78E ignition woes

[buggrin]

I'm the original owner of this bike and really don't want to give up, but......A mechanic is doing the work (I'm too dam old and blind to do it anymore) and between us cost and time involved keep going up without results. Seems like multiple issues here but they sure are hard to isolate.

After cleaning the carbs, rebuilding the fuse box, new vacuum lines, checked all places of possible vacuum leaks, changing the pickup coil wires, and reading thru everything I could find on this site the 1&4 are still dropping out. Spliced the advance wires about 3/4" from the coil fearing damage if I got any closer.

Measuring resistance across the P/U coils gives about 70K ohms on one and 80K on the other and doesn't vary when you wiggle the wires or turn the advance. When you open the throttle fast or slowly you can hear the chug a chug missing and see the advance working, but when you hold the advance and open the throttle the rpm jumps with no missing.

I'm looking for the next logical step:

Change out P/U coil assy? Are the 78 thru 81 P/U coil assemblies interchangeable? Change ign coils? Change the CDI box?

Has anyone changed an early model to the 81 or later ignition. If so, how involved was it? Bolt on or many mods required?

This bike has been my regular ride since 78 and has been kept OEM with good maintaining but this one really has me stumped and chasing an unknown with more money is getting old fast.

Any help will be greatly appreciated.

[mack]

Woes

I'm not the best person to chime in on this issue. In a couple hours hours Crazy steve, motoman and if your kucky 3 phase may come on line. They are the wizards. However, since you've got soooo much time and $$$ already into your ride, why not go ahead and buy a set of acels or mikes green coils and put them in. The fact that after all you've done so far, it's 1&4 causing the problems leads me to believe , that; that coil is the problem. As far as your age and eye sight. Well; feel lucky you've lived long enough for that to be a problem. Good luck man. You've got the flag ship of the fleet, don't give up on it.

[buggrin]

I'll check to see if he has swapped coils to see if the problem moves from 1/4 to 2/3. That should tell if the prob is in the ignition coil -- right?

Also, after rereading some info, using the Digital ohmmeter is not the way to test the Pickup coil wires so that needs to be redone. That may show that the problem is closer to the P/U coil than the splice.

Any other ideas please. I'm ready to try about anything that's not going to break the bank

[buggrin]

I'll check to see if he has swapped coils to see if the problem moves from 1/4 to 2/3. That should tell if the prob is in the ignition coil -- right? If the problem moves I'll pony up the $140 for coils

Also, after rereading some info, using the Digital ohmmeter is not the way to test the Pickup coil wires so that needs to be redone. That may show that the problem is closer to the P/U coil than the splice.

Any other ideas please. I'm ready to try about anything that's not going to break the bank

[crazy steve]

Measuring resistance across the P/U coils gives about 70K ohms on one and 80K on the other...

Change out P/U coil assy? Are the 78 thru 81 P/U coil assemblies interchangeable? Change ign coils? Change the CDI box?

Has anyone changed an early model to the 81 or later ignition. If so, how involved was it? Bolt on or many mods required?

The pick-up coils should measure out at about 720 ohms, +/- 20%. If you test at the TCI by unplugging the smaller plug, that will 'prove' the wiring to the coils. Put your meter on the 2K ohm scale to test. Tugging on the pick-up wires while testing will tell you if any are bad.

The coil assemblies are the same, but the vacuum advance cans and backplates aren't. The vacuum advance units are all year-specific, and the '78-80 backplate are the same but the '81 unit is different.

I personally wouldn't recommend swapping to the '81 or '82 ignitions, as both were one-year-only parts and are very tough to find. There's no advantage to doing so either, as they were used for emission purposes, not performance. You'll pretty much have to swap the entire ignition over to make it work.

There is a specific test procedure in the manuals, so if anything is out of spec that will be the problem. If you're only having issues with 1&4, then it's definitely ignition related. Do thoroughly check the coils, with the plug ends removed; you should have about 15K ohms across the secondary +/- 20%, 1.5 ohms across the primary. You can replace them with the 3 ohm Dyna units; you'll need to build some 'adaptors' to mount them (look in the 'mods' forum for a how-to), will need new wires, and bypass the ballast resistor (located 'behind' the left forward fuel tank mount) by connecting the two red/white wires together.

Also make sure all the electrical connections are clean/tight. These bikes are notorious for poor connections, and can drive you nuts chasing them...

[bikerphil]

Maybe loose solder connection in the TCI, JAT.

[3Phase]

Bob, are you sure you have a calibrated mechanic? From your description it looks to me like the engine is pretty close to running again so I wouldn't spend any more money on it unless something was actually bad or hopelessly broken.

Has anyone checked the valve clearance and the engine compression? If the valve clearances are off then tuning is a waste of time and so is a compression check. The valve clearances decrease as the valves and valve seats wear. They might be close enough to give a good compression reading when the engine is cold but after the engine warms up, the valve(s) won't close.

