Okay two stroke experts, TWO questions: Hows it look and home built expansion chamber

Discussion in 'Old's Cool' started by dorkpunch, Aug 15, 2010.

  1. dorkpunch

    dorkpunch Oops...

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    Popped the head off and it looks a little lean to me. Just curious what the experts thought:


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    Next question is about expansion chambers, I'd like to build one and the more I read about it I think can do it. Played with a couple of programs but I'm wondering if there are any tips and tricks I should know before I get to far? I'm doing some basic figuring but I need to go through my engine with a degree wheel and get some other measurements before I can really do anything... Suggestions on steel and welding processes?
    #1
  2. tenderfoot

    tenderfoot PRJ

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    #2
  3. anonny

    anonny What could go wrong?

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    Can we see the plug.... it's a way better indicator.
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  4. bluebye

    bluebye Skin it back

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    Actually, it looks to rich. Heat makes carbon. To much gas cools the piston at the transfers and no heat means no carbon. Start leaning it out, it will run a lot stronger. The spark plug is a good indicator, but jetting off the top of the piston is the best when you are getting close.
    #4
  5. bluebye

    bluebye Skin it back

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    And it really looks like the pipe is stopped up with carbon.
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  6. dorkpunch

    dorkpunch Oops...

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    der. Took a pic, didnt post it. Heres the plug:

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    What makes you think the pipe is plugged up? It was missing the baffle, just basically an open megaphone. I built a baffle for it and it got lots quieter and quite a bit torquier too. Will pull the pipe of though and see if I need to cook out the carbon.
    #6
  7. Valleyrider

    Valleyrider I Survived The '60s

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    doesn't look like there's much time on the topend or plug.
    Appears to be about the right heat range on the plug, but rich.
    I say this because of the rich mixture "washing" the top of the piston.
    Do you know the history of the motor....??
    #7
  8. dorkpunch

    dorkpunch Oops...

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    It sat in a barn for who knows how many years.... It was siezed when we found it. It magically un-siezed after jumping on the kickstart for a couple of weeks. We had the head off when we were trying to un siezed it, and cleaned it really good at that point. The bike has about 3500 miles on it but who knows if thats accurate. we put maybe 100 miles on it farting around on back roads and then it sat for another 12 years before I pulled it back out and I've put about another 100 on it in the last week. The cylinder is very smooth but I can still see a bit of cross hatch.
    #8
  9. dorkpunch

    dorkpunch Oops...

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    and the plug is brand new- about 100 miles on it.
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  10. Valleyrider

    Valleyrider I Survived The '60s

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    I'd leave it rich if you're looking to put a pipe on it.
    The "Seized" statement worries me a bit, and add concerns about the crank seal(s) condition after sitting for that length of time. Most times, the seal on the mag side will kinda bond to the crank over time(when sitting and not turned over). Once the engine is turned over, the lips on the seal will sometimes tear. This can cause a leaky bottom end. This can also occur on the clutch/primary side as well and will result in a vey smokey running engine and if the oil from the transmission is not kept at proper level, damage to the transmission. Other seals (transmission) can become hard and also tear or just not seal very well.
    Looks like the link "Tenderfoot" posted has all the info you would need to fab a pipe.
    Good Luck!!
    #10
  11. anonny

    anonny What could go wrong?

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    Plug looks pretty good, did you do a leak down test? Might be a good idea.
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  12. dorkpunch

    dorkpunch Oops...

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    It runs great, no excess smoke, idles smooth, and doesnt exhibit any symptoms of a bad crank seal. I have new gaskets and seals on the way for it. The leakdowns a good idea. The cylinder still shows cross hatch, but it feels and looks pretty glazed. My compression tester pooped out, need to check that too.

    I pulled the pipe off and it looks great. Almost no carbon build up at all.
    #12
  13. Foot dragger

    Foot dragger singletracker

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    OK, I'll bite,How can you tell that?
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  14. Foot dragger

    Foot dragger singletracker

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    IT is an old YG1 Yamaha or ? Ive got a few parts around for one of those.
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  15. dorkpunch

    dorkpunch Oops...

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    Its a '67 YL2, very similar to the YG1.
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  16. Grider Pirate

    Grider Pirate Long timer

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    http://www.datafan.com/TunersHandbook/2-strokefiltered.html

    18 or 20 gauge sheet steel. A conical roller really helps, but a straight roller and some hammer work will produce an okay cone. Butt weld the seam on the cone. Try for a very good fit and use a small torch tip (1 or 0) to fuse the joint, then planish the joint after welding.
    Don't consider MIG welding. If you have a TIG and want to use it, fine, but with some practice (I did it for 10 hours a day for some months), an oxyacetylene torch works better. I have both, and wouldn't fire up the TIG for pipe work.
    Is the entire barrel iron? If so, you might want to limit your excursion into performance land. More power results in more heat, and an iron barrel can't shed the heat as quickly as an aluminum barrel with a sleeve (not even going to talk about plated aluminum).
    #16