ST 2300 Compression
 

Starting to bench run a 2300 which I got last fall from a distributor NIB (China made). Followed all the advice about fuels, settings, and large tubing and have no problems in starting or running. When I started the breaking it in I noticed the engine had very little compression and with fuel in it some compression. After 1 Gallon of fuel there has been no change in the amount of compression. In breaking in a new ST 90 ringed last fall, there was all types of gray residue in the exhaust oil for first few tanks of running. The 90 has a lot of compression. There was no gray residue during the first runs of the 2300. I have a never been run ST3000 that has super compression and a friend is breaking in a new ST3250 that has a lot of compression. Will this compression level improve with time or is this unique with this engine in that as it heats up, tolerances change and compression increases. Bob Ohio

RE: ST 2300 Compression
 

Please check your engine first. Your compression leak may be due to loose head bolts or a loose glowplug. The engine should have a good compression feel. If more running doesn' t improve it, you can send it to us under the warranty.

RE: ST 2300 Compression
 

Thanks Bax I know the glow plug is tight Will check head bolts. As I pull the engine toward, TDC I can hear air going past the ring while I listen in the carb and from TDC on the down stroke , I hear air leakage on the down stroke until the piston gets to the exhaust port. Will put another gallon thru it and if no change will send it back. It is for a spring project, plane is built. Thanks. Bob

RE: ST 2300 Compression
 

Bax Did have two head bolts on let side which tightened about 1/4 turn more. Engine is sounding better and compression improving. Will loosen tomorrow and tighten in a sequence tomorrow. Thanks

RE: ST 2300 Compression
 

If the head gets tightened-down evenly and still has problems, let me know. You may need something as simple as a new gasket, or you may need a new head...the original one could have become warped.

It's normal to have some leakage past the piston ring when you turn the engine over slowly. You should hear some hissing.

With a fast flip of the propeller, though, you should only hear a "pop" as the exhaust port opens after each brisk flip.

RE: ST 2300 Compression
 

Went thru and did a head re tighten and much improvement. Got the exhaust pop, some decent compression, easier starting smoother running. Thanks for the advise. Bob