weak spark # 2

[Skyguyz]

Video of weak spark # 2:

https://www.youtube.com/watch?v=01-KTL8z0bY


So a good friend of mine picked up an early kettle. It supposedly ran great until recently.

The symptoms:

#2 cylinder not firing. *Pooling of injection oil & some gas under the # 2 exhaust.

*I inspected the coils and the plug wires and caps. All looked good.

reinstalled coils and connected plugs and now it magically started including the # 2 cylinder. But......The # 2 was running about 90 degrees F and # 1 & 3 were run-in about 130 F - 140F.

Plug inspection of # 2 looked like it was wet. Not a good sign. The bike ran fine above 4000 RPM but had a definite "Bog" below that.

The bike has an Accent electronic ignition. so no messing with points, condensers, etc.

Here is what I tried:

- swapped plugs with new plug. same results

- checked voltage at yellow coil wires. All 3 at 11.73 V. Batt volts 12.35 V.

- swapped battery with known good battery. same results.

-swapped voltage regulator with known good regulator. same results

-swapped all coils & plug wires with known good set. same results.

-looked at Accent electronics under side cover. put side cover back on, (Nothing to see or adjust here.)

-swapped carbs, #1 & #2. Same results, (bike has Mikuni flat slides, easy swap.) *Thinking possible pilot jet issue, but weak spark is obvious.

-Ran bike cold and ran bike after warmed up. Same results.

*Bike running with weak spark issue. Idles fine but has a bg at low RPM. High RPM is good:



I am just about out of ideas. I have been swapping parts with my 75 kettle that runs perfect. The last ditch effort might be to remove Accent electronics and swap with my OEM good points setup. That is something I don't want to do right now.

Any suggestions, options are always welcome.






Sky.




PS: I have not been on here in a while. Busy with restorations. Here is my very tired 73 Yamaha RD 350 project being transformed:


https://www.aircooledrdclub.com/smf/ind ... ic=60967.0




.

[Alan H]

Battery voltage is a little low. Should be up to 12.8v fully charged - although if your battery is tired it will be less. If it's lead acid, check all the cells are up to the levels ok. 11.73v at the coils with engine stopped isn't too bad though.
Remember that the wiring goes from battery, via fuse, to ignition switch, kill switch, several plugs and sockets before it gets to the coils, so lots of opportunity for a bad contact 'somewhere', so I'd suggest a temporary wire from battery (via a new fuse) direct to the coils to see if that makes a difference. Make sure the earths to frame and harness are clean too.
Also remove the plug caps and cut a 1/4" off the ht leads and put the caps back on. I always use non resistor caps on points systems, but electronic ignition likes resistor caps. You can measure through the caps - should be about 5000 ohms.
When it runs on all three, get it out for a few miles to clear out the exhausts and engine generally. Are the baffles clear of gunge?
That should give you something to get your teeth into.

[teazer]

Take the sris valves out and drain out the surplus oil and then remove the exhausts and let them drain. Sounds like excess oil drained down from the oil tank through the pump and oil feed manifold.

If it really is the ignition, go to the 6 pin connector to the coils and remove the black and yellow and swap it in the connector for either black or the white from one side of the connector. That way, the "wrong" coil will be triggered. Next, the plug leads over for those two coils. That way it will use a different coil for #2 cylinder.

IIRC, White = left, B/W=center and Black=right, but check your to be sure.

But before you do any of that, did you replace the plug caps and trim 1/4" off the plug leads

[Skyguyz]

Battery voltage is a little low. Should be up to 12.8v fully charged - although if your battery is tired it will be less. If it's lead acid, check all the cells are up to the levels ok. 11.73v at the coils with engine stopped isn't too bad though.
Remember that the wiring goes from battery, via fuse, to ignition switch, kill switch, several plugs and sockets before it gets to the coils, so lots of opportunity for a bad contact 'somewhere', so I'd suggest a temporary wire from battery (via a new fuse) direct to the coils to see if that makes a difference. Make sure the earths to frame and harness are clean too.
Also remove the plug caps and cut a 1/4" off the ht leads and put the caps back on. I always use non resistor caps on points systems, but electronic ignition likes resistor caps. You can measure through the caps - should be about 5000 ohms.
When it runs on all three, get it out for a few miles to clear out the exhausts and engine generally. Are the baffles clear of gunge?
That should give you something to get your teeth into.

Alan,

As always your knowledge in this area of expertise is invaluable. I will try some of your suggestions and report back.

Thanks,

Sky

[Skyguyz]

Take the sris valves out and drain out the surplus oil and then remove the exhausts and let them drain. Sounds like excess oil drained down from the oil tank through the pump and oil feed manifold.

If it really is the ignition, go to the 6 pin connector to the coils and remove the black and yellow and swap it in the connector for either black or the white from one side of the connector. That way, the "wrong" coil will be triggered. Next, the plug leads over for those two coils. That way it will use a different coil for #2 cylinder.

IIRC, White = left, B/W=center and Black=right, but check your to be sure.

But before you do any of that, did you replace the plug caps and trim 1/4" off the plug leads

teaser,

I will also try your suggestion of black/yellow swap and will report back. Thanks for posting.


Sky

[Skyguyz]

Well I tried most of what was suggested. I ran a fused line from the battery to the hot yellow coil wires and although it bumped the voltage at the coils up to over 12 V, it still didn't fix the low spark issue at the # 2 jug. I also checked the grounds on the wiring harness as well as the engine to frame ground. Did some switching of the wiring harness ground and still the same issue. I also cut off about 7 mm of the # 2 plug wire and re-screwed the cap back on, same issue. I did run a different set of coils with plug wires, same issue.

I also removed the Accent electronic ignition and replaced it with a good set plate of working OEM points, etc. After timing the points to 3.42 mm BTDC and using a testing light to ensure proper timing, it ran even worse???

*I did switch# 1 & 2 Mikuni flat-slide carbs, no improvement. (Easy switch to do.)


Hummm.

Rehash: The bike runs great above 4000 RPM. It does idle nice. When you add throttle from idle, it kind of bogs for a bit and then as revs increase, it runs good above 4000 RPM.

*The # 2 plug is still showing signs of being wet when removed after a trial run and using a temp gun, the # 2 header pipe is running about 43 C and # 1 & 3 about 60 C,
(The # 2 should always be hotter by a little bit, not colder.)\


Although the bike runs, it is just short of being "Crisp" from 1000 RPM idle to 3000-4000 RPM.

*The weak spark video again:
https://www.youtube.com/watch?v=01-KTL8z0bY


I'm wide open for suggestions.

Sky





While your pondering this issue, here is few of my 2 stroke to watch:
*The GT750 with the 1976 tank is now in the hands of a very fine chap in England!


https://www.youtube.com/watch?v=LoBNrVaE5g0&t=58s

[canaletto5]

It looks like everything "easy" has been tried. Have you checked barrel compressions? If they are in range then the only other thing I can think of is a leak down down test to check crank seals. Kev

[teazer]

Did you try swapping plugs from say 1 to 2 and see if the weak plug is OK in #1 and the good plug is weak in #2?

Are you 100% sure that the new plugs are genuine NGK? I read that there are a lot of copycat plugs out there.

[slosher]

Are the carbs balanced Sky with a lower temp header pipe may be the problem

Cheers Dave

[canaletto5]

Was this ever resolved? Kev