Question for FCR adopters (2011)

A few questions for those using the FCR35's on their Commandos....
This will pertain to the as delivered jetting and those who may have altered their jetting...

I'm wondering how the engine gets along with a quick opening of the throttle and the feel of the accerator pump in action.

In reading about people who've used the FCR in other applications, some complain of bog or hesitation, mostly in 4 stroke engines due to the short duration lean out condition upon initial opening of the slides I have further read about modified covers for the accelerator pumps that utilite an adjustable "leak jet" to control the amount and duration of the fuel stream injected into the cylinders with quick use of the throttle. The claim of the manufacturers and by the users of these products is that they solve this problem and the hesitation / bog can be dialed out of the response, making for a much crisper throttle.

so...... wondering if these adjustable leak jet accelerator pump covers would be a worthwhile addition to these carbs?


edit..... discovered these adjustable kits will not work with the FCR's from Sudco as they do not have a replaceable leak jet in their bodies (the kits require replicing them with a plug). SO they can't be used. in this FCR application even tho they are all advertised with working on ALL FCR applications.

JD

If the FCR carbs are for a road bike running on petrol, would it not be just as easy to get the correct size pump jets fitted?

Bog? Hesitation? Not problems, not in the least. Buy the carbs; forgo the extra parts.

The as-delivered setting was way too rich. I had to experiment but ultimately dialed it in. I've posted my final jetting in other threads; let me know if you can't find it and I'll dig it out.

EDIT: Here it is:

In response to the request for original settings, here are the settings I am using, along with the "OEM" settings as received from CNW.

The current settings are the result of a lot of experimentation over an extended period of time. Took quite a while, but these work great for me. Power, mileage, and plug appearance are all very, very good.

The FCRs are awesome carbs!

140 main jets (came with 152s)

Needle clip in #2 slot (from top; there are seven slots; the needle clips came in #5 slot I believe)

Stock pilot jets

Slow air screw out two turns (were originally out one turn)

Slow fuel screw out 5/6 turn (Right side was originally about 2/3 turn out. Left was originally 1.5 turns out)

Can someone confirm what the stock pilots are.
Currently have 58 pilot.
200 air jet.


Thanks...

Mine came with 58s. And they’re correct.

Thanks, what the air jet behind the horns.

Sorry, I don’t know.

No worries. 200 is probably correct.
I think I have other issues..

Like what ?

Very erratic, won't settle down or idle. Needs big throttle to keep running.
These are used FCR's. The float bowls were a little nasty with semi melted rubber rings.
Everything is cleaned up and all passages cleared with a copper strand and air.
The accel pump at the check valve was especially clogged. Cleared with gas and compressed air.

It's running so poorly reminds when I installed the vacuum plate upside down on my KTM.
Plates are correct. No reason to believe they've ever been apart.

The 200 air jet is largest they make. Apparently that's was used on Ducati's.
Wondering if it is correct? No reason to believe they were replaced.

Running a Trispark and getting big kick backs from time to time.
Thought they weren't supposed to do that.

1. Internal issues in mid body of the carbs. Kinda of big deal to get into these.
2. Electronic issues.
a. Trispark is malfunctioning, I thought they either worked or didn't.
b. I did just install 2 new coils, not sure why they would cause this.

Firstly, can we separate the above issues?

Was the bike running fine with Tri-spark before fitting the FCRs? Ditto the coils? Or were they all fitted for the first time together?

In my experience modern carbs are great... but FAR less tolerant of issues than Amal’s. I had a hell of a time once with some round slide CRs, they were being really upset by dirt that was little more than a barely visible powder that was in the tank. Amal’s would have just passed it straight through without fuss!

So... your gummed up second hand carbs would be my main suspect. You have to remember that ‘cleaning out’ orifices with ‘gas and air’ simply proves that they’re not 100% blocked. It DOES NOT demonstrate whether or not there is a partial blockage, and given the precise nature of these instruments, a partial blockage can screw things up immensely.

I’d be inclined to get them to a professional carb cleaning / servicing provider who can clean them in a proper ultrasonic bath etc.

BrianK said:

Bog? Hesitation? Not problems, not in the least. Buy the carbs; forgo the extra parts.

The as-delivered setting was way too rich. I had to experiment but ultimately dialed it in. I've posted my final jetting in other threads; let me know if you can't find it and I'll dig it out.

EDIT: Here it is:

In response to the request for original settings, here are the settings I am using, along with the "OEM" settings as received from CNW.

The current settings are the result of a lot of experimentation over an extended period of time. Took quite a while, but these work great for me. Power, mileage, and plug appearance are all very, very good.

The FCRs are awesome carbs!

140 main jets (came with 152s)

Needle clip in #2 slot (from top; there are seven slots; the needle clips came in #5 slot I believe)

Stock pilot jets

Slow air screw out two turns (were originally out one turn)

Slow fuel screw out 5/6 turn (Right side was originally about 2/3 turn out. Left was originally 1.5 turns out)

Click to expand...

Are yours on a 750 or 850?

Rubber O ring around the accelerator pump adjuster and rod. It's a dirt bike trick. I could probably take a photo if someone would post it.

Googled it -

Fast Eddie said:

Firstly, can we separate the above issues?

Was the bike running fine with Tri-spark before fitting the FCRs? Ditto the coils? Or were they all fitted for the first time together?

In my experience modern carbs are great... but FAR less tolerant of issues than Amal’s. I had a hell of a time once with some round slide CRs, they were being really upset by dirt that was little more than a barely visible powder that was in the tank. Amal’s would have just passed it straight through without fuss!

So... your gummed up second hand carbs would be my main suspect. You have to remember that ‘cleaning out’ orifices with ‘gas and air’ simply proves that they’re not 100% blocked. It DOES NOT demonstrate whether or not there is a partial blockage, and given the precise nature of these instruments, a partial blockage can screw things up immensely.

I’d be inclined to get them to a professional carb cleaning / servicing provider who can clean them in a proper ultrasonic bath etc.

Click to expand...

I agree. Going to separate the issues out,and then go from there.
Already put the Amals back on, similar issue.
I think I have an E issue. Need to verify the ohms on the coils, then change out modules. Probably put back an old Boyer.
Was asking about the 200 air jet because I am going to order some more jets and wondered if I needed to change this.

jseng1 said:

Are yours on a 750 or 850?

Click to expand...

On a stock 850, for now. Had these on a Hot Rod 880 years ago and liked them ALOT.

Steves said:

Rubber O ring around the accelerator pump adjuster and rod. It's a dirt bike trick. I could probably take a photo if someone would post it.

Googled it -

Click to expand...

Yes, I have done this to my KTM.
Have you done this to the street version?

Is that o-ring addition recommended for street Commandos?
I'm running in an 850 with those carbs and haven't had any problems - although I'm not using WOT yet.

I dunno how many variants of these carbs there are, but the cNw ones I’m running do not have the same mechanism as shown in that vid so the mod is not relevant.

I’d also imagine that a dirt bike rider would be a lot more likely to yank on the throttle ( which is very quick action) compared to a classic Commando road rider.

jseng1 said:

Are yours on a 750 or 850?

Click to expand...

850

Hi Brian,


Wasn't sure if you were still around?

Is the 200 air jet standard?

I don't know Michael. Haven't touched mine.