Driveshaft phasing

Beebop · Jun 10, 2021

Hi Guys.
2004 GS Adv, 183000km.
How far out is acceptable for the driveshaft phasing ?
The adv has the key, so I cant change the orientation, but
I have noticed that it doesnt align 100%. There is about
30 degrees offset. I do have a speed related vibration, and
this may well be the cause.
Just to add some history, at 100000km the front universal failed.
I sourced a damaged shaft from someone, which had a good front universal.
I had a propshaft shop turn off both shafts, and reweld to make one
good shaft, which I have now used for the past 83000km. Both universals
still feel fine, but I'm concerned that the phasing is causing the vibration.
Is 30 degrees going to give me the problem, or do I look elsewhere ? The
vibration is only evident when I run above 160kmph.
Thanks for the support you guys offer.
Cheers

Steptoe · Jun 10, 2021

Beebop said:
2004 GS Adv, 183000km.
The
vibration is only evident when I run above 160kmph.
Thanks for the support you guys offer.
Cheers

I just cracked a rib laughing .... At that speed on one of these old barges I’m surprised it hasn’t shaken to bits... it’s been so many years since I last rode my 1150 over 100mph I can’t even remember if it vibrated or not.

theoneandonly · Jun 10, 2021

mine vibes @ 4250 rpm in top .

the uj's on the shaft should be aligned with each other. ( same as Guzzi's )

Steptoe · Jun 10, 2021

theoneandonly said:
mine vibes @ 4250 rpm in top .

the uj's on the shaft should be aligned with each other. ( same as Guzzi's )

The later factory keyed/indexed shafts can only be fixed in one position and can't be altered.. The two joints are slightly off but doesn't seem to cause any vibration.

theoneandonly · Jun 10, 2021

see , you learn so much here.

Wrigsby1 · Jun 13, 2021

Steptoe said:
I just cracked a rib laughing .... At that speed on one of these old barges I’m surprised it hasn’t shaken to bits... it’s been so many years since I last rode my 1150 over 100mph I can’t even remember if it vibrated or not.

Ha ha

On all the Oilheads I have had they are only OK up to the ton and then you run out of patience... When they were new out and I sold them I remember getting 120 out of an 1150RT on the A38... About a mile 1 1/2 run up, all the revs and downhill...

She's gonna blow captain...

Hay Ewe · Jun 14, 2021

If they are keyed, but about 30° out, and you say you got the foward section from some where else, then i suspect thatbthe shaft is made as a matched pair.
Conseqently, yiur two halves are not matched.

I suggest that you need another complete drive shaft assembly that has both halves as original matched.

By not having them matched, the output rotational velocity is accelerating and decelerarating with each rotation and a) causing the vibration b) not be mechanically sympathetic to the bearings.

When i first pulledbthe drive shaft from my standard gs, i didnt know about phasing, it would fall in to a corner and be harder to go the other corner. I dont remember which way it ws, as in did it fall into the right or left.

Ian J Hartley · Jun 14, 2021

Maybe the reason for the slight miss alignment, is because of the the bonded rubber joint, which will flex slightly under load, which it is supposed to do, and when I does, it will bring the drive shaft into phase.

The drive shaft has to be in phase under load not static…… :rob

Steptoe · Jun 15, 2021

Ian J Hartley said:
Maybe the reason for the slight miss alignment, is because of the the bonded rubber joint, which will flex slightly under load, which it is supposed to do, and when I does, it will bring the drive shaft into phase.

The drive shaft has to be in phase under load not static……

But the load is variable - accelerating from standstill to cruising at a constant speed impose different loads. I doubt the bonded section gives that much. The factory indexed shafts don’t align perfectly. A few years ago I posted a picture of an indexed shaft laying on a flat surface showing how the two U/J’s weren’t phased 100%

gog · Jun 15, 2021

stop worrying, at 100mph on an oilhead, theres gonna be some vibration

my 1100 has a vibe @ 4k rpm, but it goes away again around 4.2k. mate's is the same.

Driveshaft phasing

Beebop

Registered user

Steptoe

What a waste.

theoneandonly

looking over the edge

Steptoe

What a waste.

theoneandonly

looking over the edge

Wrigsby1

Well-known member

Hay Ewe

Active member

Ian J Hartley

Well-known member

Steptoe

What a waste.

gog

Well-known member

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