Jig - center motor or build around?

[Scoobydude]

Opinions on buildjing a jig around motor mounts or engine vs building a frame then aligning motor in it?

Im pretty close to retrying my frame build, and im debating maybe trying to build the frame and then putting the motor where it goes, its gonna be a tight fit.

Chopper handbook shows building the frame then worrying about the motor and trans???, but i havent seen too many threads on thay way of doing it. Pros and cons? For a sporty.

[farmall]

Since the metal structure you are fabricating must fit the engine AND allow most maintenance with the engine in the frame unless you hate yourself, I'd use the engine. It doesn't cost anything, you already have it, and seeing it in place is better than imagining it in place.

IMO piss on tight fits unless it's some fagstastic showbike abortion you don't intend to ride. Tight fits alone aren't an accomplishment.

Styling can work around reasonable maintenance access.

A really interesting option which could give you a tight fit but make it easy to R&I engines would be to make one frame rail removable the way Honda etc do it with fittings (which you could slice from wrecked frames or easily make if you have mill access) and socket head cap screws. That would end the usual Sporty engine wrasslin' and you could probably bring front down tubes closer to the engine.

Since all sidestands which aren't traditional Harley eat leper anus, a three bolt pad to take them would be a useful addition unless minimalism and shitty stock style Sporty stands are vital.

Whatever you do, having the engine in place will let you see and test instead of pray and shoot in the dark.

Your front motor mount is worth thinking about, though the stock Sporty design with separate plates isn't bad.

[Scoobydude]

After some thought i think your right. Ive been rwligiously lookin thru instagram and seems alot got an engine in there .i really am kind of intimidated tryinh to figure out how to position the motor. Ive never read anything on aligning. The bottom of the sporty case has that flat pad thing going, maybe i can rest it on that. When its in the old frame the flat spot looks very parralell with the ground. Im more curious on lateral placement between the rails.. Should i find spacers and figure out what the gap is when in a stock frame? Spooked out on alignment, how do you get it deads nuts?

Gnarly idea on the frame rail deal. The tight fit is to get it in a 3 up BT type frame. I just used the '48 blueprint and i think itl work. Made a paper bp of sporty engine(cant find one om the internet anywhere) and put it in full scale drawn 48 frame. Last frame i did was pretty close to the 48 so i said f it, see how close i can get.

[farmall]

All the engine cares about is rear pulley alignment with drive pulley. Figure your rear tire centerline to match your front tire centerline and of course the centerline of your steering neck.

The rest could look like spaghetti so long as it's strong enough.

A digital level with or without a laser is nice to have. My machine shop owner bro tested his Craftsman (which is nothing special) against his expensive Starrett machinist level and uses the Craftsman when setting up parts in milling machines.

Long straight edges (including levels) are handy for fab. You have various points on the sides of the engine which are machined flat. You could use those for reference.

The primary cover gasket surface is long and perpendicular to the engine centerline.

Practical Machinist forums are outstanding. They are directed at professionals so there's a shitload of useful reading.

http://www.practicalmachinist.com/vb/fabrication-cnc-laser-waterjet-plasma-welding-and-fab/best-layout-tools-fab-sheet-metal-276060/

For some interesting pics search "Honda Shadow (or anything else with removable steel rails) frame rail" on Ebay then look at the joints. You could find a wrecked frame to cut joints from. They appear to be plug welded and of course have a 360-degree weld around the fitting. You might harvest by drilling the plug, grinding the bead then twisting with a pipe wrench until they break free.

Remember it's a rubbermount engine unless you make it a solid mount so you can't get extremely close with tubing or the engine and frame could chafe each other.

[xMPRx]

do you have a stock sportster frame to use as reference? If you are building a frame jig it would be a good idea to use your stock frame and take the measurements from that. then you know the exact relation ship between the engine mounts and the head tube and axel plates. then you can go up or out on you neck and have a reference. just building a frame without knowing exactly where you components are mounted seems like a bad idea.