Quick question... yz450f - bear to start - not valves - starts right up when warm.


37 replies to this topic
  • grayracer513

Posted August 28, 2006 - 08:45 AM

#21

... how exactly do you find the compression stoke well kicking it over :thumbsup:.

¿ :ride: ? Uh, that's the stiff spot in the stroke you feel when turming it through slowly....

  • Jaycycle

Posted August 28, 2006 - 08:49 AM

#22

yeah yeah yeah I know. Im trying alright!

  • rooster wrooster

Posted August 28, 2006 - 09:01 AM

#23

I also had problems starting my '06 until I started priming with 2 full twists of the throttle. It was at least 15-20 kicks. I also have a zip-ty fuel screw and a #45 pilot jet. But the throttle blipping before kicking is what worked. Now its 1st kick.

  • Jaycycle

Posted August 28, 2006 - 09:59 AM

#24

haha You guys know why I was getting so confused?? It was because I didn't know that the pilot screw was the same as the fuel screw. :thumbsup:

  • shade

Posted August 28, 2006 - 12:49 PM

#25

you talked about your foot being sore,kick it easy,just roll through it.the kicker lever will wear fast and almost turn backwards making your foot slide off easy.do you still have the stock flywheel on it?

  • Jaycycle

Posted August 28, 2006 - 01:15 PM

#26

you talked about your foot being sore,kick it easy,just roll through it.the kicker lever will wear fast and almost turn backwards making your foot slide off easy.do you still have the stock flywheel on it?

Yeah I bruised it a little bit yesterday from trying to find the best way of starting it... I wasn't kicking to hard, the problem was that the shoes I was wearing had a hole in the bottom from kicking it so repetitively. Then I was smart enough to change my shoes. And yes I'm pretty sure the stock flywheel is still on it. But I think the fuel screw is what really did it. I'm going to try it again grays way later when I bring the bike in (for sale in front of house).

  • tags

Posted August 28, 2006 - 02:38 PM

#27

I know my yz400f is a bugger to start if I don't shut off gas after a ride and it cools with gas on, it takes everything to get it started. My start up is: turn on gas, pull chock on, Pull decompression lever, kick to tdc release lever, kick over once and repeat and on second kick she starts right up, no extra gas required other than choke, if gas was left on then I kick it till the cows have come and gone, then it starts, just stubborn, like some other things I know!!
Worth a try! Good luck!

  • outlaw44

Posted December 01, 2007 - 02:30 PM

#28

I just got an 03 yz450f from a friend and it wont hold an idle its all stock,gas on choke on,couple kicks it lites but got to keep throttle going,kill choke it wont idle,why ? any ideas

  • MacJammer

Posted December 01, 2007 - 02:53 PM

#29

My '06 was getting harder and harder to start one weekend while out riding at the sand. Until it just up and wouldn't run any more. I did all the stuff you have been talking about and finally decided that it was timing so with the valve cover off and rolling the crank looking for top dead center I noticed that I could't get top dead no matter what I did. Long story short the timing chain had stretched and jumped 5 or 6 teeth on the exhaust cam. I went down to get a chain at the local dealer and a buddy of mine is a mechanic down there. They had 5 other '06 YZ450F's in there with the same problem. I replaced it retimed it and now it is just like it was when it was new. (Check the timing chain) that is my advice. I was lucky enough not to have it jump any more and throw the valves into the top of the piston. Good luck.

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  • Michael Cahill

Posted December 01, 2007 - 08:32 PM

#30

I have an older YZ (a 98 YZ400f) and it starts right up the first or second kick, every time.
what i do is: 1. turn on gas, 2. pull chock, 3. turn throttle 2-3 times to get some fresh gas in engine, 4. pull in decompressor, and turn engine over a couple of times, 5. find compression stroke (find stiff spot and go just a lil past) and then fire it! :thumbsup:

and if it doesent fire the first kick, just kick it again, and she lights right up!

Ah i love my bike!

  • Frostbite

Posted December 05, 2007 - 12:30 PM

#31

When cold starting my 99, which is most of the time, I can't even touch the throttle barrel or the engine won't start. I have to rest my hand on the crossbar. 3 to 5 squirts of AP and kick from TDC. I also have to wind the idle up a bit. Since my idle cable is frozen during cold starts, I turn it up 1 1/2 turns when I park it after a ride, so it's set for starting in the morning.

I've found that if the idle is off a bit the engine will not start. When I'm doing everything right and the engine won't fire, it's the idle adjustment.

  • k0ncept

Posted December 05, 2007 - 01:12 PM

#32

The way I get my 07 Started when cold is to pull the cold start lever, kick it a few times, 3 or 4, if it doesnt fire up I turn off the cold start and pull the compression release and kick it a couple times and then pull the cold start lever out once more and it usually fires right up....

