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  1. #21
    PWCToday.com Is My Home Away From Home jetman624's Avatar
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    Re: high compression head

    You can't trust your gauge unless it is a top quality one or you have checked it for leaks-- and even good ones can leak a little. But all things being correct, 29cc domes should put you in the 170ish area if your bore is in good shape and your head isn't leaking. Most compression gauges are only good for checking deterioration in the top end, not getting an absolute value in PSI. If both cylinders are reading dead on the same PSI, there is a good chance your gauge is just bad. Check the PSI with a couple different gauges, check your squish or pull the domes if you are unsure about having the correct domes for the base gasket you have.
    '02 SXi Pro: Factory Limited pipe, ported SXR cyl, SSP stearing system, WORX ride plate, skat trak intake grate, blowsion tubbie II, 3DR SS hull extensions, 3DR trued hull, 3DR pump shoe mod, bored pump nozzle

    '92 X2: Mostly stock, except for the 750

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  2. #22
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    Re: high compression head

    I never checked my compression for that very same reason. You can't trust the gauges and they all seem to read a little differently. 120psi is real low. You should try another gauge and let us know what you get. I will probably throw a gauge on mine this year to see where I am.

    Anyone out there running a lightened flywheel by Group K? I'm about to send 2 out to them and want to make sure its worth it. Do I lose reliability? I run the stock pipe on my boat to maintain reliability. We run out in the ocean a lot and go pretty far off shore. Its not worth getting stuck out there. Let me know what you think.

  3. #23
    PWCToday.com Is My Home Away From Home jetman624's Avatar
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    Re: high compression head

    I have put lightened stock flywheels on a few skis-- can't say I noticed a difference.
    '02 SXi Pro: Factory Limited pipe, ported SXR cyl, SSP stearing system, WORX ride plate, skat trak intake grate, blowsion tubbie II, 3DR SS hull extensions, 3DR trued hull, 3DR pump shoe mod, bored pump nozzle

    '92 X2: Mostly stock, except for the 750

    '91 X2: #718

  4. #24
    PWCToday Newbie kvogt8000's Avatar
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    high compression head

    Ok tried another gauge now I'm reading 165 steady in each cylinder. That's with the 29.5 domes and the .062 base...
    Also ballzee I just put on a tbm lightweight flywheel and have yet to run it as its still very cold here in Pittsburgh, but I'll keep ya posted on that...

  5. #25
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    Re: high compression head

    Quote Originally Posted by kvogt8000 View Post
    Ok tried another gauge now I'm reading 165 steady in each cylinder. That's with the 29.5 domes and the .062 base...
    Also ballzee I just put on a tbm lightweight flywheel and have yet to run it as its still very cold here in Pittsburgh, but I'll keep ya posted on that...
    Will you be running a pipe? or are you maintaining stock?

    That's why I never checked my compression. If I saw 165psi, then I would want to get the 28.5cc domes to get me closer to 185psi (pump gas). Does anyone know what pressure the 29.5cc and 28.5cc domes should yield?

  6. #26
    PWCToday Newbie kvogt8000's Avatar
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    high compression head

    Yes my setup is dry pipe, tbm head with the 29.5 domes,.062 base, v force reeds, carbs jetted, choke plates removed and blowsion filters, stock bore with fresh top end and a tbm flywheel.... Haven't ride it with the pipe or head on yet....

  7. #27
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    Re: high compression head

    I've checked this site high and low and haven't been able to find any information on TBM domes and thier associated expected compression. I understand every boat is different, but it's nice to know where you should expect to be (ball park). As I said before I'm running 29.5cc limited drop domes with the 0.062 base and wanted to know if I could get away with 28.5cc domes on pump gas. I was also contemplating adding a Advent ignition if this would give me some sort of security if I was on the line. I am running the stock exhaust if this matters.

    I found a lot of info on other heads, but I don't think they correlate between manufacturers. I see a lot of people are running 28cc domes on their ADA heads. Any info is appreciated.

  8. #28
    Top Dog mattyv's Avatar
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    Re: high compression head

    Have you tried calling TBM directly? Are you running the timing advance?
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  9. #29
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    Re: high compression head

    I spoke to Tim when I purchased the head and he first recommended 30.5cc domes, which was very conservative and I ended up going with the 29.5's per the recommendation of one of my peers. I'd would like see what others are getting to base my desision on that. I couldn't find anything on the this topic.

    I am running a timing advance bypass right now.

  10. #30
    PWCToday.com Is My Home Away From Home jetman624's Avatar
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    Re: high compression head

    Which ignition are you running now? Stock with a timing advance?

    There are A LOT of factors that determine dome size-- simply going to an advent ignition on the domes you have now may put you out of pump gas range, depending on which curve you went with.

    You have a lot more digging to do.

    All domes are not created equal, just because someone runs 28s on an ADA head, doesn't mean you can get away with it on your TBM head. The domes have different squish angles, the amount of squish clearance is different, etc...
    Last edited by jetman624; 03-13-2013 at 12:01 PM.
    '02 SXi Pro: Factory Limited pipe, ported SXR cyl, SSP stearing system, WORX ride plate, skat trak intake grate, blowsion tubbie II, 3DR SS hull extensions, 3DR trued hull, 3DR pump shoe mod, bored pump nozzle

    '92 X2: Mostly stock, except for the 750

    '91 X2: #718

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