Blowin Smoke

5 replies to this topic
  • trickwarrior

Posted November 01, 2007 - 08:33 PM


What are some of the possible reasons my motor would be smoking upon start up??? Just wondering where to start to get her back up to speed. 1999 wr400

  • Desracer

Posted November 01, 2007 - 08:57 PM


Time to spend the money and freshen up the top end. Rings and valve guide seals can cause smoke problems. But due to the age of your bike in may get real spendy to fix. Wear parts will need replacing, piston, valves etc. Price the parts and labor vs a newer bike. It sounds bad like this but you can find a newer better bike for less money than parts and labor. Unless you have friends with aweome tools.

  • JSanfilippo

Posted November 01, 2007 - 10:23 PM


+1 to what desracer said.

Look at it this way, you got about 8 years and god knows how many miles out of the bike. That is amazing from an all out race engine...

If you have a knack for all things mechanical and a decent assortment of hand tools, you could probably do the piston, rings, timing chain, and gaskets and save some money that way with the help of a manual. You'd have to take the head into the shop unless you had a valve seat cutter, valve spring compressor, media blaster cabinet (to clean the head) and some other things I might be forgetting.

BTW the head work is assuming your valves are shot...there is a very good chance the valves and the valve seats are fine and that just your valve seals need replacing. Trouble with that is since you're taking the damn thing apart you might as well put fresh parts in it.

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  • xrmarty

Posted November 05, 2007 - 09:27 PM


What are some of the possible reasons my motor would be smoking upon start up??? Just wondering where to start to get her back up to speed. 1999 wr400

How much smoke are we talking about? Some smoke is expected on an older bike, especially if it's been sitting for awhile. I wouldn't worry about that too much. Chronic bluish thick smoke on every start maybe a sign of worn out guides (not rings-when rings are warn out it smokes all the time-not just on start up). Either way, not a terribly expensive fix especially if you do the disassembly/assembly yourself and just send out the heads.

  • angello714

Posted May 03, 2014 - 10:30 PM


you will have to look at the top end of the engine. it is most likely that your valve guide oil seals are bad.

  • ncampion

Posted May 04, 2014 - 10:23 AM


The 400 is by far the most durable engine of the 400 - 450 line.  They will run forever with simple maintance.  It's just not that difficult to do a top end on one.  More info on the smoke problem could probably nail down the problem a little better.  The 400 motor does not use TI valves so even valve replacement is not that bad.  I would say that if you like the bike either live with the smoke or do the top end.


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