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Re-Ring, Dodge VR and Starter Clutch Springs

Discussion in 'The Garage' started by tstidham, Jan 22, 2022.

  1. tstidham

    tstidham XS400 Enthusiast

    Hello all again, I have still been working over my recently acquired 1978 XS400E and thought I'd post an update on all the things I've done so far.

    1. As in a previous post, I had a cracked head. I bought a used one off ebay, lapped in the valves, new valve guide seals and also decided to re-ring the engine while I had it apart. I ball honed the cylinders, cleaned everything up real nice and got it back together without too much hassle. Compression went from 115 psi Left cylinder - 100 psi Right to 155 psi on both cylinders.

    2. Rebuilt the carbs but had to use single strands of copper wire to really ream and clean out the carb ports and pilot jet holes. Prior to using thin copper wire, I just could not get the idle mixture screws to adjust or make any RPM change. I used the copper wire everywhere I could then spray cleaned everything liberally with brake cleaner. I originally left the old needles and seats, but later tore them down again to replace them. Now the carbs are running and adjusting very well and are very snappy when blipping the throttle.

    3. After running for about 40 minutes, she would start stalling out. When I limped it back home I found the battery was reading 11.9 - 12.0 volts and I knew it was fully charged prior to the ride as I had my battery charger on it in maintenance mode for a few days while doing all the other work. So now I was having a charging issue and needed to test the stator, field coil, rectifier and regulator. Thanks to this site I have the manual, so I ohmed everything I could and found everything in spec. There was no ohm test for the small solid state regulator my bike came with, but if I grounded the green wire to my field coil, my "alternator" would start pumping out 15-18 volts at the battery. I read a lot of posts on the Dodge VR-125 or AMC R292/291 (VR-115) regulators. I opted for the AC Delco C603Z version of the VR-125 and wired it in. I now get 13.6 to 14.2 volts at idle, but I do top out to 15.2 at 3500 rpm or higher. Hopefully this will be OK.

    4. The last thing I had problems with was the electric starter clutch (or one way clutch or sprag depending on what you like to call it). Mine would grab and slip, grab and slip and was not reliable. It got worse the hotter the bike got to the point it just spun free at full temp. So since I was having charging issues and I want to inspect the stator wiring for cracks, I popped the side cover off and took apart the flywheel and starter clutch. I found one broken spring, but no excessive wear or cracks in the housing or rollers. I tried to order new yamaha springs, but was informed they no longer make them. So I measured up the original springs and did my best to guesstimate the spring pressure, then went on McMaster-Carr and found two possible matches and ordered them. The one spring had WAY too much tension, but the other seemed just perfect. It is McMaster Part #9657K692, made by WB Jones and their part number is C06-014-048. They are slightly shorter but the tension assembled seemed about the same, maybe a teener tiny bit more. The starter now engages very well and once running I don't hear any noise or dragging. Time will tell how long the will last. Yamaha wanted $7 dollars per spring, I bought a bag of 12 of them for $6, so I could redo it 4 more times if needed (or send some to a fellow board member if anyone needed some).

    5. My original vacuum petcock did not open under vacuum, but did not leak. I bought a rebuild kit off amazon for it. It leaked fuel while turned off, but did open fully under vacuum. It just wouldn't shut off and with bad float needles in the carbs, it dribbled fuel out the air cleaner. So I replaced it altogether with a mechanical one, and also bought new needles/seats for the carbs. So that is all working great and no leaks even if I forget to turn off the fuel. This one was off Amazon as they had Ok reviews on it and it was the proper 46mm bolt spacing.

    6. The last thing I am waiting on is my electronic ignition from MikesXS to replace my points but that should arrive in just a few days now. I picked up new coils and wires from them as well since this bike is still rocking the originals from 1978.

    So I have this thing all tuned and repaired up just in time for wicked cold 20 Deg. F weather here in PA. Oh well, if a nice day happens, it will be ready to go!
    Last edited: Jan 27, 2022
  2. Macabry

    Macabry XS400 Enthusiast

    Thanks for that info on the springs :) ... sounds like you're in a similar predicament to to me weatherwise, getting the bike all set up but it's too cold for a nice ride ... let's keep dreaming of that warm summer sun :bike:
  3. tstidham

    tstidham XS400 Enthusiast

    Well, after doing some further testing with the Dodge VR, I am seeing spikes of 16.5 volts at higher RPM ranges and I'm not sure why. This is too high and would result in me going through batteries as they get over charged. I thought maybe I had some voltage drop on the sense wire or ground but I don't. If I supply battery voltage to the sense wire of the VR or connect direct negative battery to housing, it acts the same. So I decided to order the other recommended VR from the early '70's AMC/Jeep/International models. I'll let you know how that works. The MikeXS electronic ignition is now here, but I want to make sure my charging system doesn't over voltage the thing first.
  4. tstidham

    tstidham XS400 Enthusiast

    Well that didn't work at all. With the AMC/JEEP style VR, I don't get any voltage out of the system. It just shows battery voltage, slowly dropping as the bike runs. I assume this is because the Dodge VR is for a ground regulated field coil and the AMC\JEEP VR is for a positive regulated field. In my testing, grounding the green wire of the VR plug caused the alternator to go full output. I guess I could change the wiring to the field coil as a test, after all that coil is not going to be polarity sensitive. It just needs a positive and a ground to work and they can go either way, I just suspect I'll get the same over 16 volt results if I do. Well this is annoying. I'll have to go back and reread those old posts on folks messing about with their VR's.
  5. CaptChrome

