No compression on ASP engine
 

I've got extremely low compression on my ASP .75 Glow engine. It's so low that when i rotate the prop i barely notice it at all. The story, i bought this engine used and was told it was in good condition, when i bench tested it worked fine, except for a problem holding idle without dying. Well i slapped it onto my airplane and was having a lot of trouble getting it to idle without dying at the field, finally got it to somewhat cooperate and took to the sky. On climb out i pitched up about 30 degress and she died. I set the plane down flat in a bush field with only slight damage to the left wing, no big deal at all. When i found it one of the muffler bolts was gone and the other was still there, so i thought that was the reason for the dead engine, the muffler came off in flight.
I inspected the engine and saw no damage or dirt on the engine, spinner and prop, but the carb housing part was slightly turned to the left. I rotated the prop and no compression. So what's wrong? Can it be fixed without spending a lot of money? I bought the engine for $50.00, i'd hate to have spend a lot to fix it. Any help would be great, i fly mostly electrics so Glow engines are still kind of new to me. Thanx

Kyle

RE: No compression on ASP engine
 

Sounds like it needs a new ring.

The rings from Frank Bowman are not very expensive [email protected]

Frank C Bowman (505) 327-0696 1211 N Allen Ave, Farmington, NM 87401

You should put bearings in it too while you are at it

http://rc-bearings.com/catalog/index.php

RE: No compression on ASP engine
 

I don't know a thing about ASP engines but I was curious and went on eBay where I found one. It's a 2 cycle. If it has a piston ring I would start with an inspection of that. The ring could be broken into short pieces. The wrist pin could have loosened and scored the cylinder wall = new piston and cylinder liner. The connecting rod could have broken. I doubt that the loosening of the muffler would have caused you to pancake your aircraft but at least you saved the muffler. Two cycles aren't too challanging to disassemble. Pull the head and inspect the cyllinder bore. If you can turn the prop and see no movement of the piston with the head off it's got to be the connecting rod or a sheared-off connecting rod journal on the crankshaft. You can also view piston movement through the exhaust port - it's the quick and dirty way.

As far as the muffler screws go try using medium strength Locktite on the threads. If you use high strength Locktite you will need dynamite or lots of heat to remove the screws.

For some reason my fellow RCU members seem reluctant to reference eBay so I won't give you the item # but I would advise you to check it out. My apologies to the RCU staff if I have overstepped myself.

Good luck.

Bill

RE: No compression on ASP engine
 

The ASP .75 is an ABC engine so I suspect that the liner/piston set up is shot[:o]

RE: No compression on ASP engine
 

Check also that the head-bolts are not loose.

RE: No compression on ASP engine
 

First, the ASP 91 2S I had had very little compression when turned over by hand, but it would run like a scalded dog once the fire was lit. Compression only tells you part of the story. Sure, the cylinder/lining fit could be worn a little, but that doesn't make it useless. As for it dying, it sounds lean to me. If it doesn't idle well, and dies when pitched upward, try richening the low end some. Make small adjustments until you get it to idle and transition good, then hold the nose up while at WOT on the ground and see if the RPM's drop. If they don't, then you have it set right. Make sure there are no air leaks anywhere causing the lean condition. If there are air leaks around the carb housing, or in a fuel line somewhere, then you will chase the needle settings all over the place and it will never settle down and idle right.
I would get the mixture fixed before I counted the engine as out.

RE: No compression on ASP engine
 

Did you check the compression when cold? If you had a lean run causing it to overheat, it will have low compression till it cools off. Goes for both ringed and ABC engines.

RE: No compression on ASP engine
 

Thanks guys, i'll go recheck it and take it apart to see whats going on in there. Thank you for the help.

Kyle

RE: No compression on ASP engine
 

I have an OLD ASP .61. When you flip the prop it feels like the glow plug is missing. It still has power when fired up. Try running fuel with a little more Castor oil in it. I know mine does not like full synthetic oils fuels.

It does not have as much power as a new 61, but mine runs great. Will idle all day long without loading up. I am running a Fox Miracle plug or an Enya #3. Have also had good lick with Thunder bolts.


Dru.