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78 xs 400 E rebuild and modify

Discussion in 'The Garage' started by Tyler Shiells, Mar 30, 2017.

  1. Moving forward, I found 2 NOS pistons (part # 2L0-11635-00) from 2 different sellers in Texas, as well as rings (part# 2A2-11610-10) from a seller in Germany.
    Those are all in the mail. The local machine shop will bore the cylinders for $60 hole.

    This little O ring fell on the floor and cant figure from where. Its beside the oil plug for size reference. Any idea?

    20191019_212017.jpg 20191019_212035.jpg

    In the meantime, some cleaning.
    I will end up painting the engine once all the dirt and grease is removed. The aluminum is very oxidized and scarred up. I will ended up baking an engine enamel on. I do have a oven in the garage for that purpose and had good results on the TW 200.

    The following pictures are just an idea for the rear end. Constructive criticism please?
    20191021_124127.jpg 20191021_125127.jpg
    That is the old handle bars I bent to match the frame. It will need to be shortened slightly. The tubing is the same size as the frame so why not? Works for me.

    20191021_191300.jpg 20191021_191236.jpg 20191021_191300.jpg

    Now for some ideas on relocating the fender and lights. I figure maybe use longer bolts and spacers for the top shock mounts to attach the fender. Then weld a cross beam near the back to attach a nut and bolt. The lights then fit right into the old mounting holes.

    How are people finding the clearance while riding when the fender gets lowered?

    20191021_194721.jpg 20191021_194800.jpg 20191021_195314.jpg

    Then, I figure Ill bend up a small plate of steel to make a bracket that'll use the existing holes in the rear part of the fender and mount the taillight and a plate holder?

    I do wanna use the OEM lights as they are DOT and there is noway Ill get it past safety here without DOT lights. Plus, this way doesn't cost anything but time.
  2. xschris

    xschris a lifestyle not a trend Top Contributor

    O-ring looks to be for the right side rocker shaft. It goes between the bolt and the shaft.
  3. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    With that rear hoop, I think your clearance will be tight. You may only have about 8cm unloaded. Definitely not enough room to mount the tail light and fender like that. The fender will pretty much have to be resting on the hoop for it to work. I ended up running without a fender.

    I agree with Chris on the O-ring.
  4. Hmm. It does but I haven't removed those two rocker shaft bolts. I'll double check they both have that oring tho.
  5. 20191023_145951.jpg

    The smaller o ring and bolt are off the valve cover and its noticeably smaller.
    The oring in question is a bit bigger.

    I've looked through the parts diagrams and still cant figure it out...

    It fits over the cylinder block alignment dowels but the actual one that is over the oil passage is wider and accounted for.
  6. motoTrooper

    motoTrooper XS400 Addict

    Hard to tell about the o-ring, reminds me of the one on the oil filter cover bolt?

    With respect to your rear hoop, it compliments the stock taillight but if you decide to change to another style later it may seem a bit square(y).
  7. The oil filter bypass bolt is slightly bigger and accounted for.

    And about the tail end, thanks, didnt look at it as a compliment to each other. Looks better now that you said that.
  8. 20191026_211521.jpg
    The ol bent handle bars, surprisingly fit the contour of the rear frame quite well. IMO.

    As for clearance, near the bottom of the dampener stroke, the wheel comes past the frame and makes contact with the new frame hoop.
    20191026_213234.jpg 20191026_213309.jpg
    I now see why Yamaha made the room under the seat for this.

    How does everyone accommodate for this?

    How much weight/force does it take to compress the spring enough to make contact?
    Big enough impact the wheel will bump into the new seat pan before it hit the bump stops. :umm:
  9. Update..
    Last weekend was cleaning.
    Many hours later the engine cases are cleaned.

    I've decided I'm going to have to angle the back up in order for there to be clearance for the wheel. I will also accommodate for the space when I make a seat pan.
    Not sure I'll use that fender. May find a different way to mount the taillight.

    The main thing I took care of this weekend was that stuck fork cap in the fork tube. 20190919_111627.jpg
    It was completely stuck.

    I first drilled out 5/16 hole and tapped it.
    After many hours of trying to hold the tube try to back it out with a bolt, all that ended up happening was the bolt snapped and it didnt budge a bit. 20191103_141104.jpg 20191103_153723.jpg

    So almost admitted defeat and left it for the day.

    Looked on ebay for what a new tube goes for. Nope. Too pricey. Then thought I'd have to get it lathed out.

