View Full Version : '08 DX Running Rich

05-11-2009, 10:40 AM
I have a 2008 VRSCDX, 1250cc, SC air cleaner, air box cover ON, stock computer, & Fat Shots. Up to 11 disks & it seams to still be running rich. Haven't dynoed it, but more disks "appears" to be lowering midrange tourque without improving top end. '08's have the dual ox sensors. Should I keep adding disks till it starts to lean out? Is the computer trying to over compensate?



05-11-2009, 10:54 AM
8-10 on a stock bike is typically the magic number. How 'rich' is it? smoking? bogging?
Typically,more discs, you would see a slight drop in bottom end and a slight increase in top, depending on fueling of course.
It may be throwing more fuel at lower rpm/throttle setting/load making it rich, and not enough at higher rpm?
Interesting, have not noticed that or heard of it.

05-11-2009, 01:26 PM
Not somking, but black soot on the exhaust & plugs. Runs fairly strong across the power band, no pops on deceil. Also, has a mid range flat spot or stumble when cold. Have not tried it above 12 disks.

05-11-2009, 04:18 PM
Hard to say without seeing it. Just for giggles you might try taking all the discs off and running around the block to see what it does?

05-11-2009, 06:52 PM
Open, no end cap right?. I'll try it this weekend.


05-12-2009, 08:41 AM
Yes, completely open.
Ideally, you would do this with new plugs and take a reading (search NGK's website for proper color info).

05-18-2009, 10:37 AM
I would suggest taking your bike to the nearest facility which has a dynomometer where you can actually see what the air/fuel mixture is.

Then I would suggest installation of a race tuner, finalize you discs, and then have you motorcycle tuned to the specific number of discs you chose. (More added=Louder/leaner
Less added=Quieter/torque)

The ECM cannot adjust for the open exhaust and free flow air cleaner like the H-D race tuner can.

07-02-2009, 09:51 AM
Hard to say without seeing it. Just for giggles you might try taking all the discs off and running around the block to see what it does?

Well, it took a bit longer than I thought it would, but here are some results:
As it turns out, the soot is from the cold start circuit, it just doesn’t seem to go away from the disks.
The motor was a weak suck with no disks, in fact it was flat until I got down to 11 disks. The plugs looked a little lean, but not scary. Guess the EFI tunability is a bit limited.
With 10 disks the thing pulls hard, the plugs were a nice light tan, with no pops or pings. Which seems odd, it is your recommendation to run 10 whither we have an 1130 or 1250cc motor. I was running 21 disks on a 95 inch motor with a Super Trapp 2 into 1. 20% more displacement, but with about the same amount of disks. Displacement most not be that big of factor. Maybe it’s the amount of air moved vs. rpm?
Anyway, thanks for your help. Wish you guys made a black 2 into1 for the Night Rod Special. :cool:

07-02-2009, 10:03 AM
Good to hear, sounds like you on the money-or very close too. Tan is good on the plugs. Ride it and have fun.

Displacement, HP, type of engine are all factors. Then throw in core design, number of mufflers, cam profile, use of vehicle, sound/emission requirements, etc, then you have a few of the tuning factors.