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Discussion Starter · #1 ·
Hey, my 1974 CB360T has been having issues with the spark plugs fouling out with carbon deposits (not oil from what I can see). Everyone says it's running rich, but I don't know how to fix it. I purchased the bike in April, and replaced the battery, spark plugs, plug boots, and carbs. Had the carbs professionally installed, but I'm still concerned if it was done correctly. I keep losing power to the left side of the bike too, and I'm not sure what to look for next. The plugs seem to foul out really fast too after only riding about 60 miles or so. I was going to buy new coils and a condenser too, but others are telling me the points may be the issue. I also have a new wiring harness because I'm concerned if everything is connected properly. I'm a novice with working on these bikes, so I appreciate any advice you guys have. I do have a couple difference manuals on the bike from Honda and Clymer too. Thanks.

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Maybe your carb guys swapped the main jets for parts from one of those aftermarket carb kits, aftermarket kits are notorious for having the wrong size jets.
 

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Probably tells in the factory service manual. You might try switching to one step hotter spark plugs before you dig into the carbs, see what that does first.
 

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Discussion Starter · #5 ·
Probably tells in the factory service manual. You might try switching to one step hotter spark plugs before you dig into the carbs, see what that does first.
I actually tried one step hotter plugs and got the same result. The manual also doesn't have the sizes for the jets either.

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Jet sizes right there in that chart.
 

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That chart is not correct. Primary should be 68, secondary 95 (depends on which carbs) to 110, and idle 35.

if you have the removable air jets under the diaphragms, make sure they are in their proper place, as some of them can be swapped.

There are many many threads on 360 jetting here and over at DTT.
 

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You need to figure out where your bike is running rich before you can fix it.

First set your idle mixture, there are a million descriptions of this out there, but basically you twiddle the mixture screw to get the highest idle. Idle speed should drop off screwing the screw in and also out from the ideal, if it doesn't there's a problem there. I don't think this is your problem though.

Fit new spark plugs put a plug spanner in your pocket and take the bike out, find a long hill and run up it at full throttle, just at the top cut the ignition with the kill switch, pull in the clutch and pull out the plugs and look at the colour. If they're brown your main jet is OK. Repeat with the throttle at 2/3, this will test your needle.

Clean your plugs and tool around at lowish revs and no more than 1/4 throttle, this will test the primary circuit and it is where I suspect the problem will lie. If your plugs are black from this then I can't help you, I've been battling this problem for a year.
 
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