Handlebar Vibration At 45-50Mph... Help!

So I recently replaced my front fork springs and swapped my OEM shock with an F4i shock.

Bike: 2006 VFR800

I weigh 220lbs

Front springs are .95kg/mm

Rear spring is rated at 1200 lb/in

I was able to get the rear dialed in quite nicely. Compression and rebound damping seem to be working as they should.

The problem is the front of the bike. Overall, the suspension feels great. However, at 45mph I get a moderately violent vibration in the bars. I would say the bars shimmy back and forth within about a half inch of travel. Like i said previously, its really only noticeable around 45-50mph.

I suspected it was the valving on the forks (Oem forks with no external adjustment capabilities), so I swapped the oem 10wt oil with 7wt oil. This did not fix the vibration issue.

Spacers for the new springs were appropriately sized via the previous spring/spacer measurements. Oil level is dead on at 100mm.

Recently had new tires mounted and balanced. Dosen't look like any wheel weights have fallen off.

So.... any insight on what's causing this vibration? Overall the suspension feels great but when I take my hands off the bars around 45mph it gets REALLY shaky.

Thanks in advance  :beer:   

Have you checked your head bearings for wear? Worn bearings produce precisely those symptoms. New suspension unmasks formerly "hidden" issue?

I agree, the symptoms do sound like a steering head bearing issue. However I checked the bearings for free play when the front wheel was off and it felt solid.

My '09 (7,000mi.) is doing the same thing, noticeable on deceleration around 55-45, hands off.  Not noticeable with hands on. Only started happening after installed new tires.  It has to be the tires, nothing else has been changed since bought new.  What's the cure??

What kind of tires? I'm on a brand new set of Diablo Ross II's. I'm going to double check my steering head bearing again. Make sure it's not too loose. I'm also going to take the front wheel back to the shop and have them re-balance it. As max noted, the problem may have been masked by the old tires or old suspension setup.

Dunlop Qualifier Performance tires.  No high speed vibration detected. Just that window of speed when slowing down and taking hands off bars. Wasn't there before, it is the tires or the way they are mounted, ie, non-perfect bead seat, surely.

I have the exact same problem on a 2007. Only it has been there since I bought it, and it is only noticeable with hands off the bar, so it doesn't bother me too much. But if I get up to an indicated 100 (which is more like 85 mph in reality), the head shake returns, more noticeable through the bars at this speed. Since I rarely go that fast I don't worry too much about it. It has been this way over about 10,000 miles with no change, despite balancing original tires, installing a new full set of tires, and just this weekend, installed 0.90 kg/mm springs (did not touch anything else up front) and a 1150 lb F4i shock from Jaime.

It may be possible that you had it all along and never noticed it. I only noticed mine when I let go of the bars at that speed. I bought the bike with 1,500 miles on it, and it did it then - I don't know what the previous owner could have done to it to ruin the steering head bearings in only 1,500 miles. It's not like this bike is a wheelie monster.

I have this exact problem as well. There is no play in the head bearings, but there is a definite "flat" spot on them. With the bike on the centerstand, sit on the bike so that the front wheel is off the ground. Starting from center, slowly  turn the handlebars one direction to lock, then all the way to the opposite lock. Do this slowly. If you feel any spot that are "notchy" then you need to replace the headbearing from what I am told.

I discovered this problem after taking the front wheel off to be powder coated. I had the front of the bike hanging by the top yoke via straps to the rafters. Dumb I know. My own fault.

I had this before re-spring and re-valve forks and F4i shock, but we also replaced the steering head bearing with All-balls tapered...the shake was gone after the work was done.

+1 on the tapered bearings. Cant tell you how many VFRs and GL1800s I have seen with the same list of symptoms and occurring after a tire and suspension overhaul. I think it becomes noticeable after fork and shock work because we are usually altering the setup to accommodate rider weight better, which shift load onto the front. Mine was only noticeable after an Ohlins instal and raised rear ride height. Felt a little notch in the bearing, swapped them for a set of all balls tapers and its back to perfect. The only tradeoff is a very slight, almost imperceptible increase in steering effort at low speed. But the front feels more stable and confident, and the shake is gone. They should have come this way, as the CBRs do.

So.... any insight on what's causing this vibration? Overall the suspension feels great but when I take my hands off the bars around 45mph it gets REALLY shaky.

Thanks in advance  :beer:   

You are experiencing a deceleration shimmy and it's normal... some
bikes shimmy decelerating through the 45 mph range... keeping your
hands on the bars should arrest most of the front end shimmy... some
bikes shimmy more than others and it's no big deal with your hands on
the bars in the critical speed range... your bike should be immune at
speeds above 45 mph...

Deceleration shimmy is chiefly the product of non OEM or a worn
tires... it ain't the product of tire cupping... but low pressure or
loose steering head bearings defeat the tire's corrective efforts...
because every bike has this instability... it is held in check by
damping forces created mainly by the tire's self-correcting
tendencies...