starts, idles, revs great, but misses under load above 2k

[Flyinfool]

When it hiccups, what does the tach do?

Does the tack instantly drop to zero, or does it continue showing engine rpm as your speed bleeds off and the bike momentum is keeping the engine turning over?

[Razorback]

Tach only drops about 300-400 rpm recovers so fast I don't lose any speed

 

 

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[dingy]

Check the connector from the pickup coils to the harness. This is near rear shock dampener, left side by passenger footrest.

There are (2) six pin connectors in that area. Pickup coil is one with 5 wires in it.

I have seen this connector cause intermittent operation before.

Gary

[Flyinfool]

Since the tach is dropping but the bike speed is not dropping that means that you are no longer sending a signal to the #2 cylinder and most likely also not the rest of them. The tach gets its signal from the wire that goes to the #2 coil. since the tach is dropping but not the motor speed, that means that the #2 coil is not getting a signal. That means it is not a coil, plug wires or plugs type of issue.

 

In addition to what Dingy said, also clean the contacts in the kill switch. A weak or intermittent switch contact can also cause this.

 

Unfortunately there are a lot of things that can cause your hiccups, and since it is intermittent and for very short times at that, testing is not likely to find it. It is going to be a try something and take a test ride type of solution.

[Razorback]

Check the connector from the pickup coils to the harness. This is near rear shock dampener, left side by passenger footrest.

There are (2) six pin connectors in that area. Pickup coil is one with 5 wires in it.

I have seen this connector cause intermittent operation before.

Gary

 

Did that this weekend: cleaned and greased.

[Razorback]

 

In addition to what Dingy said, also clean the contacts in the kill switch. A weak or intermittent switch contact can also cause this.

 

 

I'll have to give this a try.

[Flyinfool]

Another tool that can be used to help find an intermittent is to pick up a couple of 12 LEDs from Radio Shack . You can use these to connect to various parts of the circuits to see which LED blinks at the moment of the hiccup. Mount these where they are easy to see in your peripheral vision while riding, just tape them in place since they are only for diagnostic purposes.

 

Start with one on the red/white wire where it goes into the TCI. Pos wire of LED to the Red/white wire and neg lead to ground. This one should be ON all of the time when the bike is running. if it blinks OFF during a hiccup then you now the problem is on this circuit

 

Put a second on the black/white wire that goes to the TCI. Positive wire of LED to +12V, neg wire of LED to the Black/white wire. This one will be OFF while riding. It will come on when safety circuits are activated like the side stand being down. If this LED blinks ON during a hiccup then you know that the issue is in this circuit.

[Razorback]

The ride home was pretty rough after a while, not sure when it started, but over halfway home in my 40 minute commute, it started missing pretty often and drivability (enjoyment) was gone.

i didn't have time to do anything with it yesterday, but i did clean the stop/run switch. As with most all connections i've cleaned lately, it looked great before i started, but i hit the contacts with a brass brush and the contact cleaner.

I take off this morning and everything is going well (maybe a hiccup or two for a while, nothing major) until about 25 minutes into my ride. I'm running about 3800-4000rpm at 70-75mph indicated. It starts to feel like someone is yanking on the back of the bike. Before, i can kinda "sense" the "misfire" now i can definitely feel it and I think other drivers can probably see it. I seriously wondered if it was going to just shut down completely. The tach is swinging much more wildly when this happens, approximately up to 1500 rpms swings, generally 300-100 rpm swings during this time.

I would never try to drive it like this if it were continual.

 

When i slowed down and took the exit (had to stop to take the next road) It didn't exhibit this crazy behavior again. i probably didn't get over 3000 rpm and 50 mph the rest of the way to work (3 mi).

 

I also notice throughout the ride that sometimes my voltmeter shows 13.5 V and sometimes 12V.

 

I'll run out at noon and get the LEDs and see what story they may tell. I look forward to trying this.

 

I also have a guy at work bringing me a GoPro camera today. I'll try to get that mounted up and post some YouTube video links. I think it will help for you guys to see the tach behavior.

[Flyinfool]

It is sounding more and more like my trip to MD last year.

Started with barley noticeable hiccups and by the time I was half way home it was flat out shutting down for minutes at a time. By the time I got home I had jumper wires and hot wires all over the place trying to keep the bike alive till I got home.

 

The volt meter dropping from 13.5 to 12 during these hiccups may also mean that you have an intermittent connection somewhere in the charging circuit. Are you getting these voltages from the in dash voltmeter or do you have a separate meter installed. 13.5 is still a little on the low side. 14.0 is better.

[Razorback]

In dash (factory) voltmeter, and it's a guess at 13.5, although i know i've seen it squarely between 12 and 16 at times (14V? I assume).

 

As far as i know, i've disconnected and cleaned every connection related to charging and ignition circuits.

 

I can certainly look again, or re-clean or whatever.

 

Suggestion for where to start again?

[Razorback]

Just to clarify, the voltmeter isn't really "jumpy" with the tach, but will ride at different voltage levels during the ride.

 

 

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[Neil86]

I don't think I work connect an LED into the black/white....it runs at low voltage around 1.5 V..and you might backfeed into TCI.

[Razorback]

I've ridden my bike everyday except Wednesday this week, only because I needed my car that day.

I recorded some video if the tach and voltmeter , but haven't been able I upload it yet.

 

Observations of the voltmeter: starts off around 12V, will reach 14V on the highway, but will also drop to about 10V when I stop at an intersection. Will come back up to 12V when i take off and may or may not get back up to 14V in the next several miles.

 

I can't say at this point that the voltmeter behavior is necessarily correlated to the erratic "misfire" issue.

 

I'll repost when I can get something on YouTube, which I can't do at work.

