Advice on an RD 250 build

Discussion in '2 smokers' started by sprouty115, Dec 1, 2012.

  1. sprouty115

    sprouty115 Long timer Supporter

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    Forgot to add this pic. When I was fitting one of the cylinders I discovered a chunk missing from the edge of the lower cooling fin. Looked at the other cylinder and sure enough there was a chunk missing there too. Doesn't effect anything but just more evidence that the previous mechanic clearly only had two tools: a hammer and a bigger hammer.
    [​IMG]
    Cylinders bottom
    #61
  2. sprouty115

    sprouty115 Long timer Supporter

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    Started on the top end today. Measured up the ring end-gap and then looked for some specs for the TKRJ brand pistons, but couldn't find anything. So I looked at the Haynes manual, the Clymer manual, the Weisco and Pro-X websites and realized they are all different. Given these don't seem overly tight or loose, I started the assembly.

    [​IMG]
    Pistons and rings

    Got as far as trying to install the small-end bearings. Seems like there is a bit of difference between the different manufactures when it comes to bearing length.

    Top bearing is the Pro-X bearing I got with the crank re-build, which wouldn't fit in the pistons I ordered. Bottom bearing it what was in the engine.
    [​IMG]
    Small-end bearings

    Gave a call to HVC Cycle, where I bought the pistons and they said the OEM will fit. Ordered them along with the points cam I needed. Should have all of it in two weeks. Until then I'm off to find new screws for the stator-side and a new brush or two.
    #62
  3. RideFreak

    RideFreak Torque Junky

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    THe brush length difference is because the outer brush has more material passing it due to it's loc on the diameter of the stator. THe toasted stator probably didn't help ether. I'd replace the small phillips on the points etc with some allen bolts.

    RD250s with a 350 jugs make a pretty hot little bike due to the difference in primary gear ratios from the 350. Match porting the pistons helps it run a bit better with no adverse affects too.
    #63
  4. sprouty115

    sprouty115 Long timer Supporter

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    Ah yes, longer path of travel, makes sense. And thanks for the other tips. Right now my plan is to get it reliable and see if my son is into the bike. If he is, I'll see if he's into doing a proper restoration.

    Other than that I'm sort of on hold for a few weeks while I sort out some house projects. But I will be back to it soon. I also may have gotten a bit ditracted by a new toy I picked up for myself (a KTM 690 Enduro), but that's another thread...
    #64
  5. sprouty115

    sprouty115 Long timer Supporter

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    OK, it's been awhile but I'm back at, this time with my son working with me. We've got the cylinders and heads mounted as well as the stator-side all back on.

    Now we're working on the oil injection system. We rebuilt the pump but are a little confused as to how to connect the hoses to the carbs. There are two connection points on each carb (4 total) that are the right size for tubing and two connections to the autolube pump. I've searched and can find lots of info on proper adjustment, but I can't seem to find a clear connection diagram.

    Some basic questions:
    - Do all four fittings on the carbs get attached to the pump? I thought that only the fittings that are behind the slide got connected, but I'm not sure. Also if this were true, then I'd need some type of "Y" connector and I don't remember seeing one on other bikes.
    - Does it matter which delivery port on the pump gets connected to on the carbs? In other words does the top port go to right carb and the lower port to the left (or vice versa)?

    I've numbered the following photos, so if anybody can shed some light it would be much appreciated.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
    #65
  6. klp

    klp Been here awhile

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    This is a guess but I bet the two inner ports are for the oil pump, numbers one and two. The others are vents or something. Your pump outputs can be routed to either carb, I don't think it matters.

    Nice work on the build, I have a 400 that has been a blast to ride.
    #66
  7. sprouty115

    sprouty115 Long timer Supporter

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    Thanks, it's been a lot of fun. Especially this week with my son and me working on it together.
    As for the connections - called a local dealer and he found the old microfiche. He said the connections are the ports in the front of the carbs (#3 & #4 in my pics). I'm inclined to agree based on the photos of Mikuni carbs I've seen while searching the web - not many with ports fo oil, but quite a few with vents on the barrel. He also indicated, like you mentioned, that it didn't matter which carb the delivery tube on the pump goes to.
    #67
  8. sprouty115

    sprouty115 Long timer Supporter

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    So here it is in it's current state.You'll notice the carbs are back off and the autolube assembly is stalled again.

