Breaking Motor Mounting Studs OCC Chopper

[joanthandirtbiker]

My occ chopper keeps breaking rear mounting studs. Im using the u bolt mount from live fast motors.
Ever since I built this bike I have had a never ending problem with breaking mounting studs. I have drilled and retapped the mounting studs to 5/16-18 Grade 8 and I still continue to break motor studs about every 100 miles. Ive tried using no rubber and rubber under the mount and the studs still break. I have about 3,500 miles on this bike and have replaced the studs at least 12 times. The rear studs are the ones that usually break but sometimes the front ones will go also.
if anyone knows what I can to fix this problem that would be great. Thanks Jonathan

 

[2door]

We need to see a good close up photo of your mounts.

Get ride of any rubber or resilient material you might be using but also concentrate on making sure you have good full contact with the engine and the frame. Any gaps between the two will allow the engine vibrations to be transmitted to the fasteneres assuring early failure.
Show us close ups of the mounts and we can offer more help.
Tom

 

[joanthandirtbiker]

Heres a slide show of pics I took.
This video Is like 3 years old but im using the same mounting technique but I have added a piece of rubber inbetween the mount and frame and I now have 5/16-18 studs.
http://www.youtube.com/watch?v=BOiVvbEKgRs

 

[2door]

That's a nice photo show but we still need to see close ups of the mounts.
Tom

 

[DaveC]

I kept breaking mine, too. I slipped some 5/16ths fuel line over the bolts and stopped breaking them. It stopped the side-to-side movement and the nuts stopped backing out, too.. My frame was so tight that I couldn't use the stock rear mount, the part that goes against the block. There just wasn't any room. I matched the angle of the mounting strap on the motor to the frame by making a wedge of epoxy putty and matching the angle that the motor mount wanted. Without the inside motor mount the motor wanted to pull the chain and shorten the distance between the motor and wheel sprocket, breaking the studs. With the fuel line over the studs it couldn't torque around anymore.

 

[Al.Fisherman]

That's a nice photo show but we still need to see close ups of the mounts.
Tom

I agree close up pictures are needed. If the engine is mounted correctly, (and do away with any rubber) I can't see how they broke. After changing to Metric 8.8 studs, I myself have never broken any stud in 5 engines.

Here are some mounting tips.
http://s982.photobucket.com/albums/ae309/Ron-Becker/Engine Mounting/

Here is a HT mounted on a Chopper.
http://s982.photobucket.com/albums/ae309/Ron-Becker/Tommys Chopper/

 

[azbill]

I used livefast's mounts in the past,,,
(got hem because he is local to me)
3 of them were bad stampings and broke studs due to bad fitment !!!
barry's (ebay) mounts are much higher quality

just sayin'

 

[rustycase]

I've got 2 cents that I hope might help...

Without seeing a better pic of the mounting system, I think rubber is not beneficial.

the problem I can see is that secondary chain running from the motor to the jack shaft.
...it seems way too tight.
my guess is it might be transmitting a harmonic that is causing grief at the mounting bolts.

Also, what are the gears used?
the ratio may be causing a harmonic in that chain???

a better pic would help...
perhaps there is flex in the frame putting stress on those bolts???
maybe an additional top motor mount would help???

...similar to what Sportscar Pat uses on his racer?

Good luck
rc

 

[Texhun]

I agree with Rusty. If your drive-chain on the engine side is too tight it will put alot of strain on your mounts. Try loosing both chains a little.