This is info that can be of benefit to anyone using IC engines, so I copied my post to this forum also.
#11. "RE: PA 75/65/61 Venturie O-rings"
In response to Reply # 10
Sat Jun-14-14 04:05 PM by Randy Smith
Good post for ANY engines . So some may not think, as the title suggest, only PA engines have this.
PA engines really have no place in the title about leaking old hard O-rings, they are not PA Engine products, and they are made by O-Ring mfg. companies.
ALL IC engines do exactly the same thing to O-rings, whether it is Sup Tiger, OS Max, and ENYA Magnum etc... O-Rings will get hard and deteriorate after several years of use; this has been going on for as long as they used O-Rings to seal carbs and venturies.
The black Nit rile O-Rings used in most all model engines are in fact very good sealing products, but as Dave has found, need to be replaced every few years, or in some cases every 10 years.
Normally the O-rings swell after exposure to heat and fuel/oil, taking care of the sealing even better, I find it is only when they start to get hard, that the problems arise.
If you want an alternative that can sometime do a better job of lasting, I recommend you try one of the silicone red O-rings, they last a long time, but are more delicate, as they will chip, or break easier. just be careful with them, those are the only 2 types I use, as I do not like the Viton O-rings for sealing, they do not do as good a job as the other 2. But try what you will, never hurts to test things.
Regards
Randy