Vibration in 5th gear. Not sure where to look

Ok so I was heading to work this AM, while in 4th gear around 60mph taching out at 3000rpm It felt ok. Once I shifted to 5th the rpm dropped to 2500rpm and the bike was vibrating.

 

Where should I look for the cause?

The driveline ?

Carb Sync?

or what?

just as a side not:

I've synced the carbs many times and it seems to be different everytime.

Ok so I was heading to work this AM, while in 4th gear around 60mph taching out at 3000rpm It felt ok. Once I shifted to 5th the rpm dropped to 2500rpm and the bike was vibrating.

 

Where should I look for the cause?

The driveline ?

Carb Sync?

or what?

just as a side not:

I've synced the carbs many times and it seems to be different everytime.

At 2500 RPM you are close to lugging the engine, depending on what you are doing with the throttle, so an out of sync carb might take it over the line. You will get better mileage if you keep the engine at or above 3000 RPM. Since it is free, might as well sync again and see if that fixes the vibration.

I did a sync last night with the RPM set around 1200 to make reading the carbtune easier. I got it pretty close. So today was the test ride. I ripped her upto 90 in 4th 4000rpm, and 5th gear 3500rpm or so and she kept gaining speed. No vibration like before.

 

As far as lugging, if im putzing around town 3rd gear or 2 gear not even 2500rpm and it dont sound like its lugging.

2nd, 3rd and under light conditions 4th dont mind 2500 rpm but in the hills and against headwinds 4th and 5th like 3000+ or it lugs and fusses a little. Unless I'm basically coasting I dont even kick into 5th gear until i'm at 60-65mpg.

As far as lugging, if im putzing around town 3rd gear or 2 gear not even 2500rpm and it dont sound like its lugging.

It normally would not be lugging at 2500 RPM but out of sync carbs might just make over the line since the cylinders might be fighting with each other. In any case, you will find RPMs below 2500 will not give you good performance or good mileage. The Venture really picks up her skirts between 4000 and 6000 even right up to the red line.

 

Shifting at 7500 makes the front end bounce.

'03 RSV

 

I've noticed when loading the engine (low speed, high gear, throttle up) the engine vibrates a little. Not a big worry, just presumed I'm lugging the engine. Dropping a gear gets it back to smooth running.

'03 RSV

 

I've noticed when loading the engine (low speed, high gear, throttle up) the engine vibrates a little. Not a big worry, just presumed I'm lugging the engine. Dropping a gear gets it back to smooth running.

Yes, that's pretty much normal. I have ridden on the flat at 30 MPH in 5th without noticeable vibration. Applying throttle under those conditions requires a gentle and gradual touch though. Also, it requires more gas, ie: more throttle twist, just to get a small increase in speed compared to when using a lower gear. To me that indicates the likelihood of poorer gas mileage and is not the best choice for normal riding..