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Thread: 350x 12:1 piston help

  1. 04-06-2011, 09:14 AM #1
    MarkM
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    350x 12:1 piston help

    just bought a 350x (yeah for me). The trike was not running at the time the owner told me the bike was starting to smoke and his son bought the parts but never got around to rebuilding the motor. I pulled the motor and found the case was cracked at one point and jb welded back together (problem one). I started to open the boxes and found a new jug and a new weisco 12:1 piston. I want my bike too be quick but more importantly I want it to be reliable. What other mods will I have to make to make the piston combo work, do I need to run race gas, please help
    ANYBODY WHO HAS EVER FOLLOWED ME KNOWS SIZE MATTERS
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  2. 04-06-2011, 05:19 PM #2
    SWIGIN's Avatar
    SWIGIN
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    yes you'll probably need race fuel. I'd get a Megacycle full race cam and HD springs to go with that piston. A large cam will bleed off cylinder pressure and reduce the chance of pinging.

    I always turn the dome off of 12-1 pistons in my lathe if I want to run pump gas. I have this done to my current ride and it runs great with 92 octane. I have a old 10.5-1 350x piston I keep around just so I know how much of the dome I need to turn off to get roughly 11-1.

    I have also seen guys use a belt sander to remove the dome of high compression pistons.....food for thought.
    80s......185 atc, Yamaha tri-moto 200, 85 200x with tons of work
    90s......89 Suzuki quad racer 250 (raced 250 A class for 6 years, late 90s.. custom framed 250x with long travel shocks and a built 350x motor.... built Honda 110
    00s...... chomeoly framed 350 RX with all the goodies (thanks to my bro)
    2012.....Replaced the 350x motor for a 444cc YZ426
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  3. 04-07-2011, 04:42 AM #3
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    RubberSalt
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    12:1 is usualy 91-93 octane, 14 for race fuel. E85 would probably be your best bet, but you'll need to jet for it.
    I just wanna go fast. If your not first, your last!!
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  4. 04-07-2011, 04:25 PM #4
    SWIGIN's Avatar
    SWIGIN
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    I wouldnt say that 12:1 is usualy ok for pump gas but it can happen. Depends on how it is built.
    80s......185 atc, Yamaha tri-moto 200, 85 200x with tons of work
    90s......89 Suzuki quad racer 250 (raced 250 A class for 6 years, late 90s.. custom framed 250x with long travel shocks and a built 350x motor.... built Honda 110
    00s...... chomeoly framed 350 RX with all the goodies (thanks to my bro)
    2012.....Replaced the 350x motor for a 444cc YZ426
    WWW.HREATV.COM
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  5. 04-08-2011, 09:36 AM #5
    MarkM
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    how can I build it to handle pump gas and still be reliable what jets do I need to be running
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  6. 04-08-2011, 06:55 PM #6
    SWIGIN's Avatar
    SWIGIN
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    See post 2 but add a decent port job to the head.
    80s......185 atc, Yamaha tri-moto 200, 85 200x with tons of work
    90s......89 Suzuki quad racer 250 (raced 250 A class for 6 years, late 90s.. custom framed 250x with long travel shocks and a built 350x motor.... built Honda 110
    00s...... chomeoly framed 350 RX with all the goodies (thanks to my bro)
    2012.....Replaced the 350x motor for a 444cc YZ426
    WWW.HREATV.COM
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  7. 04-29-2011, 01:38 AM #7
    Nubbinz
    Nubbinz is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Don't know on the mods but as far as fuel I'd say go ahead and use race fuel. I know this isn't a trike but on my bros engine swapped Honda car with 9.5:1 he has to run 93 octane, with 12:1 id say race fuel def wouldn't hurt but once again i don't know much about high compression trikes...
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  8. 05-18-2011, 08:23 PM #8
    3Wheelermaniac3
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    which is the full race cam from megacycle
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  9. 05-19-2011, 10:18 AM #9
    The Goat's Avatar
    The Goat
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    There are way too many factors to say that it will or won't work definitively. However, I'd bet money with swigin, on pump gas you will be pinging like crazy. E85 is fun until you realize exactly how much fuel you're using... A LOT!

    Turn it down to 11:1, keep it on 93, and don't use fuel supplements besides seafoam, ringfree, or benol/xylene blend.

    I've found that with very high load applications in a Honda air-cooled motor it is possible to ping even on 10.25:1

    Mixing in a little two stroke oil and xylene in equal parts and jetting for the displaced fuel seems to correct those issues.

    But this was not in a high revving race bike, it was in the bike in my avatar.
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