Originally Posted by Dirtsampler
I'm finishing a refurb ( mechanically sound, but not really beautiful ) on
a 1982 that I plan to race in Evo class and general play ride. I'd appreciate
any tips on kick start mechanism health and assembly. The motor has new
piston / rings and healthy lower end and seals. The hope is that with a
good tune and proper start drill I can avoid broken cases and start gears.
Yamaha did an update to an internal part of the kickstarter in starting in '84 or '85 on the YZ490. The tab that hits the stops to define the lever's stroke was manufactured differently, stronger. I don't remember all the details, but I remember holding both the new and the old parts in my hand once, when my buddy bought the new part for his '83 YZ490. I would expect that same part would drop into your '82 IT as well. Spend some time on Yamama's online parts catalog, looking at the kickstarter parts for the YZ490s from '83 to '85, and you'll spot the P/N change.
My buddy ran an iridium BR9EIX spark plug in his YZ490 for a couple of years (that one plug lasted for quite a while!). He's running cheaper plugs now (replaced more often), and he denies any difference, but I swear his bike was easier to start with the fine wire iridium plug.
The biggest starting problem the 490s (all the 465-490 engines, actually) have is twofold. First, a stroke of the kickstart lever doesn't get you much stroke of the piston. It takes the right kind of kick to get enough momentum built up to carry that crankshaft enough to get it to fire. Second, the lever is ridiculously long and positioned way too high, making it tough to give it the right kind of kick. By comparison, the '94 KTM 440 I ride is a peice of cake to start. The lever pivot is lower, and the lever stroke moves the piston more.
For cold starts, my buddy usually leans his 490 up against a tree or something (with the bar end), stands up on the pegs, hops up, and drops his 175-ish pounds on the lever. He doesn't use much muscle at all to actually "kick", like you would on a little bike. I think the trick really is to catch yourself with the other foot just before you hit the stop, to avoid breaking stuff. Also, beginninging with two halfhearted kicks seems to help "prime" the cases, saving your energy for a good third kick that will (hopefully) start it right up.
Luckily, I would expect the IT state of tune would lend itself to easier starting than the YZs.