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  1. #1
    Resident electronics hacker UnityRacing's Avatar
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    Engine pressure testing

    Does anyone have any how to's or other info on performing an engine pressure test? (Not a compression test)

    Not really sure how to seal it up to perform such a test.


  2. #2
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    You basically need to block off the intake and exhaust of the motor and then pressurize it. I use 10 PSI. If it holds for 10 minutes its good to go. I made block off plates out of 3/8 aluminum. one each over the intake manifold holes, and one over the exhaust outlet of the exhaust manifold. I made rubber gaskets to seal under the aluminum plate. I use one pulse line fitting to pressurize the engine and connect a pressure gauge to the other pulse fitting. If you only have one pulse fitting, put a t in the line to add the gauge. If you have a leak use soapy water to find it, and correct the problem. The 2 biggest problem areas I have found are the flywheel housing at the front of the motor and the reed cages.



    The fitting on the other end has a schrader valve in it so I can use an air compressor or a bike pump to pressurize the engine
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    Last edited by Mr. Matrix; 02-17-2015 at 12:18 AM.

  3. #3
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    A few other things. Make sure you have the spark plugs torqued down, and the coupler is threaded on. If the coupler is not on, you will blow that little collar right off the crank when you add pressure.

    When you assemble the motor, use the case sealer on both sides of the base gaskets. If you ever have to tear down the motor again, the gaskets peel off clean. Not to mention they will seal much better. I also use case sealer on the reed cages. Makes sure they are sealed.

  4. #4
    Resident electronics hacker UnityRacing's Avatar
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    Are you using 1194 or 1211 on the base gaskets?
    I have a 1200DI so no pulse lines.
    Are all 3 cylinders connected internally, I thought they were separated internally?

    My thought was to make a plate for the exhaust port and seal with rubber. Tap a hole in it for a gauge.
    Do another plate for the intake with a connection to an air feed.

    Sounds like I might need to make a plate for each cylinder. If each cylinder is internally connected then I don't need to swap my gauge / feed plates between the cylinders. Does that make sense?

    The aluminum plate and rubber, is that something that home depot or lowes would have?

    Also i'll be running the Fusion reeds and they have a rubber lip to them. Will that be enough of a seal?

  5. #5
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    The OEM reeds have the rubber seal on them, but I still use the case sealer on them. I think the 1194 is the same as the Polaris OEM sealant. Its what I like to use. The exhaust manifold will connect all 3 cylinders together.

    If you have no pulse fittings then tap fittings into your block off plates.

    Here is where I got the aluminum plates. Order the size you need. They will cut and ship.

    http://www.speedymetals.com/default.aspx?

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    I will get out all of my pieces tomorrow and post a pic of them.

  7. #7
    Resident electronics hacker UnityRacing's Avatar
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    Here is my exhaust manifold. No way to easily block it off. I'd have to use the same method you use on your intake manifold, and make a plate for each exhaust outlet directly on the cylinder. That would effectively seal off each cylinder then right?
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  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by UnityRacing View Post
    Here is my exhaust manifold. No way to easily block it off. I'd have to use the same method you use on your intake manifold, and make a plate for each exhaust outlet directly on the cylinder. That would effectively seal off each cylinder then right?
    Click image for larger version. 

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    Can you put expanding rubber stopper inside the large log pipe exit? I am thinking of the expanding plugs sold to block plumbing drain pipes, typically with a huge wing nut that expands the rubber plug as the bolt tightens.



    All Polaris 2-stroke engines have what is effectively a labyrinth seal between cylinders. There is still a path for air pressure to (slowly) work its way from one cylinder to the next, right through the crank bearings. The only rubber seals on the crankshaft are at the front and rear outer ends of the crank. This is why we can pressure test a sealed engine by applying air pressure or vacuum to just one cylinder port, yet the entire engine gets pressurized.

  9. #9
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    Quote Originally Posted by UnityRacing View Post
    Here is my exhaust manifold. No way to easily block it off. I'd have to use the same method you use on your intake manifold, and make a plate for each exhaust outlet directly on the cylinder. That would effectively seal off each cylinder then right?
    Click image for larger version. 

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    Stupid log pipe.......

  10. #10
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    TB 1211 is more caulk-like... and easier to coat gaskets with... little slower to get tacky ($20+ tube). I've used TB 1184 on gaskets and it works fine... just gets tacky quicker ($10+ tube). I prefer TB 1184 for running a bead (case sealing).

    Found this online... looks like 1184 replaces 1194.

    ThreeBond Gray Liquid Gasket Sealer - TB1184
    A semi drying synthetic rubber liquid gasket which is resistant to oil, water, chemicals and gasoline. Application areas include sealing transmission case covers, 2-stroke crank cases, timing chain cases, side covers, 2-piece cylinders, clutch housing bolts and oil filter mounting surfaces. After it is applied and dried, it will form a rubber-like elastic body. Since it excels in padding property, it shows a high sealing effect on bonded surfaces that have poor flatness and large clearance. In addition, it has excellent resistance to water, oil and gasoline. Temperature range from 40° F to 302° F.
    3.4 oz. (100g) tube.
    Direct replacement for:



    • Threebond 1104 (Discontinued because of hazardous chemicals)
    • Threebond 1194 (Discontinued because of hazardous chemicals)
    • Honda Bond
    • YamaBond 4
    • Suzuki 99000-31010
    • Kawasaki Bond 56019-120


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