  • grayracer513

Posted December 05, 2007 - 02:30 PM

#33

When cold starting my 99, which is most of the time, I can't even touch the throttle barrel or the engine won't start.

That may be, but a 450 is a different thing. Unless you're running a really oversized pilot jet, they need a good 2-3 twists on the the accelerator pump to get going when cold.

The way I get my 07 Started when cold is to pull the cold start lever, kick it a few times, 3 or 4, if it doesnt fire up I turn off the cold start and pull the compression release and kick it a couple times and then pull the cold start lever out once more and it usually fires right up....

Your '07 doesn't have a compression release, and it shouldn't ever be necessary (or productive) to use the hot start lever when it's cold. An '06 or '07 generally needs at least as much priming as the older 450's. If mine won't start in two, I prime it again. Never takes more than 4, even in 40-50 degree weather.

  • Frostbite

Posted December 05, 2007 - 05:50 PM

#34

[quote name='grayracer513']That may be, but a 450 is a different thing. Unless you're running a really oversized pilot jet, they need a good 2-3 twists on the the accelerator pump to get going when cold.

Hi Greyracer
I did mention the 2 or 3 AP squirts, but I don't twist while kicking. I twist first, then take my hand off the grip and kick. In the interests of science, I tried holding the throttle closed while kicking, but no deals. The idle is the fine tuner for my cold starting.

If I screw up the idle adjustment and the engine won't fire, I use kOncept's procedure to clear possible flooding - by turning off cold start, decomp lever in, full throttle and kick 5 or 6 times. This will clear any flooding and I can start from scratch again.

I think the problem is a bit too lean fuel enrichment circuit. I worked at a bike shop a few years ago when the Honda 250 SX 3 wheelers came out. The national parks guys bought a few to roam around the highlands, but quickly found that the bikes wouldn't start in cold weather. Honda recalled them and sent us drill bits to enlarge the fuel enrichment jet.
The fuel enrichment circuit is either on or off, unless you hold it up halfway, which I do sometimes after the bike starts. With the old chokes you could set it the way you want. Maybe a much larger starter jet and jamming up the knob so it'll stay 1/2 way is the answer, making it more rider adjustable.

  • grayracer513

Posted December 05, 2007 - 09:19 PM

#35

I did mention the 2 or 3 AP squirts, but I don't twist while kicking.

Sorry about the oversight. And you're right, the two-stroke twist-and-kick routine will get you nowhere.

If I screw up the idle adjustment and the engine won't fire, I use kOncept's procedure to clear possible flooding - by turning off cold start, decomp lever in, full throttle and kick 5 or 6 times. This will clear any flooding and I can start from scratch again.

And that works, but again, the '07 model k0ncept speaks of has no decomp lever. The lever on the left lever perch with the clutch is the hot start. So, he isn't doing what he thinks he is.

Your info is pretty much spot on for earlier bikes. The first FCR carbs had a fairly well deserved rep for being hard starters, and were very touchy with regard to idle mixture and speed with respect to starting. In about '01 they were refined a little and got a bit better. Then in '06 again, there were some more tweaks made. Unless an owner fattens the jetting way up, they aren't quite that particular any more.

  • BergArabia

Posted December 07, 2007 - 03:30 AM

#36

I read this thread before going out this morning riding and sure enough had the same problem..

Couldn't get it started with my normal routine..
Kicked and kicked..
3 twists of the throttle just before kicking and she was away.. first kick.
So I am thinking maybe time to clean the carby.. esp the pilot jet..??

  • BergArabia

Posted December 07, 2007 - 04:18 AM

#37

I have put some fuel system cleaner in my petrol..
Yeah I know I am very lazy idiot etc..
however I am definitely a 3 twist convert now..
The bike starts absolutely first kick after the three twists.. hot or cold..

BTW, had an excellent ride out today..
I took both my bikes out to the desert, YZ and CRF but I only rode the YZ. We were in very loose soft sand and the paddle really shone. Made some converts to the sand tire amongst my riding buddies I think..

The YZ still rocks...:busted: :thumbsup:

  • Frostbite

Posted December 07, 2007 - 07:43 AM

#38

I have put some fuel system cleaner in my petrol..
Yeah I know I am very lazy idiot etc..
however I am definitely a 3 twist convert now..
The bike starts absolutely first kick after the three twists.. hot or cold..

BTW, had an excellent ride out today..
I took both my bikes out to the desert, YZ and CRF but I only rode the YZ. We were in very loose soft sand and the paddle really shone. Made some converts to the sand tire amongst my riding buddies I think..

The YZ still rocks...:busted: :busted:


Kool.:thumbsup:





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