What might cause vibration ?

[HWB]

Just wondering my bike is vibrating after a new build. I dont not take the engine out of the frame so there are no loose engine mount bolts, vibration is pretty strong to the point when i come off the bike my hands are all tinkly and still with feeling of vibration, under accel my whole head vibrates and my vision sometimes gets fuzzy because of it.

Mighy it be cams ? Or is it just like that bcz of the hi comp build and the way the cams are timed ? 

I dont think flatslides doe tgat either..right ?

[Gixer1460]

If you are experiencing those symptoms after just (what sounds like) a top end build - then you have some MAJOR problems. You haven't given much away as to what you have actually done ? ? ? Cams - No! High Comp - V unlikely! Cam timing - again unlikely unless really wrong, then engine wouldn't run! Flatslides - maybe but you'd notice that before riding! More info required!

[Swiss Toni]

You did put tyres on the rims, didn’t you???

[imago]

As @Gixer1460says, not much info to go on. So my first guess/question would be, are you sure it's running on all four cyls? If one was down it'd still tick over reasonably well, but anything above that and you've basically got a half kilo flyweight not timed to anything in particular.

[Dezza]

What bike is it? When you re-fitted the exhaust does it clear the sump as it should? If it touches this can cause weird vibration.

[HWB]

Heres the specs, 748 D,ot head ported with flush cut guides on 1127 barrels cams timed at 105°/105° 38mm brand new 38 flatties with ramair ontop 55mm velocity stacks.pingel dual output. Dyna 2000 ignition set at true 40° on degree wheel, ohlins rear, adjustable bones, yosh full system (clears the sump, had ot for 13years+ now) bridgestone r10r set, EK chain well maintaned had about 10k kms on it so fairly new, brand new silicone spark wires. Domino grips, barracuda light weight bar ends, hayabusa 2018 master clutch, gsxr 2014 master brake, earls front braided brake lines, earls braided clutch line. And some stickers for added hp 

Edited December 21, 2022 by HWB

[Gixer1460]

New grips / bar ends? - usually good for hand felt vibes, but yours sounds more serious if affecting vision ! Has it been dyno'd or is it guestimated tuning?

[Duckndive]

Did you dry build and check valve to piston clearance before final assembly 

[HWB]

1 hour ago, Gixer1460 said:

New grips / bar ends? - usually good for hand felt vibes, but yours sounds more serious if affecting vision ! Has it been dyno'd or is it guestimated tuning?

Not dynoed yet

[bluedog59]

Lightweight bar ends ? The stock ones are that weight for a reason.

Put the standard ones back on and go for a ride. At the least it will show if they are (not) the cause of some or all of the problem.

[HWB]

3 hours ago, bluedog59 said:

Lightweight bar ends ? The stock ones are that weight for a reason.

Put the standard ones back on and go for a ride. At the least it will show if they are (not) the cause of some or all of the problem.

Been on the bike way before the build, didnt have that problem before so its not that

[george 1100]

15 hours ago, Duckndive said:

Did you dry build and check valve to piston clearance before final assembly

This 

[HWB]

27 minutes ago, george 1100 said:

This 

I did not. Stupid i know, but the engine turned over by hand smoothly so i took the go.

Are ylu suggesting the pistons kissing the valves ? Wouldnt that have broken the engine by now ? It has 4k kms on it already

[Gixer1460]

2 hours ago, HWB said:

I did not. Stupid i know, but the engine turned over by hand smoothly so i took the go.

Are ylu suggesting the pistons kissing the valves ? Wouldnt that have broken the engine by now ? It has 4k kms on it already

Well, if you are running guestimated fueling over 4k kms and excessive fuel has worn the rings to allow excessive rock, then yes the pistons could be kissing the valves but I still don't see vibration - noise yes but not vibes. Something is broken / out of balance to cause those sort of vibes. Is this suddenly or long term?

[coombehouse]

Is the vibration engine speed related or road speed related?

If it's road speed related, then it could be a problem in the transmission, chain or wheels.

[HWB]

4 hours ago, Gixer1460 said:

Well, if you are running guestimated fueling over 4k kms and excessive fuel has worn the rings to allow excessive rock, then yes the pistons could be kissing the valves but I still don't see vibration - noise yes but not vibes. Something is broken / out of balance to cause those sort of vibes. Is this suddenly or long term?

No mate, fueling at idle is at 14.7 afr measured with an AEM afr guage, at full throttle it goes about 12. So mostly perfect for a carbureted bike.

 

Vibration is strong from idle at standstill till about3,4k goes away comes back a bit at the top.

Guessing loose valve clearances ? Crank slapping the tappet ?

[Swiss Toni]

This is a bit of an enigma! If the vibes are bad enough to effect your head, and give you Tingly fingers, there’s something drastically wrong somewhere! There’s got to be something touching the frame to transfer the vibes upwards?
But what???

[TonyGee]

im probably talking shit but could it be the fairing vibrating and sending it back through the frame ?  i know they can vibrate and be noisy ????    

[george 1100]

11 hours ago, HWB said:

I did not. Stupid i know, but the engine turned over by hand smoothly so i took the go.

Are ylu suggesting the pistons kissing the valves ? Wouldnt that have broken the engine by now ? It has 4k kms on it already

It's possible. Also maybe cam timing is out. Did you use slotted cam sprockets? Bolts may have worked loose. Bent rod or rods maybe. Piston may have smacked the head

Was it there from day one or did it gradually appear or suddenly appear. How was it performing?

I'd be taking the valve cover off for a looksee and checking comp as a starting point 

Edited December 22, 2022 by george 1100

[Swiss Toni]

Personally, I just wouldn’t ride it! You’ve done 4K on an engine, that from the outset, you said wasn’t right. You’ve spent a lot of money on the spec, why risk it all? Go through it methodically, from the top down. Find the problem, and fix it. One step at a time. There’s no getting away from it.

But, look for the obvious first! You’ll get there!

[HWB]

Ok so did a compression test and all is well, readings are 180 psi for all 4 cylinders except cyl 4 185 psi so all good. Sparks look good too! 

Ill be taking the cover off soon to check cam sprockets as george said but i highly doubt the have moved since when i built the engine and did a comp test i also had 180 all over except cyl 4 185 so its exactly how it was. Changine cam timing will change comp readings, so thats not it probably. Last thing would be valve clearances. That would conclude that its not an engine thing.

Carbs are balanced but lets just argue imbalanced carbs might cause it ? 

[HWB]

[Dezza]

Putting a dot head on an 1127 engine is going to raise and alter the angle of the carbs. When the tank goes on, is there still clearance under the fuel tap, under the tank, or for the throttle cable bracket? If something is touching the base of the tank this can result in weird vibrations.

Edited December 23, 2022 by Dezza

[HWB]

I modified the tank so everything fits, it wasnt that way but everything is now ok, i will check again tho, velocity stacks are way way too close to the frame, maybe with engine on its touching ? Will check thanks

[Oilyspanner]

Your head and vision problems maybe due to the open carbs,  even with foam filters, my flatslide carbs are deafening above half throttle and 6k revs - earplugs are a must for spirited rides.  You could check all the engine mounts for tightness as well as the other suggestions.