Riddle Me Guess This........

[EuropeanAM]

(1B159185 for example).

Ok, someone's recent post about a Leakdown Test reminded me of something that I helped another dealer with a few years back.

115hp Fourstroke 4 cylinder engine. Runs well but 4900 RPM's is the best it will do (and it seems pretty noisey above 4800).

Compression: 195/198/191/155.

Leakdown: 1-4%, 2-3%, 3-4%, 4-3%.

So... how do you explain low compression but excellent leakdown on only ONE cylinder?

[low slung cruiser]

wrong spark plug in that hole?

[MichaelJ3]

Valve Seat Bad? Allows valves to seal under gradual pressure increase (ie leakdown) but not under the fast compression of a normal compression stroke? (Seems kind of far fetched...)

Or, something awry w/ the intake valve mechanics (lifter or cam), such that intake valve not opening fully allowing Air (in case of compresson test) or Air/Fuel mix (when running) in...so you don't get a full charge of air on compression stroke, and thus compression is low?

[bshort]

Rod bearing

[Rangerdawg]

Water in 4 stuck ring

[howieranger]

Bent rod from water ingestion.

[Lrrsme]

Bent rod on 4

[sterling11]

Bent Rod.

[Dontheduck]

Hg leak between cyls...

[quikcarl61]

Valve isn't closing all the way, but when leakdown done, it forces valve closed, bad rocker arm maybe

[12many]

cracked block. but no damage at top of stroke. so leakdown shows good.

id guess if u bent a rod enough to drop tdc that much to lose 40lbs it would side load the wrist pins hard and grenande.

l

[EuropeanAM]

Bent rod from water ingestion.

Ding Ding Ding- First correct answer.