HELP!!!!!!!!! Starting issues with a thumper newbie

Help please!! I just bought a 98 YZ 400. Very nice. VERY Strong. 1 small problem.....I can't start the damn thing. Here is my drill; let me know if I am missing something here.

Gas on


Find Top Dead Center

Pull in decompression lever

Move kick starter about an inch or two.


After about 2 or 3 kicks it sounds like it wants to start. OK I'm thinking this is time. But no. After 2 or 3 more kicks the choke refuses to stay on. Pull it out....pops right back in. Now I either kick for 20 or 30 minutes until I am in a rage or I get lucky and it fires when I am too exhausted to ride.

The previous owner said it was a cold natured beast, but he could get it going in 10 or so kicks. When I went to look at it it was cold and he started it in 8-10 kicks. When it is hot I can get it going pretty good, especially if it is on a stand.

The previous owner was 5'10" about 190 Lbs. I am 5'8" 167 Lbs. I am a little weak in the legs due to a back injury, but damn! I love this bike, but if this is going to be the story then I am going back to the 2 smoke 250! I really don't want to do that so ...........HELP!

Does it have fresh gas? Did you drain the old gas from the bowl? Also, hold your decomp in to get it past top dead center, then let it go and kick.

New plug, fresh gas. If it's still "cold natured" try a bigger starter jet (do you even have a starter jet :D ). They control the choke circuit. Maybe try cleaning the whole carb too. If it starts good hot, the pilot circuit is probably not the culprit.

The gas in it is about 4 weeks old. I would have never ran 4 week old gas in my 2 smoke....guess I thought the thumper would be ok with it. Is it??? :D

Also the last time it was ridden a friend of mine chugged it down and stalled it. A rainstorm was brewing so we loaded up and didn't try to restart. Perhaps he fouled the plug. Why is the dang choke popping close after about 10 kicks?? Will not stay open. Is this supposed to happen to prevent flooding?

sometimes it helps if u hold the decomp lever in and kick it through 5 or 6 times good luck with ur 400 great bike :D

A friend owns a '98 YZ400 that has never even had to have its valves shimmed. It starts every time on demand, within 1-2 kicks. This is even better than my '04 250F.

First, find neutral, pull in decomp. lever, kick down until the hard spot (TDC), return kickstarter to max height, let go of decomp. lever, and kick down forcefully.

The gas in it is about 4 weeks old. I would have never ran 4 week old gas in my 2 smoke....guess I thought the thumper would be ok with it. Is it??? :D

Maximum storage time for gasoline in a plastic container is three weeks. Without the addition of fuel stabilizer, it turns to junk. If you seal the gas in a metal container (think VP race gas), then it will last much longer. The two-stroke doesn't like old gas, and neither does the four-stroke.

YZippy, I can't really tell over the internet whether there are jetting issues, or other things contributing to your starting problems, but having had a bad back injury, and subsequent operation, I can offer this:

First, obviously make sure all tuning/jetting is correct, then, I would (and have done.....) fit a YZ450F exhaust cam', and you'll need to re-shim to suit. The old 400 probably needs the top end inspected anyway, and the auto decomp' 450 cam' will make the 400 feel like your 250 smoker to kickstart. There's a sticky post on this 450, with about a million replies/questions about the 450 cam'. Read it, it sounds like it would really help you, especially with the bad back. :D

After 2 or 3 more kicks the choke refuses to stay on. Pull it out....pops right back in.

That really bothers me that your choke is refusing to stay out, I think you should take the carb of and really go through it and clean everything really well, and inspect the plunger for the choke.

Fresh gas and new plug....................kicked for another 20 minutes to no avail. I see a "for sale" sign in my future. I really don't think my 5'8" munchkin self can kick it hard enough.

Don't give up. I went through the same frustrations when i bought a 99 WR400. Keep your hand off the throttle completly. I found it likes a long smooth stroke raher than to hammer it down quickly like i used to do on my 2 strokes. I also found after doing a carb breakdown some water and corrosion. Cleaned all that up and i use fuel stabilizer when i know it will sit for a few weeks. It starts up no problem for me now. Valves can be a problem as well so check them.

