BCS 735 ACME AL330 MOTOR-NO COMPRESSION

[edinottawa]

Greetings! I have an opportunity to buy a 735 that the owner could not demonstrate the motor running. Said "it ran last fall" (where have we heard that before?). I went prepared with some tools and put a compression tester to it and after several pulls there is no compression reading. When pulling the starter cord there is some resistance so it would appear there is compression? Does this motor have a compression release? Stuck valve(s)? What else should I be looking for (besides seeing it run)?

The thing comes with three attachments so I hope not to miss the opportunity as attachments are rarer than hens teeth up here in Ontario. And very spendy...

All opinions welcomed. Thanks

 

[Captain Dirty]

According to the ACME motori workshop manual for spark ignition engines series ALN 215W/290W/330W, a special camshaft with centrifugal compression release is mounted in engines having electric starter or recoil starter or both. Engines with standard rope (you wind the rope by hand each time) starter do not have the release.

Joel at Earth Tools has been very good at helping me keep my ACME motor running. He can probably help you with spare parts or a replacement engine. See his website at earthtools.com.

 

[edinottawa]

Thanks for the reply. This is a recoil start motor. I'm hoping to avoid having to replace it. So having no compression would be normal until it starts? I'm not very knowledgeable about motors with compression releases.

 

[Lnk]

Thanks for the reply. This is a recoil start motor. I'm hoping to avoid having to replace it. So having no compression would be normal until it starts? I'm not very knowledgeable about motors with compression releases.

Basically it has a centrifugal cam that prevents the valves from closing all the way until the engine spins at a running speed. This makes it easier to pull over. Once it fires the engine speeds up on firing and the cam allows valves to close. You will not be able to spin it fast enough to check compression.

 

[edinottawa]

Thanks all. So if i translate the above correctly, a leak-down test would be the proper way to test compression/valves? Or is evaluating the condition of the engine just not possible? It either runs or not?

 

[m7040]

The Acme engine if it has a carb problem can be an issue because parts are not available. My 735 engine had a leak in the float and I replaced the engine with a Kohler from Earthtools.

 

[Captain Dirty]

The ACME engine is a third-world engine; I have often quipped that one could probably rebuild it with a Leatherman. The following is illustrative. When I had a carb problem, the mechanic at the importer responded, "Oh yeah, the throttle butterfly shaft end has probably worn so the disk is catching on the inside of the venturi. There are 2 brass screws that hold the disc on the shaft; loosen them and move the disc up so it clears the venturi. And it wouldn't hurt to use some fine emery or crocus cloth on the venturi while you have the shaft out."

The original carb failed because of a float problem around 2004. Joel at EarthTools sold me a replacement carb from another manufacturer that remains in service. Such a replacement may or may not still be available.

Another quirk: Chaff tends to lodge between the cooling fins near the exhaust valve. The extra heat may cause problems, so blow the chaff out with compressed air often.