Exhaust smoke i have honda 250 hornet when i was start the bike huge black smoke comes with the silencer. reparing engeenier told me to replace the air filter . he remove the air filter and seen me with out black some . i had huge confuse about this i resonantly change the air filter

SOURCE: engine timing, hornet 250

there is normally marks on the flywheel. sometimes 3 sometimes less. find the mark that makes the left piston sit at top dead centre on the compression strocke and it should be lined up correct. make sure that u are happy before u try starting otherwise it could end up very expensive.

SOURCE: engine sound and oil leak

crank main bearing sounds like its gone and oil seal gone i had same problem needs imidiate rebuild before more damage ocures looking at an expensive job

SOURCE: 250 cc giovanni dirt bike is smoking bad and looks

Has the bike been laid over? Could be possible that your air filter is soaked with oil and is burning off( smoke) or being forced out of the muffler.

SOURCE: having trouble with my honda 2001 cbr

There are several possible causes; fuel mixture is too rich, air filter is clogged, or worn piston rings and/or valve guide seals. The latter, however, will most likely produce blue smoke - under acceleration means worn rings, blue smoke under deceleration means bad valve guide seals. Also make sure that the crankcase vent is not obstructed as this will tend to force oil up, past the rings and into the combustion process.

Generally, an examination of the spark plugs will give you a good clue as to what the offender is. Black, sooty spark plugs indicates too much fuel (clogged air filter or mixture too rich). Oily spark plugs means worn engine parts, as mentioned above.

SOURCE: exhaust pipe comes out white smoke when start bike on side stand

Continuous or just for the 5-10 seconds.
If continuous you may have oil seeping past your pistons oil rings or valve guides oil seals.
Check your spark plug see if they are fouled badly (covered heavily and oily) or just covered by oil and sooth lightly.
If 5-10 sec it is normal as the engine is heating up there are normally a little oil seeping past the seals.

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