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Thread: Amazing 2 valve head work. 225DX performance boost.

  1. #1
    Join Date
    Mar 2019
    Location
    Missouri
    --
    35

    Amazing 2 valve head work. 225DX performance boost.

    Just wanted to pass this along. We sent a head to zforce motorsports (zfore227) on ebay and the results were fantastic.

    The original purpose was to just have the seats cut with an airfloat cutter to get a great seal on the new factory Yamaha valves for a 225DX head, to take full advantage up the bump in compression from the XT225 piston. Although he doesn't list every single air-cooled 2 valve head for service on ebay, I just sent him an email asking if I could just purchase the service for a CRF50 and send in the 225DX head instead. He said yes, no problem.

    Head was cleaned decently, disassembled and sent with new valves, and all of the rest of the valvetrain parts. Came back, head was blasted, the deck had been machined flat, valve seats cut, exhaust port was cleaned up and everything was assembled. The engine fired up right away and after some jetting has surpassed my performance expectation. It legitimately feels like the power doubled from a piston (stock size but can be gotten at 1mm over, special order 2mm over), head work, intake and exhaust. The DG is way too loud, it sounds like a beast.

    I think the head work made a huge difference and at 80 bucks total for shipping and service it was a great deal for something I don't have the tools to accomplish. I have no affilliation with the guy he just does good work and deserves the mention, and there's always been a lot of issues here with people that would have saved time and $ by sending their head to him, and ended up with more power.

    He has 100% feedback which is how it should be for an engine builder. Not like some Disney characters I know of.

    Here is the link to the CRF50 auction, be sure to email him and let him know what you'll be sending, but he told me any air cooled 2 valve head is fine:
    https://www.ebay.com/itm/HONDA-CRF50...YAAMXQHDlRcL9r

    Here is a pic of the bike finished, I will look for and post any build/engine build pics i have if anyone wants details. I think there is video of it running for the first time somewhere. It just wasn't a big deal to document the build this time, just wanted to get it built.

    Click image for larger version. 

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  2. #2
    Join Date
    Jul 2005
    Location
    Manheim, PA
    --
    5,742
    Heads are important on these older 4 strokes. Im getting a ytm ported with 5 angle valve job this year. You can deck the heads to bump compression too then using a heaiver piston.

  3. #3
    Join Date
    Mar 2019
    Location
    Missouri
    --
    35
    Quote Originally Posted by oldskool83 View Post
    Heads are important on these older 4 strokes. Im getting a ytm ported with 5 angle valve job this year. You can deck the heads to bump compression too then using a heaiver piston.
    I did mean to weigh the pistons just for comparison but know these things when worrying about the weight of a piston on a single cylinder engine...

    1. The weight difference between a flattop and a dished piston isn't much on a small piston. That being said, some aftermarket flattops can be very heavy (read wiseco)
    2. On a single cylinder, there are no other pistons to fight the weight reciprocally, so in theory, the extra weight is actually more mechanically efficient on the downstroke, and will be all but immeasurable for at least a 1/4 of the upstroke.

    While I don't disagree that a lighter piston is better when possible, the increase in pressure and the combustion characteristics of a flattop make the weight difference in this case not even worth discussing. As was mentioned, the head was decked as well. The piston choice is also a no-brainer in relation to valve clearance, whereas serious decking to gain compression takes knowledge in precise measuring. Which is fine also.

  4. #4
    Join Date
    Oct 2010
    Location
    ky
    --
    88
    Thanks for the info, what was the turn around time?

  5. #5
    Join Date
    Mar 2019
    Location
    Missouri
    --
    35
    Quote Originally Posted by morgan View Post
    Thanks for the info, what was the turn around time?
    IIRC it was a couple weeks, although we told him we were not in a rush. It ships to and from there by priority mail so if you had a deadline for a race or something I'm sure you could call and let him know.

    And there is a typo in my first post, it should read "zforce227".

  6. #6
    Join Date
    Oct 2018
    Location
    Arroyo Grande
    --
    16
    Love this bike. Thanks for sharing.

  7. #7
    Join Date
    Jun 2019
    Location
    Partlow, Va
    --
    12
    first and foremost that a nice ride! secondly you said you sent the head in for work, which i am looking into myself but as far as the cylinder goes, did you just hone and replace the piston? or did you send that out to have worked as well?

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