PW 50 Jetting

7 replies to this topic
  • rippin x3

Posted September 20, 2008 - 08:44 AM


Hey Guys, I recently purchased a PW50 for my youngest for $300 (not sure of the year). Totally went over the bike. New seat, plastic, graphics, 412 grips, eliminated oil tank, UNI filter, new throttle cable, tires, coil, plug and reeds. I also cleaned the carb and burned all residue from inside the pipe. Bike looks brand new. Before I redid it the plug looked very black and gummed up. Now, after all that work, the plug looks a little too white for my liking. Mixture screw is about 1/2 turn out. Will a bigger pilot fix this or do I need a bigger main also? Just to make sure - the mixture screw in is richer and out is leaner - Right?

  • rippin x3

Posted September 20, 2008 - 08:49 AM


Forgot to mention that I'm running 40:1 pre-mix


Posted September 20, 2008 - 03:22 PM


yes out is lean and in is richer, i always change the main first, is he using the bike at over 1/4 throttle most of the time? if is so change the main first,
then if its still to lean change the pilot,
if you are only 1/2 turn out this seems like it is running to lean so go 1 size bigger main and see how it runs from there make sure you only run the bike for 15 minutes or so before you check and make sure you use the same plug, a new plug can take much longer to read then a older plug that has been ran on before.

if you put the bike on a stand and run the bike for 15 minutes at only idle to 1/8 throttle or so then read the plug this will tell you if the pilot circuit is to lean, if you run the bike for 15 minutes using 1/4 to full throttle most of the time then read the plug this will tell you how you main circuit is jetted,
but usually its always the main that makes the most difference.

  • rippin x3

Posted September 22, 2008 - 01:20 PM


Thanks for the reply, this gives me a place to start.

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  • entrpner71

Posted February 01, 2009 - 09:06 PM


I know almost nothing about jetting, where do I go to learn about the principles involved with it? What is the stock setting? My boy is only 2.5 so I am not looking so much a boosting performance but just making it run nice and smooth. Thanks.

While I am at it where can I find service info about them. I think I need to refill the bottom end very badly (making a rattling noise... it's an '82) but I don't know how exactly how to check it, what wieght to add, or even the mix ratio for the 2T oil. Don't think it is injecting the oil manually. Went through almost a tank and the oil reservoir is still full.

  • sportbiker929

Posted February 01, 2009 - 10:44 PM


they don't use much oil. The rattling means you probably need a top end. very easy to do. where are you located?

  • entrpner71

Posted February 04, 2009 - 11:08 PM


Bonsall (just east of Oceaside, which is in the North county San Diego). What are some of the things I should replace, keep in mind it is an '82. It is probably jetting but I don't doubt that engine work might need to be done. Question I weight about 255lbs the bike rarely can get me moving from a dead stop without me giving a push, is that to be expected? Thanks again!

  • sportbiker929

Posted February 05, 2009 - 08:01 AM


order a top end kit from north county yamaha and pull the top end and take new piston and cylinder to racer machine in escondido.


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