IcePrick Posted April 29, 2013 Share Posted April 29, 2013 Last fall, I noticed a mid-range miss between 3000 and 4500 RPM. When I put the XX to sleep with a high loading of Seafoam (hook up a bottle of it to the fuel lines, run the bike at ~3k until it dies), I promised to tear into the carbs early this Spring to get a look around. Yeah, I didn't get around to that. I used one of them heat sensor gun thingies on the header, looks like #2 is cold at idle (~135*, the rest are in the high 200* range). Good spark from the plug. I checked the needle (clip @ 2nd from top) and the air screw (@ 3.5 turns out). Without tearing it apart completely, any other ideas, actions, or a diagnostic path? Possibly a stuck needle/float? Thanks for any help! Mike Quote Link to comment Share on other sites More sharing options...
HANKSXXX Posted April 29, 2013 Share Posted April 29, 2013 Last fall, I noticed a mid-range miss between 3000 and 4500 RPM. When I put the XX to sleep with a high loading of Seafoam (hook up a bottle of it to the fuel lines, run the bike at ~3k until it dies), I promised to tear into the carbs early this Spring to get a look around. Yeah, I didn't get around to that. I used one of them heat sensor gun thingies on the header, looks like #2 is cold at idle (~135*, the rest are in the high 200* range). Good spark from the plug. I checked the needle (clip @ 2nd from top) and the air screw (@ 3.5 turns out). Without tearing it apart completely, any other ideas, actions, or a diagnostic path? Possibly a stuck needle/float? Thanks for any help! Mike I'd drop the #2 float bowl and unscrew the pilot jet, looking for some crap stuck in it. You could also try screwing out the fuel screw a turn or so and see if that causes a change in exhaust temp. Quote Link to comment Share on other sites More sharing options...
DBLXX Posted April 29, 2013 Share Posted April 29, 2013 I know a buddy selling a superhawk if your interested. Let me know. Quote Link to comment Share on other sites More sharing options...
IcePrick Posted April 29, 2013 Author Share Posted April 29, 2013 I know a buddy selling a superhawk if your interested. Let me know. Meh - I'm after a Miata - a TRUE sportscar! Gonna trade 28 AR-15s for one. Quote Link to comment Share on other sites More sharing options...
evelakes Posted April 30, 2013 Share Posted April 30, 2013 just did the job on my wifes CBF 600 , lot's of dirt in the needles. It's worth it to clean the carbs . Quote Link to comment Share on other sites More sharing options...
DBLXX Posted April 30, 2013 Share Posted April 30, 2013 I know a buddy selling a superhawk if your interested. Let me know. Meh - I'm after a Miata - a TRUE sportscar! Gonna trade 28 AR-15s for one. The Miata is perfect for you.....and the rest of the midgets on the planet .....and Midget fatties like me. Quote Link to comment Share on other sites More sharing options...
rockmeupto125 Posted April 30, 2013 Share Posted April 30, 2013 Without tearing it apart completely, any other ideas, actions, or a diagnostic path? Possibly a stuck needle/float? The best luck I have had without tearing things apart is to pour Yamaha carb cleaner in the carb and let it set for a day. If that don't work, it comes apart. Quote Link to comment Share on other sites More sharing options...
IcePrick Posted April 30, 2013 Author Share Posted April 30, 2013 Back in the days when I worked at marinas, there was a product called OMC Engine Tuner. It was impressive. I'll look for the Yamaha product and give it a try. Dropped the bowl last night, pulled the main, cycled the float, all looked good - no obvious obstructions, everything seemed okay. Put it back together, and that cylinder is at least now generating some heat - not what the others are, but within 30* now. I think it is at least firing, so that's an improvement. I'll see how it runs in the next couple of days - no riding today or tomorrow, suits and meetings both days. Quote Link to comment Share on other sites More sharing options...
IcePrick Posted May 2, 2013 Author Share Posted May 2, 2013 Backyard mechanic diagnostic mode: feeding in about 3/4 choke cleans that miss right up. One of those cylinders is hungry... Quote Link to comment Share on other sites More sharing options...
partsman Posted May 2, 2013 Share Posted May 2, 2013 Take 'em apart ,Seafoam is just not gonna do it.I've found the Honda and Suzuki carb cleaner also work just fine,all three may very well come from the same place,who knows. A little surprised it's also not happening at idle,if that pilot jet to that carb is slightly blocked you should notice from idle right up to about where you describe. And take a real close look at the float needles,ethanol destroys them in no time. Quote Link to comment Share on other sites More sharing options...
eliXXir Posted May 2, 2013 Share Posted May 2, 2013 If running with the choke solves the issue, then I suspect you have one of the secondary/idle circuits with gunk in it. You can put your hand over the intake of that carb while it is running and reduce the air intake (thus increasing the vacuum to the fuel) just to it to prove it out. If that is the case, then you're likely in need of a fully disassembled carb bath. 1 Quote Link to comment Share on other sites More sharing options...
IcePrick Posted May 3, 2013 Author Share Posted May 3, 2013 Looks like it's time for a teardown. Thanks for the input, everyone! Quote Link to comment Share on other sites More sharing options...
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