Alternator rotor - is this normal ??

[toravir]

On my 2008 Suzuki GS500F,

The alternator rotor slips on the engine crank shaft. Removing the rotor was quite easy - i located the possible problem - i see a rough surface at the contact area - where the shaft meets the rotor. I have attached a pic here.



I am guessing this rough surface the main problem. How do i go about fixing it ? some pointers i got was to put in epoxy, or a shim (really thin metal ring) or replace the shaft and rotor..

i bought this bike 3mos ago - so not sure whether this problem is an indicator for more problems. what are the likely ones ??

thanks,
ravi

[ben2go]

Lightly sand the rough areas with 600 grit wet/dry sand paper.Just enough to smooth things up.You will need to remove the starter clutch by removing those 3 allen bolts.When you reassemble,make sure everything is clean.There should be no oil on the shaft or inside the rotor where it attaches to the shaft.Install the starter clutch,using red loctite,and 15 foot pounds of torque.Install the rotor using red loctite and 96 foot pounds of torque.Let it set for about 15 minutes for the loctite to set.Pour a little oil over the starter clutch while spinning the gear.This will make sure the starter clutch and gear have oil on first start up.

[ben2go]

I should add that I am going through something like this with my bike.

Here's my thread. http://gstwins.com/gsboard/index.php?topic=56037.0

Verify that the ring gear spins on the shaft before reassembly.If it don't,replace the entire starter clutch assembly.Got mine at Bike Bandit online.If it does spin,make sure it only spins toward the rear after reassembly.I am going to do a starter clutch install thread when my parts get here.There will be pics.

[toravir]

thanks ben
Do you mean put red-loctite in the contact point of rotor/crankshaft ? I will put some in the bolt that goes in to the crankshaft as well.

how do i remove the three allen bolts that hold the starter clutch to the rotor ? It is really hard with a simple allen key.

[ben2go]

thanks ben
Do you mean put red-loctite in the contact point of rotor/crankshaft ? I will put some in the bolt that goes in to the crankshaft as well.

how do i remove the three allen bolts that hold the starter clutch to the rotor ? It is really hard with a simple allen key.

Red loctite on the bolt only.An allen key should remove them but the bolts will need to be torqued down at reassembly.

[toravir]

Didn't help - still slips. I polished the rotor and the crankshaft. Put it together with the red-loctite on the crankshaft screw. I must have let it sit for ~30mins for the loctite to set. After putting the engine oil in and started, it slipped Since the crankshaft has lot more smooth surface - am thinking of buying a new rotor and trying it on.

when i took it apart, the bolt was loose i was able to unscrew it with my hands (may be when the rotor was spinning, it helped unscrew it) - or shd i have waited lot more for the loctite to set ??

[moosehead28]

This happened to me as well after rebuilding my starter clutch,

You need to ensure the proper torque on the bolt holding the rotor on, which I believe is around 95 ft lbs, I dont have my manual with me, so you should double check that number

you should not be able to remove the bolt by hand if it is properly tightened, So there may be an issue with clearance on the crank

[ben2go]

This happened to me as well after rebuilding my starter clutch,

You need to ensure the proper torque on the bolt holding the rotor on, which I believe is around 95 ft lbs, I dont have my manual with me, so you should double check that number

you should not be able to remove the bolt by hand if it is properly tightened, So there may be an issue with clearance on the crank

Moosehead has it covered.96 foot pounds of torque is required to hold the bolt and rotor on.Anything less will let the rotor spin.There can absolutely be no oil or anything between the shaft and the hole in the rotor.You should have loctite from 3 threads from the end of the bolt up to the last 6 threads before the shoulder on the bolt.It kind of sounds like the rotor bolt may be bottoming out and not putting enough torque against the rotor snout.Even tho the rotor bolt is grade 9+,it will still stretch ever so slightly with all the torque needed to hold it on,so measuring it probably won't help.If you try a new rotor,get a new bolt as added insurance against having a weak bolt.And please,make sure that bolt is torqued down to 96 foot pounds.

[toravir]

Thanks ben, moosehead. I tightened it to ~85+ Ftlbs - didn't have enough strength to tighten more... and let the red loctite sit for 24+ hrs. It runs fine now.

Thinking back, i think it is entirely up to the bolt to hold the rotor to the crankshaft. The contact surface between the rotor and crankshaft is not subject to much pressure.

[The Buddha]

Most bikes have a woodruff key between the tapered crank and the rotor... but then most of those bikes also have the ignition timing on it.
To make an ignition advancer you need to make an offset woodruff key, and an sv ignition advancer costs lie $50 and you get this tiny thing about like your thumb nail clipping.
Cool.
Buddha.

[sledge]

Its the taper that provides the grip between the rotor and the crank. If the rotor has broke free and spun on the crank the tapers will be scored and wont provide enough interference to hold the rotor tight. The male and female tapers need to be lapped together otherwise torque, heat and inertia will eventually cause the rotor to loosen off

You need a dab or two of very fine valve grinding compound on the taper, hold the rotor on the taper and spin it 180deg each way under moderate pressure until you get a nice dull grey finish all over. You probably wont remove all the scoring but you will remove the highspots and it will result in a tighter and better fit. When you are satisfied with the result remove ALL traces of the grinding paste with petrol.

If you dont relap the tapers this way your rotor WILL loosen off again in the near future regardless of how tight the bolt is or how much locking compound is on it.

[toravir]

@Buddha: Are you referring to this: http://gstwin.com/ignition.htm ? Am a newbie to engine mechanics, could use some more details on understanding how to have this woodruff key and avoid this problem in the future.

Most bikes have a woodruff key between the tapered crank and the rotor... but then most of those bikes also have the ignition timing on it.
To make an ignition advancer you need to make an offset woodruff key, and an sv ignition advancer costs lie $50 and you get this tiny thing about like your thumb nail clipping.
Cool.
Buddha.

[sledge]

Woodruff or parallel keys serve only to index the rotor or flywheel to the crank for ignition timing reasons, they dont transmit the torque between the rotor or flywheel. This is done by the taper and is why the male and female halves MUST be a perfect fit to function reliably.

The ignition advancer on the GS is indexed with a pin fixed parallel to the axis of the crank.......not a woodruff key

[starwalt]

~A collective gasp comes from the audience with wispers of 'I thought he was dead!' ~

Was the rotor holding bolt tightend to spec after you removed it and the rotor?

Being tapered the only way it could be slipping (assuming it is not totally shot) is if it is not pressed onto the shaft properly AND the bolt not to spec 79.5 to 94.5 lb-ft, 110 to 130 Nm.

Perhaps this is not the original bolt and someone put one in that is too long and it bottoms out before the rotor is corrrectly pressed on?
That is speculation only. Usually these suckers are a bear to get off a crank.

Sledge's advice looks like the best recipie for repair without replacement of all parts.

[sledge]

Hello Doug

Are we about to see the greatest comeback since Lazarus 

[The Buddha]

Yeaaaaaaayyy ... starwalt is back.
How you been my friend. Still in SC ... may just have to get over there one day and bug ya ... coming to think of it, haven't bugged darrell in a while either.
Cool.
Buddha.