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Question for the gasoline engine gurus

Old 04-09-2015, 02:46 AM
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Mike2735
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Default Question for the gasoline engine gurus

I have an SV50 cc twin 2 stroke gasoline engine. It is crank trigger fired. I was wondering if there is any reason I can't modify the crank trigger so the engine would run in a clockwise direction as opposed to the counter clockwise direction it runs now? I have a project that requires the engine to run clockwise.

Thanks in advance for you responses.

Mike M.
Old 04-09-2015, 06:10 AM
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av8tor1977
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That could be a tough one. Reed valve or piston ported two stroke engines can be made to run in either direction just by changing the ignition timing. However, with a twin you could possibly run into problems with one cylinder running richer than the other if you make it run backwards to the way it was designed. If the engine had individual carbs for each cylinder, that would not be an issue.

Another issue with making them run "backwards" is that the prop hub and/or prop retaining bolt or stud needs to be left hand thread to run in reverse. Otherwise the power strokes act like an impact wrench, quickly causing the prop hub or prop to come loose. Careful with that, as the prop can come right off in a lively fashion. (Don't ask me how I know....)

AV8TOR

Last edited by av8tor1977; 04-09-2015 at 06:20 AM.
Old 04-09-2015, 08:09 AM
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Mike2735
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Thanks for your response. This is a reed valve engine. Both pistons are in the compression (outward) stroke at the same time. Thanks for reminding me about the retaining nut. I will have to make sure I use a nylon locking nut and possibly a jam nut with it.
Old 04-09-2015, 02:19 PM
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tande
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Originally Posted by Mike2735 View Post
Thanks for your response. This is a reed valve engine. Both pistons are in the compression (outward) stroke at the same time. Thanks for reminding me about the retaining nut. I will have to make sure I use a nylon locking nut and possibly a jam nut with it.
Aahh.......Not recommended....
Old 04-10-2015, 07:26 AM
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WRK
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If you pull about the same RPM in the reverse direction with a similar prop you are good, I think it will probably work.
Old 04-10-2015, 08:48 AM
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Mike2735
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Thanks Everyone. I am going to try it this week end to see what happens.
Old 04-10-2015, 08:53 AM
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Cyberwolf
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Use some blue locktite on the original nut instead of the nylon nut and tighten it up good all should be good to go.
Old 04-10-2015, 09:01 AM
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av8tor1977
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I've tried double jam nuts, the high strength RED Loctite, and I've even tried thin super glue, (CA). The props still come loose when the engine runs backwards. Be careful.

AV8TOR
Old 04-10-2015, 10:17 AM
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Mike2735
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This engine is not actually going to be turning a prop. It will have a pulley on it turning 2 ducted fans. (A project I am working on. The fans need to face forward and the motor would mount better if it was mounted facing the rear. That's why it needs to run in reverse.)
Old 04-10-2015, 03:09 PM
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tande
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Originally Posted by Mike2735 View Post
This engine is not actually going to be turning a prop. It will have a pulley on it turning 2 ducted fans. (A project I am working on. The fans need to face forward and the motor would mount better if it was mounted facing the rear. That's why it needs to run in reverse.)
Oh, well now.......a completely different argument from a "Safety" point.......if it were a prop & you choose to put yourself in harm's way, that's one thing......to include everyone around you ,is another story.......

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