Carb mixture

I have a RevTech 100 w/Mikuni 42. Recently it's started to run rough at times. Accelerating with about mid-throttle it's missing a little, but not bad. Accelerating hard (WFO) in 4th gear it starts to get rough at around 70 mph. Then if I back off on the throttle just a bit there is a very noticable stumble and then it smooths out.

I did just recently change the exhaust for the V&H HS, but it was occasionally like this with the previous exhaust. Thought maybe it was bad fuel, but after a tank of Chevron super, it still is acting up.

Pulled the plugs, and they look fine.

If it's the jetting, where would be the place to start?

Thanks gang

OK, nobody has responded, so I'll respond to myself.
From what research I have done, it seems that I may be running too rich.
Looking back, I did clean and service the filter around the same time that the rough running started. Could I have over-oiled the filter? Sure hate to start swapping jets around if it was something simple like that. Plus the fact that it use to run smooth and strong.

Sorry, been fishin'

Easiest way to tell is to remove the element and go fora ride. If it runs normally, look at the filter. If you are running a K&N it is very easy to over oil and it will take a while to suck it all in. While you are at it, drian the float bowl to flush any debris out.

From what you are describing it could be several things but really sounds like a lean out. I would check the fuel supply, bowl level etc.

Finally pulled filter and went for a ride. It ran great. So, now that I know it's running rich, should I go 1 jet size or 2 jet size's leaner?

Carb

If it is rich try moving the clip up one groove on the needle which lowers the needle leaning out the main jet slightly. Dutch

I went 1 size leaner on the main jet and ran for a couple of days. Great on top end but still stumbled mid-range. Last night I pulled the jet needle, and raised it 1 slot. Today I'm running strong pretty much throughout the full range.

Thanks for everyones input.