2003 SV650 Powerband Problems

[bdomenz]

I have a 03 SVS 650.

Had motor work done to it. Manual cam tensioners, M4 High mount exhaust, Power commander, 1mm over, removed a layer of the head gasket, etc. And I'm running VP U4 fuel.

Overall it gained very nicely - dyno is much improved over stock all the way through the powerband.

But - when it reaches about 8800 RPM the powerband levels off completely flat instead of continuing that gently slope before tailing back off. It was also oscillating about 1500 RPMs at idle.

So, we had the secondary butterfly valves removed, sync'd the carbs and put ignition timing back to stock (was advanced 4 degrees).

This helped the idle smooth out, and gained about 500 rpms of additional pull. But it still flattens off at 9200 RPM'sh, instead of that nice final slope.

At Road America I could really feel this. If I was coming out of a turn, as I accelerate and the RPMs hit around that 9000 mark, it almost feels like you've hit a soft rev limiter.

Valley Racing is doing the motor work, and we've tried a bunch of stuff, but we can't find the fix. He even re-wrote a Yosh map to the stock black box (?not sure what this means?), and has played extensively with the powercommander to no avail.

His two thoughts are:

1) Get rid of the high mount exhaust and going with the sport mount (which has less bends). Which might improve flow.

2) Try a different stock black box. Because this one had this same 9000RPM flat spot characteristic when I purchased the bike Bone Stock.

Anyone have any suggestions on what the most logical next steps should be?

We're stumped.

Thanks.
- Bob


__________________
Bob Domenz
#364 SV650
www.3dracingonline.com
bdomenz@avenue-inc.com