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!
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!
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... 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 
