cb450 idling problems

goodfornothing

goodfornothing

Spicey!
Hello guys, I'm pretty much finished with the 450 project, but now I'm having a real doozy with tuning.

The Problem:
For the past week, the bike started out idling fine, but until a few days ago and especially tonight, it keeps dying! It doesn't seem to want to idle. I can start it up and after a few tries it'll idle for about 15-30 seconds and then die. It will sometimes "cough".

The timing is set correctly as well as cam chain and valve clearances. When the bike died I cut the fuel and checked the float bowls. The float heights are set right because the bowls had gas in them. I'm also getting spark, but I'm not sure if it's weak or not. What kind of spark would I be looking for?

The carbs are clean as well; when I mess around the air mixture/pilot screw, I can get the rpms up and down, so that means the carbs are clean for the most part. Perhaps I need to clean out the jets? Does it also matter what kind of gas I am using?

I think my air/fuel ratios are right, but I don't think that would really affect idling too much, would it? I really want to get this thing running right so I can get some riding down. The cb450 is proving to be a lot of work, so I may be selling it in the coming weeks. I've definitely been wrenching more than riding.
 
Borrow a compression tester from Autozone or wherever and check your compression. If it is low, that is most likely your problem. It was mine. Check your compression with the engine warm, choke open and throttle wide open. Hook up the gauge to your spark plug hole, turn the kill switch to off and run the starter. It should read 160 or more psi after a few cranks. You will see when it maxes out.
 
Thanks Mike, I'll be doing this tomorrow.

I also think I might need new coils. I read that bad coils will fail after they get hot. My only option would be dyna coils. Would I need a new condensor as well? Where would I find a replacement?

If my compression is low, I'm definitely going to be selling this bike. I'm on the fence about it if my problem ends up to be the coils.
 
Sorry to threadjack here:

Is compression also to blame for my CB360 idling perfectly at first but then after riding for 15 minutes it dies after idling for more than 15 seconds or so?
 
That could be the case but you have to check everything to be sure. I'd start out with checking compression, the. Move onto coils. The problem you described is just like what I'm experiencing.

I went to the local auto store to borrow a compression tester but they didn't have one. Useless. I'm going to have to pick one up from harbor freight.
 
Well I just cranked her a few times with half choke and she started to idle. I was able to go for a ride up and down the block and no stalling. I turned up the idle a bit because it seemed like the rpms were going a little down once I stopped riding.

I pulled the plugs to check the spark. They're blue but they aren't that bright. I also noticed that when I cranked the engine without the spark plugs seated I heard a kind of popping/floppy noise coming from the left cylinder as I cranked the engine. The sound is like when you pop your finger out of your mouth while making a circle with your lips. I didn't hear that from the right cuclinder. Could that mean anything?
 
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