engine mount bolts

Discussion in 'Motorized Bicycle General Discussion' started by Beetle Juice, Jun 12, 2009.

  1. Beetle Juice

    Beetle Juice New Member

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    My rear engine mount bolts are to short I thought I saw a post about someone who put longer bolts and even went up to an 8mm bolt. Is that true or can I stick with the 6mm just longer and be fine? Any suggestions on any other bolts would be great. Or should I just make another rear bracket that will wrap around the post???[/FONT]:-||
     
  2. Nashville Kat

    Nashville Kat Active Member

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    For my front mount, to get around an oversized frame, I bought some longer bolts at an auto parts store, and cut off the bolt heads to make the studs-

    Then- scientifically bending them around the frame and back, as well as the grounded out motor side, gave me the secure frame hugging I desired-

    I'm going to try to put some pipe insulation type styrofoam in them soon, to cut down on vibration while riding.
     
  3. Beetle Juice

    Beetle Juice New Member

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    you were able to find 6mm bolts at auto part store
     
  4. azbill

    azbill Active Member

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    the bolts are 6mmX1.0 pitch
    most hardware stores have them
     
  5. Beetle Juice

    Beetle Juice New Member

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    Mr Bill Thanks
     
  6. reg454

    reg454 New Member

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    make sure you by the grade 8 type so you dont break the bolts when your tightening them
     
  7. 2door

    2door Moderator
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    Here's another place I can make this suggestion. There is no need to use studs in the engine mounts. Replace the studs with Allen head cap screws available at Ace Hardware. There is no need to use studs or cut off heads of bolts to make them. To get the length you need simply screw a stud into the engine as far as it will go. Mark it and remove it then measure the length of thread that was in the block/case. Add what you need to reach your mount then subtract 1/4" and that is the length bolt you need. Allen heads make for a clean installation, are easy to tighten and most are grade 8 if they are black. Do not use stainless steel for any high stress/vibration application.
    Tom
     

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  8. Nashville Kat

    Nashville Kat Active Member

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    That's a good suggeston- but do they loosen with vibration?

    with long studs you can double up the nuts for a secure lockdown.
     
  9. marvin martian

    marvin martian New Member

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    You should use locktite on ALL bolts on your bike. Trust Me, I found out the hard way :(
     
  10. 2door

    2door Moderator
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    I do not use LocTite anymore, red, blue or any other color and I've never had a bolt loosen, fall out, break or fail. I know that as far as vibration problems I've probably been fortunate in that vibes have never been a real issue with any of my engines. I tighten the bolts against a lock washer just enough to flatten it then give it a slight bit more torque. (very slight) If you are shearing studs then there is a good possibility that you are over tightening them and/or tightening them too often. Poor fitting engine mounts will allow movement even with minimal vibration and this can lead to metal fatigue which is often blamed on poor quality Chinese fasteners. If the engine mounts fit the frame and have good contact throughout the circumference of the mount and if the fasteners are torqued properly and not overtightened, then the probability of fastener failure is greatly reduced. This goes for studs with nuts or bolts. Improper installation is still the biggest culprit with these kits and this opinion is shared by several others here who have years of mechanical experience to back up their claims, me included. I like the Allen head cap screws in place of the kit studs for reasons other than strength. They look cleaner, are easy to install and remove and there is far less chance of overtightening them than with a ratchet and socket; use an Allen wrench and your ability to overtighten is reduced due to less leverage And, they're easier to keep track of than a handfull of nuts for eyes as old as mine. Another plus is that there is only one set of threads to worry about. With studs you have to be concerned with those in the engine and those in the nuts. A bolt reduces the thread involment in the fastening. That being said you might ask why I do not use bolts instead of studs for the cylinder and head. The Chinese have done something here very odd. Look and you'll find that bolts long enough to hold the head and cylinder to the block are difficult/ next to impossible to find. That's because bolts of that diameter and length are only available in a 1.25 thread pitch and the studs the factory uses are a 1.00 pitch. I do replace the acorn nuts with hex nuts because I've found a couple of them that had bottomed out on the stud and would not allow a proper head bolt torque. Hope this answers some questions but it will probably ruffle some feathers and stir up dust too. So be it.
    Tom
     
  11. Creative Engineering

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    No ruffled feathers here Tom...GOOD POST!

    There are so many misconceptions about fasteners...again: good post!

    These engine kits really do require a seasoned mechainc and/or someone who is very capable of understanding written instructions to execute a good installation.

    It's the little things that add-up to a great installation.

    Jim
     

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