Advice on an RD 250 build

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

  1. sprouty115

    sprouty115 Long timer

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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.
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    Cylinders bottom
    #61
  2. sprouty115

    sprouty115 Long timer

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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.

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    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.
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    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 Junkie

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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

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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

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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.

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    #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

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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

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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.

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    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.

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

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    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.

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    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.

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    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...
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    #68