98 WR400 extremly hard to start need help fast!


16 replies to this topic
  • WR400Fdunk

Posted January 23, 2006 - 05:36 PM

#1

hey, i'm new to TT... i just bought a 98 wr400 its in really good shape the first owner bought it new in 99, he installed a whitebrothers e series pipe some time befor selling it to some local guy due to rusted original pipe. the local guy changed out the plastic in an attempt to make it look like a yz. it has various mods very few to the motor. i bought it for 1500(a steal) the motor and frame are clean enough to eat off of it has seen the track but never water or mud, no rust or cracks. im curious about the jetting, the thing is really hard to start. i understand how to start it. but the thing backfires like crazy and wont idle unless u rev the guts out of it.. it takes atleast 25 kicks to get it running and anyones who owns a 400 knows how much compression they have.. by the time i get it going im to tired to ride it.. the bike never came with any disc for the exhaust i dont want to buy any i just want to get it where its easy to start. im curious if anyone has had this problem and can help me with what jets i should buy, or tell me what im doing wrong. also is there a half choke on the carb, most carbs i have seen have a closed,half and full choke. i wasnt sure if mine was sticking in the half way position of if it even has a half open position. any help would be great thanks alot... wayne.. oh and by the way as far as i know the carb has the stock or original jets in it. the thing backfires and pops constantly even when warmed up, somtimes it backfires really loud when kicking it.. please help if you know anything.. thanks

  • TTBILL

Posted January 23, 2006 - 05:39 PM

#2

sounds like its to lean

  • dbailey223

Posted January 23, 2006 - 05:52 PM

#3

Because you are not certain about the jets (they could have been changed), I think you need to remove the main, pilot, leak, and starter jets and post here what sizes they are (I assume your carb has all these, but I am only familiar with the 03 carb from what I have read about and put into practice from TT).

Sometimes valves that need adjustment can be a source of starting troubles.

  • ncampion

Posted January 23, 2006 - 05:57 PM

#4

I have an 89' also and have had similar problems in the past. I don't think its jetting, but I bet somewhere you have a plugged jet or passage that is causing the problem. Most likely a pilot jet or the fuel screw. These are the ones involved in starting and idling. You are definitely lean, but I bet its a blocked jet if it is as bad as you say. Best to take the whole carb apart and go through it. As you can see, I finally got tired of mine and replaced it with an Edlebrock carb which is awesome.

  • WR400Fdunk

Posted January 23, 2006 - 06:37 PM

#5

i figured i was running lean, can someone give me a step by step on how to remove the carb. its obvious that yamaha was trying to center mass when they made this bike and im going to have to take the hole thing apart to get it out of there. thanks for your replies and help i will keep you posted.

  • ncampion

Posted January 23, 2006 - 08:02 PM

#6

Comes right out the left side. Remove the hot start button.

  • WR400Fdunk

Posted January 23, 2006 - 11:12 PM

#7

can someone explain how the choke button "should" work.. mine seems to be sticking out.. im not sure if its sopost to be sticking out as far as it is.. is there a half way open position? thanks

  • Nodrog

Posted January 24, 2006 - 02:33 AM

#8

Remove the Blue wire on the Neutral Sensor for a start , this makes a huge difference . I would also suggest giving the carb a good cleaning , to iliminate any doubts - Also check your diapraghm on the Air System - I had it before on my 99 model , where it was shut closed and gave me all sorts of hassles .This is the domed unit on the left side of the carb , with all the hoses going into it - Remove the cap and make sure the rubber isn't stuck - Don't lose the spring ...I hope this helps .

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  • Dirt_rebel

Posted January 24, 2006 - 07:49 AM

#9

98 wr400f is notorious for the breakage of the throttle slide.. from wat i've read ur post, i think dat u have a cracked throttle slide which makes ur bike difficult to start..
my suggest to u is to go n change ur carb to the second generation of fcr carb..i've replaced my carb wif a yz426 carb n i'm having a blast..

  • Team_Oatmeal_Pie

Posted January 24, 2006 - 10:04 AM

#10

I would rec going to the dealer and buying a manual before you do anything else.
2nd I would pull the tank dump the gas and look inside with a flash light. If theres gunk in the tank then theres probably gunk in the carb.
3rd you can pull the carb off or slightly loosen it / rotate it enough to get at the jets with out pullind the whole thing apart. Does make it easier if you disconnect the subframe down by the pegs and rotate it up towards the tank/bars. You can get to the bottom of the carb and clean it out, and pull the jets, clean and record what you have in there.
Often a plugged pilot jet will keep it from idling and will pop and back fire if you try and ride it.

4th the choke should be pushed in for off and pulled out for on. Hot start will be your red knob, same thing for positions.

Lastly hard starting can be a sign of valve clearance issues. But try one thing at a time.

Good luck and get that manual or have a TT member make some copies of needed pages before you do anything.

  • WR400Fdunk

Posted January 24, 2006 - 10:43 AM

#11

thanks guys i'm going to take it appart today and see what the problem is. hopfuly its dirty carb and jets but i will keep you posted

  • WR400Fdunk

Posted January 24, 2006 - 12:09 PM

#12

well i was reading all the starting tips for the WRs and i found out why it was so hard to start.. when i was kicking it over i was hitting the throttle a little even though i thought i wasnt. and it was flooding i guess.. but anyways it will start between the 3rd and 10th kick which i can deal with but im sure the jetting is off becaues it runs like crap and backfires and stuff.. but im going to get a manual befor i start taking it apart thanks for all your help.. wayne...

  • dbailey223

Posted January 24, 2006 - 02:23 PM

#13

Aren't the manuals online to download? I got one with my bike new, but I believe the pdf version that I have I found online.

  • tcmII

Posted January 24, 2006 - 06:50 PM

#14

Oatmeal's post is a great start. I bought my '98 WR used in December and let it sit until spring. I spent days replacing plugs and checking connections, nothing but a sore ankle (watch that backfire).

Did three (really two) things that solved the problem:

1 & 2 Make sure the gas is fresh and the tank has enough. The WR tank drops below the petcock on the right and will seem like it has enough gas, but not really.

3 Make sure the carb is clean. Check the float and the accel pump bowls and make sure the jets are clear.

Throw in a new plug, follow the starting proceedure (check posts or ask) and, assuming all else is good, it will start with ease.

  • bluebike1999

Posted January 24, 2006 - 07:50 PM

#15

oatmeal and tcm
sounds exactly what was happening to me and turned out to be dirty fuel ( water ) but i was reluctant to suggest that given my limited know how and not wanting to sound too simplistic.
heres what happened to me
http://www.thumperta...ad.php?t=264153
and this, the ol' plug thang
http://www.thumperta...ad.php?t=223022
and this
http://www.thumperta...23&page=1&pp=10
I can ride a bike and steer a computer, but cant fix a bike.
hope this is of some help.

  • bluebike1999

Posted January 24, 2006 - 07:56 PM

#16

I forgot about this one
hope it helps
http://www.thumperta...ad.php?t=274047

  • 1rkcooper

Posted January 25, 2006 - 12:10 PM

#17

can someone explain how the choke button "should" work.. mine seems to be sticking out.. im not sure if its sopost to be sticking out as far as it is.. is there a half way open position? thanks



Maybe I am reading something wrong here.

You say the choke is sticking out. Are you sure that is the choke and not the hot start. The choke should pull up and down, the hot start should be side to side(in and out). If it is the hot strat you are using that would be your first point of being lean. Just a thought.
Clean the carb and fuel system and check and adjust the valves.




 
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