I greatly admire your ingenuity and skills so please take the following as constructive "advice."
As a tool maker,engineer and fabricator with many projects under my belt I'd like to offer some suggestions.
The BW frame uses the engine as a stressed member. Since there is no lower engine cradle,the engine itself has to provide the strength to hold the frame together and stabilize it.
Your engine will be strong enough but the mounts you have made will not.
The front mounts may be good enough but would be considerably stronger if you weld the plates to the frame.
The back mounts need some more work.
If you land this from a jump,the frame will try to "open the horseshoe" that is the engine cradle.The front mount will try to pull the back of the engine away from the swing arm pivot.
The lower mount using the u bolts will do little to prevent this. They will break or deform as the angle iron is already doing from the bolts being tightened.
The upper mount is two "L" shaped pieces of iron bolted together. If you make spacers to fill the gaps between the brackets and swing arm you will have good side to side strength but virtually no strength when the motor tries to move away from the swing arm bolt.Simply welding the two pieces of angle together will not give you the strength you need. The forces will try to straighten them out. You need the top plate to hold the bracket in the shape it is now.
Laying a shaped plate on the top and bottom of these two "L" brackets,that covers them from one side of the engine mount to the other side and extends backward out over the swing arm bolt,and then welding all together will greatly strengthen this area.Do top and bottom if you can.
My concerns are this,if you ride this very hard at all, this frame will be a "flexible flyer" and quickly break.The results could hurt you.
Please go back and look at the conversion I did with the two stroke.I fabricated new lower frame rails to tie everything together and then used a thick aluminum skid plate on the bottom as a stressed member also.
Please take this from a fellow BW'er that would rather not see you get hurt and continue to develop your obviously creative fabrication skills.
I'll be glad to help you in any way I can. If welding is an issue, you can send me anything and I'll weld and send back.
Shercoman screwed with this post 09-03-2012 at 05:38 PM