Not firing on cylinders one and four

Hi all,

I'm in the Pittsburgh area and have a 1981 xj650 maxim. It was running great till the other day when it decided to no longer work on cylinders one and four. I suspect my TCI.

That said... Immediately prior to the sudden not working, I removed a shim on each of my carb needles. I had shimmed it due to installing a 4 into 1 exhaust when my old one rotted out. Today I put the shims back, thinking that was inexplicably the issue. It had been running decently with the shims, but I felt it was missing some on the top end and decided to take them out to see the effect. Given the net change here is zero, I don't think this is my culprit, but I mention it anyway in case someone knows something I don't.

Thus far I've done the following:

Pulled spark plug wires while the engine is running. One and four had no effect. It died immediately when I pulled two and three.

Pulled one spark plug wire at a time, and fitted a spare plug. Verified spark (albeit weak looking) at each wire.

Outright swapped my coil packs. Swapped the plugs leading to them as well as the wires on plugs. Same behavior when pulling plugs.

Checked resistance across the coils. Got about 12k from wire one to wire four (without the boots). This was the same on both coils.

Checked resistance across the boots. Each one was just under 5k.

Anyone have any guesses? I'm flummoxed. Valve clearances were adjusted this year about a thousand miles ago, carbs were synced at the same time. Running stock airbox and filter with a 4-1 exhaust.

 

Bad plug caps or possibly corrosion at the end of the plug wires. Unscrew the plug wires and see if there is any corrosion. If so, and if you have enough room snip off about 1/4 inch and see if that helps. In any case, it sounds like the problem is with the wires or caps, assuming the plugs are ok.

 

The plugs both tested at 5k ohms, and I got 12k ohms from the tip of wire one to the tip of wire four. Could they still be bad even so?

 

Not sure about ohms testing. K-mode or xj550 know more about that stuff. I know that on my XJ700N the number 1 and 4 have resistor caps.
Are the sparks you are getting on 1 and4 similar to 3 and 3? If so, I would expect some fuel issue.

 

this doesn't test the plug that's in the engine

if you swap a good coil onto a bad plug this is expected.
get a new set of plugs and end that mystery
shimming needles doesn't usually solve anything, one size main jet is all it should take, maybe not even that.
make sure the diaphragm is seated when the top goes on

 

1 and 4 fire from the same ignition coil . could be a bad pickup coil not making the tci fire it needs to be ohmed out with a meter

unplug the connector at the tci it will have a black ,orange and gray wire ohm between the black and gray and the black and orange. also ohm black wire to ground should get no reading for the black to ground

Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range. do this for any connector you unplug

clean the tci connectors with electronic contact cleaner and apply a little silicon grease to them before replugging them

 

For the top plug (4 spot) I got

Grey-black 12 ohms
Orange-black open circuit
Black-negative terminal of battery : continuity

Does the position of the crankshaft affect the above readings, or should I get the numbers specified no matter where the motor is?

For the lower plug (6 spot) I had no continuity anywhere. But that's the output of the TCI, right?

 

that's not good. lay down and take a close look at the wires from the tci to the pickups.
crank position doesn't matter

 

4 position is tci to ignition coils you can read ignition coil primarys from plug but if off then read at the ignition coils connectors under tank.

open for orange and black is why you have 2 cylinders not firing if you check the coil pack you should see orange wirs connecting to the pack on left for sparkplugs 1 and 4 and orange wire running from tci,
12 ohms is bad as well .

as suggested open up left crank cover you will see pickups follow wires back both black wires will be spliced together but you should not have any continuity to battery negitive.
you may have a shorting wire to frame or internialy from pickup coil to base(frame).

you will find that the wires run betweeen lower frame and motor to tci

edited out incorrect info

 

I pulled the crankcase cover and took another set of resistance measurements. I apparently was hasty the first time when I got an open circuit orange to black because both measurements came in at about 12 ohms this time. These measurements were taken with the key in off. When I took them with the key on (I didn't crank, just turned it on) , the resistance climbed into the Megaohm range. Is this expected?

Visually, I can't see a whole lot troubling. No obvious signs of impact or wear. No frayed wires or signs of maintenence gone wrong.

