Hey all,
I just thought I'd share a frustrating experience I'd had over the past two-days involving power-loss. I have a couple of thousand on a well-running 66cc. I picked up some new 2-stroke oil from the local Ace Hardware, and inadvertently chose their synthetic-blend. I was "on the road" and my portable supply was exhausted. My usual blend is standard ashless 2-stroke blended with castor-oil. After using the new blend, the engine ran fine for about 50-miles, but then suddenly my power dropped. It was sort of like it was running at half-choke. The motor ran much quieter. I always have a spare top-end since it's just the right thing to do, and I was tempted to simply swap the old one out and call it a day. Instead, I went thorough an exhaustive troubleshooting procedure. The engine ignition behaved like the compression was shot, although its start-up pressure felt normal. The spark seemed normal, although I cycled through different CDIs, plugs, and coils. I carefully re-lapped the mating surfaces...no improvement. I was, however, reusing my existing head-gasket. I was careful to clean its surfaces off with a razor-blade to make sure it'd crush cleanly. Well, this morning in the sunlight, it was visually evident that there'd been some blow-by on the underside of the head-fins. There had been no expected blow-by noise though...the popping and squeaking. I grabbed another unused, thinner head-gasket, re-lapped, and replaced the head. Sure enough, I was back in business. In fact, the thinner gasket increased pressure, and I was easily doing 3MPH faster than normal. So, does anyone believe that the blow-by could have been triggered by the oil-change? The head-bolts showed NO signs of loosening, and the old gasket was not visibly damaged. It's as if the existing seal became compromised after the synth was used.
I just thought I'd share a frustrating experience I'd had over the past two-days involving power-loss. I have a couple of thousand on a well-running 66cc. I picked up some new 2-stroke oil from the local Ace Hardware, and inadvertently chose their synthetic-blend. I was "on the road" and my portable supply was exhausted. My usual blend is standard ashless 2-stroke blended with castor-oil. After using the new blend, the engine ran fine for about 50-miles, but then suddenly my power dropped. It was sort of like it was running at half-choke. The motor ran much quieter. I always have a spare top-end since it's just the right thing to do, and I was tempted to simply swap the old one out and call it a day. Instead, I went thorough an exhaustive troubleshooting procedure. The engine ignition behaved like the compression was shot, although its start-up pressure felt normal. The spark seemed normal, although I cycled through different CDIs, plugs, and coils. I carefully re-lapped the mating surfaces...no improvement. I was, however, reusing my existing head-gasket. I was careful to clean its surfaces off with a razor-blade to make sure it'd crush cleanly. Well, this morning in the sunlight, it was visually evident that there'd been some blow-by on the underside of the head-fins. There had been no expected blow-by noise though...the popping and squeaking. I grabbed another unused, thinner head-gasket, re-lapped, and replaced the head. Sure enough, I was back in business. In fact, the thinner gasket increased pressure, and I was easily doing 3MPH faster than normal. So, does anyone believe that the blow-by could have been triggered by the oil-change? The head-bolts showed NO signs of loosening, and the old gasket was not visibly damaged. It's as if the existing seal became compromised after the synth was used.
