timing setup on an '83 500XC

[Old Geezer]

In the process of resurrecting my bike after sitting for a good 4 years - and checking things with intentions of backing off the advance a bit and fiddling with the carb throttle slide to ease starting, I pulled the timing cover and was suprised to find an internal rotor Motoplat. My understanding is that my '83 500XC should have an external rotor. Hmmm....why would someone swap out for an internal rotor? Also, upon dismantling the carb, it's fitted with a 3.0 throttle slide (probably a good thing for starting, vs. the stock 2.0 that's supposed to be in there) and it's jetted with a 400 main vs. the stock 360(?).

Ignition timing appears to be close to the stock 18 degrees rotation - from looking at the rotor and stator marks and how they line up. Will eventually check the mm of piston travel BTDC

Opinions would be appreciated. Looks to me like the previous owner(s) had this bike tuned for top end power.

 

[Gasitt]

Gday old geeza i should have it all back together on the weekend i also have decided to go with the internal rota i have a 420 4speed and i find the down change is slower on it with the fly wheel ignition and the 500 is a 3speed so i will find out the only concern i have is the starting some say the fly wheel helps starting because of more spinning mass cant say i noticed any difference on the 420 but 18 deg or 72 thou on the dial gauge BTDC is where i will be setting the timming my main is a 390 and a 55 pilot with a 2.5 slide the carby is a 38mm not the 40mm on some 500d's. I think you should be mindful of the stail fuel gremlins with your bike 4yrs is a fare while.

Gasitt!

 

[Old Geezer]

Gday old geeza i should have it all back together on the weekend i also have decided to go with the internal rota i have a 420 4speed and i find the down change is slower on it with the fly wheel ignition and the 500 is a 3speed so i will find out the only concern i have is the starting some say the fly wheel helps starting because of more spinning mass cant say i noticed any difference on the 420 but 18 deg or 72 thou on the dial gauge BTDC is where i will be setting the timming my main is a 390 and a 55 pilot with a 2.5 slide the carby is a 38mm not the 40mm on some 500d's. I think you should be mindful of the stail fuel gremlins with your bike 4yrs is a fare while.

Gasitt!

Thanks for the input. Yes, stale gas after 4 years....well, I had drained it out prior to going into storage and spent last weekend dissmantling the carb and reeds, and cleaning out the fuel tank. Everything looked good.

You are correct about the smaller internal rotor; it does supposedly result in harder starting because of the lower enertia, which was a huge issue with mine and is why I'm looking to replace it with an external rotor. Plus, I'll be setting my timing to something closer to 12 degrees (about 1.8 to 2.0mm piston travel BTDC), vs. the stock 18 degrees/2.8mm. I'll play with timing first, see how she starts, play with jetting, then consider a different rotor setup if needed. Gotta do this in measured steps, ya know?

Exciting news last night: I found another '83 500XC for sale practically in my back yard. Supposedly runs (the seller says it "just needs a coil wire"....yeah, right!). I think I can get it for less than $400. If anything, a great source of spare parts.