The cause and effect of maint (engine kabooms)

yes another thread, just trying to understand completely how cause and effect works in the 4 stroke world in terms of maint.

Cause: Dirty air filter, never cleaned or torn etc, basically allowing dirt into the combustion area



Dirt goes into combustion area, covers everything including valve lips, and valve seats. When the valve comes back to the home position and seals, the dirt inbetween the lip and the valve acts like sandpaper and grinds away at the valve and valve seat. Seats and valve lips become worn, valve clearance decreases and compression suffers. When the valves leak,this leads to hard starting, possible backfiring and flameouts through the intake. Can also cause poor performance as the engine loses power (lost compression). I can see no reason why valves would drop on an engine with a dirty filter. Are there any valve related kabooms due to a dirty air filter?


cylinder walls collect dirt in which the dirt acts as sandpaper between the wall and the rings scraping away the nikasil coating deteriorating the seal for the rings and lubrication to the piston. Possible piston siezure can happen and/or excessive blowby and burning of oil. Also will cause hard starting and poor performance.

Cause: Poor oil maintenance. Oil is not changed regularily, loses lubricating qualities or there is just not enough or both


Valves: Camshaft is not lubricated properly causing premature sleeve bearing wear on the intake and exhaust camshaft sleeves. Camshaft could sieze up slightly causing the timing chain to snap and the valves to stop moving. Piston hits the valve and you have a kaboom.

Valve seals and guides are not lubricated properly causing possible sticky valves and/or siezure. A sticky valve will not move freely in the valve guide and will not come back to home fast enough resulting in a "tapping" or "clicking" noise coming from the engine due to the vamshaft hitting the bucket due to excessive clearance. If the engine RPM is high enough the valve will not return home fast enough in which the piston then hits it and you have another kaboom.

If valves guides are starting to sieze and/or are getting gummed up due to dirty oil resulting in "clicking" or "tapping" the camshaft slaps the valve bucket. This causes premature wear of the bucket and the cam on the camshaft itself resulting in excessive clearance. Excessive clearance can again be associated with hard starting/poor performance.

If there are any parts that you guys think are wrong, please let me know and tell me why you think/know so. Just trying to learn :ride:!!!!


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now