Intermittent Missfire

[OzDave]

Hi Guys,

I've got an 86 that's misbehaving on me and driving me up the wall. What's happening is that she'll run fine for 15 minutes to half an hour then starts misfiring like a horror. I think its being caused by something warming up because once she starts misfiring she wont stop, however if left to cool down overnight, the next day she starts up fine again.

What I've done so far is check fuel and replace filter, filter was full of crud, small red dots that looks suspiciously like a spray on tank liner that causes all kinds of problems in triumphs. Drained fuel and checked it, nothing in the tank.

All spark plugs replaced.

I've been having a read, and I'm thinking my next logical step is going to be the plug leads, but I'm based in Perth West Australia. Vmax wasn't sold local and nearby dealer makes my life a misery when I try to get in parts for it. Definately want to pay the money and fix it right, but ordering the wrong parts is a very expensive mistake for me, so throw myself on the mercy of those who know what they're talking about. Go for the leads next? Been readin about the COP mod, seems like a good way to go, but dont want to be making modifications until I know the original stuff is working right.

Cheers,
Dave.

 

[TURBOVMAX]

Sounds like your CDI might be the culprit. If it's heat related and electrical a lot of times what I'll do is try to cool the component I suspect. There are sprays at the electronic store or simply use ice in a plastic bag wrapped with a towel to absorb the sweat. Do you know someone that might lend you one to try? How many miles/km on he clock?

 

[OzDave]

37,000... apparantley... she's a relatively recent import from Japan, though given the condition of everything else on the bike I've gotta say I'm a little suspect on that number. When I first bought her she did fry her old CDI during a test ride. At the time I had a look around and figured it was a common enough fault for the age, so when the shop swapped it out for an R6's I told em to leave it at that rather than track down another original one. Swap was probably done a year ago now.

Just to double check I'm reffering to the right thing though I'll add a picture, around these parts we use english terminology, american terminology and our own when referring to parts, so just make sure I'm talking about the right thing.

Is there a test to perform to see if it's the CDI misbehaving?

Sorry about all the newbie questions, you guys have probably heard it a thousand times, I've torn apart a few bikes and cars in my time, but electric's have always been my weak point, can plug em in, and I can program them, but when I've got to get the multimeter and start trying to follow circuits its a slippery slope!

 

[gamorg02]

i think you're talking about your R&R in that picture and they are known to go bad, esp on the older models. your CDI is something else. not sure where it is, but i bet someone knows.

 

[mr.maxx]

thats the voltage regulator in the pic. obviously located in a non stock location.

im not shure where the cdi is either. i think if yure voltage regulator was bad yure battery would go completely flat. ive seen yure symptoms on yamaha viragos of the same yr. the cdi was the culprit....

 

[dannymax]

The cdi is located under the faux, above the front coils.

 

[gamorg02]

The cdi is located under the faux, above the front coils.

seen a lot of issues with these lately.. hmm. .. i bet someone on here has a working one they'd be willing to send ya to test out...

not sure where it is on a microfiche, so no idea how much $$ new.

 

[maleko89]

Test your charging system and make sure you are over 13.2 volts at idle. AT 2500 rpms it should be close to 14 volts at least. Next, test ignition components including wires, plugs, plug wires, boots, p/u coils and ignition coils.

 

[dannymax]

seen a lot of issues with these lately.. hmm. .. i bet someone on here has a working one they'd be willing to send ya to test out...

not sure where it is on a microfiche, so no idea how much $$ new.

New thru Ron Ayers-$467, not cheap!

If you feel it's heat related Turbo's idea of temporary cooling would be a good trouble-shoot. Get a couple 'cold-paks' from the local drug store, and apply them to the cdi when the problem shows up.

Correction: Ron Ayers price-$344.69

 

[jfeagins]

I suspect what's happening after your initial 15-20 min warmup time could be the fan switching on. When that happens, it takes additional current to run and your overall voltage available to the CDI probably drops down below nominal level causing weird stuff to happen. AKA:random misfiring.

