Bonneville America Forums Forums Technical Forums Performance Mods FCRs finally got em right

It has been a couple of years since I put the 39mm FCRs on my speedmaster. It ran great with the modified CVKs, good power, good throttle response. Straight out of the box the FCRs were awesome on the throttle speed and top end but I always thought that I should be getting a little more out of this motor. To that end I have been tweaking these carbs for the last 2 summers and likely made things worse but did it slowly enough that I couldn't really tell.
Last month I was able to get a Dyno run in ( and I will not be posting it) I had the bike pretty far out and had lost more than 15 hp.
Taking the Dyno info in hand and sending lots of PayPal money to jets are us, I started over on the FCRs. Mains, pilots, needles, and screws, it's all different.
Today was the first time that I had some time to really ride her since this revamp of the carbs. I rode around for about 20 miles, good warm up, got on a empty back road and then dropped the clutch at 4500 rpm (right where it comes on the cam) I was not expecting quite what happened, with the rear spinning the front end came up! I have never been able to wheelie this bike ( in spike of many past attempts) it certainly caught me unawares.
Needless to say I am very impressed with what is hidden in this motor. Sucks it took me so long to figure out how to get it out.
And this was on 93 ethanol, no fancy 115 racing fuel this time. Don't think I need it.
Damn I' m happy

Cool. Care to share the tuning?

always wondered if those carbs were set up properly out of the box, i know they set them p based on where yo live, elevation and intake and exhaust and all that nice stuff but i can't see it being anywhere near as good as a local dyno run in the place you are running the bike. Good to hear ya figured it out, what ya through in there would be nice to know for some i bet.

That sounds like a kick in the pants!

I'm thinking I want to go to the FCR's eventually too. I really like the power I got from my bored stock carbs, but you know, if there is more to be had, then I want it. Micah, you thinkn they would bolt up to those billet intake manifolds I have?

I don't know if they will fit as is. It seems to be the billet manifolds were all made to fit the Bonnie's. I am using stock manifolds with the rubbers flipped over.
If you want to take a close up picture of what you have now that would help. The other thing would be if the angle has to change, your billet manifolds could be machined to suit. I could probably find some milling machine time.

My manifolds are not like any others available. They have the angle for the carbs to sit level already

i beleive that if you bought the ones from British customs they allready have the angle built into them unlike the ones that come from Triumph performance, theirs i think were more for the 100's. I bought the manigolds from BC and the angle is good.

then the FCR's should bolt up with no problems. 2 things come to mind; you will need to gin up a carb brace and you will have to tighten the bend radius on the carb end of the throttle cables. The layout of the linkage on the carbs sets higher and more offset than the CVKs so the throttle cable housings won't clear the frame. The engine not being centered in the frame does not help.

I have Barnett throttle cables and the bend is already pretty tight. The FCR's don't have a crossover linkage tube (whatever that thing is between them, you know what I'm talking about) like the stock ones do? What about the TPS? No more?

Could the frame spine be used as a conduit for the throttle cables? A small hole saw and a electricians fish tape to thread the cables along the desired route?

the FCRs are connected by a common fuel tube (ridged) fuel comes into the center, very similar to OEM. And by a hose between the accelerator pumps. Also a solid 'rack' bar holding them together.
the throttle linkage is similar to the OEM set up as far as how the cable ends go into a roler assembly with shafts going out to each carb. This is closest to the left side carb. Balancing is different, you set that at each carb because of the rocker type of slide lift.

very easy carbs to work on, so far as mains and needles.

TPS is still there and I am using mine. Did the little calibration procedure and it works pretty good.

Interesting idea on running the cables thru the frame. some electrical stuff would have to move and maybe work around the engine brace. I am sure it could be done.