question:alternator rotor bolt

[750S3]

Can somebody confirm if the alternator rotor bolt (No.25 in the picture) is a righthand (clockwise to tighten) or lefthand bolt? MG 750S3. The bolt is striped and I need to take it out and replace it. I understand it is a very tight fit and not sure yet how I'm going to do it.
Thank you.



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[Antietam Classic Cycle]

"Normal" right-hand thread.

[750S3]

Thank you Antietam

[Roy gardner]

Stripped, really, the the bolt thread, or the in hex of the screw head? 

[750S3]

Stripped, really, the the bolt thread, or the in hex of the screw head?

Sorry I should have clarified, yes the hex of the screw head is stripped and I can't get a hex key in to turn it.
Kind of important for timing work, point gap etc..

[n3303j]

Sorry I should have clarified, yes the hex of the screw head is stripped and I can't get a hex key in to turn it.
Kind of important for timing work, point gap etc..

Use the rear wheel with bike in highest gear to bump the engine into correct position to set rockers and points.
It's a lot better than abusing the bolt on the rotor.

[750S3]

Use the rear wheel with bike in highest gear to bump the engine into correct position to set rockers and points.
It's a lot better than abusing the bolt on the rotor.

Yes you are probably right, and I have done so. Still would be nice to get the bloody thing out.

[Chuck in Indiana]

Yes you are probably right, and I have done so. Still would be nice to get the bloody thing out.

Ok, if you are ready to have a go at it.. make yourself a peen punch. That will be a piece of hardened steel like a drill blank with a hemispherical radius hand ground on the end and polished. It doesn't need to be much of a radius, just not flat.
Now, take your copper hammer and this punch and peen the end of the bolt by working around the circumference. That will close up the hex. Cut off a hex key, and drive it into the bolt head with your copper hammer. Hit it with your impact driver.
You are out exactly nothing if the bolt doesn't come out.. but it very well may. If not, you are no worse off because you'll have to drill out the bolt anyway.

[n3303j]

Just try some sharp jawed vise grips first.
Don't hurry to drill this one out because once the cap falls clear you are blocking the rotor extraction threads with the reduced body diameter of the screw you just beheaded.

A flat filed either side of the cap would allow fitment of an adjustable wrench. That screw should be 14 ft/lb maximum tension.

[Chuck in Indiana]

Just try some sharp jawed vise grips first.
Don't hurry to drill this one out because once the cap falls clear you are blocking the rotor extraction threads with the reduced body diameter of the screw you just beheaded.

A flat filed either side of the cap would allow fitment of an adjustable wrench. That screw should be 14 ft/lb maximum tension.

Uhh, memory may have failed me again, but isn't that screw head down in a counterbore? If so, I don't see how you could do any of that stuff..

[guzzista]

Uhh, memory may have failed me again, but isn't that screw head down in a counterbore? If so, I don't see how you could do any of that stuff..

Your memory is just fine, Chuck. Not a heck of a lot of room there for implements such as vice grips. Your method may just do the trick unless drilling the head becomes the next step

[nc43bsa]

Left-handed drill bit.

[pehayes]

It is a really odd bolt and setup. The bolt has one set of male threads.  The rotor and the nose of the crankshaft each have separate sets of female threads.  In an ideal situation, you would install the rotor onto the crank taper.  Then insert the bolt and turn it through the rotor's threads until it went all the way through and popped free internally. Then  you would continue pushing and threading to insert the bolt into the threads of the crankshaft.  After an ignorant mishap, I fabricated a PULLER bolt to remove the rotor.  Uses a 'slap hammer' between the forks after you remove the wheel and the front fender.  Anyone who needs it may borrow it.  You just need to have enough of the original bolt out of the way to allow the puller tool to thread into the rotor so you can slap it off.

Patrick Hayes
Fremont CA

[Charles in Lake Charles]

Get the tool from MG Cycle http://www.mgcycle.com/index.php?main_page=product_info&cPath=80&products_id=4631

[n3303j]

Uhh, memory may have failed me again, but isn't that screw head down in a counterbore? If so, I don't see how you could do any of that stuff..

Yup, another senior moment for me. Been 2 years since I've needed to look at the rotor.
Bolt head is hidden. Sorry for the falso hope.

[wirespokes]

There are several possible solutions before drilling off the head, which would still leave the rotor securely locked to its taper mount. Chuck's method makes the most sense for the first try.

Chances of success are better if using an impact driver.

Another solution is using an imperial sized bit - quite possibly there's one just slightly bigger that will jam in there.

Or, another good idea is a torx bit.

Another possibility - mix some filings (aluminum, steel...) in with some epoxy like JB Weld and and glue the wrench in place.

How about grinding down the head of a bolt so it jams in there, then double nutting to make your own allen key?

