Hey guys, I bought another CBR. This time it's a '95 F3. Not much different than the F2 aside from having a TPS, coolant lines in the carbs and ram air. Bike has 14k on it and I'm having an issue where the bike only runs on 2 cylinders. An even 2 cylinders. As in, it sounds like a 500 but with about half the power since they're fighting the compression from the other cylinders.

My issue starts with the fact that I just took the carbs apart and the jets are extremely clean. Nothing plugging them up at all (well..one slow jet was clogged a bit but I could still see through it). My concern is that I might have a bad coil. Since our bikes run on a waste spark setup if the coil stops working 2 cyl stop working. Since the cylinders are opposite each other the bike actually doesn't run unbalanced (1 - 3 and 2 - 4).

I'm not sure how to go about checking them. I'm about to finish up the carb clean and want to make sure I don't put it back together without fixing the problem. Any input guys?

 

You can use instructions in the manual for checking the coils.
In the old days, we just used to take the spark-plug out of the engine, connect it to the coil, twist the throttle all the way open (prevents the bike from starting) then rest the spark-plug on any part of the frame/engine to create ground contact and press the start button. If you see the spark then its fine.

 

and the cylinders dont fire at the same time....its 1-2-4-3 all in order and one at a tim......that should help u

 

Thanks, but that's a given, I was labeling which coils correspond to which cylinders.

 

I'm going to test to see if the coils are getting power. If they are getting power then I'll check for spark (I have a dummy plug I can use). Whichever coil isn't putting out a spark I'll replace and hopefully be on my way.

 

Actually, that's not entirely accurate. Plugs 1-4 fire at the same time, and 2-3 do as well.

 

So you're saying the coils might not be my problem...? I figured if the coil went bad then it'd drop both cylinders that fire on that coil.

 

So I'm just wondering. Is it possible that the carb's might not be delivering fuel to 2 cylinders despite everything in there being honky dory? I also noticed that even though they're so clean the throttle is very sticky and doesn't snap back like it should.

 

You're correct, if a coil does go bad, it would drop 2 cylinders. Any idea which 2 aren't firing? If you don't have a temp gun, spray some water on the headers to see which ones are cold. Or you can pull #1 and #2 plug wires and see which one isn't firing (they are on seperate coils). Is pulling jets all you did to see if it's clean? There's alot more to cleaning the idle circuit than just checking pilot jets. Spray some carb cleaner through pilot jet hole and see if spray comes out tiny hole in front of butterfly. Then pull fuel screws and spray again with good steady stream. It should come out pilot jet hole and tiny hole in front of butterlfy. That passageway is very small and easily clogged. Also use good quality carb cleaner (HIGHLY recommend Chemtool B-12, used it for years).

 

I see. I guess I could check to see which ones are getting spark and which ones aren't. I'm going to have the carb's looked at by an expert to make sure everything's how it should be. I'm not experienced enough to be confident of what I'm doing at this point (unless I can find a picture guide or a video guide somewhere).