96 m900 fcr41 carb leaking issue

[ducpainter]

That's the Mikuni pump that ca-cycleworks sold. It's a lower volume pump than the OEM.

My bike takes 3+ tries at 50 degrees. Maybe 5 or 6 at 40.

[ducriderinct]

Hmm. Maybe you need the pump I have But seriously, why would you want a lower volume pump? I figured it was a higher volume pump to work better with the FCR's.

[koko64]

The OEM pentagon pump is the highest flowing low pressure pump I've come across.

[scaudill]

My 01' 750 has the small rectangular pump, think the PO changed it.  For the type of riding it is more than enough .  I have the Mikuni carbs.

[ducpainter]

Hmm. Maybe you need the pump I have But seriously, why would you want a lower volume pump? I figured it was a higher volume pump to work better with the FCR's.

At one point there was not a good source of quality parts for the OEM pump and the pump you have is relatively inexpensive.

I found that the rebuild kit for the dual outlet Mikuni pump that Sudco lists works fine in the OEM pump, and I rebuilt mine for roughly the same price as the small pump you have. A lot of shops, and owners don't want to rebuild stuff due to labor costs, and that small pump seems adequate.

I don't think you could ever use as much fuel on the street as that little pump delivers. 14l/h is a bunch of fuel.

[ducriderinct]

I still have a good working stock pump. What's the life expectancy on one of them?  Would it be worth putting the stock pump back in for any reason? The damn thing is huge and there's not a lot of space in there.

[Howie]

Since the pump is off I recommend you rebuild it.  You want a genuine Mikuni kit, here is a source  http://sudco.com/Catalog37Digital/index.html#/522/

That pump will supply a big ol'e American V8 with enough fuel so there is a lot of grace.  Your rectangular pump is sufficient as long as it is close to 100%.   Lasted on my old bike for maybe about three months.

[ducpainter]

The 002-026 kit is what I used. There's 2 extra gaskets.

Here's what Eric said re: my FCR set up.

"Oh and your pilot is a 60
fuel screw is at 1 turn out. Air fuel warmed up was about 12:1 ish so it is on the rich side when warm."

Starts hard...runs great!

[greenmonster]

1,5 turns in/up on the idle lever when cold staritng (20C) and a quick throttle pump, starts 1 try, idle jet 60. Maybe 1 turn is just a tad to little?
Exept for first start ofter 6 months winter rest, lotsa fiddling.

[clubhousemotorsports]

In climates that have large temperature swings we have to strike a compromise with carburetors, we cannot all live in Hell like Speeddog  

If you jet the fcr's to start easily in cold temperatures they will be fat when they do warm up, conversely if you jet then to cover that large range of start up and running temps you will have a start up routine. It is normal to have FCR's start and then stall on start up if you use the accelerator pumps as your enrichener, the bike will burn off the excess fuel and lean stall. Usually after you have done this once or twice the engine has some heat in it and will no longer be lean causing the mixture to be correct.

If you jet the pilot jet or fuel screw rich then you are probably fat when at running temperatures. We prefer the bike runs better than it starts but it still needs to start. an ideal setup would be an enrichener circuit or an adjustable fuel screw where you could richen it for starting and then lean it back out when warm. that's not needed most of the time if you have the patience and can follow a start up procedure.  

In painters case his pilot went down from a 65 to a 60 and the fuel screw went from 1/2 out to 1 full turn out. Cold start is pretty normal with 1 or 2 stalls before idling and his air fuel is just about 12:1 when warm. If I richened his pilot to a 62 then the fuel screw might go in some to be in the 3.5-5.5 CO range I shoot for  BUT when warm he would be rich below 12:1 and over the 5.5 CO. Always a trade off. If our temperatures were higher and stable then we might allow the pilot to be even leaner as there would be less of a swing from cold to hot.

The smaller rectangular pump is not what Ducati used but I have had one on a Bimota DB4 with FCR's and it worked just fine it was oem on that bike.

[ducpainter]

1,5 turns in/up on the idle lever when cold staritng (20C) and a quick throttle pump, starts 1 try, idle jet 60. Maybe 1 turn is just a tad to little?
Exept for first start ofter 6 months winter rest, lotsa fiddling.

My bike sits...

a lot. That could be part of the equation too. When Eric and I went for our ride the thing would be running as soon as I thumbed the button. Started better hot than it ever did with the Mikunis. I drain the bowls, or let the bike run out of fuel after every use because it gets used so little. I also keep stabilized fuel in the tank.

It's time to fog the motor and put it to bed for its winter nap.

[koko64]

Hibernation.
With our fuel down here 60 slow jets foul plugs in '41's. With hi comps when using our 98 RON pump gas with 60 slow jets its like having a choke on. Soon as the motor warms up it stalls. Clearly a result of kangaroo piss additive. The Japanese import Formula 400 racers came with the smallest slow jets avaiable, but that was a rich setting down here.
I have run 50-52 slow jets in '41's and 55-58-60s in '39's for a 900.

[ducpainter]

My motor is not high comp. Stock 900.

I run 87 octane (R+M/2)

[koko64]

Do have to run e10 fuel in NH?

[ducpainter]

Do have to run e10 fuel in NH?

Yup.

There are a couple of stations that sell ethanol free, but they're pretty far.