CDI

First off, I am new here. I have searched high and low, and cant find this answer.

I have a 1982 XJ650 Maxim. I done a total rebuild over the winter months. I got it back together and now I have no spark. I know the coils are bad. I have resistance on the primarys, but none on the secondary of one coil, and very low resistance on the secondary of the other. Also had recommended resistance at the pickup coils. I was going to replace the coils, and possible the CDI Ignitor Box. Here is where the question comes in at. Not having to much money left after the rebuild, I was going to resort to ebay(For the time being) I have found a bunch of coils for the XJ750. The ones I have found for the 650 are being listed from bikes that had bad electrical systems. I am having the opposite luck with the cdi. I am finding good xj650 cdis, no 750 cdis.

OK Can I mix the two. Meaning---- Can I run 750 coils on with a 650 cdi, or vise-versa?

 

OK... I think I just answered my own justion. Search a little more after post this. I found a picture of an XJ750's cdi unit. The numbers match 100% to the cdi on my 650 maxim. And I just found a few pics of the 750 coils. Some of the coils I found for the 750 has the same part numbers as the 650.

 

The coils will interchange. The CDI's or TCI's will interchange but with performance changes. There is a slight timing difference between the 650 and 750.

 

Thanks for the information. I didnt know that about the timing. Glad to know the coils will interchange with no performance change. Although I have found that part out, I was just chatting with a buddy, and he is convinced that if I use the 750 coil, I will need to regap my plugs to match the slight increase in the spark power. From what I have research, the two coils(650 and 750) produce the same voltage out. Is this correct?

 

Yup. You will not need to change the spark gap. 0.028-0.032 and you are good. In practice, I find good starting charateristics at slightly less than 0.030. Good luck.

 

Thanks...... Once my coils get here(just purchased a good looking set from ebay) I will let yall know how it goes.

 

So pursuant to this thread, if I have, for example, a working 650, and I take the suspect TCI and coils from a Seca 750 and stick them on there, TCI first, then coils, is it a valid test?

From what I read here, it should work, at least well enough to ride around the block. The coils should make no difference, if they work, though the TCI's timing differences will make it runs a little strange?

I don't plan to leave it this way. Just looking for ways to test some of the 750 parts while waiting to obtain others.

 

You would be correct Rhys.

 

Well, got the coils in. I am takin the CDI box is fried. I hooked the coils up, still no spark. These coils bench tested good. Oh, well. On to the CDI. I might get it back on the road before the seasson is up. The coils I got was from an 85 xj700X. This wouldnt cause a problem would it. I did have to mod the monting of them, as these coils are about 1 inch shorter them my xj650. According to the manual, when testing the xj650 coils you should have x-ammount of resistance on the primary and secondary. The xj700x coils tested within those limits. Here is what I have tested thus far.

Fuses-good
coils(secondary/primary) good
pickup coils-good
safty relays-all good

That leaves the CDI/ignitor box.......Right???

 

Could be the wiring harness. Check for continuity. (That's the last thing I can think of.)

 

Check the main power lead that comes off the starter solenoid and goes to the fuse panel. ( Supplies 12 volt power to ignition etc.) Pull the plastic connector apart and check it.

On mine this was badly corroded and the plastic basically just crumbled away.

This cured my hard starting as the bike wasn't getting enough juice to crank and fire at the same time.

In addition you should be able to establish the coils are getting juice with a voltmeter. Electrical problems are always a pain but fairly easy to isolate as long as you trace the wiring and locate where the conectivity stops.

 

So long as the resistances on the XJ700 coils are really close to the specs on the 650/750, you shouldn't have any problems.

 

The amount of cranking power available is a good point. If you suspect that as a problem - regardless of WHY there isn't enough power - one possible test for that is to hook up jumper cables to a car battery. Whether your bike has a weak batt or some other weak link, the car battery should be able to overcome it.

I used this to prove that my battery was shot. It would turn on the lights and even crank the engine, but not well enough to start. Hooked it up to a car battery and it started right up with just the slightest touch of the starter button. Replaced battery, no problems since.

(Nowadays, I put my 650's batt on a charger if it has been over a week since I rode it.)

 

Thanks guys, for all the tips. I will be sure to try them all(after all the rain moves out) Man, I need a garage It is suppose to be dry sat. so, I will give all the advice a try.