Yeah I was frustrated when I posted that. The motor is fresh and strong. I pulled the plug today to "read" it and it looked good. Tan, some wear, but looks ok. Went to a little hotter plug (CR7E). I'll try tomorrow. Don't get it. When it is hot I can fire it up fairly easy.

Maybe I am just to short and weak. Used to work out and was in awesome condition. Back injury, family, work and age have taken their toll. Still thin, but not nearly as strong as I was when I had a 250 2 stroke.

Fresh gas and new plug....................kicked for another 20 minutes to no avail. I see a "for sale" sign in my future. I really don't think my 5'8" munchkin self can kick it hard enough.

Four-strokes dont need to be kicked "hard". You just need to know how, when to kick it to make sure the motor rotates one and a half revolutions so it fires. Once you get it, no'll be loving it.

I also had trouble at first starting my 99 yz400 before some jack*** stole it from me. Anyway, that is another story. I am 5'7" and about 185, short legs was my problem. I ride mostly trails so I had a kickstand on mine. It was much easier to start if I did it from the stand. Once I learned the drill for my bike, it was never a problem again. I do have a question though, you say it starts fine when hot. You probably don't choke it when hot do you??? If you do then your pilot circuit is part of the problem. If not, try starting cold without the choke, possible that your pilot circuit is too rich and choking is just making it worse. Also, try to find a place where you are not trying to hold the bike up and kick at the same time. As stated before, keep your hand "OFF" of the throttle. Even a minor twist can cause you problems. It takes some getting used to, especially if you are used to a two stroke. After moving through TDC, be sure you are letting the lever all the way back up before kicking through again. Hope this helps, I am sure you will be very happy once you learn the tricks to your bike.


I just recently bought an 01 yz426, and turned to these guys for help starting my junk. Here is the reply from Grayracer:

"On starting, the biggest single mistake made by two stroke riders is that they twist the throttle with every kick. You will absolutely never get your 426 to start this way. If it's running right, it will start most of the time with the throttle completely closed, at idle. If you can't break the habit, put your hand half way up on the throttle housing to keep you from turning the grip.

Cold: Choke on. One to three twists of the throttle to prime. bring it up to compression and take the pressure off the crank. Pull the compression release and move the crank down just an inch. Release the decomp lever, reset the kickstarter all the way up, and give it a full, smooth kick all the way through with the throttle closed. Repeat as necessary. Should start in two.

Hot: No choke! Open the hot start (at low altitude or in cool weather, this may turn out not to be needed, but most of the time it will be). Position the engine as above and kick it, again with no throttle. If you stalled it or dropped it, you'll want to clear the engine by kicking it through several times with an OPEN throttle (just hold it still, don't pump) and the compression release held down.

Once you get it, you'll be unstoppable, but the decomp mod is still the best approach to take."

Take it and use, now mine fires on 1-3 kicks---hot or cold----

Thanks everyone. I am not twisting the throttle as I hold the master cylender. I was taught right away that that was the kiss of death as it relates to starting it. I usually have it on the stand when trying to start.

I am really beginning to believe my legs are just to short and whimpy. :D The thing I find most troubling is the inability of the choke to stay on. I'll try today if possible. We have the edge of the Hurricane passing through here on Tues. so I have to get some things done before the deluge.

Thanks again everybody :D

try starting it with your left foot on a picnic bench or a rock or some thing it is much easier than trying on a stand or you can push it while running next to it and jump on standing up and you'll be able to balance while kickstarting it

Mod for carb is a cable tie round the rubber seal (not to tight) this will hold it out untill you want to push it in, also try giving the throttle 2 quick full turns to pump plenty of fuel into the engine. It works for me, you have nothing to loose GOOD LUCK. let me know if it works for you?

Why is nobody addressing his choke problem ???? :D

I looked over your drill sequence. Are you giving it 2 or 3 twists of the throttle before kicking? I give my '00 3 twists when cold, 1 or two if it's been setting for an hour or so and no twists if it's warm.

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