Fl



10 replies to this topic
  • Harold_in_So_Cal

Posted January 03, 2001 - 10:21 PM

#1

I have been having a big problem starting my 2000 WR 400 after I fall or occasionally after a stall. A few weeks ago I went on a really hard ride up a mountian with a lot of rutted out switch backs. Dropped the bike at least 3 times going up. Each time I would pick it up, open the hot start, find TDC and try to kick it over, it wouldn't start. Then I would pull in the compression release, kick it through about 10 to 20 times and then find TDC and still it wouldn't start. I was very carefull not to touch the throttle. I would kick wait kick wait. Never any hint of starting. Then 10 to 15 minutes later it would fire. This even happened a couple of times when I stalled.
Any help is appreciated. This set me back about an hour or more and I was almost dead by the time the thing started. Other than that no starting problems (for those of you who remember my Moab difficulties) however, still backfires when I kill the engine.

Thanks- Harold

  • Hick

Posted January 04, 2001 - 08:11 AM

#2

It sounds to me like your hot-start circuit is clogged or not working.

The button pulls a plunger, uncovering a passage which allows the motor to draw air from above the slide into the front manifold (bypassing all the fuel circuits). If you remove the button and plunger you may be able to get an aerosol carb cleaner nozzle in there to clear out the small passage from the plunger hole into the front manifold.

But blowing air into the plunger hole only doesn’t prove anything, air can and will escape out the air inlet into the air box. You may have to remove the carb to really get at the plunger-to-manifold passage and determine if it is clogged.

I suppose the button could break as well and the plunger could remain lodged in the passage even with the knob pulled. Unscrewing the hot start button and having a look won’t hurt anything.

I have a Ty Davis remote hot start which, to prove I could screw up anything, I installed wrong initially. The result was symptoms exactly as you describe but easier to diagnose (I just checked the last thing I fixed, that’s usually the problem :) )

[This message has been edited by Hick (edited 01-04-2001).]

  • Harold_in_So_Cal

Posted January 04, 2001 - 10:07 PM

#3

Thanks Hick- I have a Ty Davis tank and a Ty Davis hot start. I will check the hot start out. Ever since I got the hotstart my bike has backfired when I cut it cut it off.

Harold

  • Hick

Posted January 04, 2001 - 12:14 PM

#4

I got confused when I timed mine trying to remember where the outlet was as I screwed the fitting into the carb. I finally relented and marked its location on the fitting with a dremel. If you have the attachment off by more than about 35 degrees air will still travel through the hose (and out the back of the carb into the air box). If you are at least this close, but not on the money, you can blow in the hose as you turn the fitting until you find the position that allows the most air into your engine. The mistake I made was being off by too much which led me astray to the point that it was blocking the passage completely. I was blowing air into the hose and it was making an audible sound in the air box, I mistook this for a sign that air was reaching the motor. Not.

Anyway perhaps your hot-start fitting has come lose enough to rotate away from the passage (which sits at about 7 to 9 o’clock if I remember right) and block it. What you are experiencing sure sounds like what happened to me when I installed the fitting with the air passage in the wrong location, right down to the 10 minute wait to relight my bike.

The backfire doesn’t strike me as a related problem or a particularly worrisome trait (unless it is unusually loud). Maybe the kill switch isn’t completely opening the circuit and a spark is sneaking by after you kill the motor, igniting the last unburnt mixture in the headpipe.

The plug fires on every revolution so if you kill the spark on compression stroke and release the button it will fire on the next revolution with the exhaust valve open (if the motor spins around this far), I assume this is what causes the occasional, dull “pop” from my bike. My motor usually stops spinning on TDC-compression, though (makes sense when you think about it). My new habit is to make sure the valves are closed when I park my bike for the week (at least).

BTW, once you are sure the new fitting is properly installed you should check air flow at the bar mount by blowing in it with it open to make sure the hose isn’t getting pinched somewhere.

I hope this is all that is wrong with your bike!

  • Boit

Posted January 04, 2001 - 03:04 PM

#5

Hick: I bought one of those digital tachometers and a timing light from Kowa recently. Just for my own curiosity, I wanted to see how low the 426 could idle without stalling. Mine will idle at ~1140-1160 RPM's at normal engine temperature. That's pretty good considering the high performance nature of the bike and the relatively low flywheel weight. This tachometer is very handy as it's not much larger than a credit card and can be set for nearly any engine configuration out there. And you are correct in that the 426 fires every time the piston comes to the top of it's stroke. It was really handy when doing some jetting changes and seeing if I was hitting the rev limiter. I just zip-tied it to the crossbar pad for a readout while riding the bike. Way cool!

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  • Glen_T

Posted January 04, 2001 - 07:03 PM

#6

Hey is this the Harold from southern cal that followed a bunch of yucks up a trail marked "down only" in Hungry Valley? If so, get that thing fixed so we can try it again.
:)

GLEN

  • Harold_in_So_Cal

Posted January 04, 2001 - 11:31 PM

#7

Glen- yes I'm the same bike dropping fool. The only difference is the last part of Snowy trail with all of the switch backs and ruts is even harder than the trail we did that day.

I'm going to get this problem fixed and then go back to both of those trails and kick ass. I want revenge.

Good to hear from you.

Harold

  • Hick

Posted January 05, 2001 - 08:01 AM

#8

Originally posted by Boit:
Hick: I bought one of those digital tachometers and a timing light from Kowa recently.


I think it’d be great to have some kind of idea what RPM range you use the most. It would be a good tool to determine what kind of motor upgrades (like what kind of pipe to get) and could help with troubleshooting. My Snap-On timing light is helpful for this but I’m not willing to zip tie it to my handlebars and divide by two while negotiating sand whoops…

So I’d like to know, where’d you get the tach? I’ve never heard of Kowa, is that the brand or the store where you bought it? Did it give an accurate RPM or did you have to do some math?

  • JBM

Posted January 05, 2001 - 01:51 PM

#9

Hey Hick,
I think Boit is referring to www.kowatools.com.

  • Hick

Posted January 05, 2001 - 03:48 PM

#10

Wow, thanks for the link JBM, that may come in handy. Mostly road-bike oriented but lots of stuff that works for dirt like chain breakers and tire tools.

Kind of pricey though, it must be quality stuff then :)

  • Boit

Posted January 06, 2001 - 12:03 AM

#11

Hick: sorry about the delay getting back to you...was offline for a while. I see JBM gave you the Kowa website. The digital tach I opted for is the smallest one but very expensive. When I zip-tied it to the crossbar pad, I put a small section of foam rubber under it to absorb vibration. It has a clip that goes on the spark plug lead and it has to be set on the 2-stroke single cylinder mode because the YZ has that waste ignition cycle that you mentioned. It's extremely accurate and you take a direct reading...no math involved. I don't have a wife...(yet)....so I can spend my money on my toys... :)





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