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OS GGF-120SII Conversion |
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Aug. 10, 2015 This OS FS-120SII engine started as a CDI conversion some time ago. The old fuel regulator was not working and parts are not avialable. It was waiting for me to make the parts to mount a Walbro carb to run gasoline and spark ignition. OS released the G5 glow plug in the mean time and I decided it was time to finish this project and give the plug a try in this engine. |
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A spacer was required for the manifold to make room for the much larger carburetor. This part was machined on an Emco PC Mill 125. This is the first part I made on this machine and was glad to see it go well, other than the feed/speed error on the drill. |
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| This is the manifold adapter for the Walbro carb. It was turned manually, then the flange was cut in the small CNC mill. | |
| The manifold spacer and carb adapter on the engine. | |
| The new backplate was first turned manually. | |
| Then, the back was CNC milled. | |
| A carb mount of Nylon plastic was milled again on the CNC, parted off in the lathe, then milled flat. | |
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Two holes were drilled manually on the small flange to thread into the new backplate. |
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Everything bolted together. The carb position was almost perfect. The manifold spacer was shortened by 0.5mm to make it right. |
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Another view. |
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The engines starts easily and runs well with the plug lit. It misses and drops a lot of RPM when plug heat is off. I think increased compression ratio will improve running. |
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Prior to increasing compression ratio, I machined the glow plug seat. This allows the plug to protrude deeper into the combustion chamber. The plug depth now matches FS-120SIII. Test running showed improvement at full throttle, but not enough improvment at idle to be reliable. The next step will be more compression. |
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