The one thing I did notice was a number of metallic filings that were clinging to the pickup coils due to the magnetic attraction. I'm not sure where the metal dust came from, but I blew it all away with an air compressor. I should have taken pictures. It was all clinging to the base of the pickup coil. Could this have been a grounding path?

Attached are pictures of my pickup coils, and my resistance measurements.

 

The 4 pin connector that goes to the TCI is for the ignition coils:

R/W power, B ground, O (orange) 1 and 4 coil, and Gy (grey) 2 and 3 coil, so you are checking the primary side of the ignition coils if you are ohming from R/W to O and R/W to Gy. If you are measuring from B to O and B to Gy you are going to get a strange reading as that is effectively measuring from battery to ground, which has all sorts of things tied to it.

The pick-up coils are on the 6 pin connector that goes to the TCI:

O to B for 1 and 4 pick-up, and Gy to B for 2 and 3 pick-up.

 

I redid my resistance checks on the six pin connector, and this is odd. It looks like orange to black is actually checking out. About 640 Ohms. But I'm showing an open circuit on grey to black. So the pickup for the cylinders that aren't firing, is correct, and the circuit for the working cylinders isn't... Wut?

 

Yep, that will happen and it is how the TCI works. If only the 1 and 4 pickup is good the 2, 3 cylinders will fire. If only the 2 and 3 pickup is good the 1, 4 cylinders will fire. This is why you can't be logical and think if one pick-up is bad the bike should run on 2 cylinders. It will instead backfire when trying to start as the spark that is occurring will be 180 degrees out. I can't explain how in your opening post you seemed to have the bike running on just two cylinders as it really shouldn't do that - unless the black label TCI is a bit different than the red label that I tested. I can't quite see what your meter is set to, but maybe try the next higher scale to see if you get any reading - it could be the pick-up is providing enough of an input to the TCI to sync to the correct cylinders, but that is just a guess.

 

For the resistance measurement that came back as an open circuit, I had set the multimeter up all the way to 20Mohm. So it can't really be scaled up further.

Is this my smoking gun then? The 2-3 pickup coil has gone bad?

As far as how my bike ran on just two cylinders... Really not great. It was enough to move the bike down the road. I went about ten miles like that (not my druthers. I don't want to wash my cylinders). But riding conditions were rough and it stalled frequently. It was WAY down on power.

 

The pickup is bad or you have a broken wire on that one. It should be spec around 650ohms. I'm in the midst of troubleshooting my 550 first-fire after a rebuild and going through all of this stuff.

 

set meter at 2K range
Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range. do this for any connector you unplug

 

Since I was 95% sure of my issue, I engaged in a little bit of destructive testing. I stabbed my multimeter probe through the wire insulation of the gray wire approximately 0.25" from the pickup coil and measured continuity to the plug at the TCI. It had continuity easy, so I knew I didn't have any issues with the wire between TCI and pickup.

I'm going to roll the dice with a used ebay part. There are a handful on there at reasonable prices. I'm not super keen on equally as old electronics going in where it just failed, but, for the price, I'll take the risk.

 

Just wondering how this works. I thought 1 &4 pickup would be linked to ignition on cylinders 1 & 4. Just interested can you explain in more depth thanks. I am missing something here.

 

when you get the pickups you can remove them from plate and install them on existing plate. easier than removing the plate. make sure you put them in proper location

 

Yeah, I was thinking about pickup orientation as well but with the way the wiring is done and the grommet it's hard to get them backwards. Which wire is assumed #1 from the TCI to the pickup? Orange? The #1 pickup should be almost touching the plate when the U timing window is pointed to by the stationary metal timing tab on the case.

 

I wish I could give you the exact reasoning behind this, but it centers around the Hitachi HA1825P IC, which is a proprietary device so no data sheet was ever released on it. All I know for sure is the test set I built for it I was confounded when I first applied a signal to the Orange input channel and noted that the output signal was actually on the opposite channel - the grey wire.

I did do some other testing but never really completed it, but one test I did try was to disconnect one of the pick-ups to simulate an open and see if the bike would start and run on two cylinders - it would not start and all I got was a couple of backfires, which kind of quickly led to be discontinuing that test.

