Generator / Rotor Bolts - Sheared and Damaged
 

Hello everyone! I was glad to find this forum, and hopefully I can get some advice in a dire situation.

A few weeks back my buddy was riding his 2001 GZ250 home, and he heard some metal-on-metal noises coming from the engine, followed by a lockup. I came over and helped him look at it, and we were able to get it push-started after a decent number of attempts. I ran it maybe 150 yards-- it backfired a lot and died when I came to a stop. I thought it was a timing issue. Turns out, I was half right..

There are three bolts holding the generator (edit- These: http://i.imgur.com/JW40nuA.png) onto the roller bearings that touch the crankshaft. As soon as I took off the left side cover, I could see that one of the bolts had sheared off and was stuck in the gap of the large starter idle gear. Turns out, two of them sheared off and were being grinded up and stopping the engine from rotating cleanly.

Without further ado, pictures of the damage:

Back of the generator area. You can see one bolt still standing-- the others are in the bowels of the beast.

http://i.imgur.com/rB68r2y.jpg

What I'm calling the large starter idle gear-- maybe not the correct name, but still. Not a lot of damage here, but you can see bits of bolt (and the bolt itself!) in the bottom of the case.

http://i.imgur.com/4HSAqmT.jpg

This is the part I'm most worried about. Actual case damage. Could I patch this with a weld? Any other ideas on how to fix it?

http://i.imgur.com/EDMdbrK.jpg

Damage to the interior left side. That lower right hand threaded bolt hole is missing about 1/4 of the walls, where you can see it's chewed up

http://i.imgur.com/jIl4nKY.jpg

Finally, the lower half of the two bolts still stuck in the generator outside part. I should be able to drill these out, just need to take it slow.

http://i.imgur.com/pHVAens.jpg

I had seen a thread on here earlier with someone with a similar problem, but I'm having trouble finding it now. I'll keep looking and link it if I find it.

So, a few questions:
1) Those three holes on the interior case wall-- what is supposed to thread into them? I originally thought this is where the sheared bolts came from, but now I realize they came from the back of the generator. One of the holes is significantly damages.

2) Will that wall damage affect anything? I'm planning on patching it with JB Weld (or an actual aluminum weld), if that will work. Or, is it supposed to be open-- an oil passageway? I need to get a picture of an undamaged one.

3) Any other advice?

Thanks!!

I would patch the holes with quicksteel,really don't have much t offer in the way of what to do but I wish you the best. Ever find the cause?

I'm going to have to open this thread on another computer where I can see the actual damage.

In the meantime, BabBob once did a write up on the left side cover removal and replacement I think... Or was it right side? I don't recall at the moment but look for his sticky in the How-To section.

Mainlinecoffee, nope, no idea on the cause. I was hoping someone here might have an idea. Bad / non-existent locktite? The bolts are defiantly getting some red when they go back in!

Jonathan, thanks, I'll search around, and I think I actually found that thread(or another, similar one) the other day but haven't been able to find it again.

this is my tread about the same problem
http://www.gz250bike.com/forum/showt...7146#post67146

I weld the broken gear and is working

Thank you Raul, that's the one! Dang, I didn't see pictures yesterday, your gear just exploded! Did you have any damage to the crank case?

You may want to use Blue Loktite. Red is too permanent if you ever want to take it apart again.

I re-upload the pictures
no damage to the crank case

Those three threaded holes in the crankcase... does anything go in them? Looking at parts fiches, it seems like no, but why would the holes be there if not for a bolt?

Fixed it! Or at least, well on the way.

Unclogged the oil passageway, and used some JB Weld to patch it:

http://i.imgur.com/LZalCXR.jpg

New bolts, WITH blue threadlocker:

http://i.imgur.com/DVeulIn.jpg

My day's 'Workstation':

http://i.imgur.com/IxvcvjU.jpg?1

I buttoned it back up, and it started up! Killed it because I need to 1) charge the battery, 2) change the oil, and 3) let the weld cure. So, hopefully tomorrow I'll be riding!.

raid for a day an do anoder oil change an filter to remove any metal shavings

2001 Suzuki GZ250 - idling after fix: https://youtu.be/7dQ1U7sLxg4

As you can see, I got it back to running. I got new tires on it a few days ago, so yesterday I ran it for a bit and drained the oil yesterday, and I decided to check on my fix while I was at it. My JB Weld didn't hold, so today I'm going to pull it off again and try again with some Quicksteel. Once I get that patched up, I'll be able to put oil back in and get it back together. Closer every day!

Just a suggestion. Do not start the bike until the Quicksteel is fully cured.

Congratulations on getting it running! Even if it is leaking a bit that's progress and awesome at that. Just a thought,can you use a wad of quick steel than run a very short bolt in it or Something to grab in to the metal?

The problem is trying to patch a hole rather than stripped threads. But I do like the way you think. Tried that very same thing years ago on something and it didn't go too well. Seems the quicksteel hardened before the bolt was tightened down properly. :cry:

Oh yeah, definitely waited until it cured this time. Quiksteel worked great for this.. its malleable nature allowed me to form the shape I wanted before pressing it into place. I let it harden for a few hours, checked it, and buttoned her back up. Put fresh oil in, and it started perfectly and is running strong! Actually only ran it for a few seconds last night, no leaks as of this morning. I plan to ride it for 50-100 miles then change the oil again. I'll check my weld at that time, and if we're all good then it will be ready for riding!

Sounds good Clofan. Hopefully you will have no more worries for a long time and have a lot of saddle time this year.

