Micha7el
XS650 Enthusiast
How to press the PMA back on the Crank shaft , with motor in the bike ??
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How to press the PMA back on the Crank shaft , with motor in the bike ??
- Thread starter Micha7el
- Start date
The crankshaft is tapered with a woodruff key. No pressing required.
Just to clarify...........Some PMA sellers do not use with, or install their PMA's using a woodruff key. These PMA's have to be secured is such a way as not to be able to spin on the Crank shaft.................
mike in idaho
XS650 Addict
You tighten the nut, the taper is what keeps things from slipping. The woodruff key is basically there to time the rotor to the shaft.
It would not hurt to lap the rotor to the shaft with some valve grinding paste. This will help it stay put if you are not using a key.
I've seen a few aftermarket tapers that were quite crude and not suitable to create the "stick" a taper needs to work properly. If they can't machine a decent surface what are the odds they got the critical taper angle spot on?
exactly ! and whilst I have no doubt that Skull is correct in his statement ,I am curious to know what other methods have been employed .?
It would be madness to fit a heavy rotating component like a alternator rotor to a tapered shaft without a woodruff key or at least some machined method of preventing it spinning on the shaft.
From Hughs handbuilt PMA instructions
http://www.hughshandbuilt.com/2012/03/01/install-hughs-handbuilt-pma-system-xs650/
"See this woodruff key? It’s no longer needed, pull that sucker out! Sometimes it will come right out, other times you will need some pliers/vicegrips to grab it. I had to use Vice Grips today. Get that sucker out of there! (Previous install threads mentioned making a whole new woodruff key, but you won’t need to do so. All the woodruff key does is locate the OEM rotor on the crank for timing mark reference."
In my experience a woodruff key is a safety pin to stop a rotating mass slipping on its axis. It is not only a precaution but a necessity in case.
So when i read statements to the effect, it is not a necessity and only used as a a reference tool, then this information from inexperienced self called engineers with big followings is not only dangerous it is also reckless
http://www.hughshandbuilt.com/2012/03/01/install-hughs-handbuilt-pma-system-xs650/
"See this woodruff key? It’s no longer needed, pull that sucker out! Sometimes it will come right out, other times you will need some pliers/vicegrips to grab it. I had to use Vice Grips today. Get that sucker out of there! (Previous install threads mentioned making a whole new woodruff key, but you won’t need to do so. All the woodruff key does is locate the OEM rotor on the crank for timing mark reference."
In my experience a woodruff key is a safety pin to stop a rotating mass slipping on its axis. It is not only a precaution but a necessity in case.
So when i read statements to the effect, it is not a necessity and only used as a a reference tool, then this information from inexperienced self called engineers with big followings is not only dangerous it is also reckless
Absolutely right!!! A woodruff key is much more than an indexing tool.
Not sure of Hughs app. on his ignition I can only speak of what I have used and sold for the last `12 years or so. I use the Powerdynamo ignition. the rotor is also tapered and doesn't use the key. Never had one come loose, it is a good idea to make sure the crankshaft is clean. Maybe I just got lucky for 12 years or maybe proper installation is the key. Have at it boy.
What ever way you go make sure the securing nut is in good condition. I have had trouble with a Yamaha LC 350 rotor on an XS coming loose. It did have a key but the thread in the nut was stretched and the rotor came loose at high RPM. Not a show stopper but could have been. Fitted a different LC rotor, lapped to the shaft with no key and new nut all good so far, but will be checking it.
I don't understand why anyone should advocate removing an important safety component ?
its been deemed to be essential for high speed tapered shafts for the past 100+ years so why all of a sudden is it considered non essential . Maybe all the engine manufacturers have been wrong all those years and wasted money and time cutting keyway slots on tapered shafts for woodruff keys.
I can see that fitting a brand new rotor to a brand new crankshaft that have been machined together for a matched perfect fit at manufacture could work but advocating fitting a replacement rotor to a 30+ year old crankshaft taper with old threads and nuts by DIY fitters in their sheds with no key .............Why ?
