Coils??

[mitch]

A friend of mine, Yes i have one ! just put a set of 80 XS coils on his 82 XJ. It seems to be running great but he didnt put the resistor in will this hurt any thing? He has the resistor but needs to hack up the wiring to install it. Any toughts would be a great help. ...................MITCH

[randy]

Mitch,

Installing a lower resistance coil is certain death for the ignition box.

Take a look at the specs on the XLJ coils and compare them to the XS. The XS coils and XJ coils are most likely different resistance primaries.

It's important that you match the specs of the XJ. If not, you risk reducing the life of your ignition box.

For instance, if the XJ coil spec is 3 Ohms, and the XS is 1.5 Ohms, then install the resistor NOW.


HTH,

Randy

[TopCatGr58]

Hey there Mitch,

Randy is right, the 81 and 82 bikes use a coil with 3ohm resistance, AND the wiring diagram shows a ballast resistor. They are for the TCI boxes with the 4RO. The XJ has the 10M prefix. The 78-80 models use the 1.5ohm coils with the ballast resistor. Using a lower resistance coil draws/pulls more amperage thru the TCI and thats how it can get fried! He either needs to purchase some after market coils with the 3.0 ohm rating, or find coils from an 81-82 model, OR install the resistor!!

I just reviewed the Xj wiring diagram, they don't show a ballast resistor, but they do show a "Boost Unit" that is connected to the power leads(red/white wires) going to the coils, along with the TCI unit, so apparently during starting, this "UNIT" either cranks up the voltage or just provides full 12volts going to the coils to increase it's sparking power for startup, but after it's running, the power is probably controlled and routed thru the TCI which probably provides less voltage to keep from frying the coils!

So...if you take the resistor and wire it in series just above the connection to the coils, but below where it goes to the TCI and the BOOST UNIT, then the resistor combined with the older coil's total resistance should add up to ~ 3 ohms!!! Good Luck.
T.C.

[John]

The boost unit is a vacuum sensing device that alters the spark timing, instead of the vacuum/mechanical units on the XS. It is actually called the boost sensor and it's vacuum source is the vacuum port on #2 carb, just like on the XS.

[randy]

Guys, that's the missing link to an alternative ignoiton box for the XJ. I need to get my hands on one, even a fried one to reverse engineer it.

That along with an XJ ignition box will get me started. Any offers? All parts will be returned.

BTW, I may have posted this before, but thanks to all who contributed parts for research on the alternative ignition box for the XS. We are about three weeks away from road testing the prototype.

Randy

[John]

Randy, do you need a boost sensor? I have one that I could sacrifice for the cause.

[mitch]

Resistor

Thanks guys for all your help . I installed the resistor today and Mikes bike is running great! Thanks for the offer on the coils John but his bikes gonna be great with the xs coils!..........................MITCH

[TheDjost]

Randy, that boost sensor is just a simple MAP (manifold absolute pressure) sensor. They can be found on many cars, including a lot of suzuki from the early 90's. Just go to a scrap yard and find a swift, or tracker with FI and check on the firewall, on the left of the air filter. It's a small black box with an electrical connector, and a vacuum barb. I think it just gives a standard 4 to 20 mA output depending on vacuum.

-Justin

[randy]

Justin,

To do it right FOR the XJ I need one FROM an XJ, make sense?

Randy

[John]

boost sensor/TCI box

Randy, the 'check' is in the mail. I sent them yesterday. You should receive them in a few days.