I'm I unbalanced?

[GuzziNZ]

My 850T has a fully reconditioned motor which included getting the crank, rods, pistons etc dynamically balanced.
I am test running it now and can feel a pronounced vibration come in at around 3000 rpm, by 4000 is is gone.
Ignition and throttle balance are spot on .
Normal or not?

[GuzziNZ]

Maybe I should have Googled first ad it seem like vibs below 4 grand are pretty normal even after balancing is not usually.

[guzzisteve]

I would get it broke in 1st, then reevaluate. See if it does this under load going down the road.

[GuzziNZ]

Its under load or coming down through 3000 rpm with throttle closed. Also sitting on stand as you slowly coming up from idle and pass 3000.
Mirrors are useless at any RPM.

[guzzisteve]

I would let the folks know that balanced it, might get a rebate. OR  Drop your pan & drill a hole in ea flyweight till it's smooth (not to be taken as what I'd do)

[moto]

So, not pretending to be an expert, there is a balancing factor that is used when doing the job. I think it's a certain percent of something or other. What factor value did your mechanic use? What factor is recommended by the knowledgeable ones on this site? Using a factor that is not appropriate for the T engine could produce bad results, I reckon.

EDIT: Maybe getting a dynamic balancing job obviates my concern. In which case, never mind.

BTW, my very similar T3 motor doesn't exhibit the problem.

[Tom]

Sounds normal.  Maybe check for the carbs being balanced.  Mixture etc.

[Antietam Classic Cycle]

I would let the folks know that balanced it, might get a rebate. OR  Drop your pan & drill a hole in ea flyweight till it's smooth (not to be taken as what I'd do)

In my experience (and the shop that balanced - past tense, they will no longer do Guzzi cranks due their hardness) drilling a hole in a Guzzi crank with a hand drill no matter what drill bit is next to impossible. Even with Artu drill bits, it still takes considerable pressure to even start the cut.

Not only that, every time I've had one balanced it needed weight added to the counterweights, not removed.

[GuzziNZ]

Carbs were balanced with a carbtune at idle and 4000rpm.
Ignition by strobe set for full advance at 6000rpm.
Vibration can be felt on closed throttle going down past 3000 so mixture shouldn't be the problem.
What I found out was the balance factor was initially 50% for the V twin but changed to 52% in later model supposedly making a smoother motor.
You also have to add 26 or 27 grams to the sludge trap in the crank to make up for the oil weight.
I worked this out at 22 grams so not sure who is correct.

[wirespokes]

My 850T has a fully reconditioned motor which included getting the crank, rods, pistons etc dynamically balanced.
I am test running it now and can feel a pronounced vibration come in at around 3000 rpm, by 4000 is is gone.
Ignition and throttle balance are spot on .
Normal or not?

What was it like before reconditioning?

As I recall, all of my bikes are very smooth, even the G5 with new Gilardonis. But then again, it's possible there's some vibration around 3K, but nothing that bothers me. Evidently not enough to be irritating.

When the crank was balanced, was weight added? What was changed?

What was done at the rebuild? Just new rings, or everything?

[TN Mark]

Many years ago I had the pistons, rods and crank of a 1978 G5 motor professionally balanced by a speed shop in Costa Mesa, CA.

That engine was amazingly smooth. I joked at the time you could start it on the center stand and rev it with a wine glass on the seat and it wouldn’t fall off.

That bike and motor was simply exceptional.

[Mr Revhead]

Given its only in a set RPM range I don't think it'll be balancing otherwise It'll get steadily worse as rpms rise.

Is your advance correct?  6000rpm seems a bit high.
I thought full advance was by 4000? Maybe that's the vibes,. Stumbling around 4000rpm as too retarded?

Edit: just checked Guzziology, full advance should be 4500rpm on the T

[Frenchfrog]

Was the flywheel ,clutch and starter motor ring gear balanced too along with the alternator rotor ?
When my engine was done all of those were checked too and needed some rectification.

[GuzziNZ]

Hi Frenchfrog, Everything from alt rotor, New 83mm pistons and flywheel was sent with the crank and rods.
Will try resetting the timing at 4500 full advance and see if that helps.

[GuzziNZ]

Can someone confirm the weight of oil in the crank sludge trap that should be used when balancing?

[Antietam Classic Cycle]

Can someone confirm the weight of oil in the crank sludge trap that should be used when balancing?

From the late Charley Cole:

Be sure to tell your balance guy to add 27 grams to the crank pin weight during static balancing. That is how much oil by weight is in your crank pin while your engine is running, but it is not there during static balancing. That's a pretty big balance error, if that is not included.

[Huzo]

Dunno mate, but could you fix the thread title ?