Please help ! Magnet length on alternator rotor between versions

[Mach]

Got an used alternator rotor and it seems different only on the magnet length (starter clutch works fine), does this matter ? Need help fast because i need to return it in case it's not appropiate:

Left: Used and working (model unknown, chrome engine)
Right: Mine, broken (model 2004 gs500F)



Thanks in advance and sorry my mediocre engrish

[sledge]

Return it, its not from a GS500E, least not the `89 onwards GS500E.

THIS GS500E did have a chrome engine though, maybe its from one of them  .......Are there any part numbers on it?

 


If you are swapping flywheels I suggest you lap the tapers together to make sure they seat correctly.......but that's up to you 

[adidasguy]

Looking at you past posts, the epoxy on the ends of the magnets is not important and often some of it falls off.
If the 3 bolts holding the starter to the assembly came loose, you can replace those bolts and you are good to ride again. Once in a while they have come loose.

It is possible that the magnets changed length slightly or there is a different amount of epoxy on the ends of them. The assembly is the same from 1989 to the present. I would not be surprised with a slight difference in the length of the magnets, as they would have come from different factories over the years.

The critical dimension is the inside diameter. That makes the clearance between the magnets and the stator.

The older GS500 was called a GS500E (pre-1989) and that causes confusion. You can check the part number of what you bought, if a part number was given, or the year of the bike it came from. 1989 to today is the same part. If before 1989, it is the wrong part.

From the photo it looks OK to me. When you say the engine was chrome, was it shiny chrome or silver paint? Chrome would not be the right engine. Our engines were black or silver paint (as your 2004 is silver paint).

You should hone the surfaces of the tapered shaft and inside of the assembly before re-assembling them. I talk about it in my video.

[Mach]

Looking at you past posts, the epoxy on the ends of the magnets is not important and often some of it falls off.
If the 3 bolts holding the starter to the assembly came loose, you can replace those bolts and you are good to ride again. Once in a while they have come loose.

It is possible that the magnets changed length slightly or there is a different amount of epoxy on the ends of them. The assembly is the same from 1989 to the present. I would not be surprised with a slight difference in the length of the magnets, as they would have come from different factories over the years.

The critical dimension is the inside diameter. That makes the clearance between the magnets and the stator.

The older GS500 was called a GS500E (pre-1989) and that causes confusion. You can check the part number of what you bought, if a part number was given, or the year of the bike it came from. 1989 to today is the same part. If before 1989, it is the wrong part.

From the photo it looks OK to me. When you say the engine was chrome, was it shiny chrome or silver paint? Chrome would not be the right engine. Our engines were black or silver paint (as your 2004 is silver paint).

You should hone the surfaces of the tapered shaft and inside of the assembly before re-assembling them. I talk about it in my video.

The engine of the used bike and where this part came from is silver yes, I don't know when they started putting silver engines on them. As i said, evertyhing is identical to my eyes except for the magnet's length and a number of ¿ borings/bores ? on the magnet housing ( balancing ? ). My starter gear fits perfectly on the clutch and the clutch works as it should (starter gear turns to one side, stops to the other). The shop where i bought these parts looked serious.

The bolts came loose, yes, but... this happened  :




I was planning first getting out the broken bolts and then tapping the threads, then putting new and bigger bolts there.
Should i do that, or should i install the used part i just bought ?

[sledge]

I would not be surprised with a slight difference in the length of the magnets, as they would have come from different factories over the years

I would....The length of the magnet is generally the same length as the corresponding alternator pole-pieces 

[Mach]

I would not be surprised with a slight difference in the length of the magnets, as they would have come from different factories over the years

I would....The length of the magnet is generally the same length as the corresponding alternator pole-pieces 

Yep... i measured those and their length is approximately that of the magnets on my rotor, but the used rotor's magnets are +5mm longer...

[sledge]

or should i install the used part i just bought ?

There is two answers to that question 

Forgive me for being pragmatic but some people will say yes....it will be ok, even though they are guessing and some will say no dont.

Personally I wouldn't on the basis there is some obvious visual differences between the two and therefore a degree of uncertainty as to its suitability......but its your bike time and money and ultimately your call 

[sledge]

Yep... i measured those and their length is approximately that of the magnets on my rotor, but the used rotor's magnets are +5mm longer...

Which suggests its designed to be used with an alternator that's physically longer than the one on your bike 

[Mach]

Do you guys see viable the repair tapping the threads to bigger ones and putting bigger bolts ?

[adidasguy]

No.
If slightly off center, the rotor will strike the stator and cause lots of damage. The clearance between the stator and the magnets is very close.

[sledge]

Difficult to say  we don't know how damaged the part is and what your skills and abilities are.

