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Old October 12th, 2019, 07:58 PM   #40
DannoXYZ certified postwhore
Name: AKA JacRyann
Location: SF East Bay
Join Date: Dec 2011

Motorcycle(s): CB125T, Ninja250R racer, Ninja250R street bike, EX250F#1, EX250F#2, EX250E, VF500F, CBR600RR

Posts: A lot.
MOTY - 2018, MOTM - Nov '17
VRM is Voltage Regulator Module aka regulator aka rectifier aka regulator-rectifier aka RR. It's part that converts variable-voltage AC from stator coils into steady ~14v DC to re-charge battery and to power ignitor, lights and other do-dads on bike. Battery is only used to start engine.

Ok, I figured 2nd "vacuum" port on petcock was red-herring. Someone thought bike wasn't running because there wasn't vacuum on petcock like OEM unit... BUT... it actually doesn't have vacuum diaphragm. Confirm back of your petcock looks like this.

So they didn't actually TEST if petcock was delivering adequate fuel, they just crammed brass nipple on there and connected to carb. I suspect it may not be delivering petrol at fast enough rate which may be why bike dies after 90-seconds. Then petcock continues to flow when bike's off and fills up float-bowls and it can run again.

1. remove forward brass-nipple from petcock and plug vacuum-line from carb with tight-fitting bolt. Add zip-tie or hose-clamp on top to be sure it seals. All hoses should have clamp or zip-tie to make sure they're sealed.

2. remove fuel-line from carb and aim into measuring cup

3. turn on petcock, measure petrol-flow for 30-seconds. How much did you collect?

Do whatever's needed to keep bike running for at least 6-minutes. Get helper if you need. Easiest to adjust idle-knob. Then measure battery-voltage every 2-minutes after it starts. This will tell us if VRM/RR is OK and re-charging battery properly.

1. measure battery voltage right after bike starts
2. measure battery voltage at 2-minutes after bike starts
3. measure battery voltage at 4-minutes after bike starts
4. measure batteyr voltage at 6-minutes after bike starts.

4. I can sit there and hold throttle for 5 minutes and let bike warm up and to also blow out seafoam and junk in exhaust.. I don’t think it’s from engine.

Wasn’t doing that before I pulled carbs. It wasn’t black smoke
But your bike wasn't running before, so we can't compare before & after. On carb-cleaning, you'll want to see work-order on it and verify all steps done properly. I suspect it was not if YouTube video was used for instruction. Would you trust someone to perform surgery to remove aneurysm from your mum's brain while they watched YouTube video for help? If you don't know how many turns pilot screws are, you should re-do it yourself so you are sure.

Actually, you should probably disassemble carbs down to every last nut & bolt and replace all consumables with new parts. All O-rings, seals, all jets and float-valves with factory units. Who knows what previous-owners have done to muck up innards. Drilling out jets rather than properly cleaning is common tactic, ill-fated at best and now you have to deal with aftermath. Search here for "clean carbs ducatiman" to see what's involved in properly cleaning carbs. If you don't want to do it yourself, send them off to ducatiman for proper refurb/restoration job. Otherwise, we can never be sure carbs aren't problem here and will go around in circles forever.

Sure you want to learn, but to do proper carb-cleaning, you would have needed to disassemble and clean at least 100 carbs for experience. And you'll need correct equipment to do it: scrub-brushes of various sizes, guitar wires of various matching sizes, ultrasonic cleaner with radioactive caustic solvents, 100000psi micro soda-blaster. Unless you want to learn to do carb-cleaning professionally as career, it doesn't make sense to accumulate all this equipment just to properly clean one set of carbs.

Post photos of spark-plugs you pulled from bike.

Last futzed with by DannoXYZ; October 13th, 2019 at 09:45 AM. Reason: By
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