Is there oil pressure in that passage? If so, I doubt any cold patch is going to hold. Also, once it lets go there goes your oil pressure. If, OTOH, it's a drain, then your fix may be adequate.

I've put 150 miles on it since the fix, and haven't had any problems. JohnC, I'm not sure if it's a pressure conduit. I will be changing the oil again soon and will re-check my fix then, and if we're still good, I'm calling it solid.

New to the forum
 

Hi, I recently had the same thing happen with one bolt on the balancer. I retapped the hole and replaced the bolt. The bike wouldn't fire. I took the balancer off and saw the the key had sheared off smooth. Any ideas as to why this may have happened? Also posted some pics of it's life to help visualize.Attachment 245

Attachment 246

Attachment 247

Attachment 248

Attachment 249

Where I sit now, heartbreaking.
 

:cry:

The key serves 2 purposes. One is for proper alignment of parts and Two..........it is the weakest link in the chain. It will shear off due to metal fatigue before something else lets go and causes major destruction. This is my opinion only but seems to make sense to me. The manufacturer could make everything absolutely indestructable but then you have a 250 GZ that weighs twice as much and costs a lot more too. The key is a sacrificial item to preserve the rest of the engine.
Luckily you only had to do some minor repairs rather than push home a bike with a grenaded engine. Look at the positive side of the repair. Could have been a lot worse.

I don't think I understand, which part is the key?

This is a time when a pic is worth a thousand words. I just Googled shear keys and was amazed at the results. After 4 or 5 pages I found some suitable info pretaining to small engines. Try it yourself and see what happens. Our world could never exist without shear applications in our daily lives. Everything from small engines to bridge building or the houses we live in.

Replacement parts arrived
 

My key came in today, when I get home I'll be replacing and reassembling. I will document and post my installation procedure, maybe it can help someone in the future. It may also show someone what not to do, lol.

Oh good! I hope you can do some close up pics. I have actually never seen that part of the bike up close and personal. :tup:

If I'm not mistaken those three threaded holes are simply there to split the crankcase apart.

I definitely will get some good pics for you guys. The key they shipped me was incorrect, was an 08 not a 2000, about .045" too thick to fit in the keyway. Ordered one again should be here wednesday. Ill post some "as-is" pics today when I get home. Almost convinced myself to shave it down but im afraid it might compromise the "fail-safe" characteristics of it. Just wait on the new one. Bummer

Some close up shots of the keyway and crankshaft.
 

Ill get more during installation.

Patience is a virtue. A little more down time and doing it right the first time can't be wrong. :clap:

I couldn't agree more, I have jumped the gun before and ended up needing new heads on my Nova. Lesson learned. I'll take this down time as a good thing and do some wire tucking or something. I was going to replace the air filter box with a cone filter this weekend, I remember the first time I attempted this the bike wouldn't run correctly under a load. Only let get half RPM or so. Tried adjusting mixture but couldn't get it to make any power. See how it goes this time!

rotor
 

smooth out the case the best you can with a moto tool or sand paper for the broken bolts drill them out & use a 6mm helicoil I have a rotor with the clutch rolers & springs just take your time good luck

to use the cone filter you need to change the main jet to a bigger one, I use a 140

Just a quick update on the original post-- I changed my oil and brake pads over the weekend. 640 miles since the cold weld fix. I popped the side cover off again, and my fix is still holding! No metal shavings in the bottom of the case, can barely even tell there's a weld behind the large idle gear. I'd call this repair a success!

gzbobber, good luck on yours man!

:tup::tup:

Glad to hear you got it fixed. Always happy to hear about another GZ up and running. Good Job!! Enjoy and ride safe.

Here I am, 7 months and 1456.9 miles later, back in the belly of the beast:

[img]i.imgur.com/xWiYqMe.jpg[/img]

Same problem as when I got it, bolt from rotor sheared off and knocked off my makeshift oil passageway, jamming the whole thing up. I took her apart and replaced my bolts, this time with Red thread locker. Rebuilt my oil passageway as before and cleaned up all the metal shavings with rags and compressed air.

[img]i.imgur.com/MJY1k17.jpg[/img]

This is where that oil passageway goes:

[IMG]i.imgur.com/sN9nZzQ.jpg[/IMG]

Looks like it feeds oil into the clutch area? I could tell by the air that it went from the area close to the main shaft, up the passage, then into the above pictured chamber.

So. After letting the weld and thread locker cure, I started it up. It seemed to idle fine. I rode it up and down the street, all seemed normal and it operated fine. I pulled back into my carport, and let it rest. While I was cleaning up my tools, I noticed 6 little ball bearings that are 0.5cm in diameter. They were scattered about the floor, so there may be more than 6 in whatever they came out of. My question, do these bearings go anywhere in this side of the engine? I didn't encounter them last time I was in here, but I'm not sure what else they would have come out of. Perhaps the compressed air blew them out from somewhere in the engine?

I've been working on my lawn tractor and Honda CL350 in the same space, but I don't think they came from those either.

[img]i.imgur.com/IgX7xPt.jpg[/img]

Edit: BEARING SOURCE FOUND! Crappy craftsman stool that was falling apart

Not sure why the Images are broken on the previous post-- I've edited them into hyperlinks, so you can click them.

I looked through the parts fiches on CMSNL and didn't see any of the ball bearings I found on my garage floor. At this point, I'm thinking they must have come out of some other project. That's slightly terrifying, but at least they didn't come out of the GZ. Time for another oil change (drat, literally just changed it last week), then hopefully the bike will be good to go for another few years of riding!

I can't access the original images to fix them. Are they in a private folder on imgur or something?