Since we're on the topic of jettng, do I need to after slapping a FMF megamax and K&N on my 329cc TRX350 Rancher? Emailed FMF, got no response yet, talked to a honda dealer...said to try it and see if the engine sputters...(professionalism at it's best). I've hear I'll run lean...where can a guy get hard info on this tech?

 

Do a search for jetting on this site and you will find all sorts of info. Just go the search page, select all brand makes of atv's, and then type in "jetting" and you will find a plethra of knowledge.
JP

 

where is it sputtering at? deceleration with throttle fully closed, 1/8-3/4 throttle, full throttle???

 

how in the heck can you say this??????? you don't think power gains can come by rejetting??? i promise you if i was the one to jet his bike, it would run great. jetting changes almost daily even though most don't take the time to mess with it. as the humidity increases, you have less O2 in the air because of more H2O in the air, so air/fuel ratio is richer. this means jet down or lean it out a bit. as the warmer weather comes, the air becomes less dense, you need to jet down once again. as you increase in altitude, your getting less air so jet smaller. if you take a 400ex with a slip on pipe say at 625 feet above sea level and around 90 degrees outside and put in a 152 keihin jet and a 165 keihin jet you will notice a quite large difference. if you can't, you obviously don't know the bike too well.

i agree, you can't get power from a jet kit, GIVEN, it is already jetted correctly. i have and never will buy a jet kit. i only buy individual keihin main jets, needles, and pilot jets. soon here i may be buying a new keihin main air jet. you bet, if it jetted right you won't gain power. however, how many people do you see that have their bikes jetted "right?" what do you consider "right?" it depends on what type of racing you do. if you do constant full throttle races you usualy want to go alittle richer to prevent overheating. other alternatives help as well ( larger oil coolers, liquid cooling, higher octane fuel, etc). but, i can promise you his 400ex won't be running to its potential with a 165 keihin main jet in.


in reality the 400ex needs a different needle for a more modded bike. also, a washer under the needle helps too. the stock location on the needle is the 3rd position from the top. after modding the bike some, this was too lean in summer and winter. in the winter, the 4th position was great. however, it was too rich in summer. so, my bike wanted a position between the 3rd and 4th position in the summer. a different needle was needed for this or a washer would have worked. this washer would have raised the needle 1/2 of a clip position if placed under the needle. so, i would have been able to put the clip on the needle in the stock (3rd) position and put this washer under the needle and i would have been between the 3rd and 4th position on the needle without the washer there.

good luck

 

Hey i need to know if its ok to ride with just my pipe on and no rejetting or my K&N airfilter for one ride will it hurt anything? i need to know asap iam going riding soon thanks[img]i/expressions/face-icon-small-smile.gif[/img]

 

I wouldnt, if its leaned out from the pipe i wouldnt want to run the engine like that.

EDIT: Are you saying you already re-jetted it for the pipe but not for the new airfilter?

 

it probably won't hurt anything but i wouldn't do it. it only takes a few minutes to jet it.

 

Yeah i was just running it with the pipe no jet or K&N yet. This week it is comming in then iam putting a 165 jet in it. how much plastic do i have to take off for this?

 

no plastic. turn the fuel off. remove the 17mm bolt on the bottom of the carb. right up there is the mainjet. use a 6mm socket to remove it. then install the new one but not too tight. install the 17mm bolt and turn the fuel on and have fun.

 

is this how you would jet a 300ex too???