Jetting and new exhaust

[littlewing78]

I recently bought a nearly complete 92 KX 500 parts bike for $250.  Awesome deal I know.  It came with an FMF Gnarly pipe and an FMF power core silencer.  What kind of Jetting issues can expect when I put those on my bike?  Everything is stock right now.  
I'd also like to know what the difference is between the FMF silencer and the stock silencer.  They look to be pretty much the same thing to me.  Does that FMF sticker make it run better?

[Friar-Tuck]

The power core silencer is USFS spark arrest approved. That's what I have and have no complaints. it is a bit quieter than my stock silencer but that just may be attributed to the turned down exhaust tip.   
      I would't worry too much about the jetting unless your bike is not running well currently.  FMF has a jetting chart and the Teem Green chart has usually gotten guys close.  Have a look and take a few jets with you the first couple of rides.   
  The pipe and silencer usually calls for a richer main, but the bikes are pretty rich in stock trim.  You said your bike is otherwise stock, so swap out the pipe and silencer and see how she runs.  Take it easy for a few minutes and have a look at the plug.   You should be able to tell if the bike isn't running right pretty quickly.
  Tuck\o/

Team Green  http://www.teamgreennews.ca/pdf/2004_jetting_chart.pdf

FMF Jetting   http://ridersupport.fmfracing.com/JettingCenter

How to re-pack your FMF silencer    http://ridersupport.fmfracing.com/RepackingInstructions

[Polar-Bus]

I recently bought a nearly complete 92 KX 500 parts bike for $250.  Awesome deal I know.  It came with an FMF Gnarly pipe and an FMF power core silencer.  What kind of Jetting issues can expect when I put those on my bike?  Everything is stock right now.  
I'd also like to know what the difference is between the FMF silencer and the stock silencer.  They look to be pretty much the same thing to me.  Does that FMF sticker make it run better?

One of the things I've learned over the past 30 years of riding and wrenchin 2 strokes is the fact that aftermarket pipes are nothing more than wallet bait for the average rider. It's funny to me how so many people loose sleep over "what pipe is the fastest" . It's well known that adding a pipe is NOT going to require any drastic jet change. Scroll through our jetting thread, try to match to your specific conditions, and then you need to test and tune for your exact engine's requirements.  More importantly than "what pipe is best" is "keep your air filter clean".  I read FAR more "blown engine" horror stories than "wow my engine runs  awesome with my new Pro Circus pipe" !

[kwakman]

used same pipe on my 86, (380) main standard,(vm40, not pwk carb) and mine needed a 360 main as the pipes improved scavenging meant lower, not higher.read up on here, then read your sparkplug.K.