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running problem with CB360

alexwhoknownothing

Member
Joined
Apr 16, 2025
Total Posts
24
Total likes
2
Location
kingston NB
I have a Honda CB 360 1974 that I got from my brother who bought it to restore but gave up on it. Hoping to see it run again but I lack mechanical knowledge on these bikes lol

The issues I am having right now are following
The bike will start sometimes but has a pretty bad idle and sputters out after 30 ish seconds.
electric start won't work tho makes lots of noise
removed one of the plugs after starting it a few times and it was quite dirty almost looked like oil on it... not sure tho

New spark plugs were added B8ES
Timing was set
New battery added about a week ago
Float height in carbs was adjusted Tho not totally sure if I got it right? It had its carbs switched out 2 ish years ago to makunie racing carbs
Main jet is 90 on either side.

Any help would be appreciated! Thx! :)
 
The starter noise is likely the starter clutch needs to be rebuilt, not a big deal and most parts are readily available.

Float height wouldn't necessarily apply to Mikuni carbs, though if in good condition there's nothing wrong with using them However, pod filters can make the jetting difficult.

What you've described tells me maybe your understanding of the choke lever might not be correct. When you say it sputters out after about 30 seconds, is that after you start it and then open the choke? Pictures always help, remember we can't see what you see and words aren't always enough.
 
ok I will take some videos/photos, quite late here will take videos in the morning tho don't want to disturb the fam lol I will double check but pretty sure it is sputtering out after choke has been turned off.
 
alexwhoknownothing said:
as soon as i turn clutch off. fuel supply issue?
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Pretty sure you meant "turn the petcock off", but that isn't the entire problem - it wasn't running one both cylinders prior to it stalling, one was cutting in and out and was mostly out. Carbs would normally be the first suspect, though it could be ignition. I misspoke earlier about the choke, still thinking in terms of OEM cabrs but these carbs use enricheners that also bump the idle up when on, though there is no middle setting with Mikuni enricheners, they're either on or off.

You mentioned "timing was set" but you did not mention anything else about it. If the bike still has points, what did you set the gaps to? And how did you time it after setting the points gaps? Pictures of the points with the cover off will help too.
 
whoops yes I did mean that haha. Yah for sure ill send em timing could very well still be off lol I set them using a timing light though did not measure the gap or set it to any thing super specific... just went by the light they seem to still have a point left ill send a photos.
 
The plate is in a good position, but it's hard to tell much else. Good job on the terminals attached to the points, properly oriented to avoid shorts.
 
alexwhoknownothing said:
Here’s a better photo I hope. I couldn’t get it running this morning. It starts maybe 1/4 of the time lol not sure why
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You really need to go through the points and timing adjustments the right way. The advancer points cam is rusty which will cause rapid points gap change from wearing the rubbing blocks and without knowing the actual points gap, the timing can't be properly set on both cylinders so you will never know why it doesn't run right until you take care of all things that affect the engine's tune-up. Both cylinders' timing must be set separately, so you can't just turn the plate and expect both cylinders to be correctly timed. And no offense to your understanding of the engine and its needs, but you might not be using the correct starting procedures that these engines prefer when cold starting the bike. They start the best when cold by using full choke initially and leaving the throttle at or just slightly above idle in a steady position. Turning the throttle a lot while cranking is counterproductive and only makes it harder to start.
 
alexwhoknownothing said:
but cuts out when throttle is blipped but will accelerate slowly
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That's the difference between standard slide carbs and the original CV carbs. You can't whack the throttle open hard like that on slide carbs because they do nopt have accelerator pumps to give the engine a squirt of raw fuel to help it get started to the higher rpm you asked for. Whacking the throttle open quickly like that only reduces intake vacuum, meaning less fuel drawn from the float bowl. Totally normal for slide carbs, my 450 does the same thing with Mikunis

 
ancientdad said:
That's the difference between standard slide carbs and the original CV carbs. You can't whack the throttle open hard like that on slide carbs because they do nopt have accelerator pumps to give the engine a squirt of raw fuel to help it get started to the higher rpm you asked for. Whacking the throttle open quickly like that only reduces intake vacuum, meaning less fuel drawn from the float bowl. Totally normal for slide carbs, my 450 does the same thing with Mikunis

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Ok sweet thank you! Glad to hear that is not a problem.
 