    Woke up the next day and drilled out the bolt that was now stuck. And decided to just see if I can keep drilling larger until it could be freed out.
    Stayed close to one side which exposed the oring groove. Which then allowed me to chip out the one side slightly. Then I could get a flat head screwdriver and hammer it in between the cap and the tube...

    After about 6-7 hrs of garage time this wknd

    20191105_111343.jpg 20191105_120014.jpg

    And that's one more victory against
    Ol Grumpy.
    Last edited: Nov 5, 2019
  10. NewHavenMike

    NewHavenMike 1976 XS360C Top Contributor

    You do know that there is a little round clip that holds the fork cap in place right? It should break free with a hammer and a punch to loosen it up before popping the clip out. Then it usually will shoot out of the tube.

    I have photos around somewhere of what I did with the rear hoop. I cut my frame right behind the shock mounts and welded the hop on. My hoop is upswept 15 degrees and I dont use a fender. Ive ridden with a passenger on and the only time it ever rubbed was hitting a big bump.

    You could also just leave the back of the frame open with no hoop as long as you keep the cross member between the shocks intact. Depending on what you do with a seat, most of that is covered anyway. Ive seen some builders use the open frame tubes to install turn signals or lights.

    Not sure about your vision with the bike, but a normal "true" cafe aesthetic would have the frame terminate just before the back axle. My bike breaks this rule as you can see, but only slightly, and that is somewhat acceptable for the aesthetic. My bike is more of a brat style with the seat but no one can tell and no one cares, I sure as hell dont lol

    Attached Files:

  11. Yes. The circlip was not the issue. The cap was actually about a mm below the clip groove. It wasnt moving no matter what.
    A 5/16 bolt tapped all the way through, and me cranking on with probably over 150 ft lbs of torque just snapped the bolt. It was rust welded in there.
  12. Gra900

    Gra900 XS400 Enthusiast

    Hi Tyler, great to hear you got it out in the end, and fork tube looks ok too. Must have been real stuck to bust the bolt
  13. Thanks

    So far it was the most difficult/time consuming part to remove.
  14. I now have the new oversized rings and one piston. Still waiting on the 2nd piston. It's been in transit for almost 3 wks. Last scan was Chicago. It must be held up in customs. Not sure.


    I removed the front wheel bearings. I tried the method the book says but that was useless. Nothing was moving and couldn't get good contact on the ledge.

    Instead made a little blind bearing removal "tool".

    I rounded and chamfered a bolt. Then cut it down the centre. I spread the bolt slightly, inserted a flat head from the other side, with a light tap to set the screwdriver, then a couple good hits with the hammer and popped out easily.
    Spent less time making that bolt and removing the bearings then I did trying the by the book method.
    Gra900 likes this.
  15. Both over sized pistons now acquired.
    Curious, what year did Yamaha stop making parts like pistons for these bikes?

    This wknd I've been working on the wheels.
    I've got new tires picked out but for curiosity sake I wanted to know the manufacturers date.
    Appernetly the ChengShin tires used a 3 digit date code pre 2000. Making these tire 93 and 91..

    They were rock hard and quite difficult to remove, like everything on this bike.

    Rims got cleaned up. Was originally thinking of painting the black part only, a differnt colour but they look good once cleaned up. 20191109_162902.jpg

    Brain storming some ideas for an electronic tray.
    20191110_144911.jpg 20191110_144925.jpg
    20191110_150219.jpg 15734973231085144015115353506936.jpg
    Last photo, the black part would be the tray size and angles, but centered and the style I choose.

    Now that the tires are apart and cleaned that is essentially ever part dissasembled on this bike, except some specific engine parts. Which means from here on its rebuilding everything.

    Here is my parts/to do list I've been working on during the break down.

    Above what I've spent already on this bike($900), I've priced everything out and I'm looking at about $750 more for parts and about $150 machine shop and about $200 plus in shop supplies and material for fabrication.

    Last edited: Nov 11, 2019 at 1:42 PM
  16. Have I miss identified my year and model?
    I belive I may have...

    Would this bike have been sold as a 1979 F even tho it was manufactured January 1978?

    Reason I ask is most parts catalogues show the 78E with drum brakes.
  17. xschris

    xschris a lifestyle not a trend Top Contributor

    You have a 78-E the 78 2-E had the drum brakes. The 79 would have started production around may or june of 78. The 79-F and 78-E would use the same brake stuff anyways.
    Tyler Shiells likes this.
  18. xschris

    xschris a lifestyle not a trend Top Contributor

    The 78 vin number starts with a 0 and the 79 with a 1.

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