smoke

[ny300exrider]

hey guys,
i noticed on my 2001 400ex that after about an hour or so of riding in pits or mx once and awhile it will blow some smoke out. its only on the revs and its a whitish/blueish color. it isnt always there only after some riding that includes up and down hills and stuff. it doesnt seem like performance is affected but when i think smoke i think engine rebuild and id really love to do without that. what do you think could cause this. im wondering if the air screw could have ANY affect on this because i had the quad jetted at 175main and 2.5 out on the air screw and decided to run with the airlid on. i rejetted to a 158 but never changed the air screw so im wondering if this could cause it. maybe valve seals or something? help me out i get worried when i see it, id like to know what it could be. thanks!!

[02Yellow400]

your rings are most likely shot...Time for at least a top end rebuild.

[ny300exrider]

dammit would rings be randomly smoking? i thought if it was rings itd be smoking pretty consistently. its not that bad but im concerned. its not really that bad and its after riding hard for awhile. i havnt really ridden it hard though, a few mx sessions and a few sandpit rides. are there any other symptons that would be occuring if i needed a rebuild. and when you say topend i would have to get a piston and junk correct. sorry i havnt really looked into motor mods yet so im not very familiar with stuff. thanks for the help

[ny300exrider]

bump? any other symptons that would show it needs a rebuild

if its cold, it smokes for alittle bit while idling and after about a minute it stops and is good. could it be valve seals?also if it needs a rebuild what would be the most reilable setup without spending too much. sorry for all the questions. i havnt felt any power loss either.

[mojoe2878]

do a compression check to see if the rings are any good, if you have good compression then start looking else where for the oil to be coming from.
yes, it could be valve seals. ive seen some with bad valve seals start to smoke some for a couple minutes then stop and then start again later, it would sometimes run without smoking and then start smoking for a little bit.
another thing to check is your air boot to see if you are getting any oil blow by from the crank case vent tube that is gettin sucked into the engine some times.
if you have good compression then you may still have a sticking or worn oil ring, but it should smoke all the time if it was ring related not just periodicaly.

[mojoe2878]

Originally posted by ny300exrider
bump? any other symptons that would show it needs a rebuild

if its cold, it smokes for alittle bit while idling and after about a minute it stops and is good. could it be valve seals?also if it needs a rebuild what would be the most reilable setup without spending too much. sorry for all the questions. i havnt felt any power loss either.
that makes it sound a lot like a valve seal, some oil in the head will leak past the valve seal while its just sittin up and then when you crank it it goes into the cylinder and smokes for a minute until it burns the oil off that leaked past while it was sittin up.

[ny300exrider]

mojoe thanks a ton for the help, im not too familiar with motors, how much am i looking at to get it fixed and other than burning alittle oil, will it hurt the motor if i ride with it for a little bit longer. i want to get a few snow rides in then i can fix it. I think its the valve seal because it does exactly what you explained. it isnt smoking constantly, only once and awhile after riding for awhile. then if you let it sit for 10minutes it will barely smoke at all.

thanks again

[mojoe2878]

only thing it will hurt is maybe foul out your plugs quicker and get some carbon build up on the piston and bottom of the valves a little, but you can clean it all up when you get the chance to fix the problem.
it shouldnt hurt anything with you riding it for a while, just be sure to keep an eye on the oil level before each ride.

[ny300exrider]

thanks so much mojoe, ill deifinitly check the oil level every ride and have some plugs handy. it hasnt gotten too bad so i think ill be ok.