Are you using the correct range on the Ohm meter and checking the right wires? The pickup coils should only be ~720 Ohms, not 70,000 or 80,000 Ohms!

Have you checked and set the base ignition timing with the vacuum advance disconnected? If the engine misses when the vacuum advance tries to work but runs smoothly when you 'hold it' then the vacuum advance line is connected to the wrong vacuum port; pickup coils/wires are bad; carburetors are out of synch and/or the idle is too low; base ignition timing is off; some fascinating combination of all of the above.

The '78 to '81 pickup coils are all the same and changing a '78 to use an '81 ignition can be done but most people go the other way.

The '81 ignition controller, the TCI, was only made for that one year and it can be hard to find a good one. The '81 doesn't use a mechanical advance assembly because dynamic ignition timing is controlled by the TCI. You would have to remove the mechanical advance assembly from the '78 engine or you'd get to much ignition advance! Other than that it's mostly just swap and tune.


Double check the length of the wires by advancing the timing plate by hand.

If you've cut and spliced the pickup coil wires and made them too short then the pickup coils won't be able to move when the vacuum advance tries to advance the ignition or they'll pop out of their holders and rub on the spinning timing indicator plate which will almost immediately chew through the insulation and ground the pickup coil(s).

Stock ignition coils should be ~1.5 Ohms on the Primary and ~15,000 Ohms on the secondary with the spark plug boots removed. The stock spark plug boots have internal resistors for use with the stock, non-resistor, spark plugs.

Make sure you remove the boots before checking the Secondary coil resistance and clip about 1/4" off of the spark plug wires to get rid of any corrosion. When you're finished, add a dab of dielectric grease to the end of the wire before putting the boots back on.

Good hunting!

[buggrin]

Yep, mechanic is fully calibrated. Good guy.

Compression checked OK & constant over all 4. Don't know if was tested hot or cold but will check. Doubt that the valve clearance was checked.

Ohm meter was digital & I was looking at digits, not scale. Always had that problem with the slide rule too........... Will insure resistance is 700 and not 7000. Both checked within 20% so think it was 700. Will check again if can find analog meter.

Engine runs good when timing is advanced by hand before opening throttle. Also ran good after carb cleaning until warmed up, then started dropping two cylinders. Will make sure on base timing with vac disconnected.

OK, will NOT change to newer version of ignition.

Hand turning of timing plate shows good wire movement/clearance.

Is the procedure for checking the ignition coil resistance written someplace? I have orig shop manual.

Will pass on info re: clean plug wire connection.

Took cover off the black box & inspected. Could not see any loose connections.

Thanks for the help guys. We'll get on your suggestions & I'll report back in a few days/weeks when that's done. This is a "fill in as time allows" job for the mechanic so it may be a while.

[crazy steve]

One thing both Scott and I mentioned only in passing is the spark plug boots/ends. Do check the coils with those removed, but also check the end caps; those are supposed to have a 5K ohm resistance, and a too-high value can cause problems. You can buy new ones for about $3-5 each (NGK still makes replacements) from most metric bike dealers, Cycle gears sells them, or various online sources.

[Ken Talbot]

... 1&4 are still dropping out. Spliced the advance wires about 3/4" from the coil fearing damage if I got any closer...

Be sure to have a good look look at the pick-up coil wires where they are held by a crimp just before leaving the engine casing. Open up the crimp and give them another tug to be sure you don't have another intermittent break. Also, follow the wires from where they exit the engine case to where they plug in behind the fuse panel. I've seen them get melted into a nasty mess just inside of the driver's left foot peg from being too close to the exhaust.

[motoman]

If the engine misses when the vacuum advance tries to work but runs smoothly when you 'hold it' then the vacuum advance line is connected to the wrong vacuum port;////////////Double check it.........JAT.

[Lonerider62]

It sounds like a vacuum problem but then you mention that it appears to only affect 1&4 whcih tells me a coil problem. A guy on the FZ1 forum had a similar problem a while back and after checking everything else, it did turn out to be a defective ECU (cdi on the xs1100). Some times it is really helpful to have another like bike your can swap parts with. It's fast and can rule out possibilites that can be hard to track down and expensive to replace.

[3Phase]

TCI Test

Davinci (Randy), used to have a web page about testing the TCI and he's got TCI troubleshooting and repair nailed sixteen ways from Sunday. I don't know if he still does all of that but he'd be the one to ask!

[buggrin]

A quick update to those who gave me suggestions:

Bought a P/U coil assy and set of ignition coils on ebay. I know it's a crapshoot, but thought for the relatively low cost they would be worth a try.

Also, made a copy of this thread for the mechanic to look at. Lotta good ideas (he's tried some of them) that may contain the "golden nugget"