compression when cold?

Hi guys!! I went to load up my 00 WR for the weekend, went to start the bike cold, and could kick right through compression. The bike wouldn't start while doing this. Pulled in compression release and kicked over. Definitely kicked over easier. pushed kick starter to the point of most resistance, and followed the starting drill. Bike started in 2 kicks and runs fine. I let the bike idle for a couple minutes and shut it off. Could not kick through compression.All OK. CHecked the freeplay on my compression release. OK.(I have GYTR push lever). I checked valve clearances about 200 miles ago, they are OK.(Bike has approximately 1400 miles on it,all off road). The bike did sit for approximately 2 weeks. Should I worry about it?? I did forget to shut fuel off when I parked it. THis bike ALWAYS starts in a couple kicks, even this time I had no problem starting it, just noticed that I could kick through. Any thoughts??

Im a little lame when it comes to technical information but I have had the same problem and I dont think its anything to worry about. I always just assumed one of the exhaust valves was sticking open a little and once the bike warmed up it would unstick and the compression would return.

Im not much help, but your not alone.

By the way, I have been racing my bike hard for 2 years now and it still runs as good as the day I pulled it off the showroom floor.


Darin from Missouri - 1999 WR 400F

[This message has been edited by milkman2544 (edited 08-25-2000).]

Thanks milkman, I get a little paranoid about that stuff sometimes. I am a Ford technician by trade, I road raced a car for years, doing all the wrenching myself, and I'm still a WUSS when it comes to these little japanese motors. I went out and kicked the bike just for the heck of it, after it sat for about 3 hours, and it comes to a dead stop afteryou hit compression. Maybe the cylinder got washed a little or something.I'll go pound the living snot out of it tomorrow for making me worry!!!

Hi Dave,

This is apparently not uncommon - you dont stop you engine using the decompressor lever instead of the kill switch do you ?

I am not sure exactly how the lever operates , but according to my local dealer , a Burr sometimes occurs at the action end , and holds the valve slightly open - especially if the lever is used to stop the engine .

i guess ifit is okay now then dont worry about it , but if it does it again investigate further.

No, I don't stop the engine with the compression release, but I do sometimes bump start the engine using the compression release. I'll check into the decompession mechanism when I get home to see if there is anything unusual with it. Thanks!!

Well,I rode about 50 miles on Saturday,all woods riding, and about 10 miles in I noticed that every time i would stop to cross a road, or something, the bike would stall. Then I would have to pull the hot start out to refire it. After about the third time I finally figured it out. My idle was turned WAY out!!!It idled fine on choke,and would idle off choke but really low. So, I'll bet that is what was causing it. I have plenty of compression now, and the bike ,as always,ran flawlessly!!Now to interrogate the little kids that always flock to my machine to ooh and ahh. I'll bet that little black knob was calling to one of them!!!

I also have a tire recommendation for you guys that ride in sand and looser conditions. I picked up Michelin S12 front and rear before this ride. I had the stock tires on before. I could literally ride a gear higher than I could with the OE tires. The front tire is nothing short of amazing. I've found that I am not as terrible a rider as I thought.(close though!). Anyway I would recommend these tires to anyone in intermediate to soft conditions. Thanks guy for all your thoughts.

Michelin S-12's are excellent tires as are the Dunlop 756's. the 756's are less expensive and last much longer. The S-12's are great in soft stuff and not bad at all in every other terrain conditions. I ran S-12's on my Husabergs and ATK's. However, I'm now a Dunlop 756/756 or 756/606 man based on price and longevity.


[This message has been edited by Clark Mason (edited 08-28-2000).]

If you have the idle turned way down you can kick through the compression stroke on my 426.

Maybe when bike is left sitting for extended periods the cylinder dries up and lack of oil diminished ring/cylinder seal, allowing a little more blow-by, esp. at super low rpm of starting.

Just a theory...

I have two rides on my 756 (front) and I love it! It is by far the best front sand tire I've ridden and bites way better than the 752s I used to love so much... In short it is as gnarly as it looks, and it looks pretty gnarly.

And if any YZ owners who ride dez/off-road read this you can now get the 4 ply K695 A/T in a 19 inch size. Even though it technically has an "intermediate" tread pattern it is good in the sand and the extra stiffness is great for rocks and puncture resistance, it also seems to be wearing much better than a std. 695 and WAY better than a 756.

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