Re: F-20 Magneto Timing Question for Athol Carr, Dave Al...

Posted by Athol Carr on August 07, 2009 at 02:33:28 from (219.89.109.116):

In Reply to: F-20 Magneto Timing Question for Athol Carr, Dave Allgire , posted by Tom 43 on August 06, 2009 at 06:14:03:

The F-4 magneto was the standard on F-12 and F-series tractors 1934 onward and it replaced the E-4A magneto that was used on earlier tractors ( parts books also show a Bosch magneto as an option).
Timing is discussed in the Blue Ribbon Service Training Course "Magneto" and in the Blue Ribbon "Service Shop Service Manual, F-12, O-12, W-12, F-20 etc" It states that the engine should be cranked so that number 1 cylinder is at top dead center, at this point the mark DC on the flywheel is in line with the index on the flywheel housing. The impulse coupling should be dis-engaged by inserting a small nail through the impulse oiling cup and lifting the pawl until it engages the pawl latch (it may be necessary to rotate the impulse coupling while lifting the pawl. After the latch is dis-engaged raise the spark lever on the breaker housing as high as it will go (fully retarded (earthed)) and remove the cover from the magneto. Rotate magneto coupling in its normal direction until breaker are rubbing block is on high point of breaker cam and adjust breaker points to 0.013".
Remove the distributor block and rotate magneto coupling clockwise (viewed from coupling end) until distributor disk is in position of Number pin on distributor cover (about 2 o'clock) with the breaker points just about to open.
Without disturbing this position place the magneto on its mount (magneto bracket) and insert base cap-screws loosely. Insert the proper amount of shims between the drive coupling members and install the two coupling cap-screws, The coupling is made that so that two holes line up exactly opposite each other; the cap-screws must not be forced or the setting will not be correct.
Then, to check timing, it suggests that the engine be turned so again the DC mark on the flywheel lines up with the register on the flywheel housing the breaker should be just starting to open and the distributor disk is lined up with the contact for number 1 cylinder.
Tighten up the base cap screws, install breaker housing cover and distributor cover (block). To return impulse pawl to operating position inset nail through impulse oiling cup and lift pawl latch. Then reinstall drive coupling cover with drain hole in lowest position.
I used this approach when reinstalling the magneto on my O-12 after the engine was completely rebuilt. On full advance the F-4 magneto fires 35 degrees ahead of top dead center whereas fully retarded fires on TDC.

Replies:

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Optional Video Title: Optional Video URL: Advanced Posting Options Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.   Advanced Posting Tools   Upload Photo  Select Gallery Photo  Attach Serial # List  Return to Post

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]