> Lawrence Au Wrote:
> Triangulation my friend...
first of all, its pretty great that Larry commented and hopefully he has some more tips as the build progresses. He's a humble guy but has a lot of experience in motorcycle racing, his word is the gold standard.
I'm not even close to the same league but i have done some AHRMA racing experience and modified some vintage bikes for racing, not to mention dirt stuff that is probably more topical.
For my own race moped, i chose a pinto frame because i wanted something lightweight and tube, then i welded on a custom rear seat/shock subframe out of cr-mo tubing which pitched the entire frame forward effectively tightening up the rake because i didn't want to cut the neck and weld- the stock frame is very thin wall and its professionally coped and welded, i didn't trust myself to get it right in my garage, then i used Magnum forks with a 16 inch front wheel mostly because that was stuff i had around and the magnum forks are lighter than other forks and have hydraulic damping.
the tighter rake and trail makes it turn in really nice, it rides very similar to a mini-moto like a kx65 or XR100. i have medium wide MX bars with a mid rise so they end up about 4-5 inches above seat level. Raising up the seat was huge because it lets you get your weight high and forward like a dirtbike or mini.
the thing everyone fucks up with moped racing (i haven't actually done a moped gp event, so take this with a grain of salt) but it seems like people just want to make smaller versions with the same proportions as a motoGP road racing bike. at low speeds and tight stuff, in my experience riding supermoto and dirt, you're better off getting on top of it, just because of how tight everything is on a moped, plus getting the suspension to work right with limited options for parts puts you in a very compromised window.
anyhow, my advice is- start with the rider triangle and work your way back into a design. When i did mine i took photos of the frame and made measurements on the picture to see where i would end up, then i filled in the blanks with the parts i needed to use for practical purposes (forks, wheels, shocks) then i just 'connected the dots' between those parts. My bike looks weird as shit but it works well, hopefully next summer i'll get my program sorted out and make it to a moped GP track to actually compete against people.