Idling issues
 

When I first crank up my bike, '96 cbr1000f, I let it warm up and then after it gets to where with the choke on it jumps to about 5000rpm I shut off the choke and the bike wants to die out. As long as I sit there and give a little gas every few seconds it'll stay running, I run it down the road and get it warmed up good and then stop it'll idle at about 1700rpm for a few seconds then drop to about 1000rpm and try to die out again unless I occasionally give it a little gas. After a while of riding it'll idle and not die out but will still idle at about 1700rpm for a few seconds and then drop down to about 1000-1100rpm where I have it set. I've adjusted the air/fuel mixture screws from 1 1/2 turns out to 3 1/4 turns out in 1/8th turn increments, seems to idle best at about 1 7/8 turns out but it still not idling like it should. I've gone thru everything I can think of in my head that may be causing it and the only thing left I can think of is maybe the pilot jet is bad. It was idling rough before so I pulled the carbs and cleaned them (they were disgusting) and that helped some but it's still not doing like it should. Running down the road she runs perfectly so as I said before the only thing that I can attribute to the issue is possibly the pilot jet. I'm thinking of rejetting the carbs but I'm cheap lol, it runs just like it's suppose to going down the road, but if it is the pilot jet then I'll spend the money cause I'll feel it's something I need. Looking for any and all advice I can get on this one cause I can't think of anything else so I'm at a stopping point till I pin point the issue. Thanks guys!

Sounds like bad gas. This ethanol they are putting in the fuel is killing me.

Bike won't idle and stalls at lights. The ethanol is making it over heat.

Runs great once underway.

So....my advice is to empty the tank into your other vehicle and find a different pump before pulling carbs off.

If that's not the problem, you may have a vacuum leak.

May try a sync of the carbs?! If it is out bad enough, one cylinder could be closing off completely, and only firing on 3 (or 2?)! Does it pop through the exhaust at all when idling?

no, I'm pretty certain the carbs are in sync but it wouldn't hurt to check. better safe than sorry. I hadn't even thought of the ethanol, I know with older cars the ethanol won't really bother them but with new cars if the ethanol percentage is too high and it's not a flex fuel then it can mess with 'em. I also hadn't seen a vacuum leaks (kinda looked but didn't spray around the hoses cause I'm lazy and forgetful lol) but I'll try that tomorrow. The place I get gas at I always get 93 octane and it's never bothered any bikes I've had in the past or anyones bike that I know that fuels up there on a regular basis. Please excuse my ignorance but one way I've always been told to tell if the carbs are out of sync is if you see one (or more) of the air funnels fluttering. I know they are all working in sync, non fluttering at all. But I guess the best way to tell is to hook up a vacuum tester and go from there, thanks guys for the advice

Even though you cleaned the carbs there could still be something in the fuel or deposits ON the jets themselves from old fuel (especially if they sat for a long time at some point) that are cutting down flow just enough to mess with you when cold-- especially if the carbs were as gunked up as you suggest.

Check out jetsrus.com -- $3-$7 a piece for jets ain't too bad! (FYI I've used both Keihin and their OEM equivalent and had no problems with either.) Even if there's another problem, new jets plus an inline filter are cheap and easy ways to a little peace of mind.

Jets R Us Honda CBR1000F Hurricane

Good luck,
Aaron

when i pulled the carbs and cleaned them I also cleaned the filter on the petcock (the internal filter) which was pretty nasty, then used some 87 octane I had to rinse out the tank to make sure it was clean, and then put a new inline filter on it. Now the gas flows clear as rain, so the fuel line back is good. I did pull the jets and made sure there was nothing clogging them, but now after thinking about it I'm thinking there may be a vacuum leak. Is there suppose to be a small line coming off the bottom of each carb? There's one coming off the #2 carb and is capped (looks like factory stock work, not just a bolt shoved in the end of the line like I'd do haha). I've not even thought about it until just now even though I've seen it 50 different times since I find it easier to pull the carbs to make adjustments to the fuel/air mixture screws. And then in the workshop manual it shows 2 "air bent tubes" which I don't recall ever seeing, but that may be something that they deleted before the '96 model came out, I've got no idea

The plug vacuum port on #2 is a factory vaccuum supply for the vac operated petcock! My 98 has the same fitting on #2, and a hose from it to the petcock! Yours must not have a vac operated fuel valve?! It can be used for doing carb syncs, so plus one there!

