Another source for coils?

[Hepcat]

First off, Thanks to everyone who has helped make this site such a wonderful resource! After browsing this site for 5 months, I've saved myself innumerable headaches and feel I have a pretty decent understanding for my bike! My bike seems to have all the most common problems. When I started I just wanted to get the bike running...now I want it to run reliably and run well!

Has anyone tried using the ignition system from a four cylinder car? I have an XJ and am having the classic troubles of intermittent firing, backfires and finally now, of no spark. I'm in college in Hawaii away from my tools and just need to get an ohm meter to check out whether it's my coils, plug wires, or something else. I was wondering if maybe I could pull a solid state ignition system off of a car from a junkyard instead of spending $120 on new coils if it turns out that's what's gone wrong.

The bike I have has "XJ650" written on the coils, so I think they have been replaced once already. Are the XJ650 coils the same as the original XJ1100's?

Also, I know I've seen it mentioned somewhere that the coils for the XJ are different than the XS. I can't for the life of me find that page anymore...does anyone know what the difference is? I think it had something to do with resistances. What could be damaged by using the wrong one?

I've got my eye on a 4 cylinder Yamaha at a junkyard here (I think it's an XS). It's so completely rusted out that I poked my finger through the tubing of the frame and the engine dropped the 3 inches to the ground...it was just a matter of time before it happened on its own anyhow. I'm wondering if the coils might still be in good shape. Maybe the ignition unit too if it looks intact. The bike's been pretty well stripped over the years. When I saw it, I was looking for brake parts and was disappointed by what I found there.

(Note: I've been a member of the site for about 5 months now, but when I login with my former ID, Groelzj, I can't post.)

[John]

Hey Jon, The ignition units are different from an XS. As far as XJ650 coils in an XJ11, I don't see why they won't work. I have read that the XJ coils are physically smaller than XS coils also. Did you ever get that L/F caliper fixed? The only caliper that will interchange is just the rear I believe. The fronts are not the same. If the frame on that junkyard bike was that rusty, then chances are that the rest of the bike isn't much good

[skids]

Before you get inventive, make sure that the battery is not crapping out. If the xj11 is anything like the xs11, the black box needs something like 10.2 volts (?) just to send spark to the coils.

[buffalo]

I have been checking out coils in the auto shop where I work lately, they all seem to have primairy resistance way too low (.02 to .08 ohms). From what I have found in my research, most bikes use either 1.5 or 3.0 ohm coils. So most any 4cyl bike coil can be made to work by adding or eliminating a ballast resistor.

[Hepcat]

Ranting...

Yup, I got the brakes all working. It has been quite an experience working on this bike. I bought it about 2 months before I was going to get here over the internet. Chuck told me that it needed the rear caliper mount, so I bought that (From John) and brought it with me in my luggage. Unfortunately for me, my flight was delayed and one of my bags didn't get here for a month, and the other has never arrived. So the mount, along with my brand new helmet, never got here. I'm still awaiting payment from the airline on that one.

I got a second rear caliper mount and installed it on the bike, only to find that the left front brake was seized. I never thought to check it before then. So I had to work to get that all worked out. At that point I caught some kind of virus and was sick in bed for 2 weeks with a 103 degree fever. My parents flew me back home for the next 2 weeks to recover. Sorry I didn't get back to you on the caliper...I hope you can understand I wasn't up to doing much those days, checking email included. (Fortunately for me, one of those weeks was Spring Break.) Upon getting back to school, I had loads of homework to catch up on and had to put the bike on the back burner.

So here I am...I finally had the bike running for 2 weeks and then it got rained on and wouldn't start after that. I've got fuel and air, but no spark. Which leads me to diagnosis via the coil FAQ.

Anyhow, it turns out that the guy won't sell parts of the rusted out bike...it's all or nothing. Since I'm living in the dorms and going home for the summer, I'm not up for that.

Sorry...It just felt good to rant for a while. I won't even get into the other problems I've dealt with on the bike.

[Jerry]

From a recent coil thread:

There is some differences between the XJ and XS coils, mechanical as well as electrical. Here are the stock specs:

XJ Coils:

Model: CM12-09 Hitachi
Min spark gap: 6mm (0.24 in)
Pri winding resistance: 2.5 ohm + or - 20% at 20 deg C (68 deg F)
Secondary winding resistance: 11 Kohm + or - 20% at 20 deg C

XS coils:

Model: CM12-08 Hitachi
Min spark gap: 6mm (0.24 in.)
Pri winding resistance: 1.5 ohm + or - 20% at 20 deg C (68 deg F)
Secondary winding resistance: 15 Kohm + or - 20% at 20 deg C

Note differences in both primary and secondary resistances! Incidently, the XS coils are rated at 19KV, but there is no rating in the specs for the XJ coils.

[Hepcat]

That helps a lot!

Thanks for digging that up. I couldn't seem to put the right stuff in the search engine to pull up those specifics! I knew I had seen it somewhere though.

I asked a friend about the car to bike thing and he said it would be like trying to put a Ford ignition on a Japanese car...it wouldn't work without someone knowing a lot more about it than either of us do.

[Hepcat]

I looked up the ignition coils from the XJ650 in my repair manual (XJ650 was as close as I could come to finding an XJ1100 manual)

The data are the same for the XJ650 and XJ1100.

[Ken Talbot]

I hate to sound like a broken record, but I really don't think the coils are the problem, especially if you have been experiencing intermittent than total failure. Check the pick-up coil wires - that is exactly the way they act up. Somebody put it well in a note a few days back - something like there are XSs with repaired wires, and there are XSs with broken wires.

[chevy45412001]

xj

do us xj guys have that same set up on our pickups?I had my ignition cover off the other day didnt notice moving part on the ignition thingy,at least not were a wire would move.But than again i've been having memory lapes lately.

[Jerry]

Some '81 models (H?) and the XJ do not have a vacuum advance, so pickup wire breakage is not an issue. Ignition curve is programmed into the TCI or "black box" and does not rely on a mechanical vacuum assembly.

[Ken Talbot]

Oops - I gotta get back to paying more attention to the model in question! Here's an excerpt from the genuine Yamaha Service Manual for the XJ:
"This model is equipped with a battery operated, fully transistorized breakerless ignition system. By using magnetic ppick-up coils the need for contact breaker points is eliminated. This adds to the dependability of the system by eliminating frequent cleaning and adjustment of points and ignition timing. This T.C.I. (Transistor Control Ignition) unit incorporates an automatic advance circuit coontrolled by signals generated by the pick-up coils and pressure sensor unit. This adds to the dependability of the system by eliminating the mechanical advancer. This T.C.I. system consists of three main units; a pick-up unit, an ignitor unit, and a pressure sensor unit."

Jerry - have you got any first hand experience in how this pressure sensor unit functions or if it is susceptible to going wonky? Or, with the pick-up coils still wired in somehow, are they still subject to breakage?