One other test I did was to center the reluctor between the two coils and then swipe a feeler gauge across the coils. If the feeler gauge was swiped across the 2, 3 pick-up the 1, 4 plugs would spark. If swiped across the 1, 4 pick-up the 2,3 plugs would spark. And, just to confuse matters a bit more if the reluctor was centered on the 1,4 pick-up and the key turned on then when the TCI shut down to safe mode the 1, 4 plugs would spark. If the reluctor was centered on the 2, 3 pick-up and the key turned on the 2, 3 plugs would spark when the TCI switched to safe mode.

So, to say the least it all got a bit confusing, and I never really took it any further as my focus on other projects got in the way, but I might revisit it one day. It is interesting to note that in the initial post on this thread the bike seemed to be running on two cylinders (with a bad pick-up), which does seem logical.

 

i think someone just put the wrong color wires in the connectors

 

That is where l get difficulties with the electronic issues l am fine with the spanners but

So the Hitachi HA1825P IC which l assume is part of the TCI is causing the 1 & 4 and 2 & 3 issue and vice versa. Thanks for your reply Rooster.

 

Maybe you could remove one pick-up wire from the TCI connector and see if your bike will start :-}

 

ok, i tried that, gray wire out of the smaller connector (tci out). started right up (surprised me how easily) #1&4 pipes got hot.
then took the gray wire out of the bigger connector (tci in) and no start
so what did we do here, other than get my connectors greased up and the rr shined up with a wire brush

 

At initial appearance it proves that the TCI has to have both pickup resistances on the inputs in order to operate.

 

So I am not color blind and didn't mistakenly mis-wire the connector.

In future reference to troubleshooting tips we are more educated on what to recommend when a bike is running on only two cylinders, but because it is so easy to ohm out the pick-ups that will likely still be suggested.

You have a shiny regulator and clean TCI contacts : -)

I think it is more than that, I have resistors simulating the pickup resistance so I think it is more about the signal being present and the timing relationship. I will have to revisit that one just to be sure though, as the resistors are switchable.

 

i think the pickup coils are inductors but tested with an ohms reading

 

All coils are inductors. The resistance test is to be sure that a winding hasn't shorted, since component failure is the only thing that will matter to a mechanic. The induction value (and other associated values) only matter(s) when the circuit is designed and the coil manufactured.

 

OK, so I got my new part and was about to commence surgery and I noticed something different than expected. This whole time I'd been doing my resistance measurements on the six position plug as follows.

Orange to black (this checked out in the correct range)

Grey to black (this showed as an open circuit)

I was examining my ebay part and I noticed that at the crank I had the following colors on the pickups. One pickup was orange and black. The other pickup was grey and brown.

Wait what? I thought the black was a common ground. Looking back to the six position plug I observed the following colors. Orange, black, grey, brown.

I redid my resistance measurements on the pickup coils, this time measuring orange to black, and then separately, brown to grey. This time both my resistance measurements were in spec. Now it's looking like I don't have a bad pickup coil after all. At least my ebay parts were cheap (and they also ohmed out in the correct range, so now I have a spare).

This is all well and good, but now I'm back to ground zero on my problem solving.

I'm tempted to put it all back together and see if it behaves. If so I can blame that metal dust in the crank on the pickup rotor. Not sure if that would cause this if it lead to a ground out somewhere.

It's that or the TCI, unless anyone has any other guesses I can look at.

 

Oh no good sir. You are one step forward. You are now sure of one thing that is not causing the problem.

 

My apologies for not getting this right. The Haynes manual does show a 4 wire setup for the 1981 650 Maxim, but shows two separate black wires. For the 1982 Maxim the Haynes manual shows a brown wire, but they tie that to the black to make the black common.

From the testing that you did in your initial post the TCI could be suspect, unfortunately the best way to test it is to swap it out or try in another bike unless you have the necessary equipment to evaluate. You could also repeat your test which I think you did already, but if you swap the coil primary side connectors and 1 and 4 spark and 2 and 3 don't then that is fairly conclusive that the TCI has an issue since we now know the pick-up coils are OK.

I was also confused by this comment, where it seems to imply that spark is seen on all four plugs?

PM sent

 

I did see a weak spark at each plug, but compared to the sparks on say... My Vulcan, it was piddling. A spark is a spark though. Could just be a low battery charge. Maybe an intermittent issue where I was seeing say... half as many sparks as I really should be? At some rate, half as many is still more than I can differentiate.