    CaptChrome XS400 Addict

    Just a potential lead here that may or may not help you in your search for a suitable voltage regulator, but air cooled VWs used a three wire 14v regulator that I have thought might be a possible solution should the OEM regulator bite the dust. It is a Bosch unit with VW part number 0 190 601 017. I haven't done any real research on it and I don't have my old VW wiring diagrams to look over wire pin-outs (those shop manuals went with the vehicles when I sold them,) but it might be worth looking into should you hit a dead end.

    Either way, let us know how you make out as this is some valuable research and testing you are doing.
    tstidham likes this.
  6. tstidham

    tstidham XS400 Enthusiast

    Thanks for that info. Looking up the part number I find info suggesting it is a B Circuit style regulator, which I think means it is similar to the VR115 or the AMC/Jeep style. The stock XS400 is known as an A Circuit style and I think this just means the field is ground regulated instead of power regulated. I'm hoping to try swapping the power/ground wires on my field circuit to see if we can indeed switch ourselves between A or B circuit regulation depending on which VR's we can lay our hands on. It will be a little while though before I get back on it.
    Last edited: Jan 28, 2022
    CaptChrome likes this.
  7. CaptChrome

    CaptChrome XS400 Addict

    Yes, good catch on the different regulators. I am just now looking at the wiring diagram for my '81 and it is indeed ground regulated. The XS400 regulator has to sense the system voltage and does this using the brown (positive voltage from the fuse box) and black wire (ground). Based on what voltage is sensed, the regulator allows current to flow though the field winding of the alternator to either increase or decrease output of the alternator. This is done via the green wire between the regulator and the field coil. There are two wires attached to the field coil. The black is connected to positive system voltage, so to get current to flow though the coil, the other (green wire) must go to ground, The regulator does that switching the green wire to ground.

    Great information in your post. If I find anything that might work for you I will certainly post it here.
  8. tstidham

    tstidham XS400 Enthusiast

    Thought I'd post a quick update. The AC Delco Gold VR-125 I picked up fried pretty much right out of the gate, so I grabbed a TransPO brand C8313 Heavy Duty Adjustable and now I have perfect voltages. 13.5 at idle and 14.2-14.4 in the upp rpm ranges. I just took the bike out for a 20 mile run and not a single stall, hiccup or issue. Even at 8500 rpm voltages stayed at 14.4 volts. So I think I can now close the book on that issue and I can now install the Electronic ignition without fear of the charging system frying it right away.
    BBS360 and CaptChrome like this.
  9. CaptChrome

    CaptChrome XS400 Addict

    Good work!

    I had been looking up some candidates also (all Transpo retrofit regulators), and I had the C8312 on the list, which is the non-adjustable version of what you used. I also have about four others that looked promising as well and might get a couple of them to try out once my project is running just to try out and provide some other options. This is certainly a topic that hasn't been covered much (detailing success stories) that I can see, so great job letting us know a part that works.
  10. BBS360

    BBS360 XS400 Guru Top Contributor

  11. Kumeran

    Kumeran 1980 Yamaha XS400 special

  12. tstidham

    tstidham XS400 Enthusiast

    Probably nothing wrong with one of those. I chose the Dodge VR path since my rectifier ohmed out perfectly and was still working. Only my VR had died. Speaking of which I am happy to report we've had some pretty mild days this winter and I've been able to pile on about 250-300 miles of riding in and my voltages are still 12.8-13.0 at idle and 14.2-14.4 when cruising or really romping on it. Engine is running great, even on the old points, wires and coils. I do have all new ones and the MikesXS electronic ignition to install, but as they say, if it ain't broke, don't fix it!
    Kumeran and CaptChrome like this.
  13. tstidham

    tstidham XS400 Enthusiast

    Thought I'd give an update on my old girl. She's running GREAT! I had a little oil burning and consumption issues at first, but now that the new piston rings are fully seated in that stopped and the oil level stays consistent now. I get 14.2-14.5 volts while riding and at idle sometimes see 12.6 volts, but usually it stays over 13 volts. Maybe the 12.6 is when the regulator senses the battery is fully charged so it cuts all charging? Also, those McMaster-Carr starter clutch springs are working great, no issues with it slipping and grabbing anymore! I do need new tires, and now that I know it's a good bike, I'll put those on my groceries list real soon.

    Anyway 1000 miles added to the odometer so far and I am LOVING this bike. I'm still running the original points setup and haven't installed the electronic ignition yet. I'd rather ride than wrench if you know what I mean! :D

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