CB360 idle issues

[carkom]

So I've searched all over trying to see if I can find my specific situation but I can't seem to get an exact answer, maybe you all can help me. I just got a '74 CB360 that was sitting for a while and didn't run (obviously). I pulled the carbs apart and cleaned all the jets and needles and casings. I rebuilt the petcock and replaced all gaskets (leaking doesn't even describe what it was doing) it's good now though, keeps gas in the tank. I replaced the fuel lines and the fuel filters and I changed the oil and replaced the battery. So enough of what I've done let's move on to what I need to do.


Currently the bike will fire up but only with the choke on and full throttle. Once it kicks on it really struggles and any letting off of the throttle causes it to die. At full throttle once it's on it only get's as high as about 3k rpms. I reset the points gaps today and they seemed really sporadic. I swapped coils from left to right and it seemed like one coil worked better regardless of what side it was on but then once I fired the bike up and watched the points they seemed to be firing very intermittently, like the left would spark and the right wouldn't then the right would start sparking then the left wouldn't all the while it was definitely missing on every 3rd spark or so.


Now like I said, I've done much reading. It seems like all I can do is replace the points and condenser and get a replacement coil to see if it works better than my two current ones. But from what I've read electrical problems are extremely hit and miss, that is assuming of course this is an electrical problem, but I figure if the I'm not getting a spark on every rotation than it has to be at least something electrical, right?

 

[crazypj]

Re: CB360 starting issues

Sounds like carbs and ignition.
Check all the electrical connectors for corrosion
Re-do carbs paying particular attention to pilot jets and fuel screws (you did pull EPA caps off and remove them for cleaning?)

 

[hurley209]

Re: CB360 starting issues

Have you checked you timing?
If it was sitting for a while change the points to be safe and set the timing, adjust carb float heights to spec and sync your carbs. A combination of all three will make it hard to tune. Set all to stock.

 

[carkom]

I did check the timing and it was good. I didn't get a chance to sync the carbs (no vacuum tool). I did pull the EPA caps off and cleaned everything really well when I took the carbs out.

Okay so I got the thing running better, turns out all it needed was more air. I took the choke off and if fired right up and rev'd great.


Here's the problem now. It won't idle. I can rev it and let it drop from about 1k rpms on up to red line. I have to give it a little throttle for it to start and if I keep pumping it, it will stay on all day it seems. As soon as I let completely off the throttle it dies. I tried to hold it at 1.5k rpms with the throttle just barely turned and it ran fine, I just couldn't get it to stay there.


Some info that may help: The throttle is sluggish (doesn't pop back into place when I let off of it) I have to help it a little to come back sometimes. I tried to adjust the throttle cables but didn't quite know what I was doing and my shop manual wasn't too much help. Any suggestions to get this thing idling to where I can have it running without touching it? Thanks in advance.

 

[eram]

Silly suggestion...but you did adjust the idle speed screw?

 

[carkom]

Yeah the more I think about it the more I think it's something as simple as that. Meaning, no I haven't. So that's what I'm doing tomorrow after work. Does anyone have detailed pics of exactly where I can find this. The manual isn't super specific.

 

[eram]

Source: CB360 Clymer Manual

 

[habib]

I had a similar issue with my cb350, I did everything you mentioned. For me my left side wouldn't fire as it would stall at idle. Turned my battery being low/dead caused the whole
Issue. A new battery an I was rocking.

 

[dirtbag]

R.T.F.M.

M is here

 

[carkom]

R.T.F.M.

As I said (if you read the post at all) I did read it dirtbag. Keep your smart a** comments to yourself.


Went to adjust the idle screw and the wire from the screw was broken, looks like I'm ordering a new one unless some one has another suggestion? Thanks for all your guys input so far, I really appreciate you taking the time to help!

I had a similar issue with my cb350, I did everything you mentioned. For me my left side wouldn't fire as it would stall at idle. Turned my battery being low/dead caused the whole issue. A new battery an I was rocking.

Battery is 7 days old, so I don't think that's it, thanks for the heads up though.

 

[dirtbag]

If you did read it then you should have gone over the bike from top to bottom. Check valves, timing, carb sync, points (shape they are in), filters clogged, spark plugs, etc.

Are there any mods to the bike we should know about. How is the compression?

 

[carkom]

As stated before...I checked the timing, carb sync (I haven't done due to no vacuum tool) and points (not pitted, and cleaned them up). Air and fuel filters have been replaced with new, as well as new spark plugs, oil has been changed (including screen cleaned and centrifuge de-gunked. The bike is completely stock, no mods. Compression is good, I can't give you an exact number because I don't have the tool but it passes the "thumb" test.

 

[Sonreir]

I'd check the sync and compression before you worry about anything else. Get the tools for the job and KNOW for sure it's not a problem. While some of us like to treat motorcycles like a religion, praying and faith isn't gonna fix your issue.

 

[dirtbag]

Something doesn't seem right with your return spring on the carbs. It should spring back. While you have the carbs off check the sync by eye.

