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Message started by thabrock on 11/19/12 at 06:56:49

Title: Noob question on engine assembly.
Post by thabrock on 11/19/12 at 06:56:49
Does the coil spark twice per engine rotation?

I was thinking if the marks are lined up it could be either the compression or the exhaust stroke.
Its a matter of turning the marks 180 degrees.  

I had replaced the head on my bike and really do not want to reassemble it until I know for sure that I am on the Compression stroke.
I have the cam lobes down at TDC.  

The coil will fire a spark on the compression stroke and the exhaust stroke?  

I have the manual and read all the info.  

I may be over thinking this.  

Title: Re: Noob question on engine assembly.
Post by youzguyz on 11/19/12 at 07:20:43

55494043534E424A210 wrote:
Does the coil spark twice per engine rotation?

I was thinking if the marks are lined up it could be either the compression or the exhaust stroke.
Its a matter of turning the marks 180 degrees.  

I had replaced the head on my bike and really do not want to reassemble it until I know for sure that I am on the Compression stroke.
I have the cam lobes down at TDC.  

The coil will fire a spark on the compression stroke and the exhaust stroke?  

I have the manual and read all the info.  

I may be over thinking this.  


1. The spark fires ONCE per rotation, but that is twice per engine cycle.
First rotation is input(piston moves down) and compression(piston moves up). - spark plug fires
Second rotation is power(piston moves down) and exhaust(piston moves up) - spark plug fires, but does nothing.

2. Yes, the marks line up at TDC on compression and on exhaust.

If the marks are lined up (you are at TDC) and both cam lobes are down, then you are at TDC on the compression stroke.

Title: Re: Noob question on engine assembly.
Post by youzguyz on 11/19/12 at 07:24:47
I think part of your confusion may be what a "rotation" is.
The cam shaft rotates ONCE per engine "cycle"
The crank shaft rotates TWICE per engine "cycle"

The alignment marks are on the crank shaft.

Title: Re: Noob question on engine assembly.
Post by verslagen1 on 11/19/12 at 07:45:44

Quote:
I was thinking if the marks are lined up it could be either the compression or the exhaust stroke.

Yes it is either.

Until you put the head on.

When you reassemble the head, always have the crank at TDC, and align the cam marks horizontal aligned with the top of the head and the alignment pin at 1 o'clock.

Title: Re: Noob question on engine assembly.
Post by youzguyz on 11/19/12 at 07:59:57
Look at this:
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1256079122

Reply#10 (2nd picture) shows the cam as it should look when at TDC compression.

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