# A Quick Stupid Question

**URL:** https://forums.speedlife.net/t/a-quick-stupid-question/252662
**Category:** Shift518 Automotive
**Created:** [June 13, 2010, 5:17pm UTC](https://forums.speedlife.net/t/a-quick-stupid-question/252662 "2010-06-13T17:17:46Z")
**Posts on this page:** 1
**Showing post:** 24

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### Author: ![KrazyKid](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/krazykid/32/6371_2.png) [@KrazyKid](https://forums.speedlife.net/u/KrazyKid)
#### Post date: [June 14, 2010, 9:26am UTC](https://forums.speedlife.net/t/a-quick-stupid-question/252662/24 "2010-06-14T09:26:18Z")

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> [@pepsi center update](https://forums.speedlife.net/t/pepsi-center-update/32598/40):
>
> I do believe. Actually, that’s how Ski-Doo reverse works-you hit the button, it shuts down the motor and starts it backwards (srs).

Yes skidoo RER does that. it revs it down to 0 rpm and uses the inertia to keep it spinning down and it rotates backwards and fires back up.

> [@WTH: WHALE MODELS](https://forums.speedlife.net/t/wth-whale-models/32631/17):
>
> Iirc you can start a 2stroke backwards

Yes, thats why the rer works. 2 stroke doenst have cams and valves and shit, just ports. mechanical timing for intake and exhaust is the same rotating one way as it is the other, its all based on port heights on the sleeve.

Same as little RC car engines, you can run them in reverse too.

Also, if you were to somehow pop start a 4 stroke motor to make it rotate backwards, most cars would jump timing big time. I know my VW head would do that, the timing chain for the cams puts pressure on the tensioner in the head by rotating in one direction only, if it were to spin the other way the tensioner would actually release all the tension and jump timing.

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