 

That's a difference in the type of ignition system . TCI ignitions have a "weaker" looking spark that is of a longer duration than a CDI ignition produces.

 

if you look back at your photos you will see brown wires on both pickup coils. the wires should be spliced together and have a common connection . 3 connections in the tci connector not 4 . you can see brown wire in wiring diagram and it splices into black wire

 

Sounds more like a fuel issue than ignition.

 

unspliced tci wire with 1 wire in put in wrong location needs to combine with black wire as shown in wiring diagram

 

Ryengoths Photo from another thread

 

Are those wiring diagrams and pictures particular to the 1981 model? From what I've been gathering, there was a different set up between 80-81 and 82. From what I can see this stock setup with a brown and black each running all the way from the crank to the TCI module looks unmodified. I've had the bike about five years and 14,000 miles and I haven't monkeyed with it. I don't have a black and white wire at all, and looking at my side stand, it doesn't look like there was ever a switch on it.

 

if you look at photos you posted you see 2 brown wires running from the pickup coils,
I see you have a Black label tci it is for 81 650 the midnight model
I have a black label tci on my shelf I will check it out saturday for connection between 2 tabs and if it runs an 82 650 wiring setup
from what has been established in the forums the only differance in tci's is weather there is a black/white wire which goes along with a sidestand switch circuit
the black white wire grounds out the tci when sidestand is deployed killing engine.
wiring diagram is for 80,81 650 maxim from FSM
if your bike has been running 5 years like that it may be possible that the internal connection between tabs has failed.


no brown wire on this wiring diagram from FSM



5V2-82305-10-00

haynes

 

can you confirm short vin on motor matches frame?
.
4H7 H
4W5 LH

 

plug it in and push the go button

 

But it doesn't go very well on two cylinders

I suspect the wiring diagrams are not correct, and that the 81 has the orange, black, grey, and brown. That is what the OP is seeing (with two of them) and last night I found one just like that on Ebay, but can't seem to find it tonight.

I believe black, green, and red label TCI's tie the two inner pins (pick-up rtn) on the six pin connector together, as well as tying them to DC rtn on the 4 pin connector.

 

I think your correct . I am thinking a solder joint has failed in the tci . if he were to splice wires together it should work for him on 1 connector. he should ohm them out to see

 

do it, it's free

 

I can confirm that the stamped VIN on the frame and the VIN stamped on the clutch case match.

It is 4H7-114782 in both locations.

 

your year does not have a sidestand switch so no black/white wire.

my 82 650 starts and runs with the Black label tci no issues.
both tabs where your brown wires connects are connected on pcb. if you were to switch the positions of the brown wires it may confirm bad pick up or bad connection of tab to pcb.

use a sewing needle to slide into connector to unlock contacts.

 

where did the metal dust come from? if the ends of the pickups are damaged the pickup may/will not work.

 

Not to resurrect a dead thread, but I'm OP so I'm doing it anyway.

Just to follow up, I finally got around to test fitting the ebay ignition pick ups. After some fiddling around I got it to fire up but not stay running for more than a few seconds. I took the petcock to bypass and got it to stay running. Guess I got some gunk there to clean or replace.

Once I had it running stably, I tested by pulling plugs one at a time. Now it stumbles on any one plug pulled, but doesn't die. I'm back to four cylinder operation. I'm not back on the road yet, since this was a test fit, I didn't route the pickups properly, they are run outside the bike, but it looks like I have my problem solved. Now it's just putting the old girl back together.

Thanks all for the help. This forum is a godsend.

 

I had the same problem with plugs 1 and 4 not firing. My bike is XJ 750 SECA 1981. All measurements were OK except one the plugs that was faulty. Replacing the plug the problem seems to have been solved, but I have some doubts about it. My next move will be the replacement of the main capacitors in the TCI unit (if I can locate them) the ones sending the signal current to the ignitors. I had the same problem on another bike with a CDI unit, where the main capacitor died out after years of service, ending with a weak spark. I managed to replace it and the bike is running perfectly. An electronics mechanic that helped, said that all capacitors tendto loose strength after a period of time.