My RD250 motor is still not running right and I suspect charging issues. I found this information on Oregon Motorcycle Parts: https://oregonmotorcycleparts.com/FAQ.html
I followed these steps but as soon as I disconnected the regulator/rectifier (Ricks aftermarket), the motor shut down.
What am I doing wrong here?
Finding out if the charging problem on a R5, DS7, RD250 and RD350 is the alternator or the regulator and rectifier.
To do this, start by running the bike until it is warmed up enough to idle properly. Unplug or remove the regulator and rectifier.
Make up a jumper wire with a 2 amp fuse and run power from the positive side of the battery directly to the green wire from the alternator.
With the engine running test the voltage AC output at the 3 white wires from the alternator with
the engine running at around 4500 RPM.
If you get 40 or more volts AC the stator, rotor and brushes are OK. If the voltage
is low or the fuse blows, the problem is under the alternator cover.
run a 12v jumper from the battery to the coils. this will allow the bike to run sans regulator/rectifier. then do the test. however, 12v to the green wire on an rd is a lot. they dont see 12v normally and you may fry the rotor.
here's my suggestion:
stator:
check continuity of each white wire to itself, should be almost no resistance.
check continuity each white wire to ground, should be zero continuity
rotor:
take brush holder off. check continuity of slip rings, should be 4 ish ohms between slip rings.
brushes:
make sure the black one is grounded
with all wiring connected, check voltage on green wire with key on. i think it sees like 7 volts max? this is what excites the rotor. it turns off after reaching 13 ish volts.
if all that is ok, then its in your wiring or the rr unit.
good luck
I have checked that the rotor voltage is 10 volts, lights off, kill switch off, key on.
Quote from: 1976RD400C on September 10, 2026, 10:03:08 AMI have checked that the rotor voltage is 10 volts, lights off, kill switch off, key on.
on a 400 or 350? they work differently.
Quote from: m in sc on September 10, 2026, 11:18:52 AMQuote from: 1976RD400C on September 10, 2026, 10:03:08 AMI have checked that the rotor voltage is 10 volts, lights off, kill switch off, key on.
on a 400 or 350? they work differently.
That was on a 400
Thanks m in sc! I will try the suggested tests and report back. I should have mentioned that I already have the relay mod in place so I should be getting 12v direct to the coils.
i get it. but skip the relay and jump it direct for testing
on my 74 350 , when i got it it had a no charge condition. did all the meter checks and everything passed. put on a Ricks reg/rec and had it charging again. then about 3 weeks later a no charge again! got out the meter installed new brushes i had stuffed away and still no charge. pulled the trigger on a Vape and golden . takes the worry out of several issuies with the factory dynomo system. "No one will ever know" God bless America and never forget ! :patriot:
while i agree, thats a big nut to drop money on. fwiw, ANY rr for a sohc cb750 will work. juat has different wiring colors.
honda:
black is switched power (brown on yamaha)
green is earth(black on yamaha)
white is armature (to green wire for brush on yamaha).
red same on both, battery directly.
3 white/3 yellow are ac leads.
Quote from: axldk6 on September 11, 2026, 12:51:01 PMon my 74 350 , when i got it it had a no charge condition. did all the meter checks and everything passed. put on a Ricks reg/rec and had it charging again. then about 3 weeks later a no charge again! got out the meter installed new brushes i had stuffed away and still no charge. pulled the trigger on a Vape and golden . takes the worry out of several issuies with the factory dynomo system. "No one will ever know" God bless America and never forget ! :patriot:
When I start thinking about all the possible root causes of the charging issue and replacing one thing after another, I am seriously starting to think about Vape even though it's a big financial hit.
Here are some test results:
stator:
check continuity of each white wire to itself, should be almost no resistance
1-2 = 1.0 ohms
2-3 = 1.0 ohms
1-3 = 1.0 ohms
check continuity each white wire to ground, should be zero continuity
> Affirmative - zero continuity on all 3
rotor:
take brush holder off. check continuity of slip rings, should be 4 ish ohms between slip rings.
> 4.9 ohms
brushes:
make sure the black one is grounded
with all wiring connected, check voltage on green wire with key on. i think it sees like 7 volts max? this is what excites the rotor. it turns off after reaching 13 ish volts.
> 6.5 volts
Now the mystery deepens:
I re-checked points gap and both are in spec. With ignition on, I turn crank with a wrench to check for sparks. I get a consistent spark on left cylinder, but mostly no spark on right. However there is a spark/flash at the points. Any ideas?
ah. well. thats a different issue then. probably the wire to the coil from the points. or a bad coil. or bad points.
fuck points. :dawg:
but the charging system components seem good.
I'm so done with this 50 year old tech. The Vape is calling me. Anything I should know before I pull the trigger?
if you order it thru economy cycle make sure to get the relay.(i think he includes it).
post when you get it, i have a few tips.
Quote from: BlueR32 on September 13, 2026, 08:20:42 PMI'm so done with this 50 year old tech. The Vape is calling me. Anything I should know before I pull the trigger?
Get the heavy duty bolt and washer as well. And take out all the bolts on the vape and blue locktite everything
I just recently ,like 3 weeks ago, bought my Vape from John@Economy. yes it is pricey ( about $ 280/290 is just tarriff taxed :eek: ). do buy the upgraded retaining bolt, a new grommet , and I bought the 2 coil brackets , though I could have made it work without. be carful routing the neutral wire too. took me about 1/2 a day to get it up and running. fyi, I marked my timing mark in case I need to pull it back off , for like a pinched neutral wire :whistle:
and use the discount code ' 2SW' saves some $.
