Dead spot 4,500-6,000 rpm?

[croymans]

Purchased a nice '85 this spring with 20K, V&H exhaust and K&N pod filters. Have a flat spot from about 4,500-6,000 rpm but pulls strongly below or to red-line. Carbs, plugs, valve adjust was supposedly done not long ago. Would this be carb jetting? The elevation here is 2,900'. Any recommendations from you gurus would be appreciated!

[andyb]

Do a plug chop at 6500 and get a good read.  Needles aren't right.  Stuck possibly, set wrong, or otherwise buggered up, but you'll need to start by seeing if it's even between the cylinders or if it's a problem with the lot.

[SlowOldGuy]

RPM doesn't help diagnose which circuit is giving you the problem.  How much throttle are you giving it?  1/4 turn?  1/2 turn?

Could be fuel level.  Although the V&H pipe was known for causing a fairly severe flat spot.

DavidR.

[RichBaker]

I'm betting it's the classic 4-1 flat spot, the RPM range is correct.... you can sorta jet around it, but the pipe is the pipe. A good 4-2-1 D&D will fix it, but it costs....

[Arnie]

The pod filters aren't helping either.  The OEM airbox is tuned to minimize that mid-range flat spot.  Try replacing the airbox if you still have it.

Arnie

[croymans]

Thanks everyone for the feedback! I'll check the plugs first and see how they look. Since several of you mentioned a characteristic dead spot with the pipes/pods this may just be the nature of the beast. I'll also pay attention to my throttle position too next ride and report.

[andyb]

Flat spot from a 4-1 pipe that goes from 70-110mph in top gear?  Haven't had that problem with the V&H's that I've used.  Just gets a bit soft, centered around 6k, hard to notice unless you're in top gear and perhaps loaded a bit (or if you run a more touring gearing).  The SS2R or the SS pipe?  I know there were at least two designs of the SS2R header, one with a divided collector in an attempt to emulate a 4-2-1 of sorts.

Is it flat spot where the power sags a bit, or blubbers and farts and splutters a bit?