ancientdad said:
Sounds like it's only running on one cylinder, which would explain the weak response to opening the throttle.
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Hmm yah I can get it running consistently now! first kick or so. But couldn’t get it to move again every time I put it in gear and ease of the clutch the left cylinder sounds like it’s sputtering… tho felt the exhaust pipes and both are very hot, how do I make sure both are firing tho? I messed with the idle screw and the idle now sits around 1200rpm I’ve been told it should be around 1000rpm? The left side also doesn’t react like at all when I adjust the idle screw the carb has a 90 main jet could that be the issue?
 
alexwhoknownothing said:
Hmm yah I can get it running consistently now! first kick or so. But couldn’t get it to move again every time I put it in gear and ease of the clutch the left cylinder sounds like it’s sputtering… tho felt the exhaust pipes and both are very hot, how do I make sure both are firing tho? I messed with the idle screw and the idle now sits around 1200rpm I’ve been told it should be around 1000rpm? The left side also doesn’t react like at all when I adjust the idle screw the carb has a 90 main jet could that be the issue?
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What do you know about this engine? Do you know any history at all? If not, have you adjusted the valves and cam chain and then, since you believe it has spark and fuel and both pipes get hot, run a compression test? And have you actually gone through the points and timing by the FSM? At this point, we're guessing as much as you are, but it's easier to help when someone addresses the things we suggest so they can be eliminated for our long distance diagnosis. In the end, the time it will take you to do all the things that should be done will be less than you trying to avoid some of them.
 
ancientdad said:
What do you know about this engine? Do you know any history at all? If not, have you adjusted the valves and cam chain and then, since you believe it has spark and fuel and both pipes get hot, run a compression test? And have you actually gone through the points and timing by the FSM? At this point, we're guessing as much as you are, but it's easier to help when someone addresses the things we suggest so they can be eliminated for our long distance diagnosis. In the end, the time it will take you to do all the things that should be done will be less than you trying to avoid some of them.
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Yah my apologies lol I get excited sometimes. History not a ton minus right cylinder having a rebuild about 3 years ago. Valves and cam chain have been adjusted to the best of my ability. Tho I didn’t have a two 110 main jets on hand of from what I have heard that’s the size I am going for? Yes timing has been adjusted but hoping to check it again. I did one cylinder at a time using the marks LF and F, making sure it was on the compression stroke. getting the timing light to turn on as soon as the mark lined up the indicator mark… I hope I described that well does that method work? and can it be trusted that’s all I could find on YouTube lol I don’t think I have the correct tools for a compression test? What do you need? Yah for sure haha Me and my sixteen year old mind just gets excited to see it running 🤪
 
Ancientdad is right to say the FSM needs to be followed, even the owner's manual. Before youtube these bikes had all info printed that you need to follow. At least the hot pipes means it's firing, just don't leave the ignition on when not running and fry your coils.
 
Modern owner's manuals are pretty skimpy on info but back then they had the short and sweet version of all the essential adjustments. They are my first go to, then the FSM for deeper repair and replacement, finally youtube can be helpful for visual orientation but they often skip stuff too.
Old bikes require old ways. Fortunately, we have old guys who mostly haven't forgotten all that.
 
Ran compression test. 120psi on left and 135psi on right. I heard hose legth can affect it ? hose was 12 inches long. I heard it should be at 175 ish seems really off. Spark plugs are quite dirty too, they were clean when put in IMG_0279.jpeg
 
Why are there two different spark plugs? The top one does not look correct, what brand and part number is it?
 
ancientdad said:
Yes, though it's a resistor plug so it adds 5k resistance to a system intended to be 5k total. So you should really be using non-resistor caps.
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Ok sounds good! Found the correct plug for both now. I adjusted the valves via what the owners manuals instruction then took another compression test both cylinders now read 135 psi. Still low tho?
 
ancientdad said:
Not sure how it could run worse with better compression, something isn't right.
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I figured it out I had reversed the gap size (bigger in the intake smaller in the exhaust)I went back in and set it proper which fixed it. Then set timing and the bike now can get moving constantly. Tho needs a lot of gas going up hill or it will stall
 
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Hey, busy the last few days. got back on her today with right exhaust removed and that cylinder is only firing about 1/3 while running and cuts fully out at high speeds... i have ran through Timing, valves, jetting and they all seem to be spot on checked them a few times. But right cylinder is just not firing all the time left runs very well and never cuts on me. Am I in for a bigger fix?
 
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