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Hello all,
I am hoping someone could help me figure this out. I recently bought my first bike, a (non-running) 1983 CB450sc. Immediately I removed the tank, changed the oil and plugs, and rebuilt the carbs (in which I replaced the main and slow jets, gaskets, etc) . When I first tried to fire the bike, the right carb flooded over continually and the bike ran very rough. From reading a few forums, I figured it was the float, and I recall the right side float having some chipped plastic around the groove that holds the needle. I figured the float was not pushing the needle into the valve due to the damage so I replaced it, yet the problem continued.
Second issue, I have noticed that the bike will only fire on one cylinder or the other, but not both. I know this because I've felt the exhaust pipes (one would be hot while the other cold). Both plugs have fire, I removed and grounded them today yet still there may be some electrical issues causing the cylinders to alternate fire. However this is related to my carb flooding because when only the left cylinder was firing, that right side carb that was once flowing like a fountain suddenly stopped! But when the right side had fire, the corresponding carb flooded over.
I have the clymer manual which paraphrases something like the more complicated the system is, the more easily diagnosable it is due to the distinct symptoms. But where to begin here?!
 

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Typical Clymer!:lol:

Welcome to the group. We'd appreciate a post in the member introductions section to let us know a bit about yourself and your bike(s).It is helpful if you include your location in your profile and create a signature with the specific model of your bike. And we really like pictures!:p

Electrical issues cannot cause the cylinders to alternately fire since it has a "wasted spark" ignition system. Both plugs (or neither) fire every revolution.

I would suggest you start by browsing the SOHC fuel supply and carburetion section with this being your first stop:

http://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html
 

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Plus 1 on the Clymer :lol:
The flooding of the carb will be a bad float needle, sticking float needle or a bad float. Now that it's been flooding you really need to check your oil before you try to start it again. Good possibility that there is fuel in the oil and it'll destroy the bearings.
Drain your float bowls with the petcock off. Turn the petcock on while tapping on the float bowl. That will usually unstick a float needle if that's the problem.
 

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Discussion Starter · #4 ·
Thanks for the help. I believe the issue is the float needle. I tore the bowls apart and swapped the floats and needles, now the left side floods over. I will go ahead and change the oil to be safe too. Now I just need a needle (or two, i may replace both to prevent future frustration). Now that I've hopefully fixed the carb issue, I can start on why the darn thing will only run on one cylinder. Hopefully that's not another carb issue. Haha.
 

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The correct length float needles are a Honda only part, all of the aftermarket ones I've seen are the wrong length.
Probable issue with only 1 cylinder is the plug is fuel fouled. Replace both of them first.
 

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Discussion Starter · #6 ·
Oh yea, I'm only getting genuine honda parts through my local honda dealer. I'm not fiddling with ebay and online sources for this one. Thanks for the spark plug advice, but would a fuel fouled plug still have spark? I've grounded both against the block and they spark steadily.
 

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Yes you can still get spark in a dry environment but when it's in the cylinder full of A/F it may be grounding out because of a saturated porcelain
 

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Discussion Starter · #8 ·
Good news! Two new floats, two new float needles, and two new plugs and no more flooding!!! Now both sides have fire, but either the left side is too hot or the right side is not hot enough. The left pipe is smoking hot, while the right is sort of hot. It idles roughly and only with the choke on. Could this be carb adjustment, compression, valve timing, electrical, or a combination of all? I'm leaning more towards carb adjustment hopefully. Seems like the left side might be too rich while the right is too lean? I know I have to do a dynamic sync on carbs but I can't do that until it will run without the choke right?
 

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Electrical is pretty much not a possibility on these bikes. If it only idles with the choke on you're getting too much air somehow. A check for vacuum leaks could be a good place to start.
 

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Carb boots leaking? Spray some carb cleaner around the boots while it is running and see if the idle changes. It shouldn't.
I hope you got non-resistor plugs.
 

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+1 on vacuum leaks. Boots, air cut valves are suspect.
I would suggest going thru the entire tune procedure before doing more with the carbs
 

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Discussion Starter · #12 ·
I did notice as I've been working with the carbs that the left side boot has a small crack on the edge, and after doing some other reading I believe that may be the culprit. That means pulling the carb off once more... :/ The plugs are nkg/honda, and I got them from the honda motorcycle dealer. Would those be non-resistor plugs and what's so special about them?
 

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Replace both insulators. While the carbs are off look at the air cut valves to insure that they are good.
NGK is the preferred plug, ND is next. Nothing else will work for any length of time. Nothing fancy in plugs. If there is an R in the plug number its a resistor plug. They only work with non resistor plug caps?
 
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