    [​IMG]

    After a few minutes of rational thought we decided that investing all this time an money without rebuilding the carbs was a stupid idea. So they're now disassembled and awaiting the kit from Economy Cycle.

    [​IMG]

    The right-side carb was very clean inside and appears to have stock jetting.

    [​IMG]

    The left-side carb unfortunately has some unexpected corrosion. It doesn't appear to be anything that would cause a fuel/air issue but I'll have to see how the bike runs to decide if I need to do anything. You'll also notice that there is a brass tube that comes out of the carb body that is not present in the right-side carb. This concerned me for a minute until we realized it's part of the choke circuit and doesn't appear to be required on the other carb.

    [​IMG]


    As for the autolube pump, well, it seems that the new hose has a different o.d. than the original so the rubber fitting that holds the lines as the exit the case won't fit over them. Now trying to decide whether to buy new oil line or fab a new holder.

    [​IMG]


    And finally one of my son after finding 3 of the 4 bolts frozen into the bottom of the seat pan - that's life with a 40yo motorcycle...
    [​IMG]
    #68
  9. sprouty115

    sprouty115 Long timer Supporter

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    So at the risk of being guilty of the longest time between updates on a build thread, maybe a little closure is in order?

    Last we left off in 2013 the bike was coming along well as my son and I worked on it together. We even actually got it to the point where we added some premix and decided to see if it would start.

    And amazingly it started on the third-kick!

    I have to say, even after almost 50-years owning bikes, I was super happy. But as it was still in the basement at this point, and we had plenty of other things to sort out (not the least of which was brakes and tires) we high-fived and called it a night.

    Then, as is often the case, life got in the way. He ended up relocating to Arizona and I got busy traveling for work. So I drained the tank and prepped it for storage.

    He would come back for a visit every year and we would head down in the basement to look at it and talk about what it needed, but the time was short so nothing really happened.

    I was hopeful we could get back to it but I was also thinking maybe it wasn't meant to be.

    Fast forward to this crazy year and he is halfway through a masters program in India when he is told get out or prepare for a long lock-down. He jumps on a plane and with less than 24-hrs to spare before they shut down international flights he gets out.

    Suddenly he's home, trying to figure out what to do and each night he keeps going down to basement to look at the bike. Eventually tools start migrating over towards it and the next thing you know he's pulling the brakes apart.

    Then he got the lights working.

    After that it was a new battery.

    Then he sorted out a charging issue (rectifier).

    And you all know the routine - so many small issues and adjustments you think it will never end.

    But he plugged away got it done. I helped and guided, but it was his bike now, so he did most of the work.

    And then a few weeks ago with the help of a burly friend we got it out of the basement - straight back up a set of winding stairs.

    20200802_130908.jpg
    More stuff to sort out, and he had quite a few spins around the block only to have to push it home. But he didn't give up and today he took it for the first real ride. It was over an hour and he rode all over the city and the bike ran great.

    You can't see the huge smile under the helmet, but it was there.

    20200915_162429.jpg

    It's been a long time coming, but this weekend we're planning on our first ride together - him on the RD250 and me on my project bike, an R90/6 - both from 1975...

    20200531_135305.jpg
    #69
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  10. spo123

    spo123 Man About Town

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    One day, I too, will undertake my old Yamaha R5.......similar, with 5 speed and no reed valves.
    Beautiful /6, as I have stated previously.
    My son has an RD 350, set up with chambers, DG heads, etc. He has not ridden it in many years. He rides his KTM LC4 640 Enduro and his big Triumph Touring bike.
    Thanks for the thread update.
    #70
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  11. sprouty115

    sprouty115 Long timer Supporter

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    Thanks. Almost didn't post it, but I was so happy he finally got the time and then actually got interested so I figured why not?

    Of course don't give up on the R5. Parts are available and for me the rebuild of the engine was the part I was most worried about, but it all went fine!

    And hopefully your son comes back to his RD. The sound of that engine is amazing.
    #71
  12. spo123

    spo123 Man About Town

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    I purchased a nice R5C gas tank, many years ago, from Lyn Garland.....He has quite the reputation.
    I do hope that he is still well.
    #72
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