Cylinders 1&3 not firing

[Larrym]

Motion control

Clean any scratches in your helmet visor, check your tire pressure, Test the front+ back brakes and lighting system.

Prepare yourself for a successful road test, maybe?

Biggest decision is where and when to turn the bike around and head back home.

[TopCatGr58]

Hey Doug,

Okay, thanks for the clarification on the year/model, I was just going by what I saw in your profile, and I see that you've corrected that as well!

There is a warning in the Yamaha online fiche about not running the engine with a plug cap pulled off, because it can cause internal damage to the ignition coil since it IS a wasted spark system, and the current needs to flow from one wire thru the engine and back up the other wire back into the coil! SO...with a bad resistor cap, it can simulate the same situation as pulling the cap off, and could lead to internal coil damage!?

That 10.9 volts at the coils still concerns me. Have you replaced your OEM fusepanel?? The glass fuses are notorious for causing all sorts of electrical gremlins, along with reduced current flow to the circuits ie. the ignition circuit. One of the first upgrades that folks do is to put in a solid ATCO type fuseblock...I provide/resell them, see the tech tips or sticky thread in the parts for sale forum!

Have you cleaned the contacts for the TCI and the 2 plugs that fit onto it? I would chase the red/white coil power lead back thru the harness to the TCI, and measure the resistance between the 2 points, should find very little actual resistance/ohms. Then check the voltage on the corresponding plug on the TCI that connects with that wire, and see if you see 12 volts there!? If you get 12 volts at the TCI, but only 10.9 at the coils, then there a problem with the wires to the coils!

Also, checked the XJ's electrical diagnostics info, the 81 uses the same coils as the XJ, and the resistance of the secondary should be 11K +/- 20%, the earlier specs were for the early 1.5 ohm coils, these are the later ~2.5-3.0 ohm coils!! SO....your resistance measurements for your coils now seem well within specs!
T.C.

[schpiff]

voltage comment

My 81sh (on a 4 year old cheap ass wallly world battery) wouldnt start this morning.
It tried to start, and ran for a couple secs and died. Didnt have time to mess around so took truck.
Put my palm on the pipes and cyl. 2 n 3 were cold (btw they run a tad bit leaner that the outsides but still happy)
I put the volt meter on battery and had about 12.1 volts.
When I got home from work tonight I put the charger on battery as an experiment for only a couple minutes (10 amp) and rechecked battery at 12.9 volts.
Hit starter button and...vroom..hittin on all 4 just like always...
Seems voltage is critical
Hope this helps

[Blackdog]

Voltage

I have 10.9v going into TCI, no resistance from TCI to coil. Have 10.9 going into fuse box and 10.9 leaving. Have 11.9 at battery. I realize I need to recharge battery {new} but I don't think I should be experiencing 1 volt drop from battery to fuse box.

[Larrym]

Team spirit

Good to know you're still actively poking around in there. Pays off in so many ways!

First, I'm assuming that you are making these tests without the engine running. I mean, without your new plug caps installed you just turned on the key and checked out what was going on at these test points, right?

Without the engine running the power is coming from the battery and flowing into the fusebox where all sorts of things are asking for some of the juice. It is natural for there to be a small voltage drop as the fuse box distributes the power. The battery is under "load" and without the engine running, the alternator isn't supplying the current from the other side of the wires to keep the voltage up.

It's a team effort of the battery and alternator/rectifier to make voltages look like they're supposed to. Check things again after you get your caps put on and the engine (crossed fingers!) running and you will see the difference between the running and non-running measurements.

[Blackdog]

Yes, engine not running, key on. In the fuse box I am just measuring the ignition circuit. Strangely enough while measuring the glass fuse under left side cover next to battery it measures 12.1v. I attribute this to cheap probes on vom and my own lack of experience with it, I have a hard time getting a good contact sometimes. One of the straps that holds the fuse holder together was broken, I thought wow this is it, but it seemed to work anyway. Will fix.

[Larrym]

Whatever works

The cheap meters are ok. You just have to get used to choosing the right settings: AC Volts, DC volts, Continuity, etc.

If you're cursing those little pointy "probes" then join the club. They aren't really meant for "our" type of use. Makes you wish you had a third arm! Do yourself a favor and visit a Radio Shack (Or some place...) that carries the packets of little colored wires with insulated alligator clips on both ends. (Red, black, yellow, green)

Use the red and black wires with clips on your meter probes. Just make sure that the insulation covers well on the probe ends. Really helps out when "testing" stuff. Even better for experimenting with "circuit by-passes" or grounding a test spark plug to the cylinder head....

