Intermittent Misfire on All Cylinders

[oldfaithful]

Dingy doesn't live here anymore. You could try the VMax forums and see if he is still active there...

 

Have you checked your timing coils yet? There is a connector about halfway up the rear of the frame that has been known to cause problems. Also, the coils have been known to cause issues, especially when they warm up.

 

When you had your TCI out did you bake it in the oven at 200 to 250 degrees to bake out any moisture?? Also, you need to relocate your TCI to the top of the airbox, there is enough play in the wiring harness to do this. This has two advantages, first it is drier up there, and second, in case of failure, it is right where you can get to it easily.

 

I seem to remember a while back somebody found a manufacturer that made replacement TCI boxes that even had the same shape...

 

That's a shame about ole dingy, thanks for letting me know. So who is the resident Ignitech expert around here now?

 

I haven't baked the TCI yet. I'll have to give that a try. Thanks.

 

Yup, just checked the pickup coils and the connector...all is well in there.

[Patch]

 

I found the connector to the pickup coils and it looked fine. It got cleaned & resistance checked anyway.

 

Pickup Coil resistance:

117 ohm

117 ohm

117 ohm

120 ohm

Pickup Coil Spec (from manual): 110 +/- 17 ohms

 

I'll keep looking...

 

 

Not sure what temperature they were at when tested?

 

Anyways, these are just part of a check list, but the ing. coils are 34 years old and likely they have lost there ability to charge quick enough. They too need to be hot to get an good idea

[videoarizona]

Interesting case.

 

This is my recommendation:

 

1: Change plugs anyway. After 5K mile trip. Use only NGK's. Gap at .032.

 

2: Pull plug wires out of coils, snip off end and re-insert. If in doubt of age (see leakage test in another post), throw away...new wires are cheap on line. Exact replacements available for early Ventures. Mine are 5K ohms resistance for my 89. Don't know if your earlier model is different. I've seen some posts that say 10K ohms. Maybe that's for the 83 and 84 years. But not for the 1st Gen mk2's.

 

3: Pull stator cover off (will need gasket) and check pickup coil. Clean coil area. Check gap. (just make sure coil is mounted solid) Check wires. re-check connector and wires where they come out of case. Seal well. (I doubt this step...but maybe as a last resort)

 

4: Did you check the pressure sensor? page 7-32 on my 86-93 manual gives the test. Your manual may be different. Output voltage around 2 volts dc with 12 volts input and normal atmospheric pressure. This partially determines your advance.

 

5: Might want to check your tip over sensor to make sure it's tight on frame (not bouncing around) and clean connectors.

 

6: Did you check timing with your light? Easy to do, takes only a few minutes. Make sure you turn motor by hand in proper direction. (counter clockwise??? I forgot) This should never change unless something inside has worn out or broke.

 

Assuming the TCI is working...and you haven't mentioned checking the component side of the board yet....those resistors. Try these above things before you buy another TCI unit.

 

 

Example; This wire set(for the VMax 1200) would work as they are the proper resistance for my 89 (5k ohm) and they have the NGK caps...which I prefer and work well with our scoots.

 

https://www.ebay.com/itm/Spark-Plug-Wires-Cables-Set-Red-Yamaha-VMax-VMX12-Max-1200/263768496948?hash=item3d69d3db34:g:~C8AAOSwjqVZKmD8#vi-ilComp

 

There's not much else to check...but after a long trip...connectors get lose or dirty, etc.. I'm going to think the plugs are your culprit. My RSV has developed an interesting lope at idle (like a cam lope) after my 4K trip. (Could be same problem you have...I just haven't checked anything as it runs so good right now). I'm going to put in new plugs just for grins....I figure these little plugs do get a workout on these high rpm motors...so it's cheap insurance...

 

Hope this helps,

Edited June 29, 2018 by videoarizona

[Patch]

For the record the gen 1.5, page 7-38 the caps are 10 ohm +/- 10%

Not sure for the 1200?

[videoarizona]

For the record the gen 1.5, page 7-38 the caps are 10 ohm +/- 10%

Not sure for the 1200?

 

Really? My manual said 5K ohms. Well...I'll have to double check. Thanks for the heads up...

 

The service manual says 10K....now where did I read about 5K??? I'll keep checking.

 

Went looking through all my manuals for both bikes...and they all say the same.

 

So my mistake....10k ohms it is. Sorry guys!

(I have no idea where I got the 5k ohm idea. But that's what I've had in my 89 for 4 years!)

 

Ah found it.....in the parts that I got from a dealer up north...they listed the wires for the 1st gen Venture then a note showing the resistance for each of the wires. These were supposedly factory wires....

 

 

Guess I'd better find another set for my 89!

Edited June 29, 2018 by videoarizona
update

[Patch]

Really? My manual said 5K ohms. Well...I'll have to double check. Thanks for the heads up...

 

The service manual says 10K....now where did I read about 5K??? I'll keep checking.

 

Thanks again!

 

 

Puc.

