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Stuart P55 timing

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Ross Gordon
New member
Username: wyurry

Post Number: 1
Registered: 09-2014
Posted on Monday, September 29, 2014 - 07:05 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Hello,
I'm new to site. How do you set timing for Stuart P55 with impulse magneto? I've tried following the insructions in the manual but found plugs sparked with piston halfway down the cylinder. Any help much appreciated.
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john.kenneway
Member
Username: jbz2079

Post Number: 7
Registered: 09-2009
Posted on Monday, September 29, 2014 - 07:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Hi Ross Im not sure about how you do this
but is there a way of holding the impulse
weights disengaged so you can line up the
Timming marks to the points opening?

There has to be a simple way to achieve this
And I would like to kniw how it's done too.
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Chris Dennison
Visitor
Posted on Tuesday, September 30, 2014 - 06:35 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Hello Ross,
The important bit with these magnetos is to make sure it is not trying to impulse when you are setting the timing as this will considerably retard the ignition which sounds like what is happening to you. The Magneto mark M on the flywheel refers to the "advanced" i.e non-impulse position of firing. To set this, turn the engine flywheel forwards (clockwise) until the magneto impulse clicks and fires the plug you want to set (i.e no.1 piston). Now turn the engine very slowly backwards (anticlockwise looking at the flywheel) until the contact breaker points just close, and then very slightly clockwise until they just open. This is the "advanced" firing position of the magneto. Then you slacken off the magneto coupling and without moving the magneto shaft at all set the engine flywheel to the ignition point ("M") or just under 2" before TDC with piston 1(nearest the flywheel) coming up to top. If you do this by turning the engine flywheel in its normal clockwise direction it makes more sense! Then tighten the mag coupling and turn it backwards and forwards a bit to test that the position is correct (always a bit of backlash in these old engines, and if the magnets are any good sometimes the magneto shaft will sneak around a few degrees).
When you turn it forwards on impulse, it is quite normal for the engine to fire well after top dead centre as this set up is used to retard the ignition for starting. i.e you may already have set it correctly......!
Hope this helps,
Best wishes, Chris.
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john.kenneway
Member
Username: jbz2079

Post Number: 8
Registered: 09-2009
Posted on Tuesday, September 30, 2014 - 06:57 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Chris. That is excellent.
I am now a little bit wiser than I was
A few minutes ago.
I hope Ross can now time his P55 now.

I had endless fun trying to time my R3M
as it's quite hard to hold the magneto and the magneto


engine while trying to tighten the taper

engine still and get the taper retightened.
There is also a fair bit of slack in thr drive
chain too.
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Darryl Ovens
Member
Username: darryl

Post Number: 5
Registered: 11-2005
Posted on Tuesday, September 30, 2014 - 09:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Yes I too was thinking the impulse would delay ignition timing by as much as that and I have to agree with John, Chris'_ explanation is excellent, Just what I would have liked to write had I been more eloquent and known those engines!
Some magnetos, (like the Wico or Fairbanks-Morse fitted to Gravely tractors), have the "advanced" or normal running ignition point marked on the mag coupling. This does make it easier to get the timing close, however it still pays to do something equivalent to what Chris describes, as the marks are not that accurate and this allows for all the other variables like backlash, points adjustment, variable markings etc.
Incidentally that retardation caused by the impulse is neccessary partly to wind up the spring to provide the impulse and at low cranking speeds it (almost) prevents backfiring.

(p.s. I had to remove the possessive from Chris's name above as when followed by the word explanation, I guess the boards porn filter was putting the s and ex together and getting something else altogether). (mutter mutter dirty minds!)

Cheers

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