2000 wr400f help....please

[thomaskough]

I was riding my 2000 wr400f on the beach in 4th gear and all of a sudden my bike lost all power and rolled to a stop. I tried to kick it over, but there was no compression at all. I don't think anything i wrong with my rings or pistons because the engine will turn over, just no compression at all....can anyone tell me what they think is wrong with my bike???? PLEASE an THANKS

[matt420-46]

if you've got no compression, but you feel rings and piston are fine - you've got a valve problem.

Did it make any noises like it was eating a valve or two?

Wonder if she swallowed some sand.....

Remove your air filter, look in the boot for some dust deposits...

Likely you'll have to open up the top - it should be pretty obvious what the problem is from there...

[Frostbite]

I was riding my 2000 wr400f on the beach in 4th gear and all of a sudden my bike lost all power and rolled to a stop. I tried to kick it over, but there was no compression at all. I don't think anything i wrong with my rings or pistons because the engine will turn over, just no compression at all....can anyone tell me what they think is wrong with my bike???? PLEASE an THANKS

Simplest thing first - make sure your spark plug didn't back out.

My 400 lost compression a few times while riding, and it gradually came back after 1/2 hour of kicking (no choice, miles from nowhere) so I'm not really sure what caused it.

I believe it was one of 2 things - frozen valves or too much fuel washed down the cylinder walls. It only happened during WFO runs at below freezing temps.

#1 - I jet very rich for -40, so if it warms up to -10 for a day or 2 I'm very rich. The extra fuel may have cleaned off the cylinder walls decreasing compression. Constant kicking may have gradually lubed them back up.

# 2 - My valves have iced up overnight and my engine had zero compression in the morning, but had been working perfectly when I shut down. If a valve is open, condensation would freeze on it, preventing it from closing when I tried to start the next day. Heat up the head and full compression returned. That led me to think that they may ice up when running at full tilt. The constant blast of freezing air mixed with snow may have iced them up, and eventually the heat melted the ice and that's why the engine restarted 1/2 hour later and ran perfectly.

Since you were riding on the beach in California, I'm going to guess it isn't ice. If your sparkplug is tight, loosen it and take it out and pour a spoonful of oil into the hole. Turn the engine over a few times and then pop the plug back in and see if compression returns. If it does, then it was a problem with the sealing of the rings to the cylinder. If compression doesn't return, it may be your valves, stuck or possibly bent.

Did the bike make any funny noises before it quit. I bent a valve last year and it made lots of noise, didn't just slow to a stop like shutting off the kill switch.

[matt420-46]

Damn Frosty - I wouldn't have thought of the plug coming out, but that pretty much sounds like it may be it - you've always got the best answers - I'd send some good gas your way, but Chickenplucker didn't like a thread I made so he banned me and now I'm a newb who isn't allowed to give gas til I get my regular account back!

So anyone who reads this - give frosty gas!

[SJMC_DON]

My 400 lost compression a few times while riding, and it gradually came back after 1/2 hour of kicking (no choice, miles from nowhere) so I'm not really sure what caused it.

This is a true phenomenon:prof: Never happened to me on my 400 but my buddy's YZ 400 did this twice and both times came back mysteriously and with out cause and the bike ran for many hours with out issue afterward ?

One time, we had all but given up and started towing the bike out... he decided to put it in gear at a downhill and it rolled in gear w/o compression for a few feet and then like magic the compression appeard... stuck de-comp valve ?

[Solo]

Frostbite- any chance you had carb icing? In the climates you're in it's quite possible.

[wartsnuff]

might try checking the oil ?

make sure its not gas. washing the rings clean of oil... giving you no compression.

??? how many times did you kickit ? how long did the motor turn over dead in 4th gear ? may have just flooded the heck out of the old girl ??

hope this helps, let us know what happened ?

cheers

Warts

[Frostbite]

Damn Frosty - I wouldn't have thought of the plug coming out, but that pretty much sounds like it may be it - you've always got the best answers - I'd send some good gas your way, but Chickenplucker didn't like a thread I made so he banned me and now I'm a newb who isn't allowed to give gas til I get my regular account back!

So anyone who reads this - give frosty gas!

Thanks Matt. I like to confirm that the simple things aren’t the problem, and that’s mainly because I’ve torn things apart for no reason a time or too.

One example - I used to ice race an old 1974 XL 350 with a 412 kit in it. For some reason it would break valve rockers. One race day the engine quit and I instantly assumed another broken rocker. I had spares so I opened up the top end, and everything was perfect. Then I noticed that the coil wire plug had popped out.

There aren’t a lot of mechanics up here so I regularly get asked to help with car or snowmobile problems. Most of them are simple things, and amazingly enough, many are just plain out of gas.

This is a true phenomenon:prof: Never happened to me on my 400 but my buddy's YZ 400 did this twice and both times came back mysteriously and with out cause and the bike ran for many hours with out issue afterward ?

One time, we had all but given up and started towing the bike out... he decided to put it in gear at a downhill and it rolled in gear w/o compression for a few feet and then like magic the compression appeard... stuck de-comp valve ?

The compression loss is a mystery, and mine wasn’t the decomp. It’s easy to see and turn by hand if you have to, and I’d usually check that first. In 8 years I never had the decomp stick, but I have had the cable or lever tweaked so that it would activate the decomp when the bars were turned to full lock. The engine would stall and I’d bang the lever down a bit or check the cable routing.

Frostbite- any chance you had carb icing? In the climates you're in it's quite possible.

My airbox fills full of snow but I’ve never had an engine shut down because of carb icing.

That shouldn’t directly affect the compression, unless you mean that the icing may cause flooding, washing down the cylinder walls, and that’s a possibility – is that what you’re thinking?

I'm working on my 99 400 right now. I think I'll pour some gas down the cylinder to see if I can create a compression loss.