What kind of motor mount do you use on a 2" down tube?

Redneck in China

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I have a Giant MB and am looking at buying a lightweight Giant 23" aluminum frame. It has a 2" down tube. I really don't want to drill holes. I want to mount one of those Chinese 2-strokes. What are my options?

Thanks,
Mark
 
I am considering getting a new bike and motor,
and this is the exact problem I have faced as well.

Most modern moutain bikes seem to have this 5cm/2inch issue...

I've seen other posts detailing other solutions to this issue previously, but not been
able to find them...if anyone can find them, post em back here will ya ???
 
My front mount is a custom bracket I made that looks like an upside down T and uses the two original water bottle bolt holes in the frame and bolts to the motor with two more bolts on the bottom horizontal part.
 
Jim (Ghost0) is working on a new front mount that will fit the larger tubes.
 
I have a Giant MB and am looking at buying a lightweight Giant 23" aluminum frame. It has a 2" down tube. I really don't want to drill holes. I want to mount one of those Chinese 2-strokes. What are my options?
It's really simple....you don't need to buy anything

Bolt a metal plate to the front motor mount that either
extends up or down from the mount

Find a suitable wide clamp for the front of the 2" tube that
attaches to the plate with 2 bolts and nuts

I don't like using U clamps like muffler clamps as they are too
narrow and concentrate stress and they look like carp

Grubee's 50 cc Gen II has an updated front mount that clamps a
1 3/8" downtube but it can be sanded / filed out to accept about
1 5/8" as it has about 1 3/4" between the studs
 
Thanks for the feedback. A couple of questions though:

1) The frame I'm looking at is a pretty lightweight aluminum Giant frame. Will the water bottle bolt holes be strong enough to bolt a T-shaped bracket to? I had thought of this but wasn't sure I'd want to put those mount points through that much stress. It is just aluminum.

2) I like the U-clamp and plate idea. Here's a rough picture of what I was thinking of with the bottom two holes being the holes the motor's studs/bolts would go through:

----------------------------------------
l l
l O 2" between holes O l
l l
l l
l l
l O O l
l l
l l
----------------------------------------

I thought I'd just use a 2" muffler clamp with the plate shown above if I can find one. I don't know how hard it will be to find a 2" clamp in China. A muffler shop may have something close though.

Please let me know what you all think of these ideas.

Thanks,
Mark
 
The diagram above looks nothing like it did when I typed it so disregard it.

Basically what it is supposed to be is a plate with holes spaced 2" apart at the top and the holes at the bottom spaced at whatever the motor stud spacing is. This would go between the motor and the u-clamp.

Mark
 
Here's something I just finished a few days ago.
The bottom clamp is from the HT chain tensioner, the top plate is hand made uisng electric hand drill, dremel and bench grinder.
The plate is 5mm mild steel, the blue is "blue compression engineers marking dye" to mark out the punch holes prior to drilling.

What's being tested at the moment, is I left the engine mount studs original for now( where the cosmetic dome nuts are), so if it snaps I just ezi-out, rather than go through the hassle of trying to drill out hi-tensile bolts.
If it passes then I might replace the HT studs with the regular upgrades uisng hi tensile allen key bolts.

Also, if a hi-tensile bolt snaps on the alloy, it does much damage when owners who have ready made bikes, but not "feel" for things mechanical.
They just keep riding and don't understand minor regular checks and maintenance, things we tinkerers just naturaly do.

The next mount top plate, if this passes my bolt tests during run-in will be slightly differant, but this seems to work and much engine vibration seems to be absorb by the 5mm steel plate.
Leather helps absorb the metalics to.
 

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