yz450 f tranny or internal problem need help asap

[trevor_zr600]

hi, my friend has got an 03 yzf450 and its got some very confusing jetting issues or something to that matter he thinks. Its a canadian model, in central manitoba. It has a 168 main, 42 pilot, 3rd clip and a twin air filter. Symptoms are popping on decel, hesitation, and a strange motion in 4th like the clutch is slipping or something to that matter but it is not because it has been all checked over . Why do the 04's come with a 172 main 45 pilot and 03's with a 165 main 42 pilot? My 2003 manual just says a 165 stock with no alternative for other countries. he noticed in a 2004 manual that canadian models come with a 172 as the US models come with a 165. I myself think it is somethign to do with the tranny could it maybe be the shift fork not engaging the gear completely because 1st,2nd,and 3rd gear pull perfect but 4th just wont seem to go.help please asap summer is almost over and we havent been able to go riding with him yet because his bike is being a pain.

 

[YZ165]

The popping and hesitation sound like a jetting problem. But the fourth gear thing is strange. I'd go back to stock jetting for an '03 Canadian 450, use that as a baseline, and jet acordingly from there. If the bike is making any strange noises from the trany(grinding, clunking, bang-bang-swoosh) get the cases split before you try and jet it. Also take a look at the oil filter, if the tranz has issues, you will probably see metal flakes on it. It is possible that it has a bent shift fork, but that usualy effects more than just one gear. The only thing I can think of based on your description is the 4th gear primary or secondary gear are missing teeth. My .02.

 

[alextreme3]

tranny

 

[Chili]

If you get completely stuck give ROY BORTON a call and he should be able to get you on the right track. He is a top Manitoba wrench and has much experience with those 450's as his main racer rides em.