Low compression on 1958 3 hp Elto Model 3D15E

[Monte NZ]

Hi All
I have just done a compression check on the above motor and was surprised that I could only get 45psi
This is a real puzzle to me, as roping the motor over provides a really good bounce.
The test was done with what I regard as the most accurate of the four gauges I have and may I add that it lines up with the guages on my compressor which is a commercial job made in the UK.
The motor runs well and because it does I thought the compression would be a lot higher.

Your thoughts would be much appreciated.
Thanks.

Monte NZ

[crosbyman]

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Joining AOMCI has priviledges 🙂

• This reply was modified 3 years, 10 months ago by crosbyman.

[Tubs]

That is a puzzle.
I don’t believe it should even run
with compression that low. ????????
What do you get with your other gauges?
Tubs

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[frankr]

I agree, it should not run “well’ with compression that low.  Is the paint burned on the cylinder (as in overheated)?

[Tom]

In small displacement motors, the compression gauge needs to be one with a small dead volume between the gauge and the fitting for the spark plug.  If the gauge is at the end of a hose with significant volume, it will show a lower than actual reading.  It’s likely that your actual compression is a lot higher than your reading.

For anyone that cares, here’s one way to imagine the problem:  Consider a pressure gauge hooked directly to the end of a 50 cc syringe.  Depress the plunger to the 25 cc mark and the reading should read somewhere around 15 psi.  Then install a foot and a half  of 1/4″ copper tubing between the syringe and the gauge.  The tubing has an internal volume of about 20 cc.  Now when you press the plunger to the 25 cc mark, you’re just compressing a total of 70 cc down to 45 cc.  The gauge should read less than 10 psi.

Tom

1 user thanked author for this post.

Tubs

[Mumbles]

Your compression tester should have the check valve at the fitting which screws into the head and not near the gauge itself.  The valve at this location allows a true reading to be taken although it will take more pulls of the rope on a small displacement motor.  Try spinning the motor with a drill and see what happens.

The valve on the left is a reed style while the one on the right is a Schrader style.  I prefer the reed style as little compression is needed or lost to open the valve.  Length of hose shouldn’t matter with a reed style valve tester.

[need2fish]

WRT to frankr’s question, has the cylinder been subject to overheating ?

I have 4 of the single-cyl Gale. All 4 have brown discoloring all around the jug. Three of them are locked up (one with a broken rod) and the remaining has 50 lbs compression.

I expect #4 has stuck rings due to the high heat.

[Monte NZ]

Hi All
Thanks very much for all your replies!
Tubs ,I absolutely agree with you that it shouldn’t run, but to prove the point, I fired t up again yesterday and it started easily and ran like a watch.

Frank, your right too, it shouldn’t run and if it did, it certainly wouldn’t idle!

Tom. Thanks for you explanatrion……..my gauge is a UK manufactured “Vane” which I have had for over 50 yrs. It doesn’t have a hose(see middle of photo) and lines up with my compressor gauge as
I mentioned earlier. At the time I bought it, it was regarded as top quality. I also have two others, one made in China and the other in (no name visible and on the right) says made in USA.
The Chinese one with the hose reads 10 lbs higher on whatever motor I try it on and the USA one reads 5 lbs higher.

Mumbles, all the gauges have Schrader type valves and spinning with my electric drill gave the same readings.

need2fish,in relation to Frank’s question, yes, the paint work is a little discoloured, may I add that the impeller is in good condition and pumps well as can be seen in the video.
You will see also that someone has had the motor apart before I purchased it about 1975………looks like the powerhead had been removed going on the gasket sealer residue.

Attached are photos and video clips.

ttps://photos.app.goo.gl/Vcm2Wn17zSFc3tMeA

Thanks again
Monte NZ

[Monte NZ]

Hi All
Sorry! Looks like I messed up in attaching the photos and video clips.
Hope I have got it right this time!

https://photos.app.goo.gl/jRFri3z8XMG6HUVT7

Monte NZ

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