Varying idle and slight loss of power???

[W201028]

Ok guys, this problem is going to sound vague, so I will try to be as detailed as possible.
Ive got an 09 GS500F, at 14700 miles. I put a Jardine full aluminum on last fall, with a K&N oem mount filter, jetted it 20 pilot, 62.5 mid, 142 main, and  stock needle with that little washer on top moved underneath. Currently 3.5 turns out, but I ran for a while with 2.5, it just popped on decel a bit less.

Heres the problem - after I did all this work last fall, the bike ran great, tons more power and very smooth. Warmed up faster too.
Lately though, Ive been noticing a few things.

Idle: its getting rougher, and is unstable: for instance, after coming off the highway buzzing at 80 for twenty minutes or so, it will idle very high, around 1700~. But if I am just putting around town, and come to a stop light, the idle will drop to maybe 1000, then slowly come back up, though sometimes it stalls. If it were 2 stroke, I would call it fouling.

Warmup: after I rejetted, it was warming up quicker, but the choke was slightly ineffective at full. I had to find the sweet spot around 1/2 - 3/4. Now the choke is barely usefull at all, in fact, I am better off with no choke and just holding the throttle open a bit till it idles on its own.

Vibration: Ive been noticing increased vibration at the bars for awhile, but I have been commuting farther for work in the last year, so its hard to pinpoint. However, my right carb float bowl drain screw vibrated out on the way to work one day; long story short I rigged it to make it there and home, and put a new one in. It doesnt seem to matter if its highway speed or around town, the vibration just seems worse that it was, and ive got new tires and chain and sprokets.

Power: it does seem to be losing power, however, not just in one area. It just seems harder to accelerate, and I have to keep the throttle open quite a bit to maintain highway speed. She will still do 100+, but it seems to take longer to get there. It feels almost like there is some engine braking going on all the time.

I know this is long winded, but I really cant pinpoint whats wrong. Like I said, after rejetting, she ran great all fall and winter, but since late spring, I have been having minor problems. My last valve check was at 8000 at a dealer, and it was in spec, no adjustment made. Had the carbs synced then too.

Does this sound like its time for a valve adjustment and syncing, or is it just a weather/temperature issue with my jetting? Or is one of those emissions filters or PAIR pumps giving me trouble? Give me some ideas.

PS: at 8K it cost me 200+ dollars to get the valves and sync; I wont pay that again, I will get a manometer and spring tool and do it myself. I just dont want to spend a buttload of cash to find out it was a vacuum leak!

[weedahoe]

Ive got the PAIR system I just pulled off mine if youre interested and think thats it.

If you have checked the valves/shims, I would certainly do that. Its not hard. I just bought a nice set of feeler gauges at Advance Auto tonight for $6 along with 3 cans of carb cleaner Im going to use to clean out my carbs tomorrow. Mine are like yours, bogs down, revs high, backfires a little, ect

[W201028]

I wasnt aware I could separate that system. It looked like those air pumps and some sort of throttle sensor were integrated with the carbs. On a side note, I have noticed a slight exhaust leak from the head. If I rev it with my hand infront of the pipes, I can feel a hot breeze coming out. Hard to tell if its happening at idle though.
Come to think of it, I didnt put any exhaust gaskets in the ports when I put those pipes on. They didnt come with any, and I didnt notice any when I removed the stock system. Anybody know if I should have a gasket in there, like and Oring or something?

[weedahoe]

I've never seen any o-ring or seal. But a bad head gasket would certainly cause issues. I would try to re-torque the top end before taking it apart to replace the gasket.

[adidasguy]

You must have exhaust gaskets.
See the middle of my video.
You probably have some in there but they are crushed all the way down and you don't see them because they look like the exhaust port --- all dirty and carbon covered.

http://www.youtube.com/watch?v=4eMGNolMuEU

[W201028]

Well I took her all apart last night. After tighten down the exhaust it doesnt leak anymore, but it didnt make a difference for idle. She stalled out 3 times coming home from work, always when decelerating to a stop.
I checked the valves last night, all within spec, around .06 mm. Cam chain tension is nice and even. I took the carbs apart, clean as new, no loose jets or anything. I visually synced the throttle plates, but ive moved the sync screw several turns in each direction in the last few days and nothing makes a difference.
The only thing I can see that may be the cause is carbon buildup on the intake valves and seats. The inside of the head though, spark plugs and exhaust gaskets, is all a nice dark tan, no carbon in there. The plugs have always looked good the several times ive pulled them since I jetted it. I had no reason to think I was running too rich until I saw all the carbon on the valves.
Now, maybe I am wrong about this, but IF the carbon buildup was so thick on the valve seats that the intake isnt closing the whole way, I would see that in the valve clearance, right? I mean, if they werent closing, the gap between the cam and shim would be too large? Correct in thought, or not?

