Jonsered 910 ignition testing

[madmodifier]

Hi There,

Wondering if anyone knows how to test the ignition system on a Jonsered 910? Or if there is any other type of more rugged ignition that could be retrofitted to this saw. I just picked this up with the knowledge that it had no spark and that the parts are hard to come by. I really wanted a large bore saw to complement my 621. People have been this saw before and the lower coil is a bit cobbled.

Thanks,
Ben

[madmodifier]

Well I purchased another ignition from chainsawr and installed it last night. I used the business card to gap and did not hook up the kill wire. I still have no spark. I tested the plug in my 52 and that is working fine. I contacted chainsawr and it was suggested that I try a new plug. I am going to get one hopefully after work.

Anyone know if there is a way to check the flywheel mags to see if they are the issue?

[Jiles]

You can try this and it won't cost you anything but your time----

I read an old post, somewhere, describing how to SOMETIMES Revive a defective coil.
Of course this will not work every time because if the coil is "fried" ---it won't.
His suggestion was to remove the spark plug and also to lubricate the cylinder wall, and make sure the clearance between the flywheel and coil is correct---app. 012. Proceed to spin the flywheel with an electric drill, at about 2,000 rpm, being sure rotation is in the right direction. C/C in most cases. Flywheel may have to be spun for a length of time but I had results within a few seconds from a DEAD coil.
I am fortunate enough that I have a Lathe and it is a simple matter to set the components up and run the procedure.
I had TWO dead coils and this worked on both and the saw has continued to work. With THREE others, it did not work. Seems like when they set for a long time, they have to sometimes be woke up?
These modern day coils are complicated because many change the engine timing and also limit the maximum rpm.
Much better then a point type ignition because at 13,000 rpm there would be "floating", sometimes,  or other problems.
Good Luck--might work for you and it will cost nothing

[madmodifier]

Interesting thanks! I have a lathe as well but it seems like the drill method might be the easiest.

[Jiles]

I might also add, that you will be spinning the flywheel with the nut. It will be in the direction of loosening --just use a variable speed drill, start show and hold at top speed--REMOVE the drill from nut while spinning. This prevents abrupt stop.
I was going to post a photo of the setup in my lathe but have never figured out how to post. Far too complicated for me.
I have no problem with other sites?

[Jiles]

Interesting thanks! I have a lathe as well but it seems like the drill method might be the easiest.

Drill is easier but much rougher on engine internals. Be sure and lubricate P/C.

[sharkey]

Try a non 'R' plug.  The resistor is there to keep the spark hot.  Sometimes the older ignitions wont generate enough juice to run an R plug.  For instance, try a Champion CJ6 instead of RCJ6, same thing with NGK BPM7Y instead of BPMR7Y.

The other thing you can try is putting the coil in a toaster oven on 150-200F for an hour.  This seems to work well on old Lawnboy coils, I have no idea why.

[beenthere]

Jiles
Not complicated to post pics, just a procedure of a few simple steps. When you really want to post pics, we'll walk you through it..  ;D  no problem, and will be glad to do it.

[madmodifier]

I was told the NGK BPMR7a is the correct plug. I thought the resistor was to filter out the EM created from the engine. Makes it so your radio does not buzz.

[madmodifier]

Try a non 'R' plug.  The resistor is there to keep the spark hot.  Sometimes the older ignitions wont generate enough juice to run an R plug.  For instance, try a Champion CJ6 instead of RCJ6, same thing with NGK BPM7Y instead of BPMR7Y.

The other thing you can try is putting the coil in a toaster oven on 150-200F for an hour.  This seems to work well on old Lawnboy coils, I have no idea why.

Maybe it melt's the coating on coil wire sealing a fault in the winding? Keeping the electrical pixies in.

[madmodifier]

Happy to report after reinstalling the ignition and the new plug that the saw is again running. I think I have a bad decompression valve as it appears to blow by a bit sometimes at idle. It could just be due to sitting but I also have never had a saw with one before

Thanks all for the suggestions and thanks to chainsawr for having the parts and plug information!