They also sell little red and black alligator clips that go directly on the probe ends. I hate those things cause they always slip off the probe ends. "Whuh?? I should be getting a reading here!!" Look back and see the alligator clip still on the wire but the probe end dangling some where.

Fixing those fuse holders is a challenge, eh? While you work on that one treat all the others that have not broken like you would treat your mother's crystal:

[TopCatGr58]

Hey Doug,

See Reply #10 in This Thread/Sticky in the Parts for Sale Forum, will help solve those breaking brass fuse clips and flaky glass fuses!!

See my reply #17 above, not that I am saying that I told you so!
T.C.

[Blackdog]

Caps

Got and installed plug caps this morning, still not running on 1&3. Voltage at coil reads 10.9 not running, drops to 8.9 when running. {?}

[Larrym]

All Wet

Is (or was...) the battery fully charged before you did the run test??

The standard "wet" cell battery is seen as 12 volts but it's not like it would read 6 volts if it was half charged. The "12 Volt" battery actually has a one volt difference between between being fully charged and fully "dead."

11.8 Volts equals DEAD
12.8 Volts equals Fully charged.
(Both readings taken after resting 24 hours without being on a charger...)

Are you getting the full voltage at your TCI/battery then and seeing a voltage drop at your coils "downstream" or is there a "battery charging" issue here?

What are the battery voltage readings running/not running?

[cywelchjr]

Got and installed plug caps this morning, still not running on 1&3. Voltage at coil reads 10.9 not running, drops to 8.9 when running. {?}

Whats the voltage at the battery when running? Sounds like you might have a charging problem? Of course the voltage at the coils will vary when running as it's being switched off and on.

[Blackdog]

12.1v at battery running, still 10.8 at fusebox, TCI, and coils when running. Something seems to be dropping the voltage from the battery to the fuse box. I am not even sure what the path is from bat to fuse, whether it is a straight line or it passes through some components.

[Blackdog]

As bike is only running on 2 cyls. it is only idling at maybe 500 rpm, tried having 6 amp charger 0n when running to give extra boost, changed nothing.

[Larrym]

Light Show Tonight

These bikes have a charging system which only "kicks" in when the RPM goes up. For all practical purposes, every time we sit at a stoplight and idle, the battery is discharging. Once we get up past 2-3 K RPMs the charging system does its job.

As You're only running on two cylinders and idling low the charging system really ain't gonna do much to bring up the voltage. I would expect the battery to read a little higher though. May have a charging problem and may not...lets get back to seeing what's happening with your spark and see what that tells us.



I'm proposing that you take your tank back off and perform a little test which will let your eyes see what's going on with your coils.

1. pull the spark plug caps off the plugs which are in the engine.
2. place another set of plugs in the end of those caps.
3. Ground those plugs to the cylinder head with those nifty alligator clips/wires. (Note: just laying them against the head may not be a good enough connection. Not only may this cause them to not put on a good light show but it may cause damage to those necessary coils!!)
4. Turn on the key and try to start the engine while eyeballing those spark plugs. (Crank the starter briefly. No more than 5 seconds with a rest period of 30 seconds in between "light shows".)

Look to see with your own eyes whether or not you still have a problem with cylinders 1 +3. No spark on those two?? Then lets move on to the next step which tells you whether the problem is in your coils or lurking somewhere else.

5. Take the wires which come from the TCI and go to the individual coils and swap them. As in swap the wire for the left coil with the right coil. Do this near the coils themselves, not at the TCI. (The coils have two wires going to each one of them. Swap the ones that are seperate as in not the ones which connect together for a shared ground connection. You'll see them there near the coils...)
6. Do the light show test again and see if the other coil, 2 + 4, are not putting out a spark and now 1 + 3 are making sparks at the plugs.


Depending what happens in this test you'll know if the coil for 1+3 is not working because it's a gonner or if it's not working because it's not being told to work. Then we go on.

Make sure to switch the coil wires back to where they were originally!!

[Blackdog]

Tried steps 1-4, new plugs, old plugs had the same running characteristics. Weak sparks of about the same intensity on all 4. Will run all tests you mention tomorrow. Here again the coils fire 1&4 and 2&3. Thanks to everybody for the help I have received.