[Funderb]

how are your float heights?
what happens when you blip the throttle at idle? (just give it a hard, quick flip of the wrist and close again, like a microsecond flip)

[W201028]

When I flip the throttle, it responds pretty well. Theres only a millisecond of hesitation. No different from when it was factory. What would cause my float height to change? Ive adjusted my dirtbikes alot of times, but those are used bikes and who knows what the last owner did. But ive never messed with the floats on my GS.

[cbcanada]

you said you stall when you are slowing down to a stop... do you down shift?
if not then try down shifting and go into N from 2nd. see if this makes a difference in the stalling and in consistent idle... if it does. then in would clean your idle jets and more importantly tinker with you idle screws... try 3.25,3,3.15 or just different variations..

i had the same problem. especially in real hot weather.

i cleaned the pilots and re adjusted the idle screws (small adjustments) and went to 2 washers... and thank GOD she runs fine

[W201028]

Well I just had the carbs apart and the pilots look beautiful. That was my first thought as well.

I do downshift, always, and it seems to stall less if I bring it down to idle slowly; I.e. stop really slow.

I put new plugs in today, and she didnt stall out, but I dont know if I rode it hard enough. The idle still ran around and up to 1700 or so. Im gonna take her to work tomarrow and see how she runs.

The old plugs looked a little black on the insulator, but really not bad enough to think I am running too rich. Hows that work anyway; cold air compresses better, but do you need more fuel in hot weather or in cold weather?

I am seriously considering a K&N lunchbox to lean it out more, but I am not sure if that will solve the issue, or make it worse. Also, is there a fuel filter inside the petcock that could be clogged? The intank, or the frame mounted.

And no one has any opinion about my carbon covered valves???

[Big Rich]

I wouldn't think carbon on the valves is the problem - people run a lot more miles with dirty valves with no issues.

Have you checked for air leaks around the intake? Something is causing the hot / high idle.

[BockinBboy]

The old plugs looked a little black on the insulator, but really not bad enough to think I am running too rich. Hows that work anyway; cold air compresses better, but do you need more fuel in hot weather or in cold weather?

I'll add my limited physics knowledge and someone can correct me or fill in gaps in logic... Hot air is less dense than cool air so it seems there would be less O2 available once the air is hot... Would you need a higher amount of air to compensate? Or less fuel? ... Is this where correct jetting, clean carbs, unhindered fuel delivery come in to determine it all?

-Bboy

[W201028]

My intake is pretty tight, I cranked those suckers down when I reassembled.

I cleaned my K&N today and put some SeaFoam substitute in the tank. Ran pretty good on the way home from work, but when I took her out again tonight, I am having the same issues. Ive come to the conclusion that it only runs decent when really hot. I mean peak temp, during the day on the highway.

Seems like if I just cruise around town, and the engine is warm but not cooking, it just will not idle right, and has poor power. The longer I ride, the better it gets, but this is waaaay beyond typical warm up. I never used to stall out at the first stop light in town, and now it seems I have to loop the whole area, 4-6 miles to get her to idle half decent.

I am considering a possible vaccuum leak, that may be restricting fuel flow from the petcock. I am going to hook up the frame mounted petcock vacuum line directly to the carb vacuum and take the PAIR crap out of the equation. I will post back tomarrow.

[adidasguy]

Put petcock in PRIME position. If all works, then there is a vacuum problem to the petcock. If the same, then you are not lacking vacuum to the petcock.

[W201028]

I gave that a shot, but it made no difference.

I also checked my float height using the tube method and both are even with the bowl gaskets. I am running out of ideas.

I did notice a decent size puddle of red fluid coming from the airbox drain hose. K&N oil I am assuming, but I didnt think I saturated it that much. That overflow tube has been oily for a while now; could I have a PCV problem, with too much blow by entering the airbox and choking the engine?

[W201028]

How about the TPS?

I was just reading about some other folks having the same trouble with stalling and loss of power due to a misadjusted or broken throttle position sensor. I am going to check mine with the OHM meter now.

[NorwayGT1]

i got a 93 katana that has the exact same problem as yours... for some reason the choke does not work when the bike is cold its actually harder to start with the choke on lol. and when i decelerate when the engine is still just worm and not at idle temp it sometimes shuts off by going under 1 k idle.

i usually down shaZam! when i come to a stop and rev my rpms a little... and at complete stop i have to sometimes stay on the gas to keep it from dying. (kinda embarrassing cuz i look like a squid sitting there at the red light rewing my bike like a total dork lol..) got to do what you got to do right.

im gonna take her apart either tomorrow or sunday and ill let you know what my problem is maybe it helps.

something you might want to look into is your air lines inside the carbs... or so i was told... this might not apply to you as my bike is way older.

[W201028]

Thanks for the input norway, let me know what you find.

My TPS checked out. 5.15 Kohms at idle, and around 4.1 Kohms at full. A bit high, but within factory spec according to the GS500 wiki.

I am lost, I have no idea where to go from here. Please, give me some ideas? Something little, that could be over looked.
The PAIR system? PCV? Anything to go on, let me know

[cbcanada]

if bike runs okay when hot then bad when cold inwould say younare running lean. am i not correct?

before i rejetted my bike would run awful in the cool air.