Help: Runs rough, bad idle and stalls. - 600RR.net
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post #1 of 13 (permalink) Old 05-04-2011, 04:17 PM Thread Starter
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Help: Runs rough, bad idle and stalls.

I've been scouring the archives but no luck, hopefully someone can help me!

My bike is hard to start, runs really rough, and stalls if I'm not giving it at least a little bit of throttle. It wants to drop below 900 and I have to keep it at 1500 to 2000. I usually need to crack the throttle to even start the bike. When it does get running it sounds pretty lumpy, not smooth at all.

I pulled all the spark plugs and gave them a clean. They were covered in sooty black deposits, if you rubbed the tip on your skin you'd have a black streak there. I cleaned them and I can see the white inside, it's sort of carmel colored and spotty. I hooked up each cylinder's plug and laid them on the head, each one gave consistent purple sparks. The manual has peak voltage tests but if you can see it, isn't that good enough?

I opened the tank to look around and that's weird. If you hold the light at an angle it's super blue, like porta potty fluid. But shine the light in directly and the center looks beerish to the bottom. Is there a blue lining under the top of the tank I cant see?

I have it apart and I can see the idle adjuster is connected and functioning. However adjusting it doesn't do anything, the bike keeps dropping until it stalls.

I've done general checks as far as making sure all the connectors are snug and the wiring (appears) to be in good shape. One thing is I did lay the bike down on the right side. It started running rough until the wind knocked it down on the same, then it was smooth again. No trouble codes, I haven't seen the MIL flashing. I disconnected the MAP sensor when it was running, no difference. I have a PCIII that was on the right side so I disconnected that too.
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post #2 of 13 (permalink) Old 05-04-2011, 04:31 PM
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Just seeing the arc from the coil doesn't mean it's working properly. But it is probably working just fine.

My guess would be something with the fuel mixture. Maybe the PCIII. Did you remove the PCIII entirely and connect everything back to stock?

Also, how many miles on the plugs? They def shouldn't have black soot or be whitened.



The plug on the left is brand new, the one on the right has possibly 16k miles on it. I bought the bike used with 10k on it so I don't know if they were changed prior to me owning it.

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post #3 of 13 (permalink) Old 05-05-2011, 06:19 AM
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Do you do many wheelies?
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post #4 of 13 (permalink) Old 05-05-2011, 08:19 PM Thread Starter
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Wow Gashuffer, those are great macro pics! I'll see if I can get something that good... I'm guessing the plugs are what the bike came with, and it's at about 11k. I was hoping I could just clean these but I do have a new set available.

I did pull the PCIII completely, the harness is hanging out of the bike.

No wheelies for me Nico, and it seems like the previous owner was pretty mild too.

I was reading Honda's manual for the bike and it seems like the computer does a pretty good job of flagging any of the sensors that might be screwed up. Does anyone else have experience on that? Bad sensor but nothing from the comp? Because of that I think I'll focus on the non-sensor stuff, maybe drain the gas (the blue tint is still bugging me) or try the new plugs. I also have a gun thermostat so I can check the exhaust temp, it's pretty lumpy, but again the spark plugs all look the same so probably not.
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post #5 of 13 (permalink) Old 05-10-2011, 03:41 AM Thread Starter
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Used the thermostat, all exhaust pipes were 500 degrees (+/- 25).

I put the new plugs in and compared to dirty plugs it seemed to rev a lot better but idle was still garbage.

New fuel didn't do anything.

Due to other factors the TPS kept bugging me so I put some more work into testing it and that may be my problem. Closed it is 1.2 V and open it's 4.5 V. According to Honda it should be .4-.6 closed and 4.2-4.8 open. So it thinks it's at 30% throttle and it's dumping that much fuel in.

So any solutions that don't involve replacing the whole throttle body? I think the throttle is retracting all the way, when it goes back to closed I can feel the throttle free play. I had the airbox off and I could see down the TB, it looks like the plates were going closed all the way (might double check). How is the TPS connected, could there be something in/wrong with the linkage?
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post #6 of 13 (permalink) Old 05-10-2011, 04:12 AM
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Make sure that the 0V reference for it is actually 0V... other than that your pretty much stuck replacing the tb
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post #7 of 13 (permalink) Old 05-12-2011, 03:43 AM Thread Starter
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0 volt reference, do you mean 5 v? I put the multimeter between left and right on the plug and it's dead on 5.

