rear mounting bolts sheared :(

K

kallsop

Member
Grrrr. I didn't notice, but the spacer block is a super tight fit on my bike and there was zero give in the mount. So I go to ride the bike and notice the rear of the engine is dancing around. Both bolts sheared. Removed the engine and the spacer block was stuck to the bike downtube. I had to use a hammer to get it off. OK, I need to file the spacer and get it a bit looser on the bike. I have a set of screw extractors and hopefully can remove the broken bolts without trashing the case.

What size bolts are these anyway? I have to get new bolts.

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They're a lot longer than the normal studs. All I know is they're 6mm, and I destroyed my engine when I had your problem. I would honestly try and extract them, and if it fails, tap them out to 8mm.
 
I checked Lowes and Home Depot for M6 bolts, nothing long enough at either store. M6 threaded rod - nope. I just ordered the hardware upgrade kit at sickbikeparts. By the way, I was able to drill into the broken bolts and remove them with a screw extractor.

When the upgrade kit arrives, I'm going to file the spacer so the mouth is wider, and every bolt and nut gets Locktite Blue. I'd love to get at least a week of usage without having to fix something.
 
Hmmmm, I got mine at either Home depot or Lowe's, but I don't remember which... I got them in bags with four in each bag. Marked with the name "Hillman".
 
best deal is to find an "industrial fastener" store. there's a place here in California called MacFadden-Dale and it's a giant warehouse full of nuts and bolts and other cool stuff like heat shrink, petcocks, copper sealing washers, you name it.

as far as price goes, i just bought 16 bucks worth of grade 8 socket caps in all different sizes, and it's enough to replace every bolt on 3 engines, plus fenders, chaingaurds, and anything else i need to make look fancy or hold tight.

as a comparison, Ace hardware carries little black allen button heads i use after drilling out fender rivets for 60 cents a piece.

at Macfadden-dale, they're 8 cents.
 
OK, here we go.The bolts were loose in the block to begin with, and that's why they broke.
Very low quality to start with. You want the motor tight on the frame. I don't care who sent the motor to you there loose when they ship it. Take a center punch and a hammer, Tap the bolt on top with a counter clockwise direction. It's slow but it will move. Go to a bolt & nut place, you want 6mm all thread. 3' bars. Take a bolt with you! 6mm X 20. Loose the front ones too! This won't be your only build! Use the rest on the next, and the next :)
 
Saddletramp1200 said:
OK, here we go.The bolts were loose in the block to begin with, and that's why they broke.
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It's my second build. The first one is still running, never a bolt problem except for nuts coming loose where I didn't double nut and use Locktite. I'd already own M6 rod if Lowes or Home Depot had some, and I don't know anywhere else locally to find some. Anyway, I'm going with a home made aluminum rear rack for my next build, a 4 stroke.
 
Look for a Fastenal store. They are all over the place and they do sell retail. For another project I was working on, it cost the same to buy the pack of 100 as opposed to the pack of 10 from Lowes.

I replaced most of the nuts in my kit with nylock nuts (except for the exhaust). Although I use it, I've never been a fan of loc-tite. I'm likely forget to put it on in between the multiple test fittings and mock-ups.
 
Lock-tight, Lock washers, nylock nuts, 10.8 hardend bolts you still have to check them every so often for tightness. One of my front bolts broke off my cruiser about a month ago. And this was a good hard bolt. All thread I do not recomend. May be better than the stock crap that comes in the kits but it is still pretty soft.
 
I have never snapped a grade 5 fastener. in fact, I have never had a problem with the stock stuff, except for stripping it very easily.
 
asianflava said:
Look for a Fastenal store. They are all over the place and they do sell retail. For another project I was working on, it cost the same to buy the pack of 100 as opposed to the pack of 10 from Lowes.

I replaced most of the nuts in my kit with nylock nuts (except for the exhaust). Although I use it, I've never been a fan of loc-tite. I'm likely forget to put it on in between the multiple test fittings and mock-ups.
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I wonder if SBP gets some of their nuts & bolts from Fastenal. Whatever I order from them, each and every part is just rock solid. I wouldn't be surprised if some of the other vendors use Fastenal screws and bolts in their designs. I'm with the rest of these guys: if you can safely get the old studs out, scratg put in some from Fastenal or SBP or one of these other vendors to the let and right, if they have them. Oh, and make sure you got the right length stud before you use Locktight to keep them in there. You DON'T want to have to take out a Lock-tighted stud.
 
I use grade 5 6mm bolts and have yet to have one of them break, one needs to remember that if a bolt is over tightened it will take much less vibration stress than one that is just good and snugged up with a little tweak past that point, any grade of bolt can be over stressed by over tightening, I use red loctite on the back mounting studs and blue everywhere else, I used the blue on the back bolts at first and lost one of them out going down the road 2 different times, so I bought new grade 5 bolts that were 100mm long, cut the 10mm head off and shortened them down to about 70mm in length, used some red lock tight after cleaning the thread in the block out real good with some carb. cleaner and 530 miles later I've never had to tighten another bolt on any part of my engine and no more lost studs or broke anything, this has been the solution to the bolt breaking and loosing issue for me.
 
I had a back stud break off at the case today, I center punched it and tried to drill it withno luck, i then tried drilling into it on my drillpress, still no luck bit just wanders off and will not stay on stud, i wanted to use an easy out but cant even drill down into stud at all,must be titanium boron carbon stainless petrified steel, whatever it is my bits will not grab into it and bits are good. Any ideas?
 
chopperjoe said:
I had a back stud break off at the case today, I center punched it and tried to drill it withno luck, i then tried drilling into it on my drillpress, still no luck bit just wanders off and will not stay on stud, i wanted to use an easy out but cant even drill down into stud at all,must be titanium boron carbon stainless petrified steel, whatever it is my bits will not grab into it and bits are good. Any ideas?
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When I center punched and drilled the studs, it all was easy. Those were the original studs, pretty soft. The drill bit was nothing special, whatever they use in the Harbor Freight stud removal kit.

Try a left handed drill and maybe the stud will come out? Bash it really hard with the center punch?
 
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