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New motor install problem

Discussion in 'Nitro Engines' started by Virgilbigfish, Oct 7, 2017.

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  1. Virgilbigfish

    Virgilbigfish Member

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    Just got my new lrp 32 in mail today I took off the back plate that came on it I think it was installed to keep stuff out of the inside except it was machined anyhow I put the back plate o f my nitrostar.I have 0 experience at this when I put the back plate on was I supposed to line something up because when the piston is in the down stroke and hits bottom it hits something , gets stuck won't go through the full rotation. What did I dowromg
     
  2. NightFlier X4.6

    NightFlier X4.6 Well-Known Member

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    Can you post some pics with the back plate off please.
     
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  3. Virgilbigfish

    Virgilbigfish Member

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    15074032292461178597912.jpg 15074032292461178597912.jpg 1007171334.jpg
     
  4. NightFlier X4.6

    NightFlier X4.6 Well-Known Member

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    Wow super blurry is it possible to get a clearer pic?
     
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  5. Jam Racing 1

    Jam Racing 1 NPTB Monitor, Master of the known universe.... HPISF Staff

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    I was thinking the same thing, Blurry pics make me dizzy
    :lmao:
     
  6. olds97_lss

    olds97_lss Well-Known Member

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    Can you post a photo of the back plate that came on the engine? I have a feeling you bought a bump start engine and are trying to use a random pull-start back plate on it. These things aren't that interchangeable.

    A crankshaft that is intended to be a pull start either has a stub sticking out where the con-rod attaches to key into a slot on the one way bearing, or it's hollow with a spring/pin in it to key into the notch you see on your starter shaft.

    A crank that is intended for bump start doesn't have a stub sticking out or isn't hollow for a spring/pin.
     
  7. Virgilbigfish

    Virgilbigfish Member

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    Thankyou that's exactly what is the problem.cause it came with a machined backplate thankyou. Anyone have bump starter
     
  8. olds97_lss

    olds97_lss Well-Known Member

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    If it's going in a savage, you can't use a bump start as it requires direct access to the flywheel. It uses a starter box with a motor in it that has a large diameter rubber wheel that you "bump" against the flywheel, which starts the engine. It's why flywheels have a knurled edge to them. So the bump wheel can grip it.

    Back in the day, a basher buddy of a buddy got an LRP30-X, because he was told it performed better than the version with a pullstart. Odds are, the only performance gain was due to the lack of additional rotating mass of the one way bearing. He then spent a decent amount of money on a pull-start crank, backplate, starter shaft, one way bearing and starter housing. Pretty sure he just paid through the teeth for a pull-start version of what he already had. A fool and his money...

    Your probably better off returning it and getting an engine with a pull-start.
     
  9. olds97_lss

    olds97_lss Well-Known Member

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    After checking out the manual for the 32 spec 4 an 32X spec 4, it appears they use the same crank. For the non-ps version, the backplate has a groove for the crank stub to spin around in.

    So, you would need the following:
    back plate/starter shaft: Part # 38557
    One way: Part # 38491
    Starter housing: Part # 38556

    Looks like both the ps and non-ps backplate use the same o-ring, so if the new backplate doesn't come with one, you can carefully use the original.
     
  10. Virgilbigfish

    Virgilbigfish Member

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    Once again. Thank you olds 97 your help has been cherished I was getting on forum to ask you those exact questions its people like what's here on this forum that s making this "new hobby" a lot less stressful. Another question: when I got into this hobby I ran into a old friend he had 2 tmaxx's one ran good one ran not so good looked fun so I bought one from him, yes I bought the one that ran not so good, I h a d. A lot of issues I'd fix well now I have 16 various models. This normal I'm always working on several. Can I get a compression tester so I know when a motor is worn out?
     
  11. olds97_lss

    olds97_lss Well-Known Member

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    The easiest way to see if the pinch is gone is to take the engine apart, orient the piston in the sleeve in the same direction it would be if it was in the engine, then with light pressure, push the piston up in the sleeve. If it reaches the top of the sleeve, it's worn out. When the piston/sleeve are room temp, the sleeve should be shrunk enough at the top to bind the piston a bit above the top of the exhaust port. When it gets up to running temp, the sleeve expands and you end up with the right gap to keep compression without blow by.

    The sleeve is built with a taper in it so it gets smaller as you go up the sleeve. When the "pinch" is gone, the sleeve expands too much when it's up to running temp and allows the compression to get past the piston.

    Examples of worn piston/sleeves I've had re-pinched:
    [​IMG]
    [​IMG]
    You can see how the piston comes out of the top of the sleeve on two of those.

    Then after I got them back from being re-pinched:
    [​IMG]

    That is as far as I could push the piston by hand without overdoing it.

    I'd never replace a piston/sleeve. Just isn't worth it for most engines I own. At most, I'd get it re-pinched to get 2+ more gallons out of it. You can get one re-pinched a few times before it's too worn. Depending on who you have do it, the price is around $25.

    For what a TRX 3.3 would cost new, I'd probably just replace the entire engine with a new one. By the time the pinch is gone in one of those, the composite carb is probably worn/prone to binding up, the bearings are worn and the con-rod is worn. Not really worth paying retail to fix all that individually.

    I've had OSRocket and RayARacing pinch mine in the past. Just ask for a medium pinch so they don't overdo it and cause excess strain on the con-rod/pull-start. After getting it back, you just need to run it a bit rich the first few tanks, but since the "break-in" was already done, your just running it rich to loosen it up a bit.
     
    Last edited: Oct 12, 2017
  12. Virgilbigfish

    Virgilbigfish Member

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    Thank You very informative , I've looked all over web for those parts found 2 of them everywhere. They are back ordered.thinking about buying a another engine do you have a favorite ?
     
  13. olds97_lss

    olds97_lss Well-Known Member

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    The LRP28S3 served me well in my X. A LRP30 or 32 would probably be well suited for an XL length savage.
     
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