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Discussion Starter #1
The weather turned rather nice in the afternoon, so I took a quick spin. It started fine, and idled fine. But first I noticed misfire at high rpm (beyond 6000-6500), and it got progressively worse, and at near my house, I couldn't rev it passed 4500rpm without the engine missing and backfiring. Pulled the plugs, and they are black-ish (not wet but not sooty either, just black-ish than fox orange that I normally associate with the healthiest plugs), but it always ran a bit rich, and from the condition of the spark plugs, it doesn't look particularly any different from last year when it was running really well (till the electrical problem, which I fixed over the winter). Anyway, what's baffling me is that I took quick 85-mile joy ride just 9 days ago, and it ran perfectly at the time (and I had a very enjoyable ride). Prior to that ride, the carbs were gone through again, and, oh, now I think about it, the plugs were brand new then. So I don't know what happened between then and today, and I don't know where to begin. Only mechanical change that I made in between was rear sprocket swap, and I know that has nothing to do with it. Hence, I don't know where to begin. The engine is stock, with a bit over 21000 miles, it's got slip on (with db killer), stock carbs with Dynojet kit and open airbox with K&N filter (that's how it came when I bought it). Could anyone give me a direction/suggestion?
 

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Pinched fuel line, torn/ripped fuel line inside tank(wrong type of fuel line), clogged fuel filter, clogged pump pickup sock.
Possibly some gunk on the float bowls, not as likely as the above, imo, but the plug condition tells me it could have multiple issues. Put new plugs in and see if it runs. Look in the tank when you flip the key on without starting to look at the fuel splashing around - drain some out if you need to see it better.
 

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Discussion Starter #3
The fuel line and inside of the tank appears to be fine. Fuel filter is new, replaced last summer, so maybe I can take that off the list? But I will check the float bowl. I'll try the new plugs, that seems like one good place to start. Thanks!
 

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Dont take anything off the list just because you did something last year, check everything If you are running fuel with ethanol that crap can & will eat thru fuel lines, I know it takes time but right now what the hell else do you have. I would remove every line in the tank and pressure test it a pin hole is all it takes to screw things up, Check the fuel filter make sure it is not split at a seam, I have seen that many times-make sure the fuel is flowing freely from the petcock, make sure your fuel pump is working properly-do a fuel pressure test. Clean and oil your K&N make sure Micky has not been playing house
 
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If that fuel line inside the tank is original, replace it. If you replaced them with the filter - did you use the correctly rated in-tank hose? And finally, that pickup sock can get eaten by that shitty ethanol gas in a year.
 

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Discussion Starter #6
Hmmmm...
So far, all the fuel tank internal checked out. How do I run the pressure test on the fuel pump? The fuel flow is good. I think I'm going to clean the carbs again, just in case.
 

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Verify that your spark plug wires are solidly attached and are making a perfect connection where they attach to the ignition coils.

The stock ignition coils on my '95 literally had a nail spike that the spark plug wire pressed down onto and then a rubber boot was slid down the spark plug wire to cover that connection on the ignition coil to (hopefully) hold the plug wire in place.

My '95 had an issue very similar to what you're describing J.B. and what I found was that after all the heat cycles that the spark plug wires had gone through over the years the plug wires themselves had actually shrunk and become brittle where they made that connection on that nail spike in the ignition coils.

Both plug wires on my bike were loosey goosey at those coil connections. I ended up pulling both plug wires off the coils and cut off about 3/4" of wire and then pressed them securely back onto those spikes. That cured the problem on my bike.
Eventually I just replaced both the stock coils and wires with new aftermarket coils and wires that securely clipped onto each other at that connection.
 

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Discussion Starter #8
Mmmm...
I'm inclined to point the finger at something ignition related at the moment. The fuel supply seems to be fine (all the fuel tank internals are checked out, and fuel flow is good), still will check and clean the carbs again, but I'm wondering if it's weak spark or some such things. That was most of the work I've done this winter (new stator, pick up, regulator/rectifier, coils, igniters, etc.), so maybe that's the most suspect...
 

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Sure, fuel, air, electric - the big three. Spark plugs say rich/poor ignition. If the fuel lines look good, the shutoff valve works, no external hoses pinched - new plugs and start it to see what it looks like in an hours runtime.
If its electric, check your ground connections and swap the igniters/coils.
 

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Discussion Starter #10
Yeah, carbs this morning, and hopefully I can grab new spark plugs from the store this afternoon. It miffs me that it was just so good 10 days ago. I just don't know what has changed.
 

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Discussion Starter #11
I took advantage of the nice weather today, and cleaned the carbs, checked the electrical stuff, and all seem fine. I couldn't get the new spark plugs, so I cleaned the ones that I had, and took it for a short ride. The first couple of miles were fine, revs nicely all the way, then it starts again. Right around 7000rpm, off-throttle sputtering, and then it misfires. Hmmm...
 

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Old fuel, maybe with fuel stabilizer in it ? Maybe left the enrichener on too long ? Put new fuel and plugs in it and try again.
 

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Discussion Starter #14
Okay - first, thanks for all the suggestions. I made the lists and check them off one by one, and here's where I'm at. I cleaned the carbs, once again. This didn't make particular improvements. New fuel didn't improve the situation either. Cleaned the plugs since I don't have the new set yet, and checked the gap (my bike has Ca Cycleworks coils). I didn't feel any significant change with this either, but it felt a bit crisper, but this just may be my wishful thinking. Since the winter, the biggest change that was made is to the charging system and ignition pick up both of which I had to replace. I'm going to open the case again to inspect. Could it be ignition timing is off?, though I can't think how that could be...
 

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There's the licking the 9v battery test, but the dark might work too.

Pull each plug wire off and closely look at it for any blisters or white /brown dusty spots where electricity has leaked out. Is is evenly flexible over the whole length or does it seem to have a hard kinked spot? If the 90 degree end piece at the plug comes off, look to see if it is all burnt inside - snip off a 1/4 inch and put the connector back on the wire.
 

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Discussion Starter #19
I just took the cover off and did a quick inspection of the pickups. Well, no joke about the loose screws, it appears that the mount has shifted slightly. At this point I don't trust my eyes, so I'm not sure exactly, but I'm going to reset them regardless, and re-gap them. We'll see...
 

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Discussion Starter #20
Mmmm, done the pickups, no change. I'm gonna check the plug wires now. I'm getting a bit desperate.
 
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