Something odd I noticed (timing)

[cobrasneverdie]

Hey guys, this is regarding a hughs pma
when I installed it I torqued the flywheel to specs. My little brother was helping me out... that guy and his fragile muscles. Anyways that was last year, this year I noticed that the timing marks changed... Am I wrong to assume that a) maybe I didn't torque it hard enough b) this bike is causing so much vibration that it jiggled the bolt out of place and now the timing mark is off...?

I'm gonna try and find a way to find tdc and start from scratch

 

[scabber]

If you are not using the key it can move.

 

[cobrasneverdie]

the installation says wood ruff key has to go...

 

[I am Carbon]

well if the key is not in and it is not torqued 25 to 29 lbs the flywheel can and will move.
the woodruff can be installed with some filing it can be a challenge

 

[scabber]

I don't why Hugh would tell you to not use the key since it a fool hearted thing to do and totally wrong especially since timing is so important. Yamaha put a key slot in the banshee flywheel and rotor to prevent movement. WHY ???. is this important you may ask or not. Since things in motion tend to stay in motion my guess is to prevent it from backing the nut off. He should have had some keys made or not tell you to omit it. You are not alone Carbon had the same thing timing mark off. Put a key in it do it right and don't blame your brother.

 

[mrriggs]

If the taper is tight then a key is not needed. They key is only meant to line things up for assembly, the taper is what holds it after assembly. If the taper on the rotor does not perfectly match the taper on the crank then you will not get a tight taper fit and it could possibly move.

To check the taper, remove the rotor and color the crank taper with a Sharpie®. Stick the rotor on the crank and turn it so it's rubbing on the crank. Remove the rotor and see where the Sharpie® marks are rubbed off. Ideally, you would want to see the entire taper rubbed clean.

If the taper is good then I would think you didn't have the nut tight enough. If the taper is off then you need to fix the taper, or Band-Aid® it by sticking a key in there.

 

[cobrasneverdie]

haha I was joking around about my brother, I probably didn't tighten far enough. I still do have the key. So it'll be good to go back and re do it again.

Thanks for the info guys,

 

[scabber]

Since the banshee fly wheel really does not have to lineup with any thing. Your explanation for the reason Yamaha used the key has little merit in this case. In a perfect world nothing ever vibrates and nuts never loosen on a Yamaha. Tapers are used for quick installation in assembly line situations another example for its use. I made a valid point as to why to use a key. It makes no difference to me if one way or another if you use a key or not.

 

[mrriggs]

Since the banshee fly wheel really does not have to lineup with any thing. Your explanation for the reason Yamaha used the key has little merit in this case.

On the Banshee, the rotor is also the crank trigger, so it has a keyway.

Look at the rotor from a bike that has a separate crank trigger (like the VF500) and you will see that it has no keyway.

 

[650performance]

You can always use Loctite as an added precaution. I have an ARD rotor with no key on the crank taper and it has never slipped.

 

[scabber]

Thanks for pointing that the banchee was a crank fire. Mrriggs I did not know that or would not have made the comment. I apologize if I offended. How does the fly wheel trigger the ignition? I still think it is a good idea to use the key even if it might not be deemed totally necessary. It does serve a purpose other than just line up. Even though the nut might not have received the proper torque. The flywheel might not have moved with the key installed unless it sheared. My train of thought was vibration and inertia was a factor in the nut coming loose since it is not a left hand thread.

 

[Machi]

I put a PMA in mine and managed to include the key, even though I agree that it may not be needed.
But - its a bitch to get that little sucker to line up and hold still during installation of the flywheel!
I set in place with loctite and a slight angle up towards the back, and let it dry over night. Then carefully eyeballed the flywheel going in and cranked it down to specs. No problems so far.

 

[XSLeo]

On my Honda CM400 it has a separate winding on the stator that sets out side the flywheel. As the magnets in the flywheel pass this winding a signal gets sent to CDI to tell crank position.
The flywheel needs the key to have the magnets pass the extra winding At the right time.
I assume most crank triggered ignitions use a similar set up.
Leo

 

[mrriggs]

I just had a chance to check the taper fit of an "aftermarket" PMA rotor. It pretty much confirms my suspicion of why some people have had trouble with them moving.

 

[mrriggs]

After an hour and a half of hand-fitting it.

 

[Brian902]

Are you using valve grinding compound to do that?

Aftermarket PMA's also have a tapered grove for the key way which means the original key needs to be modified to fit.

My PMA was only about 1 mm deep at the key end and 3 mm deep at the outside end. The original key is 2 mm above the taper shaft.

PMA has 5 mm key with, original key is 4 mm.

I used a modified aluminum key just for security to hold the rotor's position.

 

[cobrasneverdie]

Thanks for the visual on the sharpie, I was a bit confused but now I get it.

I'm glad I didn't throw the key out so I'll have to work on this next year.

 

[mrriggs]

Are you using valve grinding compound to do that?

I started by taking the high spots down with a bearing scraper. Then lapped it with a 50 grit compound.

 

[kopcicle]

I started by taking the high spots down with a bearing scraper. Then lapped it with a 50 grit compound.

For obvious high spots I "peen" down with a small hammer with the end of the crank supported . Like Brett I check and file and check and lap and wash , rinse , repeat .I'm fortunate that I have an electric motor builder that can balance smaller rotating parts so the rotor isn't that big an issue . However a witness mark and a trial install will occasionally show some run-out . Lapping straight is a bit of a pain but worth it . Don't confuse crankshaft run-out with rotor run-out . check the crankshaft first , then the taper , then the installed rotor . I do NOT recommend Lock-Tite on the taper OR the threads of the retaining bolt . If recommended torque does not keep the bolt or rotor from turning then something else is wrong .

~kop