My bike (900ss engine) dynoed at 67.2 RWHP...should I be asking WTF?

[koko64]

Do the heads of your motor have a "W" scribed onto them?

[Rudemouthsky]

Exactly what silas said except I have a Roadracing full exhaust. My engine has V heads, I made sure of that before I bought it (thanks Brad Black)

[silas]

No, I swapped to the V2 heads from A 900SS a while back. Made a small difference at higher rpms (head swap prior to carb & coils upgrades).

Apparently some '98's came w the V heads but I had to switch to them .

[koko64]

Ok, thats good. Brad did the same for me too. His generous sharing of knowledge has helped many.

Im guessing your pods are the K&N RU 1750s?

Did the dyno guys test for air fuel ratios at various throttle openings or just a power run?

Straight up I would consider going up to 160 main jets and see if that improves things up top when you want to overtake quickly. Greenmonster runs 162.5s with pods (Scandinavia), I ran 160s {Australia). I'd like to see what the locals are running with pods on local fuel, but you get the trend.
Changing the main jets is easy on these racing carbs, you just need to be careful with blocking the fuel and catching the fuel spill. You access the main jet via the big alloy nut on the bottom of the float bowl. Hex head main jets require a tiny wrench 6mm iirc. Be gentle, imagine stripping that thread... Check Chris Kelleys site out. A spray can cup works well to catch the fuel. Do the work with the motor cold...
The safest place to test main jets is the dyno, but I think you should feel the difference one way or the other on a highway overtake.

Stay with the #3 needle position for the moment.

Thats step one.
Step two requires you first read Patrick Burns "Keihin FCR Tuning Procedures".
Tuning the slow fuel circuit requires patience and involves the slow fuel jets, slow air screws and idle mixture screws. They all interact and overlap at some point. A perfectionist could spend a lifetime in this area.
If the bike idles well, has good plug colors and is smooth at low speeds and small throttle openings then your settings are close.
Lumpy running, fuely idle, black plugs and poor cruising fuel economy are symptoms to alert you to fix this area. I doubt the slow fuel jets are too small.

Let us know more about the low speed throttle characteristics and we can give feedback. It will be interesting since your exhaust systems are at opposite ends of the spectrum.

Cheers and be careful.

[Rudemouthsky]

when you right click and view this, the resolution is actually quite good considering I only photo'd it. Helpful at all?

[koko64]

It is definitely too lean from 6000 to 7500rpm. Put in 160 main jets as the area of peak hp on these motors is too lean. You can see it's too lean where it counts, but that's actually a relatively flat a/f curve compared to some I've seen, but the hp bump from 6500 to 7500 is missing. The power peak looks chopped off the curve. That lean area can be felt as a lack of acceleration.

[silas]

Kiki-my bike has not been dumped. It does idle well and the plugs look good. I will try larger main jets. Relay appreciate your info & ideas! I'll post back after trying it.

[silas]

Koko-sorry, darn device

[koko64]

Kiki-my bike has not been dumped. It does idle well and the plugs look good. I will try larger main jets. Relay appreciate your info & ideas! I'll post back after trying it.

Maybe your exhaust set up may make tuning less pernickerty down low.
Chris at CCW has to provide a base setting for all comers, then us guys go and do mods!

[silas]

Yes, and mine is very close already. I Love the sounds from the pods (and the open look)

[brad black]

when you right click and view this, the resolution is actually quite good considering I only photo'd it. Helpful at all?

did someone tell you that mixture was ok?  it's way too lean.  if it has 155 now i'd be going 165 or more.  one of the reasons I am liking 39 over 41 is that the wot curve seems to be much flatter with 39.  you also run a smaller main jet, but that's due to the venturi airspeed differences.  39 on my 750 show the same lumpy air/fuel as the 41 on a 900.

[koko64]

I'd go 165s on an open airbox, but I think the pods (RU1750s) run a little richer in the midrange and top end. I thought they'd be leaner, but the ega surprised me. An extra dollop of fuel wouldnt hurt and its foreign fuel. Greenmonster is running 162.5s.

Be interested to see if the dyno guy said it was ok as it's clearly not.

Something I forgot, too rich an afr seemed to hurt hp more with pods than an open airbox. Shorter stacks in an open a/b allowed even richer again, helping midrange WOT hp/torque without hurting peak hp much.

[Rudemouthsky]

Be interested to see if the dyno guy said it was ok as it's clearly not.

did someone tell you that mixture was ok?  it's way too lean.  

Yes. Maybe I'll start with 162.5 and go from there? Or if they're cheap enough I'll buy several.

[koko64]

Cool, why not.

[Rudemouthsky]

Cool, why not.

Should I adjust the fuel mixture screw maybe a 1/4 turn in the meantime? It actually starts and idles quite well for the most part though...would rather not get too much in to fiddling with those settings   I have somewhat of a "hanging" of the RPM's and a slow drift down when I release the throttle, and it's a bit "breathy" if that makes sense.