2009 YZ450 starting issues

7 replies to this topic
  • WR450F_No28

Posted October 17, 2011 - 08:41 AM


I am having starting trouble that is hit/miss. Bike is basically stock (am at 90hrs)except for Lexx 94db SA, valves adjusted once at 40hrs (they were almost tight-adjusted to a bit loose, and starting did improve..suspect they were tight from factory.) Jetting is mostly stock but for a ZipTy adj. fuel screw, main down one size, and needle dropped one position. I run a rekluse Core EXP. Live at 4k and ride and race 3k-9k...really. Basically: Bike is a smooth rocket and love it. Compete at very high level in the 40A in XC, GP, occasional MX, Enduro, etc. Bike LOVES to pass LOUD modified 450s and up because it is smooth and strong runner. Warmed up, dead engine starts going well thanks to GreyRacer. Bike starts decent cold. Runs well all through the range. After say a very hot run, and stop...sometimes starts first kick, sometimes not. With or without hot start...when not start..it is frustratingly tough. I was told to mess with leak jet but not sure where to go (need more understanding of it..sorry)...Tried leaner/richer pilot..did not seem to help either way. Sorry for being a dope but this weekend...wet and 45°...bike was, as always, a RIOT..but again starting was hit or miss and getting a bit mad at myself for not fixing this. Thanks for any help in advance. Am at work and forgot what i actually have in the carb but above notes are correct i am pretty sure. Always clean filters (No Toil), 93 pump gas (no ethanol), and i do not tap rev limiter..i am a gear-high racer...bike is holding up fantastic...but for this one thing..it is an amazing race bike.
Also...it prefers to start in neutral with the rekluse...this makes a difference...sucks but if you try to start in gear ..it just does NOT prefer it..pop in neutral ...odds go up a TON

Edited by WR450F_No28, October 17, 2011 - 08:44 AM.
another note

  • shrubitup

Posted October 17, 2011 - 09:32 AM


1. typically a bedraggled hot start is caused by too rich of pilot/fuel screw. triple check.
2. did you do the washer mod on the clutch springs? make starting in gear much easier.

  • grayracer513

Posted October 17, 2011 - 12:28 PM


I was told to mess with leak jet but not sure where to go (need more understanding of it..sorry)...

The leak jet has nothing to do with starting; it's only effect is to allow the accelerator pump not to squirt gas into the intake during slower or partial throttle openings.

The pilot is all important, as you have learned from getting the warmed up starts to work. Hot starting (and by that I mean HOT, as in the situation you described or when stalled and an immediate restart is attempted) is very sensitive to correct mixture. If the bike is too rich, it may be the best plan to roll the throttle open slowly and kick it through slowly 2-3 times, then just sit with the throttle opened for half a minute. That usually lets it clear out.

Just about any significant weather change will mean a pilot adjustment, too, so it helps to spend some time before race time trimming things up a little.

BTW, the "washer mod" has no application to a Rekluse clutch.

  • WR450F_No28

Posted October 17, 2011 - 12:59 PM


i think "half a minute"..you just tell me that so if i get in front of you that you can pass me back! :thumbsup:
I think i may be "cross-issue" of the brain..leak jet may be on the brain (of which i have little) as i do have the occasional flameout stall (even with rekluse) in say a special test that is really brutal and rough..recent one being a slam affair thru ktm200 moosebrush/rocky creek bottom special test..i jumped a big washout and when i slammed the other side and pinned it the bike just stalled...kick kick kick...crap!
bike has no trouble getting into neutral...and perhaps i need to drop the pilot?
thanks for the thoughts. this is the bike that was 2nd 40A at the AMA Western Hare Scrambles Final at Big Sky...the bike is capable...the rider, we are wondering about him...

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  • grayracer513

Posted October 17, 2011 - 01:12 PM


... perhaps i need to drop the pilot?.

I don't know. The usual case for me is that I can make the same pilot (happens to be a 45) work year 'round and anywhere I ride, but I'm in Southern SoCal where we don't really have winter, and August's more of an off season than January is. But between summer and winter, and between 4500 feet and 80 below sea level, I do turn the knob on the extended pilot screw fairly often within a 3/4 to one full turn range throughout the year.

Read up:

Pilot adjustment Basics
How to tell if the pilot is the right size

I believe you have my thoughts on how it affects race starts and stalling already.

  • WR450F_No28

Posted October 17, 2011 - 01:52 PM


As always..thanks grayracer!
..my son has really enjoyed this bike lately (he has grown bigger than his dad) and is considering racing and riding it but is concerned about the starting...right now, he cheats: i have him on a 08 yz250...that thing always starts easy whether you like it or not. appreciate the directions

  • grayracer513

Posted October 17, 2011 - 02:01 PM


...(my son) has grown bigger than his dad...

Yeah, I remember that. Next, there's the first day that he beats you outright on even terms. I used to be 6'0 and am now 5'10". I used to carry him on my arm like a football, and now he's 6'4" and 190 pounds of Marine. Watching him ride his 450 was some of the most fun I ever had.

  • WR450F_No28

Posted October 17, 2011 - 03:47 PM


grayracer, sorry i forgot to tell you to tell your son cheers and thanks from my family..
my son is a soph in HS, 6-0 and 220 and runs XC...i am 5-10 and 175...milkman story?
he rides and races for all the right reasons..just loves it.
thanks again for your knowledge and patience!

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