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Message started by Redryder652 on 02/07/16 at 00:03:58

Title: Engine direction
Post by Redryder652 on 02/07/16 at 00:03:58

I've read in many places not to rotate an engine CW. I've done it a few times cause of a dead battery so it would be easier to bump start. I didn't know not to at the time however. What can rotating the engine backwards do? I've got a new battery and the bike starts and runs fine. I just don't understand what bad it can do. :-?

Title: Re: Engine direction
Post by Serowbot on 02/07/16 at 00:39:11

No worries... if you rotate backwards, you can mistake the compression stroke, for the exhaust stroke, when setting valve timing...
Suck, squish, bang, blow.... you'know?...

...might also effect valve lash, when you measure gap... if you entered backwards....

You did know harm...

Just don't do it so much, that your bike thinks that's what you want...
It's very gullible... ;D

Title: Re: Engine direction
Post by Redryder652 on 02/07/16 at 00:59:14

Thank you Serowbot :)

Title: Re: Engine direction
Post by justin_o_guy2 on 02/07/16 at 05:01:47

Now, you get a Detroit Diesel in a forward gear and kill the engine, pushing in the clutch and let the truck roll backwards, pop the clutch, and you'll have it running backwards.

The
Turn the motor CCW instructions are important for engine work.
Getting it off compression to make it easier to start? It dont care.

Title: Re: Engine direction
Post by Dave on 02/07/16 at 06:56:37

302F292E33340535053D2F23685A0 wrote:

Now, you get a Detroit Diesel in a forward gear and kill the engine, pushing in the clutch and let the truck roll backwards, pop the clutch, and you'll have it running backwards.

Bet it won't do that for very long......on account of the oil pump running backwards and sucking the oil out of the engine and pumping it into the oil pan

Title: Re: Engine direction
Post by Redryder652 on 02/07/16 at 07:00:12

But wait, that means the supercharger in there would be sucking out ou the intake making a vacuum, instead of pressurizing it. I think. :-?

Title: Re: Engine direction
Post by Serowbot on 02/07/16 at 07:25:40

It takes a JOG to run a engine back'erd's... :-?

Title: Re: Engine direction
Post by oldNslow on 02/07/16 at 07:37:54

310607111A070611555651630 wrote:

But wait, that means the supercharger in there would be sucking out ou the intake making a vacuum, instead of pressurizing it. I think. :-?

The engines JOG is talking about are the old Detroit Two strokes, and they will indeed run backwards, just like he described. They suck air in the exhaust and exhaust out the air cleaner.

A lot of them were naturally aspirated, especially the LN4's and the LN6's and none of them were supercharged. The ones that were not naturally aspirated were turbocharged.and if you got one running in reverse the impeller in the turocharger didn't spin fast enough to make any difference since it was then on the intake side - no exhaust gas to make it turn.

Emissions regulations put an end to those engines quite a while ago. There are probably some still around 'cause they were very long-lived, reliable engines, particularly in construction equipment and stationary generators, but GM hasn't made them for pretty close to twenty years.

Title: Re: Engine direction
Post by justin_o_guy2 on 02/07/16 at 08:22:24

And, no, you won't get going too fast. There's only one forward gear and that's reverse. I only did it once and then only for a few seconds. Pulling into the shop I bucked it going up onto the slab, it coughed, wheezed clattered and started backing up. I stomped the clutch and brake and pulled out the kill. Never lug a Detroit, they live longer at higher RPM.

Dave makes a good point. I don't know if it would oil running backwards.

Title: Re: Engine direction
Post by verslagen1 on 02/07/16 at 09:19:37

310607111A070611555651630 wrote:

To answer your question... I hope you have a '95 or later bike!
Anything built prior to that doesn't have a starter torque limiter. Rotating the engine backwards will engage the starter clutch. It takes a lot of torque to turn the starter and most times teeth will just break off instead or the journals for the gear shafts will break out.