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!
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.
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.
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....
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
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.
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?