If you'd ever seen the carnage caused by a high speed tapered crank or keyway failure where the rotor has spun and come loose at speed I don't see why you'd risk the danger for the sake of re-fitting a 2x cent component.
its been deemed to be essential for high speed tapered shafts for the past 100+ years so why all of a sudden is it considered non essential . Maybe all the engine manufacturers have been wrong all those years and wasted money and time cutting keyway slots on tapered shafts for woodruff keys.
I can see that fitting a brand new rotor to a brand new crankshaft that have been machined together for a matched perfect fit at manufacture could work but advocating fitting a replacement rotor to a 30+ year old crankshaft taper with old threads and nuts by DIY fitters in their sheds with no key .............Why ?
If you'd ever seen the carnage caused by a high speed tapered crank or keyway failure where the rotor has spun and come loose at speed I don't see why you'd risk the danger for the sake of re-fitting a 2x cent component.
Peanut, there IS a scenario where a tapered shaft woodruff key isn't used, and that's on lathe tooling, like the Morse tapers. I'd rather the taper slip before destroying a lathe spindle or tailstock.
However, it'd be a pretty serious condition that would lead to where having a slipping rotor could save a crankshaft on a bike...
However, it'd be a pretty serious condition that would lead to where having a slipping rotor could save a crankshaft on a bike...
It's a somewhat belt and suspenders argument. Like 2M sez; Machinists have been using tapers with no key for decades. Many tools on lathe and the drill press don't even have a threaded retainer, while milling machine tooling has a drawbar to make sure the taper is held tightly. Higher performance mills and CNC machines do have drive dogs to handle the loads.
When installing an aftermarket rotor with somewhat funky dimensions to an XS crank, I spent some time enlarging the rotor slot to accept the key. That was a pamco bike, so rotor timing marks are just a convenience. Will mention that while lapping seems expeditious, the lapping compound will not distinguish between removing material from the crank or rotor........... 2M has great video on grinding (cleaning up) a taper in the lathe to precise tolerance.
When installing an aftermarket rotor with somewhat funky dimensions to an XS crank, I spent some time enlarging the rotor slot to accept the key. That was a pamco bike, so rotor timing marks are just a convenience. Will mention that while lapping seems expeditious, the lapping compound will not distinguish between removing material from the crank or rotor........... 2M has great video on grinding (cleaning up) a taper in the lathe to precise tolerance.
Oh, yeah, the infamous ER-32 collet "nightmare taper project".
https://www.hobby-machinist.com/threads/retrofit-er-32-collet-chuck-to-an-atlas-craftsman-618.25476/
https://www.hobby-machinist.com/threads/retrofit-er-32-collet-chuck-to-an-atlas-craftsman-618.25476/
I have very little experience with lathes beyond metalwork at school where I vividly remember starting up a lathe with the chuck key still in the chuck.
I think the sort of rapid acceleration and deacceleration of a motorcycle engine with poorly matched shaft and rotor and small thread and nut fixing is a very different situation from a lathe where even if the taper slipped the piece couldn't fly off because its held in by chucks both ends but as I say I've no knowledge of lathes
So many ignitions do no use keys. the old ARD, PVL , ELECTEXWORLD. I have used all of them for racing ( no rapid acceleration there) and never had one come loose. I have even had the 1/2 starter nut we use to remote start come loose but the rotor does not. SO I would not call it a safety feature.
I have run an xs650 bought new in 75 and ran until 84, and it ran with points. Always ran great, but I would never go back there after running the Powerdynamo. set and forget.
And I ask all you guys who never used one to try one. With all due respect. Don't talk about something you never used.
I have run an xs650 bought new in 75 and ran until 84, and it ran with points. Always ran great, but I would never go back there after running the Powerdynamo. set and forget.
And I ask all you guys who never used one to try one. With all due respect. Don't talk about something you never used.
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Getting a bit upset there hooser................Check your spelling WADR, and telling othesr to STFU ????. Is that how you talk to your customers.............lol
so do you fit your xs650 alternator without using a key ?
All of the ones I mentioned. They come not keyed.