 

You can safely use the CDI box from a 650 Maxim on a 750. I just swapped one on my 750 Seca from a 650 Maxim and it runs the same, no difference at all. Infact, they have the same numbers on them. I assume they are the same exact part. I thought they were supposed to be different, but I was wrong.
If they are supposed to change the timing, I couldn't tell when riding. PD

 

Got the beast firing again. It turned out the CDI/Ignitior was bad. Get it firing on all cyclinders, but still wont start. Pulled the plugs, they where dry. The carbs where all gumed up. Carbs are sitting in cleaner. I will give it another go when the rain lets up. Dang, I want to ride.

 

Ok, so now I have a grimlin. I have lost spark on number 2 and 3 cylinders.

I have numbers 1 and 4 fireing(Quite well I must say. I stuck my finger in the boot and hit the start button.....WOW) Anyways, I can not get 2 and 3 to fire- Unless I which the primary 12+volt wires that plug on to the coils. After doing this 2 and 3 fire, but not 1 and 4. I ohmed the pick up coils. Good(620 ohms on the top pick up, and 632 ohms on the bottom pick up) I have even whiched the pick ups with a known good set, still the same. Pulled the harness apart, no shorts to grounds or opened wires. I think this leads me to getting another TCI box.

So my question is(after all the rambleing) is 2 fold.
1. Have I missed anything in my tests?
2. Do you have a TCI for my bike, and if so, what do you want for it.

 

Have you opened up your TCI and checked the solder runs?

 

Just spent the last 3 hours with soldering iron, rosin core solder, and magnifying glass making sure the runs and joints are good. I had a few cracked joints, but not to where it would lose connection. Fixed them, reinstalled..............and NOTHING changed. Still the same. I did notice when the tci was opened, there is a 2 terminals(-c1, -c2) Found a website telling me that was coil ground for coil 1 and coil 2. I have three different pickups, and all three pickups have the two black wires tied together in the harness, thous only using the -c1 terminal. The TCI has this "spare grounding terminal, which in the case says it is for coil 2. Does it really matter this is set up this way. I was thinking with the two pickup ground wires being together, it is essentially the same. Am I right????

 

Electrically speaking, yes. While the physical arrangement may be a little unsettling, bear with me. Whip out (gasp) your trusty multimeter and check for continuity/resistance between the C1 and C2 terminals. If they are at the same potential, you have no problems. Things are as they should be. If they are not at the same potential, you may wish to examine a factory wiring harness chart to confirm that your wiring is connected together and attached to the correct points. This diagram must be for your year and model to be useful on this particular point.

 

I will check that today. Benn super busy at work. When I get home, I will check that.

 

OK, continuity/resistance check out. The wires are good. I decided to take the cover off the tci while it was pluged in to the bike. I can "short" the power inducer and get spark. Get a heck of a spark when I jump two of the legs on the big circuit chip that is sitting up on the board. I think I am going to get another(once again) and try it. Everything else checks out. I dont want to mess around with this thing and not ride. Once I get the other one, and it is running, then I will try to replace all componets on this stinkin board.

 

I'm looking for dead TCI's. I cover postage.

 

I will dig through the shed of parts I have. I know with the few I have bought, I have one or two dead ones laying around. I will let you know.

 

Thanks! I just popped my extra 750 Seca unit open and I'm replacing capacitors and such. I'd like to experiment with them 'cause the rebuild that someone else did mentioned a different set of values for the internals and I would like more than just one perspective on this.

 

Hey guys, Thanks for all the help. I have the beast firing on all four. The power is out of this world. I have had this bike for nearly 4 years, and havent had this much power. It will hit 70mph in first, and it is only pulling 8300rpms. Shift to second and it is on down the road. Anyhow, the problem was the TCI/CDI. I repaired the old one with all new transisters, resisters, compacitors. I repaired it with parts from radio shack, for $20usd. Robert, I now have a good spare, I still have one dead TCI that You can have once I find it. I belive it needs the power transister replaced. It will not even power the coils. The transister(I belive that is what it is called) is the two "chips" that is bolted to the heat shink plate. I will pm you once I find it.

 

Congrats! It's good to know that electronics *repair* is not a lost art.

And if it makes your XJ go... WELL!

 

Congratulations Badams201! And thanks for the effort. I have sourced the correct "power" transistors for my current TCI and have also found a source for the diodes used on our boards. I'll publish my research in a little bit.