Cb360 engine troubleshoot. Need help

thrillseeker

thrillseeker

Been Around the Block
Thread Summary:

Issue:
Engine only firing on one cylinder.

Steps taken to diagnose:
1 Cleaned carbs
2 Set floats
3 Check for spark against engine(good spark)
4 Set timing(timing good)
5 Swapped the spark plugs and found out the spark plug was fouled so it showed spark outside the engine but wasnt firing inside the engine. Swapped the 2 plugs to figure this out. Put new plugs in and she ran strong.
6 Came back the next day to find the right cylinder isn't firing again and the right carb is leaking fuel. Think the float is stuck again. Also, the motor is backfiring around 3k rpms
7 removed float bowls without removing the carbs and found the side having problems was low on fuel. Re-measured, adjusted, and swapped floats and the engine is running strong. Apparently when I checked the floats before I wasn't thorough enough.


Original thread:

Hi everyone. I bought a 360 a couple months ago and am starting to work on the engine a bit. I want to start out by saying im a beginner when it comes to working on engines and carbs. I'm noticing the right exhaust has a quick "put" sound coming from it on an an average of about every 15 seconds or so. I notice it more when slowing down. It also seems like the left cylinder has a bit more power to itthan the right. If I disconnect the left spark plug, the engine stops immediately. If I disconnect the right, the engine keeps running. I checked compression and they're both around 90 psi. The right exhaust is heating up slower than the left, and the spark plug is a little darker than the left. I did notice my battery is about dead after only 2 months so I need to evaluate the charging system.

Could the low battery be causing the issues I'm having with the right cylinder? Do I need to make adjustments to my carbs possibly? Maybe right side a little rich due to the darker spark plug? The guy I bought the bike from (vintage bike collector and mechanic) did mention that he cleaned the carbs before I bought it. What are your thoughts? Is there anything else i should be checking? I'll post up pictures of the spark plugs for reference.
 
Check fuel lines to carb #1. Also, check your voltage on the battery. If it is low, replace it or charge and try again (good idea to invest in a battery maintainer/charger when you own an old bike). It sounds like either a weak spark, or a VERY rich mixture, or both. Try leaning out the mixture a bit and see what happens.
 
your exhausts dont heat up evenly because the carbs arent balanced/synced. build a manometer and do that. also check valve clearances. 90 psi is terrible btw. how are you testing? if your carbs are still on make sure you have choke off and throttle wide open when you kick it over. id buy a new rectifier because i guess these old ones suck. you can also tie the white wire from the stator into the yellow one and that will engage the third pair of coils all the time so you get better charging. not sure what the every 15 seconds thing is, probably a backfire? check float levels (18.5 mm) and clear all air/fuel jets. hope this helps! let us know how it goes!
 
Thanks guys. I do have a battery tender that it's charging on right now.

As far as compression, I just let the electric start turn it over a few times without the plugs in at all. Should I be actually trying to start it up with the kick and get it to turn over?

As far as the carbs, I'll have to look into that some more to learn how to sync and adjust the fuel mixture.

I'll also have to reference the shop manual to adjust the valves.

The sound from the exhaust is probably backfiring but I'm used to the sound of a car backfiring. This is much quieter. That's probably what it is though. Maybe so rich that excess fuel is getting ignited in the exhaust. That's what it really sounds like.

Thanks for the suggestions. Hopefully I'll be able to find time to work on it soon!
 
Rich fuel burns immediately once it gets out into the pipe. LEAN mixture will wait until there is enough fuel in the pipe and then kinda POOF or soft POP. If one side POPS at idle and the other doesn't is due to the sync being off or that side idle fuel circuit being clogged. Does the that side pick up and run when you rev up to say 2000?

IF you don have a manual, one from the download links either on here or google search "CB360 SHOP MANUAL". Read through and do the inspection/adjustment area.

IF you have 90 on both sides and it is EVEN that way then the bike WILL run just with no power. RE-BUILD or RE-RING time is 149 PSI you want 170+. Compression might go up once you adjust the valves. SLIGHT DRAG is a term that sucks to understand if you can't be shown. Use the next FULL size up for a feeler gauge to check the one you set to, it should NOT go under.

IF the engine has sat for years the rings might be stuck in the groves. Go get some PB blaster or SEAFOAM deep creep and soak both cylinders with it for several days.
 
Okay i finally had time to address these situations. I dont have a tool to sync the carbs yet but i adjusted the a/f mixture on the right carb and got the sound from the exhaust to go away. Im surprised at how little adjustment you can do to the mixture screw.

