Post Number: 567
|Posted on Sunday, February 26, 2006 - 10:43 am: ||
The following came in by email. I will direct Brian here for followup:
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.
Hervey Bay Historical Village & Museum
13 Zephyr St.
Post Number: 298
|Posted on Sunday, February 26, 2006 - 02:21 pm: ||
Is the magneto correct for the engine?
Post Number: 117
|Posted on Sunday, February 26, 2006 - 05:37 pm: ||
Brian........your Chapman Super Pup is OK. All to do with the "Bounce Start'' and probably the reversing by moving the magneto over TDC.
|Posted on Sunday, February 26, 2006 - 07:15 pm: ||
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."
Post Number: 16
|Posted on Monday, February 27, 2006 - 09:53 pm: ||
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
Post Number: 10
|Posted on Thursday, June 08, 2006 - 08:48 am: ||
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.