She smokes!!

The XR400 has been layed up for a while, replaced with fresh oil, fresh petrol. When I started her she smoked quite a bit (blue smoke) :foul:my question is is the engine knackered? do they do this as normal? or is it time for strip down rebuild?

Any sensible advice is greatly appreciated PLEASE :bonk:

if it sat for ages it might of just been burning of the oil that leaked down the valve stems. Clean the air filter and reoil and take her for a ride and see if she still smokes, dont overoil. Is the smoke constant? How long did you run it for? Got an idea of mileage?

Mine is starting to smoke on start up also. :bonk: It does go away after a minute or 2. Run great other than some smoke......

Blue smoke that seems to go away after a few minutes is usually caused by valve stem seals and poses no immediate threat. If it smokes continuously then probably the rings are worn out. Still not really a problem unless the compression gets too low or you keep fouling spark plugs.

I've got the same deal going with my xr400. I'm away at college, when i'm home and crank her up, she's ornery and smokes like the devil. I thought it must be the choke at first, but I'm not sure. Thick blueish white smoke. It wears off after a minute or two and doesn't smoke any other time. Carb adjustment? I honestly don't know. I only know the basics: change the oil, air filter, and spark plug.

"Blue" smoke comes from burning oil, "Black" smoke from carb too rich, "White" smoke... I have only seen from burning automatic transmission fluid??? What kind of oil are you using?

It's most likely the valve guide seals. Look closer at the smoke, it's probably blue and not white. It's pretty typical for this.

If you ride your bike, it probably does not smoke so much unless it sits for a few days or more right?

Hi Guys,

Well thankyou for all the comments, as I said the bike has been laid up for a while, today I actually purchased the bike and got it back to my workshop, got her started and was quite surprised NO smoke at all. Choke needs sorting and the carb cleaned and sorted but she eventually got warm and still NO smoke. Really pleased as the smoke I saw was when I first viewed the bike and was dreading the worst.

Hope to get the carb in bits shortly just to give it a good clean out, aand then get the idle sorted properly.

Thanks again everyone.

mine smokes after it has sat for a season for a few minutes at first.

my guess is maybe a little oil is leaking down. after i've been using it for the season i don't notice it. i've noticed my other bike do similar.

ride it and check the oil. if the oil stay steady then no concerns.

could also be a strong dose of fuel stabalizer burning off.

Fuel stabilizer- that could definitely be why mine is smoking. It didn't smoke when I bought it, and it didn't start smoking until I put stabilizer in the gas to keep the bike good for storage. I'll see what happens when i burn the tank out.

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