How about drilling through the two halves 180 deg apart, then pinning them together with roll pins. This will ensure they stay concentric. Then drill and tap 3 fresh holes at the original size rather than trying to reclaim the old ones.

Dunno.....just thinking 

[Mach]

No.
If slightly off center, the rotor will strike the stator and cause lots of damage. The clearance between the stator and the magnets is very close.

What would cause the rotor to go out of it's center axis ? I don't see any relationship between the threads of the starter clutch bolts and the central axis of the rotor.

[adidasguy]

No.
If slightly off center, the rotor will strike the stator and cause lots of damage. The clearance between the stator and the magnets is very close.

What would cause the rotor to go out of it's center axis ? I don't see any relationship between the threads of the starter clutch bolts and the central axis of the rotor.

True. I forgot the starter gear bolts to the rotor and the rotor is on the crank, not the other way around.
A slight off center of the starter gear would be harmless. It doesn't rotate when the engine is running. (and slight I mean it would be almost nothing as the starter gear would center itself on the crank, just the clutch half bolts to the rotor and there would be room for play there since it is a loose clutch thingy.)

[Mach]

No.
If slightly off center, the rotor will strike the stator and cause lots of damage. The clearance between the stator and the magnets is very close.

What would cause the rotor to go out of it's center axis ? I don't see any relationship between the threads of the starter clutch bolts and the central axis of the rotor.

True. I forgot the starter gear bolts to the rotor and the rotor is on the crank, not the other way around.
A slight off center of the starter gear would be harmless. It doesn't rotate when the engine is running. (and slight I mean it would be almost nothing as the starter gear would center itself on the crank, just the clutch half bolts to the rotor and there would be room for play there since it is a loose clutch thingy.)

I made around 6000km to my bike with only one bolt holding the clutch to the rotor with the other two sawed off and their heads banging, eating the threads, and the bike failed on start-up only two times , that's why i thought an improvised repair based on thread tapping would be harmless. I work on a factory where there are several drill presses and lot of tools, i lack knowledge on that territory but sure my fellow co-workers will lend me a hand on this.

[sledge]

Go for it 

You cant make it any worse.

[Mach]

Hi guys, it's done !

- Got the broken bolts out, one of them with an awl/pricker/bradawl? and a hammer, the last one drilled on a drill press
- Tapped the threads to the same metric (they weren't very damaged, only a bit of thread is missing, like 10-20% in two and 30% in the last one),
- Cleaned everything with degreaser and compressed air, small shavings and metal dust on magnets with a clean rag and patience

- Got 3 new M8 bolts, loctited them pretty heavily and tightened all as i could.
- Honed a bit the crankshaft housing on the rotor and the crankshaft end (only the conic end, not the flat side where the starter gear goes) with a 600 grade sandpaper, then cleaned with a clean rag and alcohol.
- Cleaned the crankshaft bolt and the interior thread with lots of patience and a tiny screwdriver with a rag soaked in alcohol

- Inserted everything on the crankshaft,
- Loctited the crankshaft bolt,
- Placed the idle reduction gear
- Blocked the idle reduction gear against the starter gear with an allen wrench
- Tightened with a 17 wrench
- Tightened to 128Nm with the dynamometric
- Allen wrench out

- Cleaned the old gasket   
- Covers in place
- Tightened everything
- Gearchange lever
- OIL

At this point... did i miss something ?

Started up and... noise is gone.

Thanks everyone, specially adidasguy for his excellent tutorial on yt, very helpful.

[adidasguy]

Sounds good.
You should be good for a very long time.

[sledge]

- Honed a bit the crankshaft housing on the rotor and the crankshaft end (only the conic end, not the flat side where the starter gear goes) with a 600 grade sandpaper, then cleaned with a clean rag and alcohol

Despite what some people will have you believe.........THIS is the recognised and correct way to lap a tapered flywheel. Its the only way to ensure the surfaces match correctly and its way professional engineers, machinists, engine builders etc etc have been doing it since the year dot.

http://www.youtube.com/watch?v=bezP0s0NtLc

Go ahead and research the subject yourself 

Rubbing the surfaces with sandpaper creates high spots and flats on the corresponding surfaces and actually reduces the efficiency of the tapered interface. I suggest you go back carry out the procedure again using the correct technique as you are now running the risk of the flywheel slipping in use and further damaging the tapered surfaces

However its your bike and your choice.....not only in what you decide to do but in whose advice you decide to take. 

[adidasguy]

"Never mind. Sledge is always right because the Brits have perfect teeth and great cuisine that rivals the French!"

[sledge]

The light rubbing with fine sandpaper roughens the surface so they lock together

That is incorrect, the smoother the surfaces are the more effective the interface is as the contact areas are greater.

I suggest you do some research on the subject yourself rather than blindly assuming your statements are truthful and expecting others to share the sentiment.