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Hey there -
I've got a 75 CB360T with one cylinder intermittently not firing (I think). I was riding home from work yesterday when the left side of the bike next to my leg stopped vibrating altogether (presumably the cylinder not firing). When I got home, there was oil accumulated on the air cooler outside around the spark plug, and the oil there was hot enough that it was smoking .... my ride home is only about 25 minutes, without much stop and go. The wires themselves didn't seem to be what was smoking, and they were not too hot to touch.
The cylinder problem is isolated to just the left (kickstand) side.
Also, after initial start and running for about 5 minutes it tends to backfire when I'm idling. I haven't paid enough attention to see if this is one or both sides.
Bike accelerates just fine, and can hold 45 mph comfortably in 2nd or 3rd gear at 5-7000 rpm. 60 mph in 3rd or 4th gear pretty easily, too.
I get a pretty good spark from both spark plugs, they don't look coked up, and I just replaced the battery two days ago. I've never worked on carbs before and the Clymer manual has been on order along with some parts from OldBikeBarn since January (waiting on the manufacturer, apparently). That said, I haven't touched the carbs.
I have new points and condensers coming in the mail from another source.
I'm guessing this is maybe a carb issue :( ?? (gotta learn sometime, I guess)
Sorry for the lengthy post, just trying to put out as much info as possible initially....
In the meantime, any suggestions?

-M-
 

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Your fuel petcock has two fuel drops coming out the bottom. It is possible that one of them can get plugged up [happened to me]. Just check and make sure both fuel hoses flow the same.Otherwise, it is either spark,fuel,adjustment or air.
 

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My 75 cb360t seems like it's missing

Sorry for hijacking but this post seems pretty old and i just joined the forum, so I can't make my own thread yet.

Well, on my cb 360 the cylinder isn't firing on the kickstand side either, like the problem listed above. I have double checked the timing, made sure that both sides are sparking, adjusted the ignition timing as best as I could with a bike that barely stays running, made sure that my petcock and fuel lines weren't plugged, and made sure my plugs weren't fouled.

A couple of weeks ago I pulled my carb, double checked the diaphrams for damage. I pulled the bowls off and found out that they were full of junk, so I soaked the carbs it in denaturalized alcohol, cleaned out the jets and the bowls. My father suggested I check the float height, but I haven't ever checked the float height before, and the clymer manual isn't very helpful.

It says the height should be .74 inches off of the throttle body. does that mean you measure from where the bowls seal to the carbs? and If they're not the right height, how are you supposed to adjust them? sorry I'm still learning and this is my first bike, and any help would be great.
 

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It's not much help with the carb issue, but eventually I just brought my bike to the shop and had the engine tuned and carbs cleaned... but what I hadn't known before that was there was insufficient clearance between my points and [I think it was the] spark plug; they were contacting each other, giving me problems and my oil leak.
It may or may not be part of the problem, but it's another thing to check out.
 

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75 cb360t cylinder issues

hey thanks, I'll definitely have to look into that. I have oil leaks from around my spark plugs as well. I'll check the clearance and go buy me a couple of new plugs to see if it helps.
 

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My father suggested I check the float height, but I haven't ever checked the float height before, and the clymer manual isn't very helpful.

It says the height should be .74 inches off of the throttle body. does that mean you measure from where the bowls seal to the carbs? and If they're not the right height, how are you supposed to adjust them?
When the float is high enough to close the float valve is when you measure the float height. Measure in the middle of the float. Measure up from where the float bowl attaches to the carb (the flange) to the "top" of the float (the "top" being the side away from the carb). If your float valve has a little spring loaded button, like mine, measure when the float is pressing the valve itself closed, but not compressing the button.

If the height is not correct, bend the little tab that pushes against the float valve one way or the other until it is right. Reassemble. Put the hose on the carb and hold the carb level, like how it will sit when reinstalled, open the petcock, wait a few and see if any fuel is leaking out of the overflow (probably a hose barb under the float bowl or perhaps a simply weep hole on the boottom of the bowl). If it leaks, take the bowl off again and readjust so that the valve closes sooner (ie bend the tang toward the valve). Try putting it together again and see if it leaks. Once it stops overflowing and you are as close as possible to the height you should be good. This assumes, of course, that the carb is really clean and the float valve is not sticking and is free to move up and down.