I adjusted the valves and now my compression is above 170 for both cylenders but now i hear a tapping/clicking sound from the motor. Could that mean the valves are hitting the piston or the valve seat harder than it should be? Here's a video so you can hear it.

http://www.youtube.com/watch?v=wGiELKdDkD4
 
You may have the valves too loose. they should have alight clicking sound, not a clatter. It is hard to described in words.

A loose cam chain will also be noisy, so that will need some attention too, no doubt.
 
I fixed the valve clicking but now i have a new problem. I didn't even touch the carbs other than to remove the fuel lines but after i hooked the tank back up, gasoline is pouring out of the carbs as if the float valve isn't working at all. Could the float get stuck to the bottom of the bowl if the bowl runs empty? It didnt have this problem at all before. but I did run the bowls empty when adjusting the valves. maybe I need to take off the bowls and clean them? it seems to be happening in both carbs. not just one.

Also, the loud clicking is gone but now there's still a clicking sound only at idle. When i rev the engine it goes away. Could that be the sound from the cam chain that you were talking about?

I really appreciate all the help you guys are giving me. I'm very new to working on these engines and carbs and I dont know anyone that knows this stuff so I'm shooting at the hip. Plus, I'm sure these posts will help someone else in the future as well.

Here's a video. you can hear how it stops ticking when I give it gas.

http://www.youtube.com/watch?v=4iC7QKaMQCM

and here's something to show my appreciation...

tumblr_lbqyljvbsd1qz6sg6o1_500.jpg
 
Got the overflowing fuel problem fixed by giving the carbs some good taps. Also replaced the fuel lines because the old line to the right carb broke while pulling it off. Planning on getting some clear braided line soon. Bike wont start now though because the engine is really flooded, so i took the spark plugs out to let it dry inside the cylinders and i'll try starting it again soon.
 
Some progress but still havent found the culprate. I took apart the carbs and cleaned everything. I also checked the butterflys and they're both in sync from the visual check. I still have to get adapters so my sync tool can connect to the vaccuum ports. I Put the carbs back on and still no power from the right cylinder. I then put my hand over the intake side of the right cylender while the engine was running to restrict airflow and that got the right cylinder to fire for a few seconds after each time i did it. Possibly from creating extra vaccuum? Then i decided to check the timing. The gap for the right point was off so i fixed the timing. After that, the engine started up and ran strong for 5 minutes until i turned it off and suited up to go around the block. When i started it up again, the problem was back. No power in the right cylinder. You can hear it firing intermittently now though. I took a video so you can see how its running now. Any new ideas? Spark and compression are still strong.

http://www.youtube.com/watch?v=D-LWBm8zEW0
 
Have you checked fuel tap?
There is a filter bowl on the bottom and an 'O' ring holding brass filter screen inside
It is possible for one outlet to be blocked or partially blocked
BTW, I think I'm the only person making vacuum adapters for 360's?
 
If you're refering to the petcock, the last time i checked, fuel was flowing fine through both fuel lines. And each time i take the carbs off, the float bowls have plenty of fuel in them. I have noticed a little bit of fuel sitting in the main air passage of the carb on the side that doesnt have power though. Im wondering if the plug might be grounding out and not sparking when in the engine. I checked them outside the engine but cant check them inside. Going to swap plugs tomorrow to see if that could be the issue.

As far as adapters, how much are you selling them for? I haven't looked around yet. Definitely interested.
 
Sound like float level is off rather than faulty coil
I'll PM you about adapters
 
I think i got it!

The spark plugs were firing outside the engine but that didnt mean they were firing inside the engine. So i swapped the plugs and sure enough, that caused the left cylender to act the same way the right has been. So i bought a new spark plug and they are now both running strong. It did have some hickups at first but after a few minutes of riding around it stayed running strong. Still need to run and buy a gap tool because i cant find mine. Hopefully this solves it permanantly and its not just messing with me.

The person i bought the bike from said he had replaced the plugs recently so i didnt think twice about having a bad plug. Especially since they were sparking outside the engine. Maybe i've been running rich.

Thanks everyone so much for your help. The more i learn the more i have to contribute. Now all i want to do is go ride but its cold and raining here
 
You probably want to change title as well to let everyone know it's sorta fixed ;)
 
Rain, I get, but it can't be TOO cold to ride! Especially after all that trouble.. I'd be out enjoying every minute I could haha
 
Well, looks like I spoke too soon. Got home from work to go riding and found a small puddle of gasoline under the bike. Moved it out of the garage, started it up, and only running on the left cylinder again. What a puzzler this is. So I'm assuming my float got stuck again. And maybe running so rich that my spark plug already got fowled again? I'm running out of ideas. Also, the motor backfired a couple times around 3000 rpms. A real backfire this time. No soft pops
 
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