 

I also used Jeff's led indicator idea on the red/white wire at the TCI and it never once blinked at me. Still hooked up since Wednesday morning.

 

I haven't done the led on black/white wire yet.

 

 

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[Neil86]

When at a stop in traffic with brake on, you are running the brakelights (stock 2 bulbs)plus the antidive solenoids (86-93) in the forks...so it will drop but usually to battery voltage.

[Razorback]

It dropped to 10V, right between green and yellow on every stop (2 or 3) on my way to work.

I may go run around a bit on my lunch break and see what it's doing.

Not sure what's happening.

As you may recall from earlier posts, my stator seems ok in every respect except for AC voltage output at 3000 rpm. Several posts on stator testing mention gettine 50-100 VAC, and mine was only 47-48V, although all legs were equal, and no shorting to ground, resistance reading within spece between the wires, etc.

[Neil86]

One thing to check...the dash voltmeter is tapped into the SIGNAL fuse circuit, as are the

antidive solenoids. If you have a bad connection the "indicated" voltage might drop more than normal.

 

You might have a look at signal fuse clips....test voltage on both sides at the crimp with brake lever on at idle.

Edited June 6, 2014 by Neil86

[Razorback]

One thing to check...the dash voltmeter is tapped into the SIGNAL fuse circuit, as are the

antidive solenoids. If you have a bad connection the "indicated" voltage might drop more than normal.

 

You might have a look at signal fuse clips....test voltage on both sides at the crimp with brake lever on at idle.

 

First I did it wrong, then re-tested. read below.

 

Idling voltage across battery: 12.4V

3000 rpm voltage across battery: 12.7V

 

Idling signal fuse voltage: 11.7 on each side of fuse at crimp

applied brake and let go: voltage is 10.8V on each side of fuse at crimp

 

At idle i saw the voltmeter dip when applying the brake (hand or foot).

 

I go back out within 5 minutes and test it the way you told me.

 

Idling voltage on each side of fuse at crimp: 11.0V

Idling voltage with brake lever applied: left side of fuse at crimp 9.8V, right side of fuse at crimp 9.5V. repeated that test and saw the 0.3V difference again between left and right side of fuse.

[Neil86]

How low is your battery voltage sitting?

[Razorback]

12.46V

 

 

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[Neil86]

So no increase in voltage idling vs sitting?

[Razorback]

No. And hardly any increase at 3000 rpm

 

 

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[videoarizona]

Been following this thread...very good responses. But I'm still confused.

In your last post it "seems" like there is a charging problem...but that has been checked, right?.

 

Meanwhile, The hesitation sounds like a cutout or a short within a system wire that is powering or interfering with the computer or the spark....since it effects both the engine running and the tach.

 

So two problems.

 

Question for the brain trust: What might be common to the two events as I've described?

 

david

[Razorback]

It does seem like a charging problem although several opinions are that my stator is ok based on the tests described, although my AC voltage measures at the stator plug is low.

So yes, a potential charging problem.

I also have the intermittent hiccup/sputter/misfire thing going on, which can be seen in the tach along with some other erratic behavior of the tach (not smooth during a lot of slow to midrange acceleration. Don't know if charging symptoms are related or not.

 

In the meantime I continue to drive it since it's not too bad, maybe slightly improving.

Today was a pretty good drivability day. Not to say it didn't cut up, but it was relatively minor.

 

 

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[frankd]

You know your stator is good, so with the low charging voltages you just reported I'd check the following----

 

1) Is your battery good and fully charged? A bad or dead battery could cause the voltage to be low. To see if this is the problem, hook a small (about 2A) battery charger up to the battery and measure the voltage. If it comes up to 14-15 volts, the battery is NOT causing the low voltage. If the charger can't bring the voltage up, your battery is dead or bad.

 

2) Look at the connections on the plug that connects the stator to the rectifier/regulator and make sure none are discolored from heat.

 

3) I know you checked the rectifiers, but it sure looks like that's all that's left that'd contribute to such a low charging voltage. You could by a used first gen OEM regulator on Ebay relatively cheap, and not too much goes wrong with them. I have seen 1 bad oem regulator, and it had an open diode. When I bought my 89, the previous owner had just replaced the original regulator with an aftermarket version, but I never saw the OEM unit to verify that it was bad. (I've replaced the aftermarket unit with an oem unit),

 

The Yamaha spec. for charging voltage is 14.5 volts plus or minus .5 volts at about 3000 rpm. My 89 measures about 14.55 volts @ 3000 RPM and at a hot idle (just a sliver over 1000 RPM) with the OEM radio ON and also the LED driving lights ON (1.8 amp. total draw), it hardly moves down. Yours is way low and your battery either is drawing the voltage down, or hardly charging. With such low voltage, your ignition is much weaker than normal, which COULD cause it miss under load. I'm not saying this is your total problem, but it makes sense to me to fix this first and see what problems disappear.

 

Something just occurred to me===have you measured your stator to ground with a good ohmeter? I would use an analog VOM, like a Simpson 260, set to the highest ohmeter range, but a good digital meter would be OK. You should read infinity to engine ground. The light bulbs we used to indicate stator output would not indicate a grounded stator, it only indicates a shorted or open stator.

 

Frank D.

[Razorback]

1) my 2A charger is only putting out 13.7V. I just put it on the battery and will leave it all night. I'll check the voltage on the battery in the morning. If it's not high enough I guess I could put my 10A charger on it for a little while and see if it will bring it on up.

 

2) connections are fine. No discoloration at all

 

3) already swapped it with an eBay unit since all this started.

 

I have measured stator to ground with a couple meters. Always shows open connection.

 

 

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