Quote from: axldk6 on September 16, 2026, 08:37:36 AMI just recently ,like 3 weeks ago, bought my Vape from John@Economy. yes it is pricey ( about $ 280/290 is just tarriff taxed :eek: ). do buy the upgraded retaining bolt, a new grommet , and I bought the 2 coil brackets , though I could have made it work without. be carful routing the neutral wire too. took me about 1/2 a day to get it up and running. fyi, I marked my timing mark in case I need to pull it back off , for like a pinched neutral wire :whistle:
I'm about to pull the trigger on the Vape kit from Economy. Curious about the coil brackets for the Vape coils though. Looking at the coil bracket pics on Economy website I can't visualize how they mount to the frame. By the way this is for my SRX/RD250 project where I modified the original RD coil bracket to span across the frame (hope the pics show this clearly). Would I be wasting $$ buying the coil brackets in my case?
I found some more detailed pics of the brackets on the HVC website. The brackets clamp around the top frame tube on a stock RD frame. I don't have that center spine tube so I will have to figure out a different mounting arrangement.
ive used heavy duty p clamps just run a separate ground
Quote from: m in sc on September 13, 2026, 08:25:25 PMif you order it thru economy cycle make sure to get the relay.(i think he includes it).
post when you get it, i have a few tips.
The Vape Kit arrives tomorrow. Interested in your tips, pray tell :help:
It's interesting, when I got my Vape from HVC they never had those coil brackets. Oh well.
heat the rotor to 220f when its time to install, tap on w a dead blow, thrn zip the nut down when its time.
The Vape Kit arrives tomorrow. Interested in your tips, pray tell :help:
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Take all the fasteners apart and put blue locktite on all of them before putting it on the bike. It gets expensive fast if something comes loose while running
Quote from: m in sc on September 29, 2026, 09:00:49 PMheat the rotor to 220f when its time to install, tap on w a dead blow, thrn zip the nut down when its time.
Two things a magnet doesn't like: heat and percussion
Lap the rotor to the taper using valve grinding compound, then tighten the nut slowly and torque it.
well a single gentle wrap with a deadblow is fine, and 220 won't affect it. needs to get over 400f to affect these. its an interference fit, no need to lap unless there's prior shaft damage. im running them on 6 bikes right now. one since 07. yes beating on it with a ball peen hammer a d putting it on broil is a bad idea.
Take all the fasteners apart and put blue locktite on all of them before putting it on the bike. It gets expensive fast if something comes loose while running
[/quote]
Are you talking about the three components of the stator that need to be taken apart and loctited?
Quote from: BlueR32 on October 04, 2026, 12:50:42 PMTake all the fasteners apart and put blue locktite on all of them before putting it on the bike. It gets expensive fast if something comes loose while running
Are you talking about the three components of the stator that need to be taken apart and loctited?
Quote from: BlueR32 on October 04, 2026, 12:52:36 PMQuote from: BlueR32 on October 04, 2026, 12:50:42 PMTake all the fasteners apart and put blue locktite on all of them before putting it on the bike. It gets expensive fast if something comes loose while running
Are you talking about the three components of the stator that need to be taken apart and loctited?
yes, and dont overlook the pickup. get everything setup and then check pickup gap before locktiting those
hey BlueR32, did you get it installed yet? those m3 screws that hold on the pick up will strip so damn easy, guess why they send ya 2 sets. I advanced my timing to 1.9ish mm BTDC because of the hotter spark. I also used a protractor to get that 1* on the nose/raised section and marked it . 15 ftlb on the retaining nut if you bought the upgraded bolt/washer .
Quote from: axldk6 on October 08, 2026, 01:45:26 PMhey BlueR32, did you get it installed yet? those m3 screws that hold on the pick up will strip so damn easy, guess why they send ya 2 sets. I advanced my timing to 1.9ish mm BTDC because of the hotter spark. I also used a protractor to get that 1* on the nose/raised section and marked it . 15 ftlb on the retaining nut if you bought the upgraded bolt/washer .
Thanks for the tips! Mine is still a work in progress. I had a time of it trying to get the stator backing plate to sit flush on the crankcase. Long story, but it turned out to be a minute amount of 3-Bond excess where the crankcases join at the rear that needed to be trimmed down. I have also just finished drilling and tapping the secondary stator plate for the extra two screws that have been recommended. I had a list of questions for John at Economy Cycle which he was happy to walk through with me on the phone. He also recommended 15 ft/lbs on the rotor.
More progress: got the stator mounted and wiring routed. Just set the gap on the sensor. Chuck Quenzler's guide to installing the Vape has been most helpful, but I really did not want to drain the oil and remove the clutch cover to lock the crank so I did a search and came across this:
https://www.2strokeworld.net/forum/index.php?topic=1810.msg15077#msg15077
What a great idea! I happened to have an old plug that I had modified some time ago into a dial gauge holder so with a spacer and a longer allen bolt I made this piston stop.
Finally got the Vape fully installed and fired her up this afternoon. Thanks to all who chimed in with tips, and also kudos to Chuck Q for the very helpful install guide, and John at Economy who was very patient with all my questions. Haven't gone for a test ride yet but fingers crossed all will go well.
sweet!