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wantok 12-01-2012 07:32 PM

need advice on symptoms - too lean or rich?
Hi people - need some advice on the following symptoms: I live in an area that is currently very hot & humid (close to sea level) My 950 ADV (2004) has stock carby jetting & 2 wings open mufflers. The hotter it gets, the worse the bike runs. It idles but has a big flat spot below about 3500 rpm, where on a steady throttle it misses a bit. It also backfires a bit on the overrun when you crank down a couple of gears. When the weather is cooler it runs better, without these symptoms. Whenever throttle opened right up, it runs fine regardless. Ive got a facet fuel pump & DNA air filter & run the bike on 98 octane.
Do these symptoms indicate too rich or lean?
Many Thanks

Nick (wantok)

Deepc 12-01-2012 08:13 PM

Sounds lean to me. Stock jetting with a open wings exhaust! Also, Check for the usual vacuum leaks. Also, think about installing a second fan to cool her down. I have the black dog cycle works version and it makes a big difference in traffic.

Deepc 12-01-2012 08:33 PM

And pull your rear plug. It's easy to get to and it will tell you what your looking for.

AdvGa 12-01-2012 10:02 PM

You may want to check some of these things:

1- Check your Battery (under a load tester)

2- See if your Carbs are Vented with the 10" Rear, 11" Front hoses and not the Running together in the Y configuration.

3- See if your Fuel is not Boiling -insulated Tanks
-Have you done the Flapendectomy?

- Also Run a Fuel Treatment -like SeaFoam

akarob 12-02-2012 04:58 AM


Originally Posted by Deepc (Post 20159807)
And pull your rear plug. It's easy to get to and it will tell you what your looking for.

Precisely. Your spark plugs will tell you what's going on. A correct mixture will show as a light tan on the plug. If it's white and kind of burnt looking, it's lean. If it's wet and dark, it's rich.

StmbtDave 12-02-2012 06:51 AM

I would say lean. We come to Arizona for the winters to get out of the Colorado cold. It's a lower elevation and much warmer here. My 950 goes through the exact same symptoms you are having and I found simply raising the needles one notch smooths it out. Of course anything involving the carbs can't be done "simply".


MortimerSickle 12-03-2012 10:27 AM


I'm no carb man, but to me, running better when cold than when hot sounds like a rich condition.

Chuckracer 12-03-2012 10:58 AM


Originally Posted by wantok (Post 20159435)
My 950 ADV (2004) has stock jetting...wings open mufflers...DNA air filter...

She's lean. Raise the needles one clip position and turn the fuel screws out to 2.5 or so...hang on tight. :deal

MortimerSickle 12-03-2012 11:15 AM


Originally Posted by Chuckracer (Post 20169118)
She's lean.

I think that every time I learn something about carbs, I end up knowing even less than I did before. :D

wakked1 12-03-2012 01:43 PM

Hmm, everyone seems to have missed the temperature reference. The hotter it gets the less dense the air, so the higher the fuel/air ratio gets. If it runs fine in cold temps but rough in hot, it would suggest its running rich.

MortimerSickle 12-03-2012 01:47 PM


Originally Posted by wakked1 (Post 20170313)
Hmm, everyone seems to have missed the temperature reference.

Not everyone.

Originally Posted by MortimerSickle (Post 20168908)
... running better when cold than when hot sounds like a rich condition.


Zuber 12-03-2012 10:54 PM

And the answer is: rich. Cold = needs more fuel to run good. Hot = needs less fuel to run good. You need to lean it a little when it's hot out.

Pull the carbs. Check the float levels, set them 1/2 mm lower (leaner) than stock. I remember the setting is 3.0mm from gasket surface, so set them to 3.5mm. If they are warped, one is lower that the other, then do the best you can.

Buy and install the remote fuel screws. This allows you to set the idle-1/4 throttle mix as the conditions change. All bikes are different, some like 1.0 turns, some like 3.0 turns. These are an awesome addition.

With the open exhaust, you only need to increase the mains slightly, go up one step only. But, this is not needed if it's really hot and humid.

Set the throttle sensor to the correct voltage at closed throttle. I don't remember the value (0.6v?) If this is off, it can create that big flat spot at 3500 rpm.

Are the valves in spec? It will effect the mix also. Tight = leaner, loose = richer. It's a very small change unless the valves get very tight.

Good luck. dz

Head2Wind 12-03-2012 11:17 PM

if stock jetting and no other modifications I would baseline verify that all of the jets are clean and float heights are set correctly. THEN test and re-jet if necessary.

wantok 12-04-2012 05:42 AM

Thanks for the advice
This is good stuff - thanks people

Nick (wantok) :clap

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