Weird JW compression test.

[The Boat House]

• This reply was modified 5 years, 5 months ago by The Boat House.
• This reply was modified 3 years, 2 months ago by The Boat House.

[cajuncook1]

quote Tubs:

Crank shaft seals?
What is the motor were working on?

Tubs, based on the title of the post, I think he is working on a Johnson JW 3hp. Year, not sure. Love working on those little rascals.

Cajun

[stanley]

Yes a JW13.Simple reliable and easy to work on.I’ve rebuilt 3 others with no problems other than the usual.This one is a stumper.

[frankr]

Exhaust obstructions are something to consider. Especially the above-water exhaust relief ports. Those have a profound influence on starting and idle. That is one reason why a worn out motor may start on the stand but not in the water.

[frankr]

I had a Lightwin 3 that drove me crazy for way too long. Compression was acceptable but hard start, poor idle and less than normal power. Finally, I discovered the pistons were installed backwards by some previous owner.

[billw]

I just had a 3 hp Lightwin that had some binding in the gear case. I noticed it before ever trying to start it; however, I was just thinking that if one of your 3s had more mechanical binding somewhere than the other, it could result in no/bad idle, hard start and even lower compression with an electric drill. Just speculating that maybe you’re stronger than the drill, when pulling by hand, giving the slightly higher number? Dunno, just a thought.

Long live American manufacturing!

[Author]

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