As far as the rest; I like to get a carb cleaner dunk tank from the local auto parts store. They are cheap and have cleaner and a basket for submerging parts. Take the carbs completely apart. Anything that can be removed should be. Also, take all rubber parts: gasket and o-rings (they will be ruined, especially CV diaphrams if not removed), then submerge everything. I have left it overnight before. When you take it out use some fishing line to make sure all passages are clear and a toothbrush to clean the bowl area and outside. Shoot spray carb cleaner through all the jets and air passages and then blow compressed air through all the jets and make sure you see the cleaner shooting out on the other end of the passages. Watch out you don't get the spray in your face when you do this.

After everything is clean, wipe off and blow off all that carb cleaner from every place on the carb. Install new rubber gaskets and o-rings. Screw back in anything you unscrewed. Then reassemble the carb.

Good luck!

Mike
 

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75 cb360t cylinder issues

Hey thanks for the advice, I just finished cleaning the carbs and measuring the floats. Turns out that they were all out of wack, so I set them as close to the .74 inches as I could. There wasn't anything leaking out the overflow, so I reinstalled the carb. But when I tried to start it back up, all it did was sputter a little then kill. I checked my plugs and they were pretty fouled, (looks like they were covered in burnt oil) so I got a couple new ones and tried again, but it didn't fix anything. So apparently it isn't the carb. I inspected my points again and they were gapped right, but one of my points wires looks like it is melted, so I'm going to try and repair it and see what happens.
 

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When you installed the carbs did you set the idle mixture screws per factory? Once started, can you rev it and keep it running? Is it only having issues at idle? And it is only the left carb, correct?

When you opened the carbs I assume you checked the float valves to see if they moved easily and did not stick in the closed position?

Also, check under the points cover plate and make sure that none of the wires are shorting out on the back side of the cover or against the plate.

I am also finding out, in spite of what I heard from a couple of "mechanics," that these coils go bad fairly frequently. MikesXS dot com has coils that you can use to replace the old ones if you find out that is your problem. Sometimes this problem will be intermittent.

Keep plugging away; you'll get it.

Cheers,

Mike
 

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75 cb360t cylinder issues

When I installed the carbs, I set the air mixture screws to 2.5 which I do believe is spec, but they were very loose in the carb so I wrapped them in teflon tape to help keep them threaded. Will that somehow mess with the vacuum?

When I pulled the carbs off I did make sure that the float valves weren't sticking. And the problem wan't just at Idle, it was at all times. sometimes if I was able to get it up to 5k it would start to fire on the left side, but most of the time it would just ride around on one cylinder. If I stopped for any reason it would kill, and the right side would be so hot that I didn't dare start it back up.

I did recently replace the coils but they were from a junk yard, so they might be the problem. Thanks for the site I had been googling for new coils for a while and haven't been able to find anything, but then again I didn't think about buying coils off of a yamaha.
 

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I was glad to find that site, too. Unfortunately, I found it after I fixed my bike, and had tried to rig some odd aftermarket coils (which the moment I put the front tire on the road burned up!), and finally spend good $ on used coils. I wish I had seen that site a month ago.

I know on the CB350 the resistance between the terminals on the coils should be between 4 and 5 ohms; that's how I found out mine (left) was bad. Not sure what yours should be. You might want to e-mail William Silver at vintagehonda.com and see if he has that. I ordered some service manuals from him this morning that (I think) include your bike; I could check that for you when they get here in a day or two.

From what I've read, just about any coil will work (at least that is what my 1972 Clymers manual said, recommending Walmart, who no longer carries any coils at all) so Yamahas are as good as anything. The trick is finding some that will fit on your mount under the tank so you don't have to re-engineer everything. And nowdays a bunch are dual coils made for bikes with two plugs in each cylinder and all sort of others. For these old Honda bikes what I think you will need from MikesXS is Part #17-6805. You will have to modify mounting them but they are small enough to fit. There is a sticky thread here that shows how someone did it on their CB450: http://www.hondatwins.net/forum/viewtopic.php?f=29&t=782

I don't know why your idle screws fit like that; they shouldn't. Did you turn them 2.5 turns IN or 2.5 turns OUT? Usually they indicate turning out from full closed. If those are leaking around the threads because they are loose, it is not a good thing.

