Snapped Rear Mounting Studs (3rd time!)

mapbike said:
motorizedmatt, you are doing what I was going to post before I saw that you already had the idea, and YES over tightening those studs can stress them to the point that the added pressure from the vibration can cause them to break, what I do is make my studs long enough so that I can just torque them down good and snug and then I give-em just a little tweak past that point and then with the added length I install another nut against the first one as a jam nut which will ensure that nothing comes lose you just need 2 10mm wrenches to get them tightened down against each other, and I highly recommend you use BLUE Loctite on the studs as well, I also had studs breaking and also falling out on me until I started doing what I just described and I have never had another problem since and I have almost 800 miles on one bike and 66 miles on another I just built have not even had to retighten one bolt or nut on the new one yet because of how I secure everything from the get go.
Good luck on resolving this issue and happy safe riding.
Shan
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I use nyloc nut's where ever there isn't a heat source,Also try green lock-tite on all assembled threaded connections.chain guard,fender braces,crank arm nuts,ect ect.Kip.
 
Yes Kip thats a good idea with the nyloc nuts, I also use them and as the jam nut, I put a standard nut on first and then I put the nyloc but behind it and jam it tight against the other, these never come lose on mr ever, and I also put loctite on both as well but I use the blue.
 
I had the exact same thing happen with 3 bolts and ended up having to drill & tap new holes into my engine.

I put the bolts in with no other mounting hardware and matched everything up, on the side, and realized that my bolts were a few threads too long to pull everything together tight. I also realized that a torque wrench set to 50~75 in/lbs. is tighter than I had done with my hand (I had been afraid to tighten them too much for fear of stripping/breaking things with my gorilla grip).

Make sure your bolts are the right length (won't bottom-out without pulling everything tightly enough) and a torque wrench is highly recommended!
 
Blue locktite will work just as well as the green.The green is for already assembled parts.It penitrates
like WD-40.Kip.
 
kipharley said:
Blue locktite will work just as well as the green.The green is for already assembled parts.It penitrates
like WD-40.Kip.
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Thats cool, never used that before, but sounds like it could come in handy for some situations. there ya go you just learned me something I was not aware of....! LOL

Shan

dnut
 
Most common reasons for studs to break are..

Cheap Chinese studs... I change out ALL to grade 8.8 About the same as US grade 5.
Incorrect mounting...mounts to both seat tube and down tube. Need as close to perfect fit.
I use RED locktite on all studs (if removal is desired heat is needed).
Proper torque 6mm 50-70 INCH pounds... 8mm 150-204 INCH pounds (I use 50 and 150)
I double nut with a nylock nut as the second one.
Here are some pictures of my mountings, I have never had a nut or stud, come loose, break or strip out.

Proper mounting...


I make these shims in order to get the proper torque. The nuts are too close to the clamp for a proper socket fit. I don't have a nylock nut on this illustration.


I make this "L" bracket to eliminate engine twist due to engine torque. This way I don't have to over tighten mount nuts.


Almost every bike frame needs a custom made front mount. The proper angle for the optimum mounting is 75 degrees.
..........A bought mount can be had
 
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Nougat said:
No, no - green Loctite is for "I never ever want this to come apart ever again." There is no place for green Loctite on these machines, let alone red. If you're going to use any at all, blue is all you should use.
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Green loctite works just fine.It certainly doesn't "weld" the two parts together.Kip.
 
Try grade 8 bolts, but I bet your frame will break before the grade 8 bolts do...especially since you drilled a hole through the frame.....not good-keep an eye on that area. I'm sorry that ain't more helpful but that hole would scare the heck out of me.
 
You may also try peddling more at start-up before you engage the clutch,when you do release the clutch slowly.That's where most of your torque is coming from.Kip.
 
kipharley said:
Where are you suggesting the 1/4" all thread?
In a 6mm threaded hole?
Could you explain your process.I don't get the fix? 1/4"all thread,aluminum welding rod,propane torch,tap and die,by hand?.On a motor-mount?Kip.
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I could not find the thread on boring out an hole to an little larger bolt size ; then filling the hole with hard material such as marine tex which I have used or . I may try the alumaweld stuff too. here is one good thread and I am sure there are more . http://motorbicycling.com/f3/no-more-broken-studs-bolts-me-11691.html
I am having the same problem , I have my motor on the bench right now and "will fix it :
 
I might try running a 6mm tap into the mount and access the threads to determin whether or not they need messing with.If you think they're sloppy enough maybe you should look into heli-coils.
If my advice makes sense use it,if not use your best judgement.Kip.
 
kicking said:
I could not find the thread on boring out an hole to an little larger bolt size ; then filling the hole with hard material such as marine tex which I have used or . I may try the alumaweld stuff too. here is one good thread and I am sure there are more . http://motorbicycling.com/f3/no-more-broken-studs-bolts-me-11691.html
I am having the same problem , I have my motor on the bench right now and "will fix it :
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Go and buy you a 1/4 - 20TPI Bottoming Tap and a stick of 1/4"X20 all Thread rod or just get some grade #5 or #8 Bolts that are the correct length and run the 1/4"-20 Tap into the existing 6mm holes after putting some thin oil like 3 in one oil or something simular so that the tap will not seize while retapping the hole out from the 6mm to the 1/4, just remember to run it in (the tap) 2-3 threads in depth at a time and then back out and then back in again repeating this proccess until the tap bottoms out in the hole, unscrew tap out of hole and then spray the hole out with either brake cleaner or carb. cleaner to get the alum. shavings out and then you are ready for your new 1/4" studs or bolt which ever you choose. very simple proccess use a small cresent wrench to turn tap if you dont have a tap wrench and make sure it is running straight into the hole.
 
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mapbike said:
Go and buy you a 1/4 - 20TPI Bottoming Tap and a stick of 1/4"X20 all Thread rod or just get some grade #5 or #8 Bolts that are the correct length and run the 1/4"-20 Tap into the existing 6mm holes after putting some thin oil like 3 in one oil or something simular so that the tap will not seize while retapping the hole out from the 6mm to the 1/4, just remember to run it in (the tap) 2-3 threads in depth at a time and then back out and then back in again repeating this proccess until the tap bottoms out in the hole, unscrew tap out of hole and then spray the hole out with either brake cleaner or carb. cleaner to get the alum. shavings out and then you are ready for your new 1/4" studs or bolt which ever you choose. very simple proccess use a small cresent wrench to turn tap if you dont have a tap wrench and make sure it is running straight into the hole.
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I have the short cut to this thread bike ,, in case im online ,,, i will paste it on my reply to the next person ,, snaped studs ,,, happens an lot !!! and i have learned ... do not use stainless steel too .... thanks ,,, P.S I wanted to send my motor back after the stud broke .... but this site tells me it happens a lot
 
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If anyone cares I retaped the studs to 8mm bolt and I have no problems yet and the engine is extremely sturdy, have 375 miles on it so far!
 
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