Elto Ace 1.8 low compression

[djeady]

I’m still trying to get my old Eaton Viking/Elto Ace running. The spark and fuel are good, I just don’t seem to be getting any compression.

I’ve put in new rings (couldn’t see any difference between old and new) honed the cylinder, and used gasket sealer on both sides of the gasket. Cylinder looks fine, piston looks fine. Used a brand-new compression tester as my old one was suspect. I get compression of less than 20 dry and about 25 wet. I think it should be about twice this. Any ideas where to look next?

[RICHARD A. WHITE]

Upper and lower crank seals….or lack there of…
meaning crank case seal..

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[djeady]

How do the crank seals,which are below the piston and head assembly affect compression which is entirely inside the cylinder head?

[wedgie]

The crankcase pressure is used to push the fuel/air in to the cylinder. Low compression in the crank means not enough fuel/air. http://imgur.com/gallery/eatFH

[djeady]

I understand that – don’t understand how it could affect the compression measured in the cylinder?

[wedgie]

quote djeady:

I’m still trying to get my old Eaton Viking/Elto Ace running. The spark and fuel are good, I just don’t seem to be getting any compression.

I’ve put in new rings (couldn’t see any difference between old and new) honed the cylinder, and used gasket sealer on both sides of the gasket. Cylinder looks fine, piston looks fine. Used a brand-new compression tester as my old one was suspect. I get compression of less than 20 dry and about 25 wet. I think it should be about twice this. Any ideas where to look next?

Looks can be deceiving. If the cylinder is too worn, new rings wont be enough. You can get an idea of how worn the cylinder is by measuring the gap of the new rings when they are inserted (without the piston) in to the cylinder. I don’t know what the gap should be, but hopefully someone here will have that info.

[garry-in-michigan]

Piston to cylinder clearance should be minimum .002" to maximum .0035" – The 4256 Ace uses the same 1.75" piston rings as the Lightfour – end gap .006" to .016" . . . 🙂

[garry-in-michigan]

At .004" clearance you may have to use SAE 40 wt. oil to get it to seal properly. At .006" piston to cylinder clearence bore it out and use oversize pistons . . . 🙄

[Mumbles]

quote djeady:

How do the crank seals,which are below the piston and head assembly affect compression which is entirely inside the cylinder head?

They don’t. In a two-stroke motor, atmospheric air pressure enters the cylinder thru the exhaust port every revolution while doing a compression test with the motor mounted on a stand. Leaky seals will only affect the operation of the motor as they will cause a lean condition if leaking air in or poor running if leaking the fuel/air mix out.

[stanley]

Is your compression gauge of the long or short hose variety?The smaller the motor the bigger the difference it can make.

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