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Chapman Super Pup 4 1/4 HP problems

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andrew
Moderator
Username: andrew

Post Number: 567
Registered: 11-2001


Posted on Sunday, February 26, 2006 - 10:43 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

The following came in by email. I will direct Brian here for followup:

quote:

Hi
We have restored a Chapman Super Pup 4 1/4 HP engine and have a problem.

It would appear that the gears driving the magneto are incorrect and the magneto shaft rotates at twice engine speed.

Being a 2 stroke, this gives us ignition at BDC whcih causes an explosion of the incoming mixture as the transfer port is open.

How it got to have this gearing is a mystery. Do not know history of engine at all.

Is it possible to get the correct gears?
Would you know the specs of the correct gears in case we have to get them made up?

Any help would be appreciated.
Thanks
Brian Taylor
brianne@ultratune.com.au
Publicity Officer
Hervey Bay Historical Village & Museum
13 Zephyr St.
Scarness.
07-4124 6526
WebSite: http://herveybaymuseum.museum.com/welcome.html


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richardday
Senior Member
Username: richardday

Post Number: 298
Registered: 11-2003


Posted on Sunday, February 26, 2006 - 02:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Is the magneto correct for the engine?
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peterogborne
Senior Member
Username: peterogborne

Post Number: 117
Registered: 09-2002
Posted on Sunday, February 26, 2006 - 05:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Brian........your Chapman Super Pup is OK. All to do with the "Bounce Start'' and probably the reversing by moving the magneto over TDC.
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Brian Taylor
Visitor
Posted on Sunday, February 26, 2006 - 07:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

Richard
The magneto has the letters WN 3097 stamped on the flat area. Also the words Chapman Super Pup and a number,,,cannot read.
Sorry Peter, not sure that I understand your reply "your Chapman Super Pup is OK. All to do with the "Bounce Start'' and probably the reversing by moving the magneto over TDC."
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jules
Member
Username: jules

Post Number: 16
Registered: 08-2005
Posted on Monday, February 27, 2006 - 09:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

I think what Peter means is the magneto needs a little adjustment, you may need to swing the magneto 180 degrees or adjust a little to the left/right
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gregoryan
Member
Username: gregoryan

Post Number: 10
Registered: 09-2004
Posted on Thursday, June 08, 2006 - 08:48 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only)

THey ARE MEANT to have the mag driven at 1:2 gearing, it is how the get away without having the 'impulse' spring! Yes there is a wasted spark.

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