Checking compression with drill???

[Bubbles Up]

Hey folks,

I have heard that pulling an older Johnnyrude 9.9 with the rope will produce lower readings because of the slow turning speed, what about turning the engine over with a socket and a 1/2 drive drill with a snidge of oil in the jugs so the rings are not running dry?

Your thoughts?

 

[HighTrim]

Re: Checking compression with drill???

Proper compression readings are achieved by pulling it over by the means with which the motor usually starts. So for manual starts, use the recoil. Electric starts, use the electric starter.

Using a drill just cheats the results.

Remove the spark plugs, ground the leads, and test dry. You want a baseline to measure against in the future. Using oil or the like will change the results, and you will never be able to accurately copy how much oil was used. If it helps you, a quick spurt of WD40 will help lubricate for the test.

 

[tazrig]

Re: Checking compression with drill???

+1^^^

 

[kfa4303]

Re: Checking compression with drill???

+1. On a motor that small, it's best to just do it by hand. You only need to give it 5-6 good pulls per cylinder.

 

[tpenfield]

Re: Checking compression with drill???

Hey folks,

I have heard that pulling an older Johnnyrude 9.9 with the rope will produce lower readings because of the slow turning speed, what about turning the engine over with a socket and a 1/2 drive drill with a snidge of oil in the jugs so the rings are not running dry?

Your thoughts?

Would a drill even have any where near the power to turn the motor at a faster speed than you could do by hand? I'm thinking that a drill could not do much . . . maybe break your wrist, instead of turning the motor.

 

[V153]

Re: Checking compression with drill???

Seeing's how it's just a 9.9 hp twin. I reckon it'd be possible. Unconventional perhaps, but doable.

That said, still not sure I'd wanna be the dude holdin the drill ...

 

[tpenfield]

Re: Checking compression with drill???

Looks like it can be done . . . not sure if it would spin the engine faster than if done by the pull cord though . . .

 

[HighTrim]

Re: Checking compression with drill???

Good way to overtorque the flywheel nut, possibly spreading the taper and ruining a flywheel.

 

[boobie]

Re: Checking compression with drill???

Are you going to take your drill to the lake with you to get it started ??