YPVS Loses Position(?)

[m in sc]

its very strange. it -sounds- carb related but its def rpm related and came on suddenly. its so weird  I used the 'batphone' and called Chuck Q. the carbs are def clean and sorted.  its so strange. my opinion is its electrical.  cdi/stator/coil all new and good.

[1976RD400C]

Possible 12 volt power supply to the controller problem???

[m in sc]

nope

[2steve]

Kill switch unplugged with the the hot end safely encapsulated in the headlight bucket. New ignig switch is in.

But the eagle hasn't landed. To be fair, I want to get the needles back to mid position and try it again to see where it "really" is.

The test will always be to take it out to drone away on a big highway to see if I have to pull over on the shoulder.

Had noticed on the way home from RHill that it would start to lose power, then I'd flip the kill switch and just before it died it would give me a couple strong beats first   

[85RZwade]

Could it be a wiring/conector issue? I'm thinking 40 year old harness could have a conductor that ohms out ok, but can't carry an amperage load. Do you have a way to load test wires?

[m in sc]

could be in the harness. I find it unlikely its the needles  but .... its a really odd one for sure

[2steve]

I'll try a fresh fat black coil ground wire, then a fresh orange coil wire* along with centering up the needles. Can't think of any more influential wires than those since stator and stator wiring were replaced with no change in performance.

Just ordered some more goodies from Yambits, so there's still optimism inside.

*Both look OK and ohm out at zero. Strangely, there's an extra unused old orange wire next to the actual black coil wire but the other end goes nowhere.

[RDnuTZ]

I'll try a fresh fat black coil ground wire, then a fresh orange coil wire* along with centering up the needles. Can't think of any more influential wires than those since stator and stator wiring were replaced with no change in performance.

Just ordered some more goodies from Yambits, so there's still optimism inside.

*Both look OK and ohm out at zero. Strangely, there's an extra unused old orange wire next to the actual black coil wire but the other end goes nowhere.

If you are trying to establish there is direct point to point continuity of a single wire, I believe it should read something like ~.1 to 10 OHM depending on wire gauge. If you read nothing (0 OHMS) point to point it means open circuit. Just curious if your meter is Analog or digital? Also, if you have different ranges you are able to select for reading sensitivity.

[m in sc]

i think its in the harness somewhere. the fact that it idles well, then runs like absolute ass from 2500-7 k, then cleans up, regardless of throttle position, seems electrical. also that 1: it came on out of nowhere out of the blue one day,2 the carbs are super clean, 3: over 7-8 k it runs awesome.

it feels like its 'leaking' high voltage somewhere. the odd part is that it cleans up high in the revs.

and the pvs are working correctly as well.   

IF you get a 2 carb split cable setup, we can put a set of individual ones i have for testing on. i dont have a setup for that (cable wise). 

[2steve]

Would the magnetism on the flywheel be letting me down?

Otherwise, I can't find where high voltage might escape in the wiring diagram. That coil is new, but didn't change anything.

Maybe I track the kill switch path on the other side of the new iggy switch.
Red/white wire from the kill side.

....

[m in sc]

no,weak magnet will show itself at lower rpm typically.  and, I've never seen that on sn rz tbh.

the harness does carry voltage from the ignition. im not q00% sayi g thats it, but aside from the coil being g only id be looking at the harness next

[1976RD400C]

My experiance with stock carbs: They acted up right between 5-6000 and that was it. Starting, pulling away from a stop, no stalling, and everything that wasn't in that rpm range was normal. You could watch the tach and say "ready, right now" as it hit 5000.

[85RZwade]

"If you are trying to establish there is direct point to point continuity of a single wire, I believe it should read something like ~.1 to 10 OHM depending on wire gauge. If you read nothing (0 OHMS) point to point it means open circuit. Just curious if your meter is Analog or digital? Also, if you have different ranges you are able to select for reading sensitivity."


I have to differ. The opposite of zero resistance is infinite resistance. If you short the leads of a multimeter together your meter will display zero resistance.

My experiance with stock carbs: They acted up right between 5-6000 and that was it. Starting, pulling away from a stop, no stalling, and everything that wasn't in that rpm range was normal. You could watch the tach and say "ready, right now" as it hit 5000.

I had this as well a couple of years ago with my original set of carbs, and believe it was caused by worn needles and/or needle jets.

[m in sc]

guys, when this thing goes into bog mode, it feel like its goign to just stall and die.

[2steve]

And when going 60 mph steady speed, I have to plan to pull over safely as sometimes, unpredictably, it will slowly wind down to a stop. After stop, it will kick back to life like nothing happened.

Like something got too hot?