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

[Razorback]

I think i may have electrical gremlins. maybe TCI, maybe coils or wires.

It really points to mis-fire.

I won't get to start testing bits until about Thursday, but i thought i'd throw it out there.

 

First, here's what i observe:

Currently, starts easily with about 1/3 choke when cold. Starts instantly without choke when still warm or just previously ridden same day (within 4 hrs?).

Idles smooth at 1000 rpm. Sounds and revs great (up to 3000 rpm, only because i see no need to go higher) sitting still.

When i take off though, it's a different story. Above 2000-2200 rpm is has a miss that won't go away unless I let it loaf along at about 2000 rpms. Its not a dead miss, but intermittent, like it wants to go, but the spark is not there like it should be.

I am also seeing it in the tach. That being said, I clipped the end of the cyl #2 plug wire and changed back to an old plug i had (due to similar issue in #2 below). That seemed to help initially, but it got progressively worse within a couple miles.

 

I'd be glad to post a short video, if possible (never tried), to demonstrate.

 

Status of bike and tune:

1. Carbs off multiple times, initially cleaned, new jet block gasket and o-rings supplied with kit, and float levels checked and set, until I figured out i was suffering from clogged vent hoses. Then starts, idles and revs good.

2. New plugs - although i found a "dead" one and swapped back in an old one. Cleared up a bad miss, similar to what I'm experiencing now, but it was hardly drivable. Made a world of difference. clipped that spark plug wire off and re-installed cap/boot.

3. Sync'd and double checked and rechecked after plug swap. Holding well.

4. mix screws at about 2-1/2 turns. has occasional minor lack of initial response to throttle twist only sitting still, like this morning - may need to continue tweaking mix screws.

5. Exhaust temps fairly consistent with each other. Checked with non-contact thermometer.

6. only running non-ethanol gas at the moment.

7. cleaned tank, new fuel filter and hoses.

8. checked & cleaned connectors in vicinity of rear shock damper/fuel pump. I did that because I also have a malfunctioning gear position indicator. It wants to indicate 4th gear more than anything. Neutral light still accurate though, don't know how they are related exactly.

 

 

Any other suggestions (besides seafoam since i just cleaned everything and replaced filters and hoses?) I'm not against Seafoam at all, i know it works on carb issues, I'm just doubting pilot jet problems because of great idle quality and low speed quality. I also doubt emulsifier tube or larger orifices because i've been through them so recently and they have so much larger orifices to try and plug. But I'll dump some in the tank anyway.

 

Thanks, Kenny

[shuttlebug]

Did you change out the spark plug wires? Could be cracked insulation with enough gap to run normally, but under a load with the greater resistance of a richer mixture it will jump to ground.

[Razorback]

No. They appear to be original, with the caps.

I suppose that would be good general maintenance to go with the new plugs, even though I think I had a bad new plug.

 

I plan to check the resistance on the plug wires and caps later in the week when I have a chance.

I plan to check coils as well.

[Peder_y2k]

"4. mix screws at about 2-1/2 turns. has occasional minor lack of initial response to throttle twist only sitting still, like this morning - may need to continue tweaking mix screws."

 

Lack of initial response is a lean low speed mix...... turn the pilot screws out maybe 1/2 turn..... or even more. Should have immediate response and no exhaust popping on decel.

-Pete, in Tacoma WA USA

[Razorback]

Currently don't have any decel popping, but will try another half turn out on the screws to improve the response.

[Neil86]

Is the tach reading actually bouncing more than road speed?

[Razorback]

It drops pretty consistently with the missing. Bounces back up to where it was.

It looks pretty accurate otherwise.

[Razorback]

Not sure I answered your question right.

It sputters quickly and the tach drops about 300-ish rpm and recovers faster than the resulting road speed from the misfiring, or whatever is happening.

[Marcarl]

With all you've done I would suggest new wires. Be sure to hang on to the rubber O-rings in the coil caps, they come in handy for sealing water out and keeping the wires in place.

[Razorback]

What do you suggest for plug wires? Source?

 

I also adjust my valves before putting the carbs on. I had to change every shim. Was able to reuse only 2 and buy 14 more.

