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YFZ is Broken
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Posted by: Fast400exRacer

THe YFZ kicks some ***, but now this thing is really starting to piss me off. I got it on saturday, broke it in perfect, but noticed it was running pretty hot. The header was turning blue for just about the whole length, and it bogged if given too much gas at low revs. So i decided to get some new jets and adjust the needle clip so i can run it without the baffle and lid.
I took the carb off so i could get to the needle and put it two spots down. Then i put a 165 main jet in. I put it all together and tried to start it up, but it wouldnt start unless i gave it some gas, and then it would fire up but run below about 4000 rpm. I tryed to get it to work, but it wouldnt. So after a while, i decided to put the stock jet in and move the needle back. It ran a little better, but still would not idle at all. when i would give it gas, it would stay at a certain rpm for about a half a second, then die down, i checked to make sure the throttle was not sticking, and it wasnt. I checked to make sure that i electrical connections were plugged in, and everything checks out fine. So i started to mess with the idle speed adjuster and that did absolutely nothing. I've worked on it for about 6 hours now trying to get it to work with no luck. I am about ready to take it into the dealer, to see if they can help.

Posted by: own2424

I'm sorry to hear that buddy, Hope you fix it up!
I knew this yfz450 thing was going to have problems...

Posted by: CHAUNCY

Sorry to hear

Posted by: RIDER11X

Might as well just pipe it with intake mods if your doing all of that. I know I couldn't resist that temptation with that machine.

Posted by: 86350x

Oops, was lazy and didn't read that you did that, sorry.

The 165 is right fot those two mods at sea level jetting. My 426 db hasn't turned the pipe blue yet, and I've had it for a while now. It's never given me any problems, other then being really really tall.

Posted by: 465Stroker

On the front of the FCR carb slide there is a plate that will come off when you disassemble the carb. Sounds like you may have installed it upside down. If the plate was installed upside down it would restrict the carb from letting any air into the motor which is why you would have to give it gas (which opens the slide) to get it to run.

Posted by: Pappy

quote:
Originally posted by 465Stroker
On the front of the FCR carb slide there is a plate that will come off when you disassemble the carb. Sounds like you may have installed it upside down. If the plate was installed upside down it would restrict the carb from letting any air into the motor which is why you would have to give it gas (which opens the slide) to get it to run.

Posted by: 400exBro

recently i had the same problem with my z400... but i havent taken the carb or anything else off... it is bone stock... and lately it will run excellent and the 2 days later it will barley idle. and when you let of the gas it will slow down, and ocasinally it will die... what is wrong?? this is the only the 2nd time this happened... it will run perfectly one day and the next it will run like chit.... is this normal for a z400... i am very disapointed with it so far... maybe a pipe and jets will make me and the machine happier...

Posted by: Pappy

bro...check to make sure the hole leading from the spark plug area is clean. its a drain for the spark plug well and if it gets water in it from washing or riding in water or mud it will make the quad act up. just a suggestion

Posted by: QuadJunkies

one time mine kinda ran thatway,then it would choke and sputter even backfired...turned out it was the gas I had bought, the ethanol blend(I think thats what the blend was:confused2 ) that was mixed in the gas, I had bought my gas that day at a place I dont normally and after asking found out this blend will make it run like a POS. sure enough, got some good gas and ran fine,it wqs weird within a matter of minutes my whole piped turned blue .Good luck with gettin her runnin

Posted by: 400exBro

quote:
Originally posted by Pappy
bro...check to make sure the hole leading from the spark plug area is clean. its a drain for the spark plug well and if it gets water in it from washing or riding in water or mud it will make the quad act up. just a suggestion

i will check that... becuase i just washed it down a bit before i rode...

Posted by: SAND LUVR

hey that is what happened to my wifes kawi. We fixed by getting her a honda

. just joking with ya.

Posted by: fourtrax400ex

i suggest you to check your valve clearance, i have similar problem with my 426ex after a motor rebuild, to valve was too tight and wont start if i didnt give trottle and run really bad, maybe its something similar