Tuning out a flat-spot - help..

So, after 2.5 year on/off tinkering the Radian engined 550 Seca is now officially roadworthy - according to the Ministry of Transport's appointed official - even with the make-shift Bridgestone Trail-wing rear tyre! (new Maxxis Promaxx on order) However now that I'm out on the road I notice a distinct mid range flat spot. Pick up is good and if drop a gear (or two) and give it some beans it will rev out BUT its not really as 'tractable' as I would like. I'm thinking raising the needles a notch or two might help and/or upping the pilot jet. I've a feeling the BS30 FZ600 carbs on it are on 32.5 on pilot and even a standard 550 has a 40. Thoughts?

 

Are you running pods, non stock exhaust? If so you might go up on the jets....just my thought

 

With the additional displacement it sounds like it's a bit lean.

You may want to read through the CV carb tuning tips at this website:
http://www.factorypro.com/
Click on support and then open up the Motorcycle tuning tech page.
Then click on the CV carb tuning link, then click on the High RPM link.
It's the best tuning advise available when it comes to dialing them in.

Chacal @ xj4ever.com can get you any jets you need to dial in your carbs.

BTW, how do the plugs look?

Tony

 

direct link to carb tuning at factory pro
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

 

HI All

Thanks for the remarks - plugs look good, perhaps a tad on the lean side. Airbox is original 550 with new paper element. Carbs are 'correct-ish' for the motor (FZ600 carbs Radian Motor). Will take a look at the factorypro link for sure..

Cheers

 

Thanks for the direct link, my old one was broken.

Tony

 

Hi all just wanted to wrap-up this one. Suspect was fuel starvation at mid-range causing flat spot, but in fact the opposite was true.
I did initially try lifting the needle one notch but that put it on the highest setting! Went for a test ride anyway and it was quickly apparent it was flooding out. So I then dropped the needles by 2 notches (one below initial setting and now at mid-way point) and it's MUCH better. Perhaps not 'bang on' but pretty good nevertheless.

Cheers

J