The voltage was bugging me and I wanted to see what was going on so I removed the TPS. Nothing too helpful in there, but when I put it back on I was able to adjust for what ever was up its arse. Now the volts go from .5 to like 4.3. So it's within range but at the low end, performance prob won't be 100% until I replace it.

Anyway, bike fired up but I didn't have to keep on the throttle to do it. Also my eyes weren't watering from all the fuel in the air. So it's running FAR better. It warmed up starting around 1800 RPM, but kept dropping until it was about 1000 rpm. This is with the idle screw turned all the way in, backing it out didn't make a difference. Looking past the TPS I can see where the throttle cables rest when they retract, and I can see it seems to retract OK. Could that screw be out too far, doesn't look adjustable with the throttle bodies on the bike.

I had to go but I plan to check the plugs tomorrow, but that should be good. I'd cleaned off the old ones really well and put those in, but might not get away with that, may put the new set in. I think I'll also check the starter valve synchro.
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post #8 of 13 (permalink) Old 05-12-2011, 09:09 AM
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I wouldn't worry about trying to replace the tps, to do that you need to replace the throttle bodies... and if its in spec then its in spec.

I would have a look at the IACV, pull it off and make sure it is clean and then have a look at synchronising the starter valves, although I don't think that will do the trick for you.

Also have a look at the PAIR system and make sure it is functioning correctly.
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post #9 of 13 (permalink) Old 05-15-2011, 02:19 AM Thread Starter
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I had to adjust because it wasn't in spec, it was reading 1.2 volts with the throttle closed. Now it reads .5 v.

I saw you mention the IACV in the other thread too, could you give me a link to some micro fiche or the manual page? I'm having trouble locating it.

Looks like that might be a good call on the PAIR valve. According to the manual air shouldn't flow between the exhaust and the intake when there's no power to it. Mine works the opposite of this but that seems odd. Do you have an old one lying around you could verify this on?
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post #10 of 13 (permalink) Old 05-15-2011, 03:00 AM
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The IACV is on the throttle bodies, fairly close to the TPS...

Sorry, no valves lying around... you can just do the PAIR removal mod to get rid of that as a potential problem... there are a couple of good DIYs around the place.
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post #11 of 13 (permalink) Old 05-16-2011, 01:13 AM Thread Starter
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Still no luck on the IACV. I've got a fast idle wax unit between the two cylinders opposite the TPS, and there's a coolant routing bit sort of below the vacuum routing junction but nothing on the throttle bodies by the TPS either in front or behind.

I pulled the PAIR valve and capped everything (though I think the manual might be wrong on how to check this). Didn't seem to do anything, my bike still wants to idle at around 900 rpm. I also tried putting in the new spark plugs.

Two things I've noticed. One, my idle screw doesn't seem to do anything, but it doesn't look like the fast idle wax unit isn't pushing it out far enough, the opposite side of the "teeter totter" thing isn't hitting the part the idle screw turns. The other was when I tried to sync the starter valves. If I remove the MAP and connect the vacuum gauge it flops around a bit, but if I connect to just one cylinder it's banging around like 5 or 10 psi. And it did that on two of them.
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post #12 of 13 (permalink) Old 05-16-2011, 04:34 AM
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I assume that you have an 03-06 if you have a wax unit... that would also be why you can't find the IACV...

You can have a go at adjusting the wax unit...

Last edited by Nico; 05-16-2011 at 04:42 AM.
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post #13 of 13 (permalink) Old 05-18-2011, 01:07 AM Thread Starter
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The TPS adjustment made a huge difference, I was actually able to loosely hang my radiator and ride around my now naked bike a bit. Still wants to stall at idle but felt good.

Yeah, i'm thinking the wax idle or one of the starter valves is causing trouble. I only need to hold the throttle open a bit to keep the bike running, and from reading a stunt rider forum adding a second idle adjust cable to replace one of the trottle stops is pretty easy. It's the wrong way to do it but it'd get me back on the road...

Reading around the wacky vacuum could be caused by some excessive wear in the engine, though it's a honda with like 11k so I doubt that. Note to anyone reading this, DO NOT get the Craftsman/Mityvac compression test kit. It has a 10mm adapter but the back side is too chunky and it grabs like a thread and a half even with the rubber o-ring taken off. So basically it does not work.
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