If the head gets so buggered none of that works (can't imagine that happening) I'd braze a wrench into the bolt head. But if it really does come down to the head shearing off or being totally unusable, I'd imagine the next option is destroying the rotor. Cut off the copper slip rings to allow access to the bolt head with vise grips.

[Chuck in Indiana]

I thought I did a tutorial on removing a bolt with a peen punch. Here it is on the Aero engine thread in the finished projects area. Page 11, about 2/3 of the way down.

[John A]

Chuck you amaze me !    Taking pictures and posting them with clear instructions is more time consuming, hard work than the original job.

[Chuck in Indiana]

Chuck you amaze me !    Taking pictures and posting them with clear instructions is more time consuming, hard work than the original job.

That's why I do it. Guys like Charlie, Pete, Steve, Joe, etc. don't really have time to document all that stuff. Many times, it *does* take more time to document it than to do it, but it's my way of paying back WG for all the things I've learned here.
Thanks, John, I appreciate that. 

[n3303j]

Yup, another senior moment for me. Been 2 years since I've needed to look at the rotor.
Bolt head is hidden. Sorry for the falso hope.

.......but I keep seeing that screw cap sticking up in midair and then it dawns on me.
My '66 BMW R60/2 uses the exact same screw and puller on their generator.



That one isn't recessed.
Right bolt.
Wrong bike.
Oops.

[750S3]

That's why I do it. Guys like Charlie, Pete, Steve, Joe, etc. don't really have time to document all that stuff. Many times, it *does* take more time to document it than to do it, but it's my way of paying back WG for all the things I've learned here.
Thanks, John, I appreciate that. 

Thank you gentlemen, I really appreciate the feedback, I will now print the thread and take it to the garage when I get some time to work on it.

brgds

[wirespokes]

You'll get it out - and without buggering everything up, I'm sure.

You're only removing it because it's stripped - correct? You're not pulling the rotor.

Just to be sure you know - there are instructions on the net on how to remove the rotor using a bolt and a short section of rod. I've tried that method and it wasn't successful, though it seems like it should work. I've actually heard of that method jamming the rod in the crankshaft which turned into a nightmare. Not worth taking the chance. Just get the proper tool meant for the job - it only costs ten bucks.

[Chuck in Indiana]

You'll get it out - and without buggering everything up, I'm sure.

You're only removing it because it's stripped - correct? You're not pulling the rotor.

Just to be sure you know - there are instructions on the net on how to remove the rotor using a bolt and a short section of rod. I've tried that method and it wasn't successful, though it seems like it should work. I've actually heard of that method jamming the rod in the crankshaft which turned into a nightmare. Not worth taking the chance. Just get the proper tool meant for the job - it only costs ten bucks.

The trick is to have a hardened rod. Apply a fair amount of torque to the bolt. Hit the bolt head with your copper hammer. You *do* have one, don't you? Prepare to catch the rotor, because that shock will break the holding taper between the crank nose and rotor.

[wirespokes]

Loosening the rotor bolt won't cause the rotor to pop off. It's really on there and doesn't want to let go. What Chuck is talking about is when using the tool (special bolt) to remove the rotor, hang onto it so it doesn't fly off and land on the floor. I even put a box padded with rags and foam in its flight path for a soft landing just in case it gets away from me.

[Groover]

If all fails, here is a the tool: I think you can get it other places too, but that's what it looks like. https://www.ebay.com/i/382756854837?chn=ps

[750S3]

That is correct I have no reason to take out the rotor, I just want to take our the bolt and replace it.
Should get to it sometime in July.

[wirespokes]

That's what I figured. So there's no pressure to get it out - it's not like you can't ride it in the meantime.

It's common knowledge to turn the engine using that bolt, but I never thought it was a good idea. I definitely wouldn't without the spark plugs removed, and by the time you've done that, one side's valves could already be adjusted via rotating the rear wheel.

[Chuck in Indiana]

Different strokes for different folks. I think it's a *lot* easier to turn the engine with the alternator bolt. (or nut) <shrug> The valve springs always seem to move the engine farther than I want when using the wheel, not to mention what if there is no center stand or work stand?

[Groover]

I think if you put it in 4 or 5 gear it's easier to turn the engine if I remember correctly. The bolt definitely cuts to the chase a lot faster and seems more accurate when trying to find "the spot", but at the expense of sweating it a little and fingers crossed type exercise that you don't break or strip the bolt.

[Chuck in Indiana]

I think if you put it in 4 or 5 gear it's easier to turn the engine if I remember correctly. The bolt definitely cuts to the chase a lot faster and seems more accurate when trying to find "the spot", but at the expense of sweating it a little and fingers crossed type exercise that you don't break or strip the bolt.

I don't worry about that at all. *As long as the plugs are out..* the bolt is torqued tighter than it takes to turn the engine.