5hp briggs and 1969 bird questions

[SensitiveWite]

I have a project ive been working on lately its a 1969 duck bird. I just recently got a old 5hp flathead briggs that I was super exited to use as its engine as ive really only used predators before and I thought it would be perfect for my vintage project. It was kinda a fast thing I saw the engine on craigslist for $60 it was only ran for a bit on starter fluid and then would die and I figured out the choke butterfly was cracked and it was letting way to much air in so that was the problem the carb was around $25 so not to big a deal. when I mocked up the engine on the frame I was oblivious to the fact I took the gas tank, muffler and covers off to clean them because Im going to have the engine painted nice. Then I realized it barley fit and then it hit me the gas tank was not on. Im pretty sure I can make it work by taking the old mounting plate off and then moving the whole thing more twords the front. I have some pictures on what I was thinking. would that work I know the chain would be longer so I would add a chain tensioner. Some of the pictures I have the engine forward where I want the engine would this mess up the bikes center of gravity? also what kind of sprocket for those hubs(just a six boly hub)? Also im looking for a 1969 duck bird handle bar and fork if anyone has one they want to sell please let me know!

 

[Garagebuilt]

I have a project ive been working on lately its a 1969 duck bird. I just recently got a old 5hp flathead briggs that I was super exited to use as its engine as ive really only used predators before and I thought it would be perfect for my vintage project. It was kinda a fast thing I saw the engine on craigslist for $60 it was only ran for a bit on starter fluid and then would die and I figured out the choke butterfly was cracked and it was letting way to much air in so that was the problem the carb was around $25 so not to big a deal. when I mocked up the engine on the frame I was oblivious to the fact I took the gas tank, muffler and covers off to clean them because Im going to have the engine painted nice. Then I realized it barley fit and then it hit me the gas tank was not on. Im pretty sure I can make it work by taking the old mounting plate off and then moving the whole thing more twords the front. I have some pictures on what I was thinking. would that work I know the chain would be longer so I would add a chain tensioner. Some of the pictures I have the engine forward where I want the engine would this mess up the bikes center of gravity? also what kind of sprocket for those hubs(just a six boly hub)? Also im looking for a 1969 duck bird handle bar and fork if anyone has one they want to sell please let me know!

I just purchased the same frame you have. After dropping my Briggs 5 horse in I have the same issue. I think they originally had 3 hp Briggs which I understand are shorter. For mine I am cutting the rear down tubes and raising them 2". I'm also extending the frame 4 inches. Not concerned with originality since my frame is missing all three stock parts except the forks. I think moving the motor forward wouldn't be much of an issue. I know your post has been up for a bit bit I'm curious to see what you come up with. I am also fighting out my back wheel and sprocket. I think I'm going with a normal 60 tooth sprocket and fabricate spacers as needed. I'm using a clutch brake so rear brakes aren't an issue. I'd like to see your progress.