Jump to content
Sign in to follow this  

98 Yz400f Idles Briefly Then Dies, Help!!!

Recommended Posts

hey, it's the new guy again. the 98 yz400f i just bought is acting up. when i test rode it, it ran okay, but the throttle was sticking. i talked to the stealership about fixing it, and they said no problem. i went and picked it up, brought it home, and when i rode it, i noticed it wouldn't idle. at least not for very long. i drained the tank and carb, andfilled it with premium. if it's cold, i'll choke it, ()it takes a couple of kicks,) let it run a couple of minutes, turn the choke off, and give it hell. when i come to a stop, or pull the clutch in, it will run for about a minute, then it dies. it won't restart without pulling the hot start out( i am assuming that is what the other knob below the choke is called?) if i pull it out, it starts on the first kick. it will run for a minute (give or take) then dies again. i can keep it running by staying on the throttle, or by pulling out that lower knob. it acts as if it is running out of gas after a minute or so, but i don't see how it could, because it always starts right back up on the first kick,(as long as i pull out the knob.) and to add to the confusion, sometimes it will die almost immediately after letting off the throttle. but wait there's more! maybe. does anyone know at what RPM this bike redlines, because it seems like the rev limiter is hitting way early. i ask this because if it redlines way up there, then it is also cutting out at a higher rpm. it seems to do this much earlier than my ktm 520 did. that's why i thought maybe it was cutting out. if anyone knows anything, PLEASE HELP!!!!!!!

Share this post


Link to post
Share on other sites

If I had to guess I would say that you have carb issues. Id say start by taking the carb apart and cleaning everything (carb cleaner and compressd air). Check the jetting against the book to get an idea were you are at. Check the fuel screw position. Maybe it is in too far. Lube the cables and clean the throtte housing. then try it again to see what happens.

Also try a new plug. These bikes are very sensitive to plugs. If you dont have the starting drill down it is very easy to kill a plug.

Share this post


Link to post
Share on other sites

Thats what my bike did this past weekend until I put a new plug in it.

I had a heck of a time getting back outa da woods to the truck where the tools/plug was. Man, was my leg ever tired from kicking the thing over after it died again and again and again.

That would be my first try if I were you. :)

Eric

Share this post


Link to post
Share on other sites

The spark plug :)

It will require removal of some plastic tank, etc. but I bet thats you problem.

Eric

Share this post


Link to post
Share on other sites

i know it's the spark plug, i mean what is the part no. of the replacement plug? thanx

Share this post


Link to post
Share on other sites

LOL!! :)

You will have to forgive me. I am surely over the limit on my sudafed dose.

I could only respond with 426 plugs, I know they are different for the 400.

Eric

Share this post


Link to post
Share on other sites

thanx for all the info guys!!! for those of you who have not posted a reply yet, keep 'em coming, incase i am at a standstill. anybody got any info about the rev limiter and top RPM of this bike??

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

  • Similar Content

    • By BDTRENT
      Selling an FMF Power Core 4 exhaust system off my 450FX. Exhaust has 80 hours and is 100% functional. This will also fit the 14-15 YZ450F and 16-18 Wr450F. If needed I can also include new muffler packing although it does not need it. 
    • By Woody Oakson
      I have a 2008 YZ450F with a stock header pipe and Pro Circuit T-4 Slip-On Exhaust. I'm 99% sure the slip on is shot because its loud as hell and when I take it off and shake it it rattles. I would repack it but the screws are all stripped ect.
      Anyways I've gone over the carb multiple times and I've got it running pretty well. The only issue I have with the bike is that it sputters and pops around 1/2 throttle when I hold it there. When I give it full throttle from any RPM it runs great or when I give it about 3/4 throttle it spins up like a top to redline.
      Initially the popping and sputtering was way worse I made the situation better by moving the pilot jet up in a few sizes from a 45 (stock) to a 62. The issue has gotten way better since then but I'm not super sure what to do from here. Should I keep moving my pilot jet up in size because that's a pretty large jump right? I tried changing my needle clip position but that didn't help much if anything it just made starting it worse and little to no impact on the ride.
      Any input on this would be helpful. I don't want to buy other slip on. Also as for the rest of the carb I'm very sure everything else in it is what it needs to be at. I've replaced all the gaskets and O-rings cleaned all the jets, valve holes ect. fixed the accelerator pump timing. I just thinks its strange that my pilot jet size is going so far from the stock 45, but all symptoms point to the bike running lean.
    • By Haydenbaha
      Hi I was wondering if y’all have been using a 450 on your YZ250F?
    • By RockerYZWR
      Excel Takasago 17x3 front and 17x5 rear supermoto wheels with Metzler M3 tires in very lightly used condition. Less than 200 miles total on the setup. Warp 9 spokes. Rear has a Talon hub with 45T Sunstar steel sprocket and OEM rear disc, and front has a polished OEM Yamaha WR450F hub (for the stock speedometer), with a Motomaster 320mm disc. Included is a DID gold o-ring chain, 14T front sprocket, and front brake caliper adapter for a truly turn key setup. Everything is in excellent condition, not a single scratch on these wheels. Came off my '11 WR450F, but will fit many different Yamahas with 20mm front and 22mm rear axles. Asking $1400 plus shipping.
      **Will be driving up near Atlanta, then to northern Louisiana, OKC, and down through Dallas and Houston, TX soon -- can meet or deliver if in the area (Aug 31-Sep 9)**
    • By YZ426fNC
      Hi I’m new on the forum and I was wondering if a 2001 Yamaha YZ426f clutch is interchangeable with a 2002 Yamaha YZ426f clutch thanks , Coleman
×