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  1. #1
    Lakeside518's Avatar
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    1200 65U head gasket/cooling question

    I am assembling a ported 1200 with a milled oem head. I run ADA heads on all of my other yamaha 2-strokes. My question is do you do any kind of gasket modification to allow more water flow? The holes in the gasket seem small & few compared to the passage ways in a billet head.

    Do you drill more holes or enlarge them?


  2. #2
    Pistonwash's Avatar
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    I know what you're talking about...but when you start drilling holes, you can screw up the gasket. Make sure they are balanced in the number of holes on each cylinder dome. They would put larger holes on the rear cylinder OEM gasket, if I can remember correctly. The water pressure will get you adequate cooling from the OEM, if you add another water by-pass it will increase actual water flow. If you increase size of holes, be careful, you may end up allowing too much flow to cylinders and not enough for the domes. I personally would leave them alone and check engine temp. after a wot run. Add a secondary water line if you want to increase cooling to engine. You probably knew that and have a secondary already installed...but this is a must on a modded engine, even without triple pipes imo.

  3. #3
    Lakeside518's Avatar
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    The engine is a 1100 63M bored to 84mm, ported with wiseco pistons. The head is milled for 165psi with the center cylinder drilled & tapped for a bypass. Exhaust mani is drilled & tapped for dual cooling. I just find it hard to believe that all three cylinders will get adequate cooling with so few holes and tiny at that! I will also be running a Riva CDI, triple 44mm carbs with primer, R&D intake mani, K&N FA's, V-force III reeds, Riva reed spacer, new RAD flywheel, cold fusion drive couplers, solas mag pump.

    I'll be running a jetworks flow control valve & quick disconnect flow restrictor with the various sized bushings inside it to help dry the pipe for low end punch. I also have an adjustable jetworks gate valve to help slow the flow through the pipe so I can dial in temp.

    I am so use to running the ADA heads which will flow so much more water. I will be slowing/restricting the water through the pipe so it only makes since to allow more water through the cylinder-head?

  4. #4
    Pistonwash's Avatar
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    Just try it like it is, first. Keep an eye on head temps with temp strips if you can get them. Find the ideal temp at wot and see how far off you are. The rear cylinder is your most critical piece to watch. You've got some testing to do if you are that concerned...if you are not racing I wouldn't imagine it would be as critical as you may think. Test and verify. I think you're gonna be ok with OEM. Enlarge the existing holes by a couple sizes larger drill bit if you must. Use your head when drilling...those gaskets are made of tough material and will bend before they cut..so put it on a drill press, not with a hand-held drill. And use cutting oil when you drill. It might you give you some piece of mind..so go for it and be careful.

  5. #5
    Lakeside518's Avatar
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    Thanks for your input. I may try to add a hole for the rear & center cylinders and slightly enlarge existing holes. If I screw it up, I have one extra gasket. Or I can always order an ADA head, but would rather use this seeing how I just had it milled.

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