You might want to check out my thread down in "Motorcycle Repair" titles CB350--So Close but Yet So Far and see some of the stuff I tried. Maybe it will give you some ideas.

I hope something here helps.

Cheers,

Mike
 

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To heck with the 2.5 turns on the carb screws. I started mine at 1.5 and went out and it was worse. I think now they are more like .66 of a turn. Your bike is your bike and it will tell you where to set them.
 

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another oddball thing, but check your valve lash. improperly adjusted(and on old bikes not too far fetched)valves will cause all sourts of idle and running problems
 

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75 cb360t issues

OK, so I repaired one of the points wires (the yellow one) with some 12 gauge wire that I had lying around and now it seems to be firing on both cylinders, but it won't idle and I can't get it to rev over 5500 at all. I took it for a spin around the block and it had plenty of power untill it hit about 4k then it would bog down and won't go past 5500. As far as I can tell it happens in all six of the gears, so if I keep shifting short I can get to about 50 mph before I can't go any faster... but that's not good enough.

LWRider, I just read through that thread of yours, and I have to say, great job with that 350! That seems so much like my bike, find a problem, fix it, and overall have small improvement without fixing the main issue (whatever that may be). I'm glad you stuck it out and updated your findings, it has helped me out a lot. I'm going to go check the spark advancer (since the problem seems to be only effecting the higher RPM's) for gunk, make sure my bullet connectors from my points to coils aren't corroded, test the resistance on my coils, check my gas cap ventilation, heck I might even double check to see if my carbs and or floats match. I'll have an update sometime soon...
 

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Sounds like you are making progress. Keep at it and you will soon be on the road. I have mine running well enough now to take a decent trip on it tomorrow (weather permitting) to Plant City Bike Night, about 40 miles each way.

Cheers,

Mike
 

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interesting...

I just pulled off my points and spark advancer, and both appeared in perfect condition. I was just about to reinstall them, when I noticed something interesting... The metal pin/dowell that held the spark advancer to the cam shaft is MISSING! it looks like, well, it just fell off. That doesn't make sense, because I compared it to a spare cam off of a 74 cb360 and it looks like it is solid state. I was thinking about trying to press in a piece of steel to make another dowel, but i'm not sure how well that will work. maybe i'll have to pull the cam and take it to a machinist?
 

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I can't help myself with that. I had a mcechanic at that point looking at my bike and he pulled the points plate and cleaned up the advance, so I have never seen mine. Doesn't sound right, though. Maybe someone else can speak directly to that.

Cheers,

Mike, off to PC
 

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wow i'm glad I did that...

Well, I just pulled the head cover, and found that a couple of my tappet adjustment screws have come loose and fallen out. Luckily they didn't find their way down the center hole where the timing chain loops through the motor, but got lodged behind one of the head bolts... I'm so glad I pulled that cover. I'll make sure that they are torqued right this time around.
 

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valve lash is an odd thing...iv spent about a month floging with a carb on my chinascoot only to check the lash and finding out that they r too tight
 

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Oh Yeh!

I just got her all back together, and she started up with just one kick! Idles about 1800, and when I took her around the block she was able to rev all the way up to 7k! I'm guessing that the reason it's not revving higher is that I have to re-time the ignition for the advanced spark. That and one of my tappets is slapping pretty loud, so I'm going to let her cool off then go back out and re adjust it.

So it turns out that it was a number of things that plagued my cb360t:

1: was that the carb was a little dirty, and the floats were way out of whack.

2: The yellow wire that is wired straight to the points, had melted from the extreme heat from my engine running WAY too lean, and also had been pinched by the metal points cover. a quick rewire and she was firing on both cylinders again!

3: the dowel pin on the cam shaft fell out, the one that holds the spark advancer to the camshaft so that it can rotate with the motor and advance the spark based on your rpm.

4: was the valve lash (thanks HondaIlya!) two of the adjuster screws had shaken loose, making one of the locknuts fall out, and another adjuster screw and locknut fall out. Needless to say, it was time to re-adjust.

Thanks everyone for helping me figure this b*(^h out! hopefully this will help someone else along the way.

-Tyler

Drinking a cold one.
 

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Excellent! Glad you are on the right road and that you posted back here with your results. You never know who might be reading and benefit from what you've found.

Cheers,

Mike, about to go mess with his tappetts, too, just to be sure.
 
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