OS .70 Surpass (early model) trouble
09-17-2006, 10:47 PM
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OS .70 Surpass (early model) trouble
New old stock Surpass .70 mounted inverted using Powermaster 20 20 fuel...backfires and throws props. Tank a little too high also...flooding, so I up-righted (better carb needle/tank height) and yet to run again. Has about 8 flights and 4 deadsticks from the backfiring. Adjusted low needle back to factory setting along with 2-1/2+ turns out on the high too. I noticed while rotating the prop by hand in the rotation of running, not any compression to speak of. If I rotate backwards, there is a lot of compression...normal? Or did I screw something up? I will step down to 10% nitro after seeing some posts re: detonating due to high compression on OS 4-strokes. Should I send the engine in for service?
09-18-2006, 10:35 AM
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RE: OS .70 Surpass (early model) trouble
Having a higher compression feel when turned backwards is normal for a lot of engines. That's just because the parts line up the same way as on the power stroke.
Higher-nitro fuels can contribute to erratic running if the engine's not set up for them. You usually need to lower the compression ratio and go with a colder glow plug to get good operation. See how the engine runs on the 10% first. It also may just need more breakin running at a very-rich setting.
Higher-nitro fuels can contribute to erratic running if the engine's not set up for them. You usually need to lower the compression ratio and go with a colder glow plug to get good operation. See how the engine runs on the 10% first. It also may just need more breakin running at a very-rich setting.