 

[carkom]

With the carbs off, the spring is strong and pulls the butterfly closed well. I think it may be a gummed up/dirty throttle cable. I'm just throwing that out, confirm or deny.


How do you check CB360 carbs sync "by eye"? I have the carbs off and can see the pistons through the open butteryfly valve.

 

[dirtbag]

Yah sounds like the throttle cable. Very likely.

 

[carkom]

Okay, so I used some cable lube and a tool to lube the throttle cable. It now snaps back perfectly.

I checked the compression after warming the bike up, it was 135 on the right side, then added some oil and it was about 137. On the left side it was 129 before and after adding oil to the spark plug hole. I know spec is 171 and anything below 149 is out of spec but I've heard 130 is adequate. Should I adjust the valves to see if I can bring that up?

I adjusted the idle screw and got it to idle at 2k. It was really finicky getting it there. It'd be at 4k and I'd give it a half turn and it would not idle just dieing off, then I'd get it back to 4k and give it an eighth turn at a time eventually got it to 2k rpm strong. I took it out for a spin around the block and I'd rev it up then shift and the idle wouldn't get below the 4k mark after that point. To get it back to normal while riding I have to let the clutch out while in 1st or 2nd gear while stopped which drops the rpms then it will stay at the 2k idle I set before. If I don't go through that process it just stays at 4k. I want to sync my carbs but I don't have the 6mm fine thread tool that goes in the vacuum holes. Is that my next step? Ideas I can use for syncing the carbs? Anything else I can try to fix the possessed idle? Thanks ahead of time.

 

[frogman]

Low compression bikes will not idle well or for long. I know I had one. Bike would run fine but had no low end coming off a stop and refused to idle at all. I had leaky valves and shot rings. A valve lapping and a set of low miles pistons and cylinders fixed the issue.

Sticky advances cause slow return to idle. If you wind the idle screw all the way out where it should just die and wind up the throttle and let go and it takes its sweet ass time coming back down then check the advancer springs. MAKE SURE they pull the weights back tight against the center at rest. Another thing, check for air leaks around the carb boots. That will cause the bike to not return to idle quickly as well.

Bench syncing the carbs means setting the throttle butterflies so they are at the exact same spot on each side. I use the pilot holes as reference. Adjust until they move the same and stop at the same spot.

Start with checking for air leaks around the carbs, get the bike running and spray carb cleaner around the boots any OBVIOUS change in RPM is a sign of an air leak.

Next check the timing advance unit, make sure the springs are doing there job, you can bend them sightly to at least try but sourcing new ones will be needed as they were never meant to last 30 years.

The coils are a shitty design that is a pain in the ass either way. There are many ways to fix that, mostly just getting some other style and making them fit.

Finally, the compression issue. You checked both sides with the plugs out and both the choke and the throttle WIDE OPEN right? That will make a huge difference if even the throttle is closed. You might also try your meter in a known good engine and see what you get, lawn mowers work great for this. You can check to see if your valves are leaking by pulling the exhaust and the carbs and sloooowwlllly turning the engine over. Once the cylinder gets to the compression cycle they will sorta HISSSSSSSSS if they leak. WD-40 or PB blaster on them will make the Hiss louder and may help wear the rust out.

They have to have good compression to run well and be reliable. I couldn't take mine anywhere for fear of it leaving me with fouled plugs or something silly. Now I hop on 2 kicks and it purrs like a kitten and takes me anywhere I want.

 

[eram]

...I want to sync my carbs but I don't have the 6mm fine thread tool that goes in the vacuum holes. Is that my next step? Ideas I can use for syncing the carbs?

CrazyPJ makes the adapters that are perfect for the 360s. The eBay ones and other places I think are threaded wrong? PM him maybe and see if he has any left? I know he's been busy lately with the other items, but his are worth the wait.

 

[carkom]

CrazyPJ makes the adapters that are perfect for the 360s. The eBay ones and other places I think are threaded wrong? PM him maybe and see if he has any left? I know he's been busy lately with the other items, but his are worth the wait.

Yeah, I've been in contact with him, thanks for the heads up. He's supposed to be making some this weekend.


So I finally got to check some stuff on the bike this morning. I checked for air leaks - idle unaffected. Then I moved on to the compression because that's what I'm most concerned about. No point wasting time else where if I don't have the compression I need. I adjusted the valves on the left side (only had time for one side and the manual says to start on the left) I got the valves set to spec and rechecked the compression. Now remember before I was at 129psi on this side, after valve adjustment I'm at 135psi, then I put a couple teaspoons of oil in the spark plug hole and it went up to 145psi. So with the valves properly adjusted I'm assuming all this means that I have to replace my rings and check for leaks at the cylinder, is that right? Oh, and yes, frogman, choke wide open, throttle wide open when checking the compression. My meter is brand new (last week) so I wouldn't imagine it would be off but I checked it on a buddies bike (working) just in case and got 175psi so I'm pretty sure it's working properly.