But like I said my paperback is for the 1300

[BlueSky]

The spark plug caps on my 89 checked 9k ohms and my manual says 10k plus or minus 10%. The NGK replacements I bought are 5k ohms. I just bought copper core wire from O'Reillys. I have not installed the new caps or wires yet though.

[videoarizona]

The spark plug caps on my 89 checked 9k ohms and my manual says 10k plus or minus 10%. The NGK replacements I bought are 5k ohms. I just bought copper core wire from O'Reillys. I have not installed the new caps or wires yet though.

 

 

I wonder if that's the difference. The caps are rated at 5K ohms, and the wires maybe to. 5 plus 5 = 10.

So I will have to test both together and see what I have before I go buy a new set.

[Patch]

I've been kicking this around much of the day..

Not sure why we haven't asked yet? (likely Carl's fault tho) What is the voltage at the coils? need house voltage to compare

 

Now seems obvious we would like to do a gap test for the secondaries, right?

 

But I got to think about your ride, and wondered if the plugs are bridging to much air? Know what I mean...

 

So have a look if you will because weak coils have little reserve and can miss even with a hot plug.

 

 

Blue & Video, not sure if there is a question attached to the 5 verses 10? But might be best to start a thread and not distract from OP..

[oldfaithful]

Now for today's update.

 

I installed new NGK standard plugs and the spark miss is still there. I also tried a different timing light but the miss was still there. I then ran the bike at night and saw no sparks from the plug wires to the frame nor did I get zapped when I ran my hand along the wires.

 

Next will be to swap out the boost sensor with an extra I have on hand.

[oldfaithful]

FYI, Now I've tried another vacuum/boost sensor and no change.

[videoarizona]

I know you checked the wires with water and by "hand" (grins), but have you taken the wires out of the coils and looked at the ends?

 

Last resort...have you looked at the component side of the TCI?

 

Not much else....I think you've covered most of everything...

[Patch]

Unless I missed the post, you haven't check the coils?

[Prairiehammer]

I know it's been some time since I've posted, but the ole girl has been running well for several years now...until now.

 

I just returned from a long motorcycle road trip (5k mi) and knew she needed a sync, which I did. No biggy. The real problem is that she's developed an intermittent misfire at idle. It's not bad, the idle just sounds uneven, and with the timing light you can see the spark skip every couple seconds when idling...and all 4 cylinders have the miss. If it was just 1 cylinder, that might be easier to diagnose. With all 4 cylinders sporadically missing, I'm at a loss.

 

The bike has plenty of power, and runs like it should...except at idle. No backfires, no trouble starting, typical gas mileage.

 

Has anyone ever noticed an intermittent miss like this, and might anyone have any guess as to the cause? Thank you for any suggestions you might have!

 

I am not saying this is your problem since you indicate that the cylinders misfire erratically and not simultaneously, BUT a wonky IGNITION fuse holder may exhibit similar operation. Have you upgraded to ATC/ATO fuses from the stock, old and problematic fuse block?

[oldfaithful]

Unless I missed the post, you haven't check the coils?

 

I checked two coils today and found...

Primary coils: 3.0 & 3.1 ohms at 90F

Secondary coils: 13.3k & 13.2k ohms st 90F

 

My manual says

Primary: 2.7 +/- 10% at 68F

Secondary: 13.2k +/- 20% at 68F

 

The primaries are at the high end of the range but probably still fine, if I did this correctly. Thanks for the suggestion.

[Patch]

Wow! So what is it that tells you there is a miss on all 4? You mentioned timing light but also that you couldn't track it.

 

 

The miss is both when the bike is cold or only at operating temperature?

 

If it is all 4, there must be a common link..

So proving it is all 4 is a must. I know 2 ways one uses the old cheap setup for a spark light tester ( still sold at part stores) the other is the gap tester (which can be done with a screwdriver and a ...) if you want instructions on how let me know.

 

Anyways the idea is to run the engine at ideal then increase and maintain rpms by a 1000 till you get to 5000ish allowing 30 ish seconds at each rise to see if you can pin the range or if it's throughout.

 

Be cautious that you don't overheat the old girl..

[oldfaithful]

I am not saying this is your problem since you indicate that the cylinders misfire erratically and not simultaneously, BUT a wonky IGNITION fuse holder may exhibit similar operation. Have you upgraded to ATC/ATO fuses from the stock, old and problematic fuse block?

 

Yes it's got an upgraded blade style fuse holder, and I just checked the connection there. Seems fine.

[oldfaithful]

Wow! So what is it that tells you there is a miss on all 4? You mentioned timing light but also that you couldn't track it.

 

 

The miss is both when the bike is cold or only at operating temperature?

 

If it is all 4, there must be a common link..

So proving it is all 4 is a must. I know 2 ways one uses the old cheap setup for a spark light tester ( still sold at part stores) the other is the gap tester (which can be done with a screwdriver and a ...) if you want instructions on how let me know.

 

Anyways the idea is to run the engine at ideal then increase and maintain rpms by a 1000 till you get to 5000ish allowing 30 ish seconds at each rise to see if you can pin the range or if it's throughout.

 

Be cautious that you don't overheat the old girl..

