JAP80 timing Problem

Hi Camerart, welcome to Outdoorking.

With a simple magneto ignition, the spark always occurs as the points open. If the ignition timing is fixed rather than variable, this always happens before top dead center (BTDC). Note that the size of the maximum points gap affects the ignition timing fairly substantially. The correct maximum gap is usually between 0.012" and 0.020". I think the JAP 80 has the correct gap stamped on the flywheel - it might be 0.018 - 0.020".

The engine will produce its best power output with somewhere in the region of 20 to 30 degrees of advance, but if it has an aluminium flywheel (unlikely for a JAP rotavator engine) it will be limited to around 5-8 degrees BTDC because of severe kickback when starting. With a substantial cast iron flywheel, somewhat more advance may be safe, and advantageous. I have read elsewhere on the internet that the JAP 80 timing was specified at 25 degrees BTDC - see this report:
http://www.tractorbox.co.uk/forum/forum_posts.asp?TID=7407

Remember, kickback is dangerous. Back in the days when cars were started with crank handles, people were occasionally killed by the handle when kickback occurred, and broken arms were fairly commonplace (usually due to not having retarded the ignition before cranking).

Entire Thread
Subject	Posted By	Posted
JAP80 timing Problem	Camerart	18/11/13 08:02 AM
Re: JAP80 timing Problem	grumpy	18/11/13 08:57 AM
Re: JAP80 timing Problem	Camerart	19/11/13 06:15 AM
Re: JAP80 timing Problem	grumpy	19/11/13 06:26 AM
Re: JAP80 timing Problem	Camerart	20/11/13 05:40 AM
Re: JAP80 timing Problem	grumpy	20/11/13 06:33 AM
Re: JAP80 timing Problem	Camerart	24/11/13 12:09 AM
Re: JAP80 timing Problem	Camerart	24/11/13 01:26 AM
Re: JAP80 timing Problem	grumpy	24/11/13 07:12 AM
Re: JAP80 timing Problem	Camerart	29/11/13 12:30 AM
Re: JAP80 timing Problem	grumpy	29/11/13 06:28 AM
Re: JAP80 timing Problem	Camerart	30/11/13 11:16 PM
Re: JAP80 timing Problem	Camerart	30/11/13 11:23 PM
Re: JAP80 timing Problem	grumpy	01/12/13 08:38 AM
Re: JAP80 timing Problem	Camerart	02/12/13 01:19 AM
Re: JAP80 timing Problem	Camerart	03/12/13 11:55 PM
Re: JAP80 timing Problem	grumpy	02/12/13 06:42 AM
Re: JAP80 timing Problem	grumpy	04/12/13 06:50 AM
Re: JAP80 timing Problem	Camerart	04/12/13 10:01 AM
Re: JAP80 timing Problem	grumpy	04/12/13 01:44 PM
Re: JAP80 timing Problem	Camerart	05/12/13 12:48 AM
Re: JAP80 timing Problem	grumpy	05/12/13 06:35 AM
Re: JAP80 timing Problem	Camerart	05/12/13 02:12 PM
Re: JAP80 timing Problem	grumpy	05/12/13 07:04 PM
Re: JAP80 timing Problem	Camerart	08/12/13 11:44 PM
Re: JAP80 timing Problem	Camerart	08/12/13 11:53 PM
Re: JAP80 timing Problem	grumpy	09/12/13 06:33 AM