generator mounting bolt missing

fjbiker84 · April 17, 2017, 04:28:00 PM

While looking over the bike yesterday I noticed that a bolt is missing under the generator behind the clutch slave cylinder. I have no idea how long this has been missing but fortunately noticed it before something more serious happened. No problem, ordered new mounting bolts for a couple of bucks along with a few other things I've had on a list. Here's the problem. Looking inside the bolt hole with a flashlight it appears as if the now missing bolt took with it the threads needed to keep it in place. Does this mount onto the engine block? Hopefully when the new bolts arrive I can simply replace the missing bolt and nothing more needs to be done. But has anyone run into a similar problem with threads damaged in such a location?

aviationfred · April 17, 2017, 04:41:07 PM

I have not had this happen. Yes, these bolts do thread directly into the case. To be certain of the condition of the threads. I would remove the alternator and verify the condition of the threads. The alternator is easily removed while the bike is on the centerstand or rear paddock stand. It is easier if you remove the clutch slave cylinder first.

Fred

FJmonkey · April 17, 2017, 04:50:07 PM

If the threads are stripped out then we can repair it with a Heli-coil like product. Hopefully just a missing bolt.

PaulG · April 17, 2017, 07:25:24 PM

Quote from: fjbiker84 on April 17, 2017, 04:28:00 PM
Looking inside the bolt hole with a flashlight it appears as if the now missing bolt took with it the threads needed to keep it in place.

If you haven't cleaned out the threads yet, they may be plugged up with grime. If you have/or can find a small "bottle brush" try and clean them first. Then get the proper size tap and dress the threads to clean out any other grit. Use a little oil on the tap to help it along. When you get the replacement bolt test it out first and if it's obvious or you suspect the threads are damaged then you can go the insert route. Just a quick check that might save you some time/money.

Be careful that the old bolt did not snap from overtorquing from a PO then unthread itself. If your new bolt bottoms out, well you know the story from there....

fjbiker84 · April 17, 2017, 10:05:35 PM

Thanks for the input. I'll know more in a week or so when the new bolts come in the mail. I am a little concerned that the old bolt sheered off and that's why I can see any threads. Not sure how deep the bolt is supposed to be. I know the previous owner and will ask him if he ever took the generator off but if I had to guess I'd say this is original factory installation. Will update this when the parts come in.

fjbiker84 · April 24, 2017, 09:13:34 PM

Got my new generator mounting bolts in the mail today. Unfortunately, what this shows is that the bolt broke off at the point where the threads start. Since that is the case, it would seem to me there shouldn't be that much pressure on the threaded part of the bolt that is remaining. The bolt is only supposed to be installed with 14 ft lbs of torque (I did confirm that the PO never removed the generator) and all of that pressure would be on the head. Going to try to unscrew broken bolt with a screwdriver or something? Will follow up on this after I have a chance to work on it tomorrow.

aviationfred · April 24, 2017, 09:26:01 PM

A good set of Left handed drill bits can actually spin a broken stud out. I have had to do it before on other things.

Fred

biggo · April 24, 2017, 10:40:52 PM

Quote from: aviationfred on April 24, 2017, 09:26:01 PM
A good set of Left handed drill bits can actually spin a broken stud out. I have had to do it before on other things.

Fred

Never knew you could get left hand drill bits, ( good job its not April 1st ).
A set ordered for the shed

Thanks Phil

fjbiker84 · April 25, 2017, 06:36:28 AM

I was not aware there were drill bits like that. I'll check the hardware store for a left handed bit that will reach. Thanks!

aviationfred · April 25, 2017, 08:07:58 AM

The left handed drill bits will still drill a hole in the stud if it has any torque remaining. That should not be an issue. A good quality EZ out should do the trick

Fred

Dads_FJ · April 25, 2017, 02:14:33 PM

The broken alternator bolt is all too common on the FJ1100 - which is probably why Yamaha FJ1200 bikes have three bolts instead of two. The broken bolt will probably come out easily like mind did.

Good luck!
J

fj1289 · April 25, 2017, 06:53:39 PM

Quote from: fjbiker84 on April 25, 2017, 06:36:28 AM
I was not aware there were drill bits like that. I'll check the hardware store for a left handed bit that will reach. Thanks!

Harbor Freight sells a set of left twist bits with EZ-out. THROW THE EZ-OUTS AWAY - preferably in a garbage can outside the door is the store! Then take the drill bits home. A broken EZ-out is not a fun problem to add to the middle of your broken bolt. I think I'm 2 for 3 for breaking off EZ-outs -- takes me a while to learn sometimes...

Use a good penetrating oil with the left twist bits. If you can, center punch the broken bolt so the drill bit will stay centered as you start to drill. Start small and work your way up. The heat and torque from the drilling helps break free the broken bolt. In my experience I usually work up to a drill bit nearly the size of the broken bolt (why it's so important to be centered!) before the edge of the bit will "bite into" the remaining metal and back it out. First time I tried it I was about to give up on the "whole stupid idea" in frustration - then then the drill "bit in" and spun it free like butter. I became an instant convert and threw away the easy outs!

fjbiker84 · April 25, 2017, 07:59:52 PM

Well, I went to the local hardware store and bought a bit with left twist that the salesman said would do the job. Problem is I can't get at the broken bolt without taking off the generator. And that's the problem...... the remaining bolt is frozen. I pretty much stripped the bolt trying to get it off. So then took off the tank and carbs to get at it with my vice grips but even that wouldn't work - they slipped because there is very little clearance above the generator. Maybe I can ride this thing to the WCR as is and get help there?

FJmonkey · April 25, 2017, 08:31:15 PM

Bring it to my house, we will get it fixed.

Pat Conlon · April 25, 2017, 08:31:56 PM

Can you reach in there with a Dremel with a cutting disc to cut a slot into the head of the frozen bolt?
That way you could use an inpact driver with a straight screw driver bit to fit the slot.
If not, you will have to reverse drill the frozen bolt.
To help unfreeze the bolt, some penetrating oil and heat on where the case threads are located will help.

This is now several times (over the years) where I have heard of the 2 bolt mount generators breaking the bolts.

I wonder if a bolt upgrade to a SAE 10.9 would be a good idea?

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generator mounting bolt missing