CB360 Running Issues

Hey everyone,

Just posted on HT last night as well, but figured more heads are better. I've been doing some research and testing and have been having some hard luck, so I'm hoping for some great suggestions from you guys to help me out

Quick backstory: Bought bike, hadn't run in 25+ years, changed the coils and condensers and some other mild things, started right up. 2 years later (don't ask why) I decided to start tinkering and have done some mainly cosmetic upgrades, again nothing major at all. I got her running again last week, may have been on one cylinder, not sure as it was running quite rough. Did the timing, and have triple checked it and it is DEAD on. We're getting spark, and the plugs are wet, so I'm confident I'm getting fuel. But it is not turning over even now, and it's getting quite frustrating haha. Last week, after doing the timing we couldn't get it to start and run again for more than a second or two after clearing the bowls a bit. Now, it won't even do that. So it won't even turn over. It seems like the most major thing I did was the timing that was different, but I've verified several times over that it's correct. Today, I pulled the carbs (they were rebuilt 2 years ago) and I put in some new main jets (115 thanks to pods and exhaust) as well as corrected the float bowl height, actually increased it to about 21mm.

At the very end of the night, my friend and I found that one of the spark plugs was a dud and is not firing at all, which is weird. But it did still run 2 weeks ago, AND I know these things can start and idle on one cylinder. So I will grab new plugs, but I am looking for and open to suggestions as to what other pitfalls I should be looking for.

Really appreciate any advice and am looking forward to hearing all your thoughts. Thanks very much!

TL;DR - Wiring correct, timing right, plugs are wet, fuel in bowls, good spark, no start.

Dan

Anyone have any ideas? I'd really appreciate the help! Want to get riding now that the weather finally allows for it here in Toronto.

Hi carbs working well are a big deal. I'd pull them off, check diaphragms, blow air/cleaner through jets and passages between top and bottom.

davidricci said:

Hi carbs working well are a big deal. I'd pull them off, check diaphragms, blow air/cleaner through jets and passages between top and bottom.

Click to expand...

Thanks David, have done this twice now as well as adjusted the carb float to within spec.

spark fuel compression. make sure all this is in spec in this order. valves, timing, fuel. make sure electric is at 12V obviously, CB's have sensitive electronics, give it a good charge. As far as fuel and carburetion goes for these bikes, make sure its clean, check diaphragms cause the CB's often have rips but that wouldn't be why your bike isn't idling...that would be more of a bog on acceleration and such...wouldnt be a bad idea to take the pods off and put an air box on it, run your stock jetting with clean fuel

Hey, so ya it's strange. Everything was in spec, and I tried to kick it over and over and over and nothing.

I squirted a bit of fuel directly into the cylinders yesterday, and it fired right up, first kick, and I started and ran it over 5 times and for a total of over 20 minutes. I set the idle, and it was idling and even responding to throttle input quite well. Took it for a short ride, and it felt amazing. Anyone have any ideas as to why it didn't want to start beforehand? I dont want to have to keep tools and a syringe with me whenever I go for a ride haha.

maybe the pilot jets are clogged and not getting enough fuel to start. or choke not working properly. if it worked when fuel was added to the cylinders i would guess its a fuel issue

Hrmm, strange. I did clean out all the jets as best as I could, some are even new. And it seemed to run without any hesitation for quite a while.

Do you think it might be the idle mixture screws on the outward sides of the carbs? They're set at 1.5 turns out each right now.

Look up idle drop tuning, this will ensure that your mixture screws are set properly. Make sure you are tuning your carbs at OPERATING TEMPERATURE. If you are tuning them cold you are wasting your time.

What kind of pods? Only K&N work because the cheap Emgo type block the pilot air jet.

http://www.dimecitycycles.com/39mm-k-and-n-style-air-filter-pod.html

Don't remember off hand which I ordered, but they look identical to these.

Those are the cheap ones. The rubber part has a flange inside there that blocks your pilot air jet. When you were able to get it started, did you have the filters on?

You said that you cleaned the pilot jets, but did you make sure the pilot passageways are clear?

After sitting 2 yrs the carbs are probably gummed up from old fuel.
You need to clean them properly and re-set float level to 21mm. It probably won't run over 4,500rpm until carbs are modified