900RK Idle mixture adjustment

So I had the great fortune of having PhiBe put through a few dyno runs. The whole point was to see the power and torque curve shapes along with the fuel to air. She is running on pods and a 4 into 1 with a 2" pipe and SuperTrap. Carb jets are +1 right now.

Regardless of the HP and torque numbers the silly dynamometer calculated, the lines looked good with torque hitting 50 lb-ft around 3500 RPM and creeping upwards of 57 lb-ft staying pretty flat through the run. HP increased up to around 9k before falling off. (calculated out, it's right at the factory 97 HP)

Since I'm running a SuperTrap (and I'm running all 10 plates or so on it), we had to take the back plate off and stick the sniffer down the tail pipe, so I was running with no back pressure at all. My idle air/fuel mixture was reading 17+:1, considered very lean. When on the go, she was only getting as low as ~13.5:1, still lean for wide open running as far as I have come to understand. (And I do also understand that Yamaha had these tuned a little lean for emission requirements, etc.)

So now for the query...

1) Idle mixture screws on the top front of the XJ900RK carbs get turned out or in? I want more gas and less air bringing her closer to a stochiometric burn at idle. No good to run lean on idle, too hot if you sit there for too long.

2) Is it time to up the main jets to a #107.5 ( I think that's a +5 from stock) and the air main +4 from stock if I read the posts right. The other idea for the mid-range pull ratios is to move the jet needle up a notch in the throttle slide housing helping me get a little richer in the main pull.

If you suggest a colotune plug and carbtune from Morgan or the like, I already have the webpage open. If someone has a set for me to borrow for a week, that would also be most excellent.

 

1 turn screw out for more fuel if you go to far out increase pilot jet size

if you have a gas analizer you do not need a color tune, you can make a sync tool for 5 to 10 $ a few threads on different types 1 is with 2 bottles the other is with 10 feet of tubing

 

2 bottle sync tool

 

Thanks for the link. Decidedly going to setting up the 4 tube board manometer with individual catch bottles for prevention of possible suckage.

 

It's pretty easy to fabricate a backing plate with a hole for the sniffer, so you can get more accurate readings. If you want to get carb-specific, there are gas ports in the headers (be careful backing the bolts out though).

 

I just bought a 1983 xj900, love the bike. It has 21k on it. How often should the valves be checked?
Thanks
Bucky

 

5000 miles or once a year