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Discussion Starter #1
I have a 89 cbr 600 that was running great until a couple days ago....It starts up fine and the RPMs are solid but then out on the road it just boggs down, the pitch of the exhaust gets lower and i can barely drive anymore. I already replaced the spark plugs and it only bogs down sometimes, then in a minute or two it will kick back to normal and nearly throw me off the bike cause of the acceleration...After it boggs down then goes to normal it will bog down again at the wierdest times and in any gear....sometimes turning it on and then off again will fix the problem but not for very long....Any suggestions?
 

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Rex, intermittent problems are the toughest to fix. All you can do is take a shot at remedys.
The things a motor needs to run are fuel, air, spark. You can blindly try to fix things in these areas.

Fuel - petc*ck cleaning, fuel filter or screen, drain out all old gas in tank till completely empty, fresh gas with Seafoam, drain bowls, adjust choke and confirm cable is working, check fuel lines and vent for pinching, fuel pump. Check carb boots for leaks or loose clamps.
If it's bogging, open the filler cap. if it perks up, the vent is clogged, or closed.

Air - clean or replace air filter

Spark - wires, plugs, coils, ignition module. Check for the presence of a good hot spark.

My bet is that the problem is in the fuel system.

Good luck, Welcome, and if you get a chance, please introduce yourself up in
New Member Introductions.
Rocksolid
 

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Discussion Starter #3
Is there any explanation for it being intermittent and not all the time, thats what is really stumping me, just that It sometimes runs like a champ and others it sucks.
 

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If I'm right about the vent, it will run till the vacuum in the tank gets too high, then no fuel reaches the carbs. A partial fuel clog will allow the engine to run till the fuel runs out in the bowls. Water in the fuel will drive you crazy! I got some bad gas once and the engine ran like a bucking horse. Vibration, heat acceleration of the bike etc can cause changes while you ride. Lots of reasons.

Oh, BTW, check the fluid in the battery, if it's a wet cell.

Rocksolid
 

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Discussion Starter #5
The thing is it hardly ever dies when it boggs down only when I come to a complete stop, the rpms just die. could that still be the vent? I would think it would die everytime if the fuel is not getting to the carbs, also i forgot to mention earlier when i have the bike warming up and the choke on full the rpms go really low...almost to where it dies but only when the bike is tilted on the kickstand, as soon as it is upright, the rpms fly back up....dont know if that has anything to do with it.
 

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The tilting issue is a clue here. I heard of a case where a battery was so low on acid that the plates were uncovered and the engine dies when it tilted. Have a look at the choke. The idle should be high when it's in. I'd also have a look at the petc*ck and vent for clogging, especially if this bike is gravity fed.
Rocksolid
 

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All those are possibilities, as well as a stuck carb float and (due to the intermittent nature) some type of short in your ignition system.

If the timing on that thing is fixed, then there is a wire coming up from your flywheel to either a CDI or other electronic gizmo box. If you have a short there, sometimes the timing can be affected. That would cause acceleration lag, as well as the crappy idle, and that would explain the infrequent or odd timing of the events.
 

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Being sold the wrong (unvented) filler cap just about drove me to my wit's end. Similar symptoms as yours; It would idle great, and all day long, but get out on the road and after 8-10 miles it would bog down and (most of the time) die, would restart after a couple minutes and drive another few miles and do the same thing. Like Rocksolid said, an easy way to check is to ride with the filler cap open. It could even be partially clogged/closed. Vacuum lines on the petcrock in good shape?
 

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Discussion Starter #9
Well I think seafoam might be the fix....at least for now....I put it in the tank a couple days ago and have had smooth riding since then....thanks for all the help guys
 
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