RD350 forever project

[m in sc]

ah yup. cool, good idea there. 

[Perattzi]

Well picked this up from a good friend... once I 'button up' the 350 I'll have plenty to do 😂! Always loved the slightly larger frame, rubber mounted motor, and stronger low end on the 400's.

[Perattzi]

Got some fresh vm28's and swapped my jetting over. Nice that they are already setup for screwing in air jets, no drilling and tapping. The slides are wayyy heavier. They seem to be steel instead of brass and the return springs are longer. I had to use the original top adjusters to make my cable work but no biggie. The longer springs make the throttle pull feel the slightest bit 'crunchy' as the spring coils on itself. The fuel inlets are way bigger than the petcock outlets so had to get creative with the fuel lines. Only annoying part is that the slide adjuster on the right carb is hard to get at. Oh and pretty annoyed that the left one was pissing gas everywhere 😡 for fucks sake! They're brand new! 😭
I took it back off and double checked the float valve etc. seemed fine. So I made sure the breather hoses were not
Kinked or blocked. Now seems to be not overflowing. 🤷 Will take it for a ride tomorrow ✌️

[m in sc]

mt tm32s did the same thing at 1st, overflowed for some weird reason for a day or 2, been fine though afterwards. fwiw, you can use your old sprins in there if you want. the aftermarket ones are typically designed to be run as a single carb.

[Perattzi]

Seems to be sealing now! Yeah I think I will put the original springs in. Real tough to get the needle for tuning also with the linger springs. Those slides slam shut too lol

[Perattzi]

Well, time flies! Decided to go for a little rip as it's shockingly not raining today in PDX. My headlight blew    seems I have an electrical issue. 😡
Been tending my battery all winter, measures 12.8. So I measured the voltage with the bike running and at the battery terminals I get around 14.5 even when revving. However, the voltage is spiking if I measure the voltage at the main frame ground and battery +. Which, to my brain, makes zero sense bc the wire is literally connected to the battery obviously. Measured at the headlight power wire and when revving it went to like 18v. So no surprise it popped.
I have the r/r made by Ricks sold by HVC. Also I notice about a 1v drop anywhere that's powered from the main brown(headlight. Gauge lights etc)when I switch the key on.  So I have a voltage drop and an overcharge situation, that doesn't show up at the battery itself. Need some ideas, thanks!

[STLMike]

Wow, shot up to 18V? Even an electrical dummy (me) knows that's no good. Wish I could help, your build looks killer!
I'm sure some electrical guru's here will help you.

[Perattzi]

Yeah I'm not sure how the newer r/r 'senses' the battery voltage. It has one less wire than the original, but I think that's just bc the unit is combined unlike original.

[Perattzi]

Dug around a little and found a test to perform. According to Ricks: I unplugged the brown wire to the regulator, which I believe to be the 12v 'sense' wire on a Rd350, and made a jumper to connect the brown(from regulator) directly to battery +, so it's reading true battery voltage and not a voltage drop somewhere(main switch/connectors etc). It still is overcharging by quite a lot. The black wire from the r/r is connected to frame at same point as battery so I don't think it's a ground issue. This r/r is basically brand new. Love to hear some thoughts? Thanks.

[m in sc]

well for some reason it isn't tuning 'off' the rotor magnet.    this one, correct?

https://hvccycle.net/yamaha-rd350-voltage-regulator-rectifier/

i mean, it might be a bad new unit. it happens.

3 yellows to the stator, one to battery, one to ground, and one sensor wire. this should be off a brown wire from the harness. the white wire, i believe, is the field wire to run the rotor on/off.  fwiw, this unit is really a modified SOHC cb750 unit. on those, green is ground and black is switched voltage. however, simce this came pre-pinned its hard to see how this could be incorrect.

is the ground brush at the alternator grounding? 

[Perattzi]

Thanks Mark, yep that's the part. I'll double check how everything is hooked up. So should I just test for continuity from black brush wire to frame ground?

[m in sc]

yes, it should ground to the alternator housing, and also the frame.

[Perattzi]

Ok so I doubled checked the wiring. It's pretty simple, 3 white from generator go to 3 yellow to rectifier, green to green, black to black, red to fuse/battery, brown to switched 12v brown, black ground to frame. The ground brush shows continuity (meter goes basically to zero when set to ohms)to generator cover and to frame ground point. So maybe the part is faulty. Guess I need to reach out to Ricks, dang it.

[Perattzi]

Went ahead and bought a new battery. Mine seemed a little suspect. These little 5ah alarm batteries are like $17 so why not. Is it possible that an internally damaged battery could cause an overcharge situation?

Also I am trying to determine if the voltage drop I'm measuring is normal or not. Basically with my new battery I get 12.6 at posts, 12.6 at the main red wire that feeds to main switch while grounding the multimeter at frame or any other back probed ground wire. All read the same. With no headlight just led taillight and power to coils switched off I get about .7 volt drop. I figured it was my keyed switch, so I took it apart to clean but it was perfect inside. The springs that push the contacts together felt strong. cleaned it anyway and reassembled. Now with the main switch plugged in I tested the voltage at the factory solder points that are exposed on the back. I get 12.6 at the red wire but once I turn the key it drops to just about 11.9. Both the red wire in and brown wire out drop. This is with kill switch to off so coils aren't pulling juice, also tried with taillight unplugged too, basically no load at all. This really confuses me as all my connections are new. Could this be normal? Anyway, tomorrow I will start it up and see if the overcharging problems persists and if so then new reg/rec time. My current part is out of the 1 year warranty period and I have no way to test if its good to rule it out. 😤

[Perattzi]

Ok, if anyone has this issue. Check your battery. Installed new battery and it's charging fine now. Maxs out at 14.5 and stays there! 🆒