08 yfz 450 jet confusion

[buggieman48]

just added a BUB full system..running stock air cleaner...Im doing this for the girlfreinds son..he brought me a dyno crap jet kit so this is what we got..installed a 48 pilot and needle 3rd notch from top and the only main this kit had bigger then a 155 was a 165?? fuel mixture screw is 2 turns out..here is the problem the other night we got this all done and the bike run great no backfire no hesitation..thought awesome first time got lucky w/the airbox lid off..so he wanted to run w/ a airbox lid so i picked some 1" filtered airplugs uni airbox breathers and put 6 in...in the process i noticed the oil job on the filter was pretty slim..so i reoiled and when i started the bike it idled fine but started backfiring on the mid to top if you hold the throttle steady or when you chop the throttle..took the aircleaner off so all there was the metal screen and it ran without a prob..so i thought the oil on the filter was to much...tryed it again w/o oil and as soon as i screwed the filter down it started popping on the mid to top...so this paper says im rich the question is i was always told popping flames out the exhaust was to lean or a air leak in the exhaust..oh ya this bike has had the cam mod done...i plan on going and getting a 158 and 160 or whatever the jets between are tmor..im i going the right way..still havnt put a airbox lid on but with the 6 extra holes i dont think there will be a difference...tnx for any help..just dont understand why it ran so good the other nite and like crap tnite..

[miles Machine]

well the common miss conception is that a back fire dosnt come out the exhaust its actually when it pops through the carb and that is a lean mixture...now when it pops outthe exhaust its actually called after fire and sometime depending on the condition it could be eather a lean pop or a rich pop in your case its a rich pop....one thing to remember when using a jet kit like dyno jet is that the sizing is defferent from keihn jets hence the adaptor that you had to install you said you put a 165 dyno jet jet in it is likea 182 or a 185 keihn jet which in your case is to much.

hope this helps

[buggieman48]

ok thats why the dyno crap starts with a 124 jet up to a 165..does anyone no of a site that gives a cross reference from klien to dyno sizes i will keep looking and appriciate your help

[miles Machine]

jetsrus.com

[buggieman48]

found it thanks very much learn something new everyday...didnt know they ran different numbers..i just checked that they were the same size must have something to do with the adaptor...whatever i think this will work now...thx again