Motor Sliding Down Seat Tube And Down Tube

groove9028

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I've mounted the motor as flush as i can with little to no gap with the mounting hardware. I put electric tape below each of the mounts to make it a tight fit. all the bolts have been tightened down as tight as i can, and yet it still moves. any recommendations or suggestions to fix this problem would be greatly appreciated! will post pics soon.

HAPPY RIDING.
 
Yes it is. I have a Murray cruiser from the 80's in my backyard. The frame tubes are too small for the motor mounts, and my motor has the small mounts, not the newer larger mounts.

I strongly recommend staying away from any motor mount that requires you to drill holes in your frame. Research Al.Fisherman's posts. He has photos of how his frame cracked through right where he drilled his. He is not the only one that has had this problem with the drilled frame mounts either. Drilling a hole in your frame is inviting disaster if the frame were to crack while you are at speed.

For tubes that are too small, try to work out a spacer or shim arrangement to fill in the gap. Right now I am thinking PVC sprinkler pipe, but I do not know if that would be strong enough or possibly crush/ wear down over time with all the vibration that these engines create. Perhaps if it were routinely inspected and new pieces installed when necessary?
 
More often than not, rubber mounting the engine mounts results in broken mounting studs.
 
With solid mounts the vibration is transferred to the entire bicycle frame and it absorbs it as a whole unit. Also the engine is solidly mounted and the relationship between the mounts and frame does not move.

When rubber is placed between the mounts and frame the vibration is mostly contained to the engine alone. The whole bicycle cannot absorb it. The engine mounting is flexible and the mounts can move on the frame. This movement stresses the mounting studs and the stress can lead to broken studs or worse, a broken engine case around the stud holes.
There are plenty of threads and posts on this site to support this information.
What I am trying to do here is pass on the hard lessons learned from others on this site to you.
 
I've mounted the motor as flush as i can with little to no gap with the mounting hardware. I put electric tape below each of the mounts to make it a tight fit. all the bolts have been tightened down as tight as i can, and yet it still moves. any recommendations or suggestions to fix this problem would be greatly appreciated! will post pics soon.
HAPPY RIDING.

1. If the engine can slide down the seat tube, I'll guarantee that the engine is not mounted correctly. If it were it would be IMPOSSIBLE to slide down. The front mount wouldn't allow for this to happen.
2. It is possible that the engine mount is too large for the tube. I have two different engine mounts, one fits perfectly, the other is too large. With one not large enough it is easy to fix. The clamping service can be enlarged by sanding. You can use a piece op pipe or PVC the same size as the tube, wrap with sandpaper, and sand till you have a proper fit.
3. A mount that is too large for the tube can be shimmed out, dang I hate to do this, but you can get a copper or brass pipe coupling, cut in half (from end to end), and fit as snug as you can.
4. Use proper torque.. 50 to 70 INCH pounds (NOT AS TIGHT AS YOU CAN). I find that in order to torque the nuts properly, the engine mount clamp gets in the way of the socket. To correct this I install a shim (about 1/2"long) between the clamp and nuts.

AS far as what Gear Nut mentioned above, believe it. Proof in pictures if you want.

Proper mount fit. Notice the shims.
http://www.motoredbikes.com/album.php?albumid=1018&pictureid=6909
http://www.motoredbikes.com/album.php?albumid=1018&pictureid=6663
Notice the space between the mount and clamp at the studs?

Drill baby drill....
CrackFrame2.jpg


You can see that the mount on the left is too large for the tube. Also pictured is a engine mount shim. Easy to bend, form fit and cut to fit the engine mount.
 
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