96 m900 fcr41 carb leaking issue

[koko64]

The moonshine additive leans the mixture out a bit. 

[Howie]

Also inhibits atomization at cold temperatures.  Steve (ECS) put a couple of gallons of ethanol free in my bike.  Big difference.

[koko64]

So more chance of carb freezing?

[Howie]

Freezing should not be more of a problem.  Moisture in the air is what freezes. 

[ducpainter]

The other consideration with ethanol free fuel is, generally, it's only available in higher octane ratings. I don't need to carbon up my motor.

I have a steel tank, and if you're careful you can avoid the pitfalls of the ethanol.

[ducriderinct]

So all along I've been thinking that 93 is better for my bike, and that's what I've been using.

Previous owner said he always ran 93, but based on what you just wrote, do you think I should be running 87 instead of the 93? 

I'm fairly new to carbureted engines...

[ducpainter]

So all along I've been thinking that 93 is better for my bike, and that's what I've been using.

Previous owner said he always ran 93, but based on what you just wrote, do you think I should be running 87 instead of the 93? 

I'm fairly new to carbureted engines...

About 16 years ago, Bruce Meyers of BCM, told me that the low comp Duc motors were much better off with 87 octane, and more octane was just wasting money, and carboning up the combustion chamber. Higher octane fuel has additives that inhibit combustion to eliminate pinging.

If you have high comps, or a 944 kit with high comps, then continue running the 93. Otherwise, try the 87 and see how it does in your bike. You might also add some Techron to the fuel for several tanks.

[Howie]

Your bike should be fine on 87 with the stock compression ratio.  Should be because every specimen is different.  93 is way too high.  If your bike does not ping on 87 run that.  If it does, move up one grade.  The carbon from too high an octane is made worse with the ethanol. 

[ducriderinct]

So I have another related question. After all the fantastic help from you guys, I seem to have solved the flooding issue as well as the faulty fuel valve issue.  Thank you so much to all that have contributed : )

Now that it's running (fairly) well, it's great around town, low gears partial throttle and full throttle, however, when I get on the highway and try cruising at around 60 to 65 in 6th gear at partial throttle around 4500 RPM, it sputters and pops and hiccups like its flooding or something... If I give it more gas and start accelerating it seems smooth and fine with no issues.

I never noticed any of this behavior when these carbs were on the other bike.

Is there possibly something different about this engine versus the other engine even though they're the same year and model that I need to compensate for somehow? The other bike was run on 93 octane exclusively prior to my purchasing it.

[ducpainter]

Every engine is different. Some have better ports than others and require different pilot jets, or different fuel screw settings, or different needle positions.

At that road speed in 6th gear you're at a very low throttle opening. I'd try turning the fuel screws in a 1/4 to 1/2 turn and see if it helps. If it gets better try some more until it doesn't get better. If it doesn't go away you might have to play around with needle position, or perhaps a smaller pilot jet.

The circuits in a carburetor overlap so sometimes it takes more than one adjustment.

[Speeddog]

The air jet in the carb inlet is also a quite powerful adjustment.
AFAIK, all of the recently sold flatslides come with adjustable air jets.
If yours has older fixed size jets, it's definitely worth the money to get the adjustable ones.

It's the one at about 7 O'clock when facing the carb inlet.

The overlap between pilot jet, mixture screw and air jet is ridiculous on the FCR's.
I'm pretty well convinced that it's possible to run three different size pilot jets with associated mixture screw and air jet settings, and have the bike run quite well.

Those of us with dynos and sniffers may be able to slice it fine enough to tell the difference.

[ducriderinct]

Ok. I'll give it a try
With the fuel screws. How exact do I need to be with the turns? It's kinda hard to see them way in there. If I'm a little off left to right will it affect the balance/ drivability?

I'm learning fast on here about these things

[koko64]

Buy a tiny screwdriver and mark the handle with a marker pen.

What jets and needle position (again)?

[ducriderinct]

I gave them a quick 1/4 turn and went for a spin.

Didn't make it to the highway yet, but a 1/4 turn in greatly improved the low speed drivability, so hopefully the highway will be a bit better too.

I honestly have no idea on the jetting and clip settings. I bought a bike that had these installed already so I've not been inside them. I know they came from CA-cycleworks.

[Speeddog]

I've resisted throwing down for a pair of these, at least so far:
https://www.amazon.com/Racing-Products-Flex-Jet-Remote-FLEX-TECH/dp/B005UGFIYC

But my resolve is weakening.

There's also the more standard knob, like this:
https://www.amazon.com/Factory-Effex-17-36030-Adjustment-Screw/dp/B00PUOHE14/ref=pd_lpo_263_tr_t_3?_encoding=UTF8&psc=1&refRID=Z1SJDR27V51PHFYN1WKK