right one and it would die. I only had the service manual free download off internet but did not read it yet. I only saw two screws on the carb. I started to unscrew the small one which was the pilot screw i believe. it was only 2 turns out from all the way in. I turned it about half turns out and the bike jumped to life. the carb was not allowing fuel in. I read the service manual on the carb adjustment after that and have the carbs I think adjusted right tonight. will test tomorrow. I hope this helps or might help next reader.
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Old 05-26-2010, 11:25 AM   #10
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i had the same problem on my suzuki T500. It would start up and run on one cylinder and would perk up to two cylinders above 3000 RPM. I did what you did and cleaned the carbs over and over. Turns out that one of the small brass ball bearing type thing had fallen out of its repective hole. I put the ball back in and it ran like a dream. Take a look around in the carb and see if there are any spots that look like they should be plugged up.
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Old 05-28-2010, 02:38 AM   #11
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Quote:
Originally Posted by roehlerich View Post
Just checked compression:

150 on the right side (the one that does not get hot under idle)
100 on the left side

Still no clue on what it could be.
This is really low.

Simple question, do you have spark on both cylinders?

Is the bike backfiring or is it popping? Backfire would be out of the carb side of the motor, popping would be out of the pipes.

You may want to get a manual and set the a/f mixture screw back to stock. (usually 1.5-2 turns)
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Old 08-23-2010, 02:00 PM   #12
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This isn't insight, but rather more questions along this same thread. I have a '76 CB360T that I picked up from my uncle. I just cleaned the carbs as best I could and put the bike back together. The thing pops right off when I kick start and idles perfectly on both cylinders, but when I put it in gear and put a load on the engine the right cylinder stops working until about 2-3k RPM. Any ideas?

Oh...when it is sitting idling the motor slowly accelerates...I thought that was weird but I have no idea what it could be. Please bear with me if these are simple problems with simple answers. This is my first bike. I'm treading in new territory for myself.

Also, if any of you can refer me to any other good sites/forums for info on these old bikes it'd be much appreciated :-)
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Old 08-23-2010, 06:12 PM   #13
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perhaps the carbs need proper cleaned. i used to have a k4 350 twin, and found the o rings (tiny) on the main jets were perished, so it would only fire on 1 cylinder until about 5000rpm. but the carbs can get in a real mess if the petrol has never been drained from them and stood a while.

cheers Paul
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Old 08-26-2010, 07:49 AM   #14
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Quote:
Originally Posted by CB360FirstTimer View Post
This isn't insight, but rather more questions along this same thread. I have a '76 CB360T that I picked up from my uncle. I just cleaned the carbs as best I could and put the bike back together. The thing pops right off when I kick start and idles perfectly on both cylinders, but when I put it in gear and put a load on the engine the right cylinder stops working until about 2-3k RPM. Any ideas?

Oh...when it is sitting idling the motor slowly accelerates...I thought that was weird but I have no idea what it could be. Please bear with me if these are simple problems with simple answers. This is my first bike. I'm treading in new territory for myself.

Also, if any of you can refer me to any other good sites/forums for info on these old bikes it'd be much appreciated :-)
dansmc.com directly addresses your questions . Go to the motorcycle repair course and read everything there about carburetors and you will probably find stuff you can use.
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Old 08-26-2010, 08:39 AM   #15
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Originally Posted by slumlord View Post
dansmc.com directly addresses your questions . Go to the motorcycle repair course and read everything there about carburetors and you will probably find stuff you can use.
Thanks. That is a great site! My friend can over and helped me adjust the carbs. The cylinder cutting out was all due to a bad air adjustment screw setting. I see a lot of people on this forum referencing a similar problem as what I was having. My recommendation is to be patient and slow and adjust all the adjustable screws on you Carb until the engine is running right. I thought mine was running great until the settings clicked and it really came to life.
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Old 08-26-2010, 06:17 PM   #16
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Quote:
Originally Posted by CB360FirstTimer View Post
Thanks. That is a great site! My friend can over and helped me adjust the carbs. The cylinder cutting out was all due to a bad air adjustment screw setting. I see a lot of people on this forum referencing a similar problem as what I was having. My recommendation is to be patient and slow and adjust all the adjustable screws on you Carb until the engine is running right. I thought mine was running great until the settings clicked and it really came to life.
I know what you mean.My bike will pull quick and strong to 65 in 4th, 75 or 80 to 8000 RPM in 5th,and in 6th gear-- well,I really do not ever want to ride that little bike faster than 80. Of course,I hear the rest of you guys with performance bikes laughing, but for a 150 dollar barn find,it is a good bang for the buck.
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Old 08-30-2010, 11:26 PM   #17
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Hey Everyone, I am new to this forum - well I have been reading for a couple of weeks but this is the first time I am posting. I have a similar problem I have been working on a 76 CB 360T and was hoping I can get some advice. I have cleaned the carbs and tuned in the timing. The right side runs well and strong. The left side seems to fire when it wants - very sproadically. When I pull the plug and check for spark by kicking it over it sparks yet when I fire the bike up and hook up a timing light to it the strobe lights up only when I hear the cylinder fires. I hope I am making sense. My question is what electrical components should I check? I replaced the coils/condensers with used coils and replaced the points with new points.
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Old 08-31-2010, 04:35 AM   #18
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Originally Posted by radiotoaster View Post
Hey Everyone, I am new to this forum - well I have been reading for a couple of weeks but this is the first time I am posting. I have a similar problem I have been working on a 76 CB 360T and was hoping I can get some advice. I have cleaned the carbs and tuned in the timing. The right side runs well and strong. The left side seems to fire when it wants - very sproadically. When I pull the plug and check for spark by kicking it over it sparks yet when I fire the bike up and hook up a timing light to it the strobe lights up only when I hear the cylinder fires. I hope I am making sense. My question is what electrical components should I check? I replaced the coils/condensers with used coils and replaced the points with new points.
A spark plug "test" outside the cylinder is not such a good test to use. It fires more easily outside the bike than inside. Your timing light is a much better indicator of spark strength. I would check the wiring from the points to the condenser,the coils,and the spark plug wires themselves at the boot.. On My 360,there is a bullet connector under the tank [I think from the points} that created the exact problem you describe. Clean,check the crimp,and use dielectric grease on the connector. No guarantee,but a place to start...
on edit....
You say that you also replaced the points. Others have reported that the cover can contact or intermittently contact the points or wiring or the insulation can wear thru at the cover. You could try running it for a bit with the cover off to test it.

Last edited by slumlord; 08-31-2010 at 04:43 AM..
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