proper steps for compression check 85hp?

[vscgraphics]

What are the procedures for compression checking a 1987 force 85hp?

Thanks
Joe

 

[Unbalanced]

Re: proper steps for compression check 85hp?

Generally you want to warm the motor up first, but if that's not possible you can spray some premix in the spark plug holes before you start.

Remove the spark plug, screw in the compression gauge, ground the spark plug wire that you just removed. (I just insert the plug in the wire and hold the plug to the block.) Have someone turn the key until the needle stablizes on the compression gauge - 3 to 5 rotation aught to do. Repeat for the next cylinders.

If you're worried about the engine starting during the test, you can ground the white wires on the port side of the engine block.

 

[Tim Wagner]

Re: proper steps for compression check 85hp?

throttle must be wide open too.
You'll need to defeat the neutral safety switch.

 

[john from md]

Re: proper steps for compression check 85hp?

1, make sure battery is charged
2. remove all three spark plugs
3. ground spark plugs or spark plug leads to prevent damage to coils and CDI units.
4. Jumper neutral start switch
5. Advance trottle to WOT position
6. Install gauge in cylinder 1 ( do not add oil during first check)
7. Motor engine several cycles and record reading. Do this for all three cylinders.
8. Spray WD40, LPS, or some other kind of oil into number one cylinder. Motor and record readings. Do the same to all three cylinders.

If you have an appreciable difference in the readings between the first and second tests, chances are that you have carbon build up on the rings and skirts and need to do a decarb.

To decarb, read the FAQ and the beginning of the maintenance and repair section.

After decarbing, do another compression test. If any clyinder is more than 10% different than the others, you may have damage in the cylinder or to the rings or possibly a head gasket leak. If you don't run at WOT, you can just watch it and see if your performance degrades. If it worries you, take the head off and take a look see.

Regards,

John