[Venturous Randy]

This sounds a lot like a problem we had on a friends bike several years ago. It ran kind of ragged with some missing. We changed the plugs without it helping and just on a whim, I unscrewed a spark plug cap and the resistor was very corroded. We put new caps on and the bike ran great. You can take a flat tip screw driver and unscrew the part up inside the cap and there will be a spring and a resistor.

RandyA

[Razorback]

I looked at the one in #3 where I found a dead plug, and I also took apart the cap on #2 and clipped off about 1/2" of wire and reassembled.

Aside from a long barrel shape, what is the surface of the resistor supposed to look like (color)? I think mine looked kinda chalky white.

[Neil86]

What I'm saying is the tach should be matching the road speed in what ever gear you are running (clutch engaged and not slipping).

If you are seeing rpm drops and rises at same road speed your TCI may have issues.

(tach measures firing cycles on the #2 coil)

[Razorback]

What I'm saying is the tach should be matching the road speed in what ever gear you are running (clutch engaged and not slipping). If you are seeing rpm drops and rises at same road speed your TCI may have issues. (tach measures firing cycles on the #2 coil)

 

Yes, it does seem accurate in that way.

That's what I meant by saying it will drop and pick back up very quickly without affecting road speed. It looks like there's a gremlin switching the tach on and off very quickly.

I am suspect of the TCI, but also need to rule out plugs, wires, coils, etc before contacting Gary for an aftermarket TCI.

[frankd]

I use an ohmmeter to verify that the boots are OK and not corroded so bad that they are no longer properly connected to the wires. Connect 1 lead of the ohmmeter to ground and touch the other inside of the plug boot, where it connects to the spark plug. From memory I think they should measure about 12K ohm. All 4 should measure approximately the same. It's not important if they measure 13K or 8K, the important thing is that you don't have any that are way higher.

[Razorback]

I measured all 4 from boot to ground and got anywhere from 22.4k to 23.5k. Fairly even I suppose.

[Razorback]

I also took it out just now and decided to flog it a bit, or ride it like I stole it as they say. It actually performed much better but still cuts out some.

 

Check out this observation though:

I'm running along in 3rd gear at about 3k rpm. I let off the throttle and the tach bounces up to 4500-5000 rpm, bounces around on its way back to approx 3000-ish.

 

Ideas around those observations?

 

Monday it's misbehaving so bad I abort trying to ride it to work. Tonight I'm thinking I can drive it in the morning and hope the bugs work themselves out (as though it were a carburation issue)

[Razorback]

New clues:

I've been riding it ever since the last post, which was from a parking lot as I was riding.

 

Runs like a scalded ape, but with the occasional hiccups, whatever it is.

 

Here what I'm seeing. Headlight flicker, dash illumination flicker.

I actually had to have my wife jump start me from the parking lot I was in earlier.

The headlight and high beam indicator respond to throttle twist.

The voltmeter has been fluctuating a little.

When I pulled into the carport the voltmeter dropped down to about 8 V.

 

Perhaps I've had an intermittent voltage supply issue?

 

 

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[Flyinfool]

Try another approach.

A weak charging system or a bad battery can cause all Kinds of weird things to happen.

 

Put the battery on a charger and fully charge it.

Put a good volt meter across the battery. It should read around 12.6 volts.

Start the bike, run at ~3,000 rpm. It should be about 14V with the voltmeter across the battery.

[Razorback]

I was about to hook up the charger and put my meter on it and it reads 14.28.

Charge it anyway?

 

 

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[Flyinfool]

It reads 14.28 across the battery with the engine off and the charger not connected??

[Razorback]

I had just started it before the last reply. I went start I again to see what in getting and it turned over slow with the volts dropping as low as 6-8 volts while trying to turn it over.

 

I've got a craptastic cheapo lead acid battery that is about 10 months old. It hasn't been kept up very well in that time either.

 

Probably time for a AGM.

 

 

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[Razorback]

It reads 14.28 across the battery with the engine off and the charger not connected??

 

 

It did.

 

 

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[Flyinfool]

Start it up and check the battery voltage at 3,000 rpm.

[Razorback]

I sure will after I charge it.

I tried to crank it a second time and it wouldn't, as described above. If in can crank it shortly I'll run it up to 3k and tell ya what i get.

 

 

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