When you check voltages, be sure your fan is running.

There's a ton of info here in previous posts regarding crimp fixes, improving all connections from the R/R back to the battery, etc to improve charging voltages that may help your situation.

Good luck.

 

[gamorg02]

question:

could u do a test by hooking the battery up to a car battery once it misbehaves to see if the additional amperage helps improve the situation?

 

[OzDave]

Ugghh, even with the good exchange rate atm when you throw in the shipping that's not a pretty price... that and the problem flared up litterally a week after I returned from a trip to Japan where Vmax parts line the shelves!

Just to double check my terminology is right, the likely culprit is the CDI, which in the service manual is referred to as a TCI? I think the local name for it is the ignitor, but to describe it, its basically the brains of the operation? Sends the pulse signal to the coils? If I've got the right thing its right underneath the instrument cluster, in front of the airbox?

The more I think about it, the more temperature affecting electronics sounds likely. I'd read a thread about the fan kicking in and that causing the voltage to drop to low, but we're currently in the middle of winter here, and I've got a habit of immediately looking at temp and oil pressure the second anything sounds off. When the problem flared up the temp guage was low and I've had steady power, no head lights flickering and after pulling over to try and figure out whats going on she cranked over properly on restart. That said the temperature guage itself has been on the blink lately to, sometimes I'll fire up the bike and it'll work, sometimes not... couldn't be related could it?

But speaking of winter and the cold I have noticed that in the middle of the day the problem appears in about 10 minutes, but at night-time when temperatures drop I can get anything up to a half hour before it starts. Which again has me thinking hard about the engine getting up to temperature, then the heat slowly creeping up the frame till it warms the CDI.

Probably the easiest way for me to chill it is a blast of freezer spray once she's up to temp and playing up. If it stops the misbehaving for a few moments then that'd have to be it. Which if that's the case brings me to next issue. Replacement... I'm gonna take a guess that the reason Dynatek only lists aftermarket CDI's for 1990 onwards models is because there's been a change somewhere along the line? Is it possible to source aftermarket gear that'll plug into an 86? $350 US is a lotta beer money for a part thats problematic from the factory!

 

[naughtyG]

I believe there's been talk about common problems with the TCI (transistor controlled ignition) which can be easily fixed - you just have to be very careful opening the box.

If you have a look at my five threads about doing the COPs mod (in the User Mods forum) you can see how to get to it.

On bikes from 85-92 it's an analog TCI, then from 93 to 07 it's a different one, because Yamaha changed it to digital. They are not interchangeable.

 

[Akatora]

Hello,

Your problem sounds just exactly like mine last year. The culprit was one of the ignition pick-up coils that are located under the flywheel cover (in this older model V-Max there are two pick-up coils).

This is very easy to confirm / rule out. The procedure is as follows:

1) start with totally cooled down engine (first test of the day, for instance)
- prepare multimeter
- remove the seat
- disconnect the joint socket (under the seat) where you can find black, orange, grey, white/red and white/green wires
- connect the multimeter to the flywheel side (left / lower side) of the socket, and check one by one the resistances between orange-black, grey-black, white/red-black and white/green-black wires (the resistance values should be between 94 to 126 ohms at 20 degr. Celsius (at least somewhere nearby)

2) Connect the joint socket back and start the engine, let it warm up and wait until the problem occurs. Then switch off the engine, disconnect the joint socket and conduct the above mentioned measurements again

If some value is now clearly out of the specification (or shows no continuity = infinite resistance), the culprit is very likely found. The meanings of the colours are following:

orange = pulse coming from pick-up coil 1 to TCI unit, giving fire to cylinder 1 (rear left side cylinder)
white/red = pulse coming from pick-up coil 1 to TCI unit, giving fire to cylinder 3 (rear right side cylinder)
grey = pulse coming from pick-up coil 2 to TCI unit, giving fire to cylinder 2 (front left side cylinder)
white/green = pulse coming from pick-up coil 2 to TCI unit, giving fire to cylinder 4 (front right side cylinder)
black = common ground wire to both pick-up coils 1 and 2

Bad coils can create this type of problems, because when the wire inside the coil cracks, it may still have contact in some temperature / length. But when the temperature changes, the length of the coil wire changes too, and the contact may disappear - and then return again after the engine (coil) cools down.