 

I have moved the induction light to each of the 4 spark plug wires and found a sporadic miss at idle each time. I also checked with an old school inline timing light and got the same result. There is a steady series of flashes and then a random pause, with no spark, and at the same time there is a slight change in the exhaust note. Not a backfire but more a momentary hesitation. When I rev the RPM the flashes are so fast that I can't distinguish a miss. It might still be there at higher rpm but I'm not sure. Yes the issue is there both hot and cold.

 

I must admit that I m unfamiliar with the technique you mentioned...would you mind explaining it. Thanks

[Patch]

I have noticed a common thread with the majority of members on this forum; just all seem to be way to polite, hard to say no!

 

I have moved the induction light to each of the 4 spark plug wires and found a sporadic miss at idle each time. I also checked with an old school inline timing light and got the same result. There is a steady series of flashes and then a random pause, with no spark,

and at the same time there is a slight change in the exhaust note. Ok you wouldn't really think there's much to this well phrased note, but there is. There is an effect caused to the miss, this has to do with "overlap" which is valve timing! A couple of things happen: we use exhaust velocity to scavenge. When we interrupt the high pressure flow that also interrupts the low or vacuum effect! We pickup by ear usually a bit of a stumble. This has as much to due with next cycle combustion temperature as and also the fresh fuel intake volume! In a case such as your's there is a cycle to it. It is important to not let it distract you, as the miss is the cause!

 

When I rev the RPM the flashes are so fast that I can't distinguish a miss. It might still be there at higher rpm but I'm not sure. Yes the issue is there both hot and cold. OK, it is most likely there.

 

I must admit that I m unfamiliar with the technique you mentioned...would you mind explaining it. Thanks

 

I'd like to look up the spec for your model so I'll get back to you on the home made tester.

[Patch]

Ok below is the setup I would use. It isn't expensive and again available at local parts stores.

 

Before I explain the homemade version lets look at some of the results.

 

You certainly have 1 pickup coil that is on the limits for me it is done because she hasn't the speed of the others!

Both ing coils are also just above the limits, they are suppose to be below 3! More importantly nowhere have I read the house V or the coil input voltage?

 

For the test and while looking through my shop at stuff you will likely have.. Take a 10" insulated 10ga. wire and strip 1/2" off one side, twist tight with pliers and the other side strip 1" and using your pliers and a star screwdriver make a loop around then twist it with the pliers so its neat and tight, then slip the driver out.

 

The end with the eye goes into the HT boot and the other end - while holding with insulated pliers on the wire shielding, touch that end to the top of the spark plug and start the bike!

 

Just focus on the wire and it proximity to the contact of the plug conductor. 6mm is the minimum air gap that the ignition coil must jump, lets call this a heavy 1/4" before missing! So see how high you can gap it before the miss shows up? Mark that down! Best not try to measure with anything conductive;)

 

Same plug after the above cut the gap to 1/8 +- let her run like that for 30/40 seconds. Does she miss at all? Mark that down as 1/8" test

 

Then shut the bike down and pick you next plug. Try not to run the engine without the plugs firing as we will be accumulating unburnt fuel in the circuit, this might cause confusion.

 

Sun glasses might help you during the test instead of trying to work in the dark.

 

Need I remind you "no pacemakers" around 15000V

 

My guess is that if we see one plug consistently missing on the 1/8" test, it will most likely be the pickup.

Patch

[oldfaithful]

Thanks @Steven G. For that test setup & instruction.

[oldfaithful]

This is the latest update. I'd been putting this off in hopes of finding something else. Nevertheless, I removed the TCI and opened it up. You may notice that it's still in the plastic box. I used the mill to carefully remove a bit of plastic from around the bottom edges of the box and removed the bottom as a plate. (Silicone and/or epoxy will be used to reinstall it...besides it wasn't sealed to begin with.)

 

 

The diodes look "fine" though we all know that can be misleading. I wish I had a schematic for this board. The only component that "looks" bad is this resistor in the center of the last pic. It appears to be overheating and looks slightly burned. Anyone seen this before?

 

Thanks!

[Patch]

You are welcome, I admire your resolve!

 

Do we see an oops 1/2 to the left the second nut up from the bottom?

 

Were you able to clearly show a miss on all 4 with a spark test at 1/8"?

For myself that would be a reason to point at the control box.

[videoarizona]

At 1st glance.....I see a couple of resistors that look like they got to hot. They also may not have a solder connection to the component side of the board....I would replace any resistors that look burnt, being careful to make sure you maintain solder integrity on both sides of the board. Is that a diode "zd1"(?) that looks burnt?

Edited July 9, 2018 by videoarizona
Add

[cimmer]

At 1st glance.....I see a couple of resistors that look like they got to hot. They also may not have a solder connection to the component side of the board....I would replace any resistors that look burnt, being careful to make sure you maintain solder integrity on both sides of the board. Is that a diode "zd1"(?) that looks burnt?

 

I think that is just the marking on the diode, a zener diode to show what end is what. Here is a link to wikipedia about them.

https://en.wikipedia.org/wiki/Zener_diode

 

Hope this helps.

 

Rick F.