Hi Guys,
I picked up a 94 CBR 600 earlier this week.

Started up probably 10 times when I went to look at it. Rode great, no hiccups, stumbles, stalls, etc.

Yesterday it wouldn't start (it would just crank and crank).
I choked it..no start
I tried giving it gas...no start
I drained cyl 1's carb float bowl (looked clean)

I pulled plugs 1, 2, 3 and they were wet (i assumed from bliping the throttle trying to start it).
I cleaned them with carb clean, wire wheel'd them and made sure they all sparked OUTSIDE of the head (which they did).

Put them back in and the bike fired right up. Rode it a bit yesterday turning it on and off several times without issue.

I put the battery on the trickle charger overnight.
This morning I disconnect the charger, and the bike won't do anything but crank.
I quickly pulled plug 1 and it was dry, and would spark outside the engine.

What gives?

I don't know much about past history of this bike. previous owner said he never had a problem starting it, and that it liked very little choke.

I'm thinking about picking up some new plugs, but anyone experience this problem before or have any clues?

Thanks in advance,
-Matt

 

I'll add to this... I've done a bunch of searching and some have had kill switch issues, so i'm going to have a look at that this evening.

Question.. Does the kill switch prevent you from cranking the starter, or does it just kill the ignition?
I noticed last night that the bike will crank regardless of the kill switch location.

 

The kill switch prevents the ignition coils from firing. I would definately inspect the Engine Stop/ Starter switch circuit to make sure there aren't any loose connections. I would also clean the carbs (thoroughly) cause you never know the last time they had some lovin'

 

Kill switch looked and tested out fine.

I changed the plugs, emptied out what little (possibly old) gas that was in the tank, and filled it up with fresh 93 this morning.

Fired right up first crank, and I drove it into work.
Looks like we're good!

 

Well, it seems I spoke a little too soon.

A few times it has taken WOT while cranking in order for the bike to spudder up to starting.

I want to test the petcock, but it seems I may be pulling the carbs and doing some cleaning after all.

Just seems weird...the previous owner has already put 1500 miles on the bike this season and said he never had any starting issues.

 

So they SAY, anyway, do you personally know that to be true?

Maybe it hadn't actually run as often as you were told, and having it running and jostling the fuel around has loosened up some carbon deposits (gummed up fuel), which are now blocking fuel circuits in the carbs...
+ 1 on cleaning them - it's something that should really be done anytime you purchase a carbed bike anyway.

Good luck!

 

True statement bud.

 

If it runs good while it's running I don't think it's the carbs. If they where really gummed the bike would run lousy all the time.
It could very well be a petcock problem but if all your float bowls have gas then that's not it. It could be a coil on the way out. I'd test them. Also how's the R/R? They're notorious for frying out on these bikes.
This is a long shot but I've seen it done before, even on my current bike when I bought it, check the carb vent tubes and be sure some backyard mechanic didn't plug them off thinking they where vacuum lines. The carbs will flood like crazy and also not allow fuel to flow properly if they are plugged off.
Good luck. Let us know if you find anything else.

 

It runs well when you're in the throttle, but just putting around with little throttle (I would call it the idle circuit) it hesitates and stumbles a little bit.

The fact that I have to open the throttle all the way in order for it to start tells me something isn't right.

Carb vent tubes are there, as well as the vacuum hose that runs from the petcock to the engine.

I have not checked the coils or the r/r.

 

Though it would seem a gummed up carb should run lousy all the time, the truth is, if the carbs are indeed in need of cleaning or there's maybe carbon deposits "on the loose", so to speak, you can't really expect any consistancy with things. Also, we know, that he was able to start it a few times before, and ride it to work one day, but we don't know how well it ran, and for how long.
That said, I totally agree with the fact that it could be any number of things, including what you mentioned, I'm just saying that carb/fuel issues are most definitely still a possibility.

Matt, you could do a resistance test on your coils, and see if there in spec, but since you have already said your getting spark, you could probably save that for last - testing your R/R is also a good idea, even if it's not the problem, since failure of the R/R is something that many people deal with (my stock one is still good, but I think I've just been lucky!)
Now, you said "True statement", which I assume was in response to my inquiry of whether or not you knew to be true, that the bike ran fine before...the reason I asked, is because you said in your first post:Issues like this are really frustrating, because things are inconsistent, but you are on the right course with cleaning your carbs, it should be done anyway, and it's not like it's going to cost you any money, other than carb cleaner! If you do a very thorough job, while you've got them off, at least then you can eliminate the carbs as the culprit.
The fact that you put new fuel in, and then it started, definitely seems to point to the fact that there was old bad fuel in the tank and carbs (fuel goes bad over time, much quicker than it used to).

On the fuel note, don't waste any more money on 93 octane, it will not help anything with this bike. All your doing by buying this fuel, is thickening the lining of petroleum companies' pockets with more of your money. If this motor is stock, then it was desiged to run on 87 octane, and will actually run much better on 87, all other things being equal, than it will run on 93. The F2 is a low compression engine, it does not benefit at all from high octane fuel - oh, for sure, you're going to get people telling you that their bike runs better on the "good stuff", and that they only put "high test" or "premium" in their bike, and it runs soooooo much better... that might be true if they have a modern high compression sportbike, but if it's an F2, and it has stock internals, they are either lying, or gettin' some "placebo affect" going on!! Don't trust me on this, do your own research, you don't need to have been a chemistry major to understand why what I'm saying is true.

It sucks that you're having trouble, nothing is worse than having a bike, and good weather, and NOT RIDING!! Good luck gettin' her going!