Hopefully you can get it clear soon!

Cheers,

AT

 

[OzDave]

Right, reckon I've got a testing plan now.

Seat off,

Multimeter into the joint socket, looking for 96 to 126 ohm's between all wires and black.

Check voltage at battery.

Fire it up.

Check voltage at battery while running.

Seat back on.

Let it heat up and wait for misfire to appear.

Check to see if thermofan is cycling.

Squirt of freezer spray under the instrument panel to try and cool the CDI/TCI/Metal box of tricks to see if that causes bike to temporarily remedy itself. Gonna have to be careful there to make sure the bikes not sucking the spray into the engine though. Might leave the fake tank off while testing just to prevent freezer spray getting trapped under there then getting sucked in.

Switch off and while still warm seat off again

Back into the joint socket with multimeter.

Should give me a test of the charging circuit, the CDI and the coils... I might lower a thermocouple in next to the CDI just to get some figures on its temperature... blasting it with freezer spray is a bit bodge, but because it seems to be a temperature related problem it's gotta be a temperature related problem shooting. Having a recording of the temperature at the CDI will at least give me an indication of how much it's warming up...

Right, cheers guys, just started my day at work but when I knock off reckon I'll be flat out like a lizard drinking!

 

[gamorg02]

i personally wouldn't use that spray stuff. why not just use an icepack that was in the freezer, or a big ass box fan or something? i dunno maybe i'm just paranoid

 

[Akatora]

Hello,

Better to conduct the test procedures one by one in order not to get mixed...

Regards,

AT

 

[OzDave]

Bugger it, was sure akatora had it but just tried measuring the resistance, 124 on every coil when cold, then when hot and misfiring 147 on every coil... sounded like the right answer too... still kinda leaning towards it being the prob... when it misfires its not a continuous misfire, it kinda surges then craps itself then surges again. Feels like a wire connecting then disconecting like you were describing. Was riding around the block to heat it up, then gave it an extra little bit once it started misfiring before bringing it in to make sure it didn't drop below temperature. Kept it idling while i pulled the seat off to keep it warm then had the plug apart and in there with the multimeter as quick as I could. But she gave a steady 147 on all coils.

I did notice though that when i fired it up there was a sharp crack noise... sounded almost like something shorting...

Anyways, thats it for the night, gonna have to wait for her to cool down for the next test. Next up is cooling the CDI.

 

[dannymax]

Bugger it, was sure akatora had it but just tried measuring the resistance, 124 on every coil when cold, then when hot and misfiring 147 on every coil... sounded like the right answer too... still kinda leaning towards it being the prob... when it misfires its not a continuous misfire, it kinda surges then craps itself then surges again. Feels like a wire connecting then disconecting like you were describing. Was riding around the block to heat it up, then gave it an extra little bit once it started misfiring before bringing it in to make sure it didn't drop below temperature. Kept it idling while i pulled the seat off to keep it warm then had the plug apart and in there with the multimeter as quick as I could. But she gave a steady 147 on all coils.

I did notice though that when i fired it up there was a sharp crack noise... sounded almost like something shorting...

Anyways, thats it for the night, gonna have to wait for her to cool down for the next test. Next up is cooling the CDI.

Dave...FWIW both my bikes make that sharp snap noise when I hit the starter button, I think it's normal....maybe the solenoid? :confused2:

 

[OzDave]

cheers mate. Ya know how it is when ur troubleshooting an engine, start getting paranoid after a while!

"did it always make a crack?" "was it a crack or a snap?" "Did the headlight just dim or was that a street light?"

Will try cooling the cdi tomorrow but think i'll ring around and see if i can source a cheap set of spark sticks... Just got a real funny feeling about the coils ever since they were brought up.