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Timing help needed!

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threein60(at)yahoo.com
Guest

Posted: Mon Jun 19, 2006 10:14 am Post subject: Timing help needed!

Good morning,

  Still working on the CJ but in need of a little advice...I'm trying to reinstall the mags and time them on my 285 engine. I looked thru the archieves  and have all the books but still a little confused. I reinstalled mags, Found #4 TDC, Installed flower pot and adjusted to TDC. Then moved the prop about 40 degrees BTDC, then forward to 25 degrees BTDC. Installed the mags to this angle. Mag was internally lined as per manual with white electrode aimed at line on mag case. Mag Coupling was at the correct orientation to install mag. After I installed mags, they were close but couldn't find tune the opening of points with buzz box. Turning the mag didn't seem to make any difference with point opening. There is about 4 degree split between mags and the first mag goes off at about 28 degrees BTDC. I keep to reading something about prop flange markings and you need to subtract something from something??????  I need to find away of fine tuning and I think I'm missing something

 with the reduction gears.  Any advice would be greatly appreciated. 

  Thanks

  CJ6 8181C

  Larry

Larry Pine



 		

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Frank

Joined: 10 Jan 2006
Posts: 69

Posted: Mon Jun 19, 2006 12:50 pm Post subject: Timing help needed!

Larry;

You have to adjust the point gap before the timing. Set the point gap while

the points are riding on top of a lobe and then go back and do your timing.

Frank

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dsavarese(at)elmore.rr.co
Guest

Posted: Mon Jun 19, 2006 1:28 pm Post subject: Timing help needed!

There is also a fine adjustment plate that is adjusted via an eccentric 

screw.  This is the key to properly setting and synchronizing the mag 

timing, after of course you set the point gap equally on both mags.



There are two sets of hex screws under the rotor.  Loosening the smaller set 

allows you to adjust the point gap via the points eccentric.  Loosening the 

two larger hex screws enables you to adjust the opening position of the 

points in relation to a cam lobe by rotating the small eccentric screw on 

the opposite side of the cam where the points are located.  Using a mag 

timing synchronizer, you can fine tune and synchronize the mags to open 

simultaneously by rotating this small eccentric screw.



Don't try setting the exact timing and synchronizing the mags, other than 

rough timing, by loosening the mag hold down nuts.  It can be done, but 

you'll spend 10 times the amount of time than by doing it as suggested 

above.  Get the timing close, then use the fine adjustment procedure to 

synchronize the mags.



Dennis

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wlannon(at)cablerocket.co
Guest

Posted: Mon Jun 19, 2006 10:19 pm Post subject: Timing help needed!

Larry;



You definitely need some help.

There are two distinct steps in setting magneto timing;



1. Internal timing of the mag ("e" gap setting) and

2. Installation and adjustment of firing angle on the engine.



Internal timing can be done with the mag on or off the engine. If installed 

find top dead center on the compression stroke of  #4 piston (BUT - before 

doing any of this remove ALL front spark plugs). You can do this with a 

small wooden dowel or similar to show piston position once you have 

established with your thumb that you are on the compression stroke.



finger is pointing at the timing index mark on the mag housing. The mag is 

now in position to check and adjust the internal timing. (off the engine you 

would simply turn the mag by hand in the arrow direction).



Either disconnect the primary lead at each mag or turn the mag switches on 

both. Mags are now live -  the primary reason for removing all front plugs.



Clean the points with a lint free cloth and small brush using acetone or 

MEK, etc. No petroleum solvents. Do not manually open points more than 

1/16". If there is any evidence of arcing the points may need dressing. If 

so do NOT use a point file (or any file). If necessary let me know and I 

will go through the process with you.



By turning the prop set the point rubbing block on the center of the cam 

lobe with the distributor finger pointing to the timing index. Check the 

point clearance. It should be 0.3 mm (.012"). The tolerance is 0.25 to 

0.35mm (.010" to .014"). If outside those limits adjust to exactly 3mm. 

Carefully move the tab locks, loosen the retaining screw and set the 

clearance with the adjusting screw. Tighten the retaining screw and tab lock 

both.



Attach your timing light (you should have an aircraft unit with two lights 

to facilitate synchronization in the final step) to the point spring post 

and an engine ground.

Rotate the prop backwards about 40 degs. and then forward slowly ( this is 

necessary to take up gear backlash every time you check point opening) until 

the light is on (points just opened).

Do this a number of times until you are sure of the initial opening point.

With a straightedge (6" rule works fine) check alignment of the leading 

distributor finger to the timing index. Acceptable tolerance is +/- 1/16" 

but with the gap at 3 mm it should be right on.



If necessary the distributor rotor may be adjusted by loosening the 3 screws 

and rotating to align the finger.



The mag is now internally timed and ready for mating to the engine. Under no 

circumstances is it acceptable to change the point gap as a means of "fine 

tuning" for timing to the engine.



That is step 1 but I am out of time so will try to finish tomorrow night.



Walt



 	  Quote: 	
		   



  Good morning,

  Still working on the CJ but in need of a little advice...I'm trying to 

 reinstall the mags and time them on my 285 engine. I looked thru the 

 archieves  and have all the books but still a little confused. I 

 reinstalled mags, Found #4 TDC, Installed flower pot and adjusted to TDC. 

 Then moved the prop about 40 degrees BTDC, then forward to 25 degrees 

 BTDC. Installed the mags to this angle. Mag was internally lined as per 

 manual with white electrode aimed at line on mag case. Mag Coupling was at 

 the correct orientation to install mag. After I installed mags, they were 

 close but couldn't find tune the opening of points with buzz box. Turning 

 the mag didn't seem to make any difference with point opening. There is 

 about 4 degree split between mags and the first mag goes off at about 28 

 degrees BTDC. I keep to reading something about prop flange markings and 

 you need to subtract something from something??????  I need to find away 

 of fine tuning and I think I'm missing something

 with the reduction gears.  Any advice would be greatly appreciated.

  Thanks

  CJ6 8181C

  Larry

 Larry Pine

 ---------------------------------

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- The Matronics Yak-List Email Forum -

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wlannon(at)cablerocket.co
Guest

Posted: Mon Jun 19, 2006 10:43 pm Post subject: Timing help needed!

Must learn to read before hitting send. Somehow deleted most of the first 

sentence of para. 4. Should read ------

"From the TDC position rotate the prop backward about 40 degs and then 

forward until the distributor 

LEADING -----------------------------------------"

Walt

---

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john.coffey(at)cingular.c
Guest

Posted: Tue Jun 20, 2006 10:11 am Post subject: Timing help needed!

Hi, Walt. Thanks for the info. 



Questions:

- What's the process for dressing the points?

- Why shouldn't one use a points file?



Interested YAKsters want to know. 



THANKS!

John Coffey

Yak-55m

Seattle, WA

--

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