1998 YZ 400 Will not start.

WOODSGUY

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#1
My brother just purchased a 1998 YZ 400 from one of our riding buddies. Let me tell you a liitle about the bike. It was ridden the last time in November, before he got his new bike. The bike has not been abused. Just before it was parked he had the dealer check the valves and adjust them. It was stored in a shop, it just had not been started all winter. Which brings me to my problem. So far I have not been able to get it to start. The previous owner and I tried to start it for about twenty minutes but no luck. We drained the gas and pulled the bolt on the bottom of the carb off to make sure there wasn't trash in it, and replaced the spark plug before we even attempted to start it. After our legs gave out I pulled the airbox off and looked in the carb and gave the throttle a twist and it is pumping gas in a steady stream. As he has not had a problem before staring it, the start procedure is not the problem, so my question is am I missing something? I am fairly new to 4 strokes so any advice would be appreciated. I have not tried to start it since I pulled the airbox to see if it was pumping gas. Is it possible that it is just going to take a while to crank it since it hasn't been started in a while?
 
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#2
I'm afraid the only reason my YZ400 has not started is due to procedure. Even after sitting all winter it will start after a bunch of good kicks, not 20 minutes worth though.

Be sure that you DO NOT twist the thrttle when your starting it. In some cases this leads to spark plug replacement just to get it started. Once the throttle was opened on my YZ400F before it was running and I actually had to run to the nearest dealer & get a new plug before I could ride. We spent about 20 minutes trying everything to get it started. It was running on the 2nd kick with the new plug & no throttle.

I guess I would say make sure you have compression, spark & good gas, then attempt to start it with the choke on and zip, zero, nada on the throttle, don't even touch the throttle grip until it is running. if you've done all that & it still doesn't start take it to a pro :)

-A
 
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#3
My YZF is really easy to flood; I never touch the gas when trying to start. Have you tried pulling in the decomp. lever and kicking it a few times to clear it? The biggest problem I have with mine is trying to kick it hard rather than just "following through" just my .02 good luck
 
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#4
When I first got mine, I had a problem like yours. I went throught every check I could think of. I cleaned the plug and everything. No luck. Popped a new plug in and whammo, It started. I guess once the plug is no good, then she ain't starting.
 
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#5
Like the other replies, when I first got a 400, I too went through a few sessions in the garage kicking away to no prevail. Once you learn the "procedure" though, you will be amazed at how easy these bikes start.

Check your air filter. Make sure it is not plugged. I've seen anything from too much oil in the element, to a mouse nest in the airbox causing a lack of air flow. Once you have verified it is clear, take your plug out and kick it through several cycles with the fuel turned off and while holding the kill button, and of course NOT touching the throttle. This should ensure everything is bone dry. Then install a new plug (I know you stated you already replaced the plug, but go ahead and try another brand new one just to be certain). Turn the gas on and wait a few moments for the bowl to fill up. Pull the choke button on and verify that the hot start button is not pulled out. Then, grip the front master cylinder with your right hand (to ensure you do not touch the throttle) and kick it through the "starting procedure". If nothing else is wrong with the bike, and the "procedure" is followed correctly, it’s almost guaranteed to start after a few kicks.

If you are having trouble with the "procedure", I believe there are several posts on this website explaining it in detail. Or better yet, find someone who owns a 400 and ask them to show you.

Hope you get it going and can ride soon!
 
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#6
With a tank full of new fuel. Open the petcock, wait a few moments, turn the throttle to wide open, pull the compression release, kick the bike through about 6-10 times, let the compression release go, move the kick starter until you cannot move it (find TDC), pull the compression release and move the kick starter no more than one inch, let the compression release out, kick starter to the top and kick it like a one legged mule. It should fire in two or three kicks.

If not pull the carb and clean it out very well, paying particular attention to the smaller primary cicuits, check all the jets for obstructions.

My bike fired after three kicks, post winter break. It also starts first kick cold.

Fuel screw should be 1.5-2.0 turns out.

Always run the fuel out of the bowl prior to staorage or transportation any raw fuel in the intake, will flood the bike, if it's cold.

Sorry but, have you checked for spark?

If this does not work email me through my profile and I'll see if I can help!

vetwfo'er
 
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#7
If it was stored with gas in the float bowl you may have a clogged pilot circuit.
 

WOODSGUY

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#8
Got it running!

I got this afternoon and proceded to put it back together. New plug, made sure it was firing and commenced to kicking. The thing I noticed was that I couldnt find top dead center. No matter what i did the bike would kick through every time. Not like the compression release was pulled in but still I couldn't find the hard spot. It tried to fire but just wouldn't light up. What I did next may or may not have been the right thing to do but I went ahead and broke out the 4-wheeler and a couple of tie-downs. After pulling it around the yard a few times my brother pulled in the cluth and let out on it and it fired right up. It ran fine. We killed it and I went to crank it up and low and behold top dead center. I pulled in the compression release and did the YZF start procedure and it fired right up. Starts every time. As I am new to 4 strokes could a valve have been "stuck"? Was what I did a mistake? Is there something I should take apart and fix?

Also thanks for all your input.
 
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#9
Unless you are, a one legged mule? I don't think you could kick it through TDC. You obviously had something pinning a valve open??? The first time you tried to start it, could you find TDC? Or was it only after you got it started? When it fired, were there any odd noises coming from the barrel. Like whatever had the valve pinned open, banging around. The compression release cable could have been tight and frozen and caused this??? Might want to check the routing and lubrication???

If can really trust the guy your brother bought it from, consider the bike ok.

If not pull the head. You may want to do this any way to check for damage to the valve seat. Put a little gas in the combustion side of the head and blow compressed air through the intake and exhaust ports. Look for bubbles in the fuel sitting on the valves. This will identify any damage to the valve seat.

Vetwfo'er
 

WOODSGUY

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#10
Well I am no one legged mule. Before it fired like I said it kicked through without hitting TDC. Once it started everthing seemed normal. I found TDC easily and the bike made no funny noises. My hunch was a valve was stuck. The individual he bought it from is a good friend and I know the history of the bike. Before it was in storage the bike was at the dealer getting the valves adjusted. I just think it sat up too long without being started. Today it was ridden about 40 miles with no problem. I take that back the brakes locked up. From my understanding there is a vent hole on the master cylinder that will from time to time get clogged and cause the brakes to overheat. The previous owner fought that gremlin for a while till a guy that rode one from a local shop wised him up.

Thanks
 

holeshot

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#11
valve clearances

You say the dealer adjusted the valve clearances just before it was stored. It would be easy to check the clearances (maybe the dealer goofed).
 

zsr

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#12
and I thought I'd found a friend....

Had my mates 426 (converted for road) for two weeks and the bitch will not fire. Guy lives nearby has WR and he can't start it.

2 strokes and starter motors rule !!
 

biglou

#13
Sticking valve?

Seems like I read on here somewhere that the early versions of the 400F had an occaisional problem with valves sticking open. Could this have been the case? That would definitely explain the kicking through TDC. Just curious.
 

Zoomer

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#14
Big Lou, this has happened to my 98 twice since I have had it. Most often when it sits for quite some time, valve just off the seat. The last time it happened, first time starting it this spring, I had no "TDC", bike started any way (with the pattened Yamaha starting procedure:confused: ) shut the bike down, and everything back to normal. The one thing I have never had to do with my 400 , is" KICK IT LIKE A MULE". If it does not start, it needs a plug!