View Single Post
Old 02-24-2013, 12:50 AM   #48
Andrew to most
kamanya's Avatar
Joined: Jun 2004
Location: Southern Tip of Africa
Oddometer: 1,326
Some feedback.

Beautiful engineering!

I have a 990 Super Duke engine (with an adventure gearbox) in a 2004 adventure chassis. I am using the 950 headers with a free flowing aftermarket exhaust.

I have spent 2 sessions on a dyno with a very experienced operator to get to where I am now.

Used to have a 150mm unifilters with foam skins setup on the OEM FCR carb. I had 142 140 main jets, 52 pilot jets in it. This was setup by the same dyno guy.

When the velocity stacks arrived, I mounted them with 155 mains that were supplied. It was way too rich. I went back to the 142 140 with the needles on the 4th clip from the bottom and then sent the bike off to the dyno.

What I came back with and am at the moment;

140 front 138 rear main jets
Needles second clip from bottom
50 pilot jets
198 air jets
2 turns out on the air screw bleed
1 turns out on the fuel screw bleed.

I have left the outer foam socks on until my filter skins arrive. (we dyno’d the filters with the foam on and off – it made negligible difference to the AFR’s)

The billet throttle position sensor works very well and looks factory;

Starts instantly, even when cold. Seldom have to re-thumb the starter button. Very torquey and snappy. Angry even. With my 95kg’s and 25 litres on board it was roll on wheelies in 2nd. Precise throttling. Some patience is needed balancing the carbs both at idle with the adjusters and at 5k revs with the cables. Slow technical riding is brilliant, it will tractor through at low revs and is very hard to stall. This is very cool as I am short and having to dab from a stall always means a trip to the ground. The rear tire is not very happy.

My dyno guy has been a bit slack (too busy) in sending me the dyno charts, but will post them up when I get them.

We are not sure why there is such a discrepancy between the USA main jet experience and my South African one. I am the only one I am aware of that has these stacks here so can’t explain why. Unless you have a dyno with exhaust gas analyser, or, you have huge experience and skill in tuning, then these stacks are maybe not plug and play. In anycase, I can’t imagine anyone would buy these carbs and not expect to have to go visit a dyno. Not doing so, in my opinion would be foolhardy.

It has been a long road with these carbs and I am done fiddling now… I think… I spied a 2 wheel drive project somewhere?
I often wonder where that road goes? And that, has usually made all the difference. Appologies to Mr Frost

kamanya screwed with this post 02-24-2013 at 12:59 AM
kamanya is offline   Reply With Quote