yz400f quit and wont crank


8 replies to this topic
  • zzcoupezz

Posted August 22, 2009 - 09:09 PM

#1

so ive been lookin at buying this bike. and the guy said he was just haulin down a trail and it was like he just let off the gas and the bike idled. twisting the throttle did nothing. he was able to get it to start by poppin the clutch while rolling down hill and putt home he said. and now it wont crank at all.

i went and looked at it today. it turned over fine. it doesnt seem to be an internal problem. i did have a question about whether the comp. release was needed to kick a semi fresh motor(he said about 40-50 hours since rebuild) as i could without it. it was by no means easy though. and also when i twisted the throttle i had to help it go back.

so, any suggestions??? btw im just gettin used to the 4-stroke bikes. been trying to read up on em. but this would be the first one i owned

  • USED YZ426F

Posted August 23, 2009 - 11:29 AM

#2

Unless he did a auto-decomp cam mod on the bike, there is no way you should be able to kick it through. My '00 426 locks solid on the compression stroke and won't budge until I pull the comp release.

It is possible that he timed the exhaust cam wrong when he rebuilt the topend. Or maybe he didn't replace the timing chain and it skipped time.

Either way, I would guess that there is something wrong on the topend. Checking the valve clearances and cam timing is pretty quick and simple, I would start there.

The throttle not returning is probably either a kinked cable, or a return spring not connected.

If it all checks out, then there may be something broken internally (piston ring???). Regardless, if you are comfortable with some tools, and can get it pretty cheap, it may be worth your effort.

If you don't have the mechanical abilities, I would probably walk away from it.

  • grayracer513

Posted August 23, 2009 - 11:54 AM

#3

Avoid it altogether. There are a lot of bikes for sale that are ready to ride, and even a good running YZ400F won't bring more than $1500 these days. If you don't have experience with the bike, you don't need the grief, IMO.

  • mjw1

Posted August 23, 2009 - 08:01 PM

#4

The top end probably seized, i doubt the timing chain has skipped teeth i have never seen it happen on a 400 or a 426 i have a 1999 zy400f and still has a stock timing chain and have not had to adjust the valves yet. But if it has a stock cam you will need the decomp lever to kick it over, and like gray said there are alot of bikes for cheap that run good so unless you get it for next to nothing and like to work on bikes i would look at a different bike.

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  • zzcoupezz

Posted August 23, 2009 - 11:36 PM

#5

thanks for the replies guys. well he was askin 900 and all i did was ask if he was set on that price and all in one sentence practically he said he could take 850 then 800. so i might could get it for less. you guys think that is next to nothing or should i look further?

  • USED YZ426F

Posted August 24, 2009 - 04:38 AM

#6

I would look elsewhere. Unless I could get it for around a couple of hundred ($100-200), and the rest of the bike is alright, I would walk.

You just don't know what you are getting into with a non-running engine and could easily dump $1K or more in repairs. Then you have a ten year old bike that you just dropped a C-Note in.

Alright if you plan on keeping it for a while. But, if you are looking for a bike to ride for a year and then get something else........

  • grayracer513

Posted August 24, 2009 - 07:59 AM

#7

Like I said, unless you have the experience to accurately determine what's wrong with it, walk away. It's not likely, by the description, but it could possibly take $2000 to fix. Need a project that badly?

  • zzcoupezz

Posted August 24, 2009 - 05:17 PM

#8

ok. thanks guys. ill be passing on this one. last thing i need is another project.

that does bring on another question. a friend of mine back home (out of town for work for a month) has one that runs but is leaking oil off the motor somewhere. he knows nothing about bikes, just bought cause he knew it was fast. im not sure where exactly its coming from as i havent seen the leak in person. i know thats kind of a vague description, but is there anything specific it could be? i read something about if you over fill the oil it will come out the overflow. could that be it?

btw. i can get it for the same price.

  • jbach

Posted August 25, 2009 - 08:34 AM

#9

if you buddy knows nothing about the bike. chances are that bike knows nothing about getting maintained. seriously, you can buy a great running bike for $1000 in good shape. i bought mine for $1100 2 or 3 years ago and it was showroom.





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