Jetting questions,if you don't know don't answer

[Bill Fuller]

I have been working on the jetting on the YFZ and am still having problems.I have tried many combos and thought I was close until Sundays race.It seems that the bike will roll through the throttle most of the time until I get to 3/4 to W/O.Now I know the main effect this portion of the throttle but I am confused wich way to go.When I hit 3/4 throttle the engine breaks up almost as though it's in the rev limiter.The bike has not over heated.I have a HMF full system with quiet core,stock air box with stock air filter and lid on.45 pilot,NCVQ on 3rd clip,165 main.The bike idles fine and starts easily the only problem is the stutter at high revs.I started with a 175 main and needle at 5th clip and it ran like chit.I have made adjustments to the needle and mains in seperate incraments and it got better when I got to my current position.It seems as though the bike runs good all the way up to 3/4 throttle.I would like to keep the air box lid since I race XC.Do you think I should drop the needle to the 2nd clip or change to a 162 or 160 main.I am almost to the point of saying I have a bad rectifier but I'm not willing to give up.

[Bill Fuller]

:confused:

[bigbadktm]

if you have a question about the rectifier, check out an aftermarket one.

leave the needle clip in the 3rd position, and bump the main jet up one. try that, see how it works. also check to make sure the air filter is clean, no intakes are blocked, plug is clean, and exhaust is not restricted. if you have any other q's that dont get answered here, try posting it at glamisdunes.com . there are plenty of people running that bike over there, and are more than willing to help.

hope that helps

[wyndzer]

Bill I'm running the NCVQ on the 3rd position , 170 main, 45 pilot and about 1 1/4 turns out on the slow needle, I also have a custom outerware lid and GYT-r pipe. I'm very close to sea level. Hope that helps.

[Hammer trx450r]

Hey Bill Im no pro but it sounds to me like you are to rich on the main. I would drop down to 160 main and start climbing up a jet size untill you get the popping back then go back down one size. Hope this helps. Take lid off and see if it helps then ya know u are too rich;)

[Bill Fuller]

Thanks guys!!Can anyone explain to me the different characteristics of lean and rich.(sound ,feel,smell,any thing)I don't think I need to go up on the jetting since I started out with the needle on the 5th clip and main at 175.I have gone down 4th clip,3rd clip etc....and 175 down to 172,170,168, till I got to the 165.The only thing that concerns me is most people are running at least 165 main.Dhines has a YFZ that all he needed to do when he got his pipe(HMF)was 5th clip on stock needle and 170 main runs GREAT.He is also running stock filter,box and lid on.


Again thanks for the replies.

Bill

[bigbadktm]

here ya go (http://z400central.com/invision/index.php?showtopic=1699)

ok i was wrong earlier about going up on the jet size, but i just read this...hope it helps you out

[Bill Fuller]

Cannot be displayed or unavailable:confused:

[bigbadktm]

ok fixed it, i entered the properties wrong

[cals400ex]

i would try and clean the carb out, the top and float bowl. i am also wondering if you have another problem besides jetting. i think the bike should run fine with the clip in either the 3rd or 4th position. i would probably start with it in the 4th though. also, a 170 or 172 should be just fine. is it a possiblity that some dirt got in the tank? maybe you need a fuel filter??

i would try and do some plug chops and look at the plug color and see what you find. a dark plug color is rich and a white plug color means lean. usually when you feel it cutting out is because your too rich but i really can't see that happening with what your running. i would make sure the needle didn't not come loose or fall out of place.