Coil Help

Had to replace coils on my 85 xj700n the new coils read 24000 on the secondary but old ones and also specs say they are suppose to be 12000 +/- 20% did i get wrong coils or could it be something els3

 

I purchased new coils and Ngk boots for my xj650, they ohm'd out good, except the #1 and#4 boots (long) once installed onto the wire(s) took it out of specs. I read on Ngk website that the particular # boot was resistor type. I just bought 2 new metal sparkplug connector and boot for automotive, that brought it back to spec.

 

Be aware that the Yamaha manuals that show the testing procedure for the coils are incorrect, as they show the test on the secondary side being done with the resistive plug caps still installed........whereas the resistance specs are for the COIL ITSELF/ONLY.....and not for the coil + plugs. The 12K +/- 20% are for the COILS ONLY (plug caps removed).


Checking Factory Coils:

Factory Yamaha coils need to "see" a total load resistance on the secondary side (the "going-to-the-plugs" side of the coil) of around 20-30K ohms (ohms being a measure of electrical resistance). Electrical resistance depends on a number of factors: wire size, type of material, length of material, ambient temperature, etc. etc. All readings are specified at 70-F.

In any case, all factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---have the following primary and secondary resistance ranges.


Forget watching any other video on u-tube, etc. about how to test dual-lead ignition coils; this is the only one that shows how to properly test both the primary circuit (from the wire harness) and the secondary circuit (the "plug wires" side of the coil).......with the spark plug caps removed. You can ignore the actual readings that he is showing....the specs for XJ bikes are shown below.....but the method that he shows for testing the secondary circuit is the correct procedure:

www.youtube.com/watch?v=I0TKybs6Rnw
(skip to 3:55 for the dual-lead coil)

or you can read all about it here:

www.xjbikes.com/forums/threads/how-to-test-ignition-coils-and-plug-caps.130696



For all XJ models except XJ700, XJ750-X, and XJ900 models:

Primary (input from TCI): 2.5 ohms +/- 10%
= 2.25 ohms - 2.75 ohms acceptable range

Secondary (output to spark plugs): 11K ohms +/- 20%
= 8,800 ohms - 13,200 ohms acceptable range


For all XJ700 and XJ750-X models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 12K ohms +/- 20%
= 9,600 ohms - 14,400 ohms acceptable range


For all XJ900RK, RL, N, FN, and F models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 13.2K ohms +/- 20%
= 10,560 ohms - 15,840 ohms acceptable range


For all XS1100 models:

Primary (input from TCI): 1.5 ohms +/- 10%
= 1.35 ohms -1.65 ohms acceptable range

Secondary (output to spark plugs): 15K ohms +/- 20%
= 12,000 ohms - 18,000 ohms acceptable range

 

When I was checking for spark on one of mine (without the multimeter) I got tired of holding the plug against the block and swinging to see if I had spark so I bought 2 lighted spark plug caps and put them on cylinders 1 and 4 so if they both lit up I knew both coils were good.

 

How does that help if #1 and #4 are using the same coil??

 

Left coil runs cylinders 1&3, right coil runs 2&4.

 

I didn't know Seca's were different than the inline four Maxims.

 

Me neither. Why would Yamaha do that l wonder?

 

Doesn't the crankshaft of a Seca move the outer pistons together and the inner pistons together, like in a Maxim?

 

yes, actually I'm unaware of any in-line 4 with a different configuration until the Yamaha crossplane came along.
I'm sure there are other exceptions, would sure like to hear about them.


here's the Ford Model T

 

At least my Seca has left coil for cyl 1 and 4 and right coil for 2 and 3. I believe that any other orientation is less than perfect, although I have to admit that I have decided my coil orientation myself since I just changed engine but I still believe it to be best possible for this engine configuration.

 

I have had, at one time or another, 5 xj650s Maxims and Secas and 2 xj750 Secas. They all fired 1 and 4 and then 2 and 3 together