Only reason I mentioned carb sync is because the 98 i just bought was so far out of sync, that one cylinder was closed completely while the other three were open, 2 strong and one barely! it ran, on 3 cylinders at closed throttle, but very rough, and would keep dying! if I gave it a hair of throttle, the other would open and it would run great! then, let it close, it would idle for a second, then the cylinder would dry out, and it would idle down again and die! My 1980 cb750 did the same thing when I first got it! May not be out of sync, but it never hurts to check!

Other than that, you very well could have a clogged slow jet! might try adding some seafoam to a tank of gas, and run it! I've seen sea foam perform miracles on carburetors :)

I'm not ruling out the fact that they could be out of sync but, my bike is running in tip top shape with stick coil mod and bigger jets. It is doing exactly what is quoted above. When I try to pull it in the garage, it pings, knocks and rattles. The fan comes on in only a short period of time. This is due to a fill-up I did before a 150 mile ride. I tried to top it off but the ethanol % from that one fill-up is still so high that adding better fuel has made it better but it is still crap.

It pulls hard once it gets going but stumbles coming off the line. I feel that if I didn't re-jet with larger jets I would have been left dead in the side of the road once that bad gas made its way through the lines and into the carbs. It is nasty, nasty stuff.

Before the re-jet, I would get into some bad gas and I had to keep the RPM up at 2,500 and then slip the clutch at 5,500....ba...ba...ba..ba..ba.ba.ba....vroom. Like at 2-stroke that was loaded up and then clear.

If it idles smoothly down to where it wants to die, it may not be the sync.

Any bike will ride fine regardless of sync because you're opening the throttle to where air can come in! At idle though, if one plate is so far off that it fully closes and doesn't let the others come down to an idle state it can act like a dead cylinder! I'm not saying the sync is "only cause", just a suggestion! I've seen exactly what you describe on other bikes and a sync fixed it!

I was going to check to make sure they are in sync today but I went for a ride and ran into an issue of my fan not kicking on so in town the damn thing was trying to overheat. Got back to my house and turns out wire for the fan switch had come unhooked. Was gonna take it down the road to see if that fixed it and then check on the carbs but just my luck it started raining just as I got done fixing the wire.

Lol story of my life! Well I just fine tuned my sync tonight and the bike runs like a champ! Btw, the threads for the vac ports are the same thread as a jet! I just threaded a jet into the other three ports that had bolts in them and hooked up my gauge set to them :) worked great, and you don't have to use the pesky vac sticks or buy or vac ports! Hopefully it will be a simple fix for ya!

I'm hoping so but after a little research non of the stores anywhere near me sell the sync tool. A friend of mine kind of has a shop but they don't have the sync tool (they're having a hard time getting their s**t together). So my only other option other than ordering one, which I don't really have the almost $100 to spend for a couple weeks, is to buy a single vacuum tester and do it the hard way checking one at a time, writing down what each one is at, then adjusting and rechecking from there. It'll be a pain in my ass doing it that way but the idling issue is killing me and I want to fix it now so I may just do it the hard way. Also I don't have any extra jets laying around so I'd have to figure something up on that too, but I'll get it done one way or another, the hillbilly ingenuity will prevail lol

One sign of them being out is the bike will surge in traffic when in 1st gear at low RPM. Its that pulling and dragging as mentioned.

Problem solved, #1 and #3 vacuum ports on the head weren't plugged. Fixed that, started the bike up, now she's idling perfectly other than needing to adjust the pilot screw a little which is no big thing (other than #1 and #2 being a pain in the ass to get to with the carbs on). Thanks guys, I definitely appreciate all the input from everyone

Ha Ha Ha!


I should have stuck to my guns. LOL

Edit: What about the vacuum to the petcock? (mentioned in a different part of the forum) Without going out in the rain and looking, On should be up in 12 o-clock position. OFF is at 3 o-clock and RES is at 6 o-clock. I can't remember if fuel flows in the RES position. If so it would be easy to run a vacuum line to the petcock to turn fuel off when the bike is not running.

My carbs are in synch, I spent $100 on the synchronizer, so I imagine its decent. As was mentioned previously, the ethanol is terrible in general and particularly if it isn't fresh. Mine stalls at lights now, since its summer and hotter out and it keeps wanting to die unless the idle is around 1100, it would idle with no issue at 900 in winter. I even leaned out my idle mixture with no relief.