83 CB550sc Engine Dies w/Throttle

luke000

luke000

Been Around the Block
Hello, I am just working on my brand new used 83 CB550SC nighthawk. I got some of the electrical problems solved enough to get it to fire. But now it will idle and rev up with the choke but if I use the throttle at all the engine dies... I have spark and compression all across the board but cylinder 2 does not seem like it is firing and cylinder 3 seems weak. I am judging this by them not putting out the exhaust gas like cylinders 1&4 (the exhaust is off the bike). My mind tells me that the carbs are probably clogged or out of adjustment, is my thinking correct? Any others areas you guys would suggest I look enforce pulling the carbs off?
 
It could be too rich, or the timing could be out of adjustment, or... there's dozens of possibilities.

You going to have to start from the bottom and that means removing the carbs and rebuilding them.
 
+1 clean the carbs. sounds like its probably lean. the reason it dies when you add even more air by cracking the throttle open. rpm picks up on the choke = less air, more fuel.
 
Thanks for all the input! I tore the carbs down and cleaned them today and I will re-assemble them tomorrow when my mind is fresh!
 
I got the carbs put back on the bike (no air cleaner or exhaust) and got the bike fired up. It ran pretty good (even better now) on choke but it still dies the second you touch the throtle. The 2nd cylinder seems to be furring as now there are small blue flames that shoot out the exhaust on that cylinder only. Cylinders 2 and 3 still don't seem to have the exhaust force as 1 and 4 though. The carbs were not dirty inside at all. Just a little black sediment in a few of the bowls but it was small in quantity and very fine.
 
Is there a possibilty of a gas shortage?
Had the issue with a gooked up tank/petcock.
Could be also a inline filter restricting gas to one or the other carbs.
 
Ryan Stecken said:
Is there a possibilty of a gas shortage?
Had the issue with a gooked up tank/petcock.
Could be also a inline filter restricting gas to one or the other carbs.
Click to expand...

I am running off of a bottle of fuel right to the fuel lines. I am not using the tank.
 
get the exhaust on the cylinders dont evacuate propely without it

properly clean the carbs pull all the jets and emulsion tubes the kehin 30mm you have have tiny passages

and it will take a ultrasonic cleaner to get them clean and right
 
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