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

[koko64]

Yeah, try it. With a hanging idle you usually need to  richen the idle a little, say out a 1/4 turn on the screws. Breathy?
Write down every move by the way.

[silas]

Koko, Brad, Buck ...thx for all the help. I'm not good at carbs but prefer to fiddle myself at the moment. I installed the carbs & coils...easy. My bike has not been dynoed but is the same setup as Buck's except with Arrow slip ons. I will try 165 mains and report back.
In Atlanta Ga it's usually on 10% ethanol gas. We have to go 45 mins N to the base of the Blue Ridge mountains to get 100% real gas. "Foreign fuel"-ethanol !

Buck, 'slow drift down' from what rpm? I get the hanging idle sometimes also but only when cold & avoid it by backing the idle screw off a tad more after it warms up more. Have you checked your throttle cables for kinks?

[Rudemouthsky]

Here's an email I got from Chris Kelley in RE: to my situation;

"The main jets have nothing to do with closed throttle to 1/3 throttle, which is where all of your negative symptoms are coming from. Then, you're using pods, which I normally recommend against. And finally, I don't know what's up with the race exhaust. The OE exhaust header actually flows really well, which (as usual) I had to learn the hard way to believe it.

The dyno graph doesn't tell me a whole lot other than your HP peak seems located about right (torque peak is probably near 6000) and I'd like to see that closer to 80hp than 70 . I think with the race exhaust and the pods, you're going to need to pay a shop to really dial in the FCRs. That's where they iteratively make a jetting change, ride the bike, come in, make a change, repeat. Additionally with the rideability improvement you'll be asking for, get them to "dyno tune" the main jet at WOT (like normal dyno runs) to try and improve the max hp number.

Remember that with normal riding around town, the speed or gear has nothing to do with the jets or circuits. These aren't like CV carbs, where the needle clip can affect idle and/or the mains and vice-versa. So for your 30-40 stumble could be needle clip position. The > 80 flat spot is probably the 67 hp. Slow return to idle could be too rich or too lean and can be affected by the fuel screws, slow jets, slow air screws, and float height."

[koko64]

That afr trace shows lean mixture at WOT at peak hp. That means too small a main jet with pods. Go the the 162s. Ethanol leans things out a bit, so if your fuel has ethanol definately go 165s. A fat main jet may cost a peak pony, but too lean could cost that and your motor.
Listen to Brad, hes done more dyno tuning than most. Your main jets are too small for pods, period.

Main jet isnt the cause of whats happening down at small throttle openings, you have to dial in the slow circuit to tune that.

If you are not confident about what to do, book your bike in with speeddog, duck-stew or someone like that. PM those guys for someone near you if they are too far. If the guy that dynoed your bike said the afr was good for a WOT power run, then do not let him tune your bike, honest.

[brad black]

I recall someone saying that the needles were too rich, but what they were saying or what i am remembering didn't make sense as they were talking about going to an emr, but that that's richer due to a smaller root diameter.  a larger root diameter needle may help with the low speed richness in conjunction with the smaller pilots, etc.  I hadn't thought of that before, but with the dellortos we would often drop from a 265 needle jet to a 264, which on a bevel 900 with phm40 really makes a difference to cruise mixture.  much nicer for a 0.01mm change in jet diameter.

might need to try some emu or emv some time.

http://www.jetsrus.com/photos/photo_keihin_needle_N427_OC_aftermarket_chart.JPG

[krista]

Subscribed. I'm keen to learn w.t.f. is up with the pod folks.

[krista]

I've heard/read (on here and elsewhere) that having multiples for gearing can lead to abnormally fast chain and sprocket wear.

No. Please stop the rumors.

[koko64]

Subscribed. I'm keen to learn w.t.f. is up with the pod folks.

Clearly the RU 1750s flow enough to let MBP motors make 100+hp.

When I dynoed pods Vs open airbox, I found that the pods needed a little less fuel at WOT and at 1/2 and 3/4 throttle pos-ns. It was a main jet size or two and maybe a notch to 1/2 a notch on the needle. At 1/8 - 1/4 throttle it was a tweak here and there on the slow air jet screw. I found the pods made a little less peak torque. They seemed a little more sensitive to being too rich at peak power on the afr curve. There was only a couple of ponies in it on the dyno. Shit they were loud (I must be getting old). Pods felt more responsive just off idle, kind of more revvy.
The bike has JEs and porting, so maybe less difference on a stocker (I really dunno).

Been hanging out with Cagiva Elefant folk (they're a hardy lot). I would run pods on a late carbed model Elefant in an attempt to get more airflow towards the rear of the motor. Those things shroud the rear cylinder with the tank/bodywork.

[krista]

Clearly the RU 1750s flow enough to make let MBP motors make 100+hp.

Agreed, I had them on Pongo when he was at 104hp. A bigger surprise was the OEM header was up for that, too!

[Rudemouthsky]

@ Silas: did you ever try the 165 mains? I'm retrieving my bike soon and will be fiddling with my own carbs next week when I have access to a warm garage.

[silas]

Buck, not yet.  2 lil girls & 3 houses limit my time & $ more than desired. Im on it when time allows. Def soon though. I'll post back here when I get'em.
I just found time to lower the clocks & headlight below triple tho.

[silas]

I fitted the 165 main jets this wknd. Removed the std 155's.
Big thanks to brad and koko for their help!

As a reminder, my '98 M900 has fcr 41's, arrow slip ons, Ca-cycleworks coils, and k&n pods (sawed airbox off). Otherwise stock. 31k miles. Atlanta is about 1000' above sea level and my only test ride was @ 50 degrees or so. 10% ethanol gas.

The bike def. pulls a little harder above 70 mph and in the higher rpms. No adverse effects. It's quicker to pass on the hwy now and has a fatter feeling top end in all gears. Seems to 'honk' louder/ harder when wide open, just a little. Whoohoo. The faster I go the more I notice the jetting change. This jetting feels perfect to me now, I'm no expert.
I'll post back in a few weeks of how my mpg's got affected. Typically I see 35-38 mpg's in town and mid to upper 40's on the hwy, but I have gotten 58 & 61 mpg's on a tank before while @ constant hwy speeds.