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Thread: DIY: Stop guessing, test your intake manifold seals for under $15.00

  1. #1
    Senior Member lowkey's Avatar
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    DIY: Stop guessing, test your intake manifold seals for under $15.00

    Hey all, I put this easy to make manifold pressure tester together and thought I'd share.

    I bought this rubber piper coupler and plastic cap at Lowes for under $10.00 and had the air line fitting but you could make this setup for $15.00. The coupler measures 2" and so does the cap, the manifold OD measures 2 1/2" but you can get this coupler to fit without issue. Drill and tap the cap for the air line fitting and use pipe thread tape for a good seal. I set the output on the compressor with a regulator to 15PSI, anything over this will pop the cap from the coupler and is not needed anyway 10-15PSI will do the job just fine.

    IMG_20190509_104835522.jpg
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    Once you have this on and tightened down on the manifold connect the regulated air hose and with a spray bottle with water and dish soap spray the manifold flanges, if they have a leak you will see bubbles form as the air makes its way out. I had a machinist make Oilight bushings to replace the crappy stock plastic butterfly bushing AND RTV'd the TPS to the manifold. The results from testing my newly installed manifold was a slight bubbling at the 3 wires from the TPS sensor (nothing I can do about that) but the RTV held solid here, On the manifold flanges I use James blue gaskets along with a motorcycle gasket maker which also held solid at 15PSI without a bubble showing up. I also installed new Injector O-rings but the front cylinder injector showed to be leaking under the pressure.

    IMG_20190509_192259669.jpg
    IMG_20190509_192323016.jpg

    Anyway now that I have this in the tool box, I can easily check the manifold periodically for leakage.

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    Damn! That’s pretty smart!!

  3. #3
    Senior Member lowkey's Avatar
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    O-rings for injectors are Standard Motor Parts brand PN# SK1 and come 8 in a box at your local parts store.

    As stated my rear injector is leak free even at 15PSI so these work well... the casting seat for these lower injector O-rings are rough IMO and most likely damaged the front lower one when getting it all back together, no big deal as I have 4 more new ones in the box.

    IMG_20190516_211918451~2.jpg

    I also drilled and tapped then sealed and cap screwed the emissions vac port just above the TB plate on the manifold, which tested to be leak free.

    1828.jpg

    And here is the gasket maker I used along with the James blue gaskets to seal the manifold to the heads.

    1913.jpg
    Last edited by lowkey; 05-17-2019 at 04:43 AM.

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    Are those the blue seals with the "base"?

    Like this:
    https://st-paul-harley-davidson-buel...e-seals-l2c6-1

    I always has trouble getting the manifold back on when using those gaskets on an XB. The times I tried, I had the engine in place (not rotated). Stock style gaskets fit fine, but on my XB's it was just too tight of a fit compounded by the limited working space.

  5. #5
    Senior Member lowkey's Avatar
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    Quote Originally Posted by 34nineteen View Post
    Are those the blue seals with the "base"?

    Like this:
    https://st-paul-harley-davidson-buel...e-seals-l2c6-1

    I always has trouble getting the manifold back on when using those gaskets on an XB. The times I tried, I had the engine in place (not rotated). Stock style gaskets fit fine, but on my XB's it was just too tight of a fit compounded by the limited working space.
    Yes, I've used them in the past and IIRC they tend to shrink after use. Installation isn't an issue with the engine rotated down I had them against manifold lip and flanges all the way in close to the "Y" of the manifold, no issues at all then finger tight the bolts down (chased and anti-seized) align manifold front to back between cylinders (check machined gasket neck) square up the alignment bracket that the coil mounts on (mine was biased the rear cylinder from factory) and tightened that bolt first and moved on to 1/4 turn on all four manifold gasket bolts in rotation for an even seal.

    Screenshot_20190517-134648.jpgScreenshot_20190517-134633.jpg
    Last edited by lowkey; 05-17-2019 at 08:45 PM.

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    Very clever lowkey! I'm going into the garage now to see if I have that coupling. Thanks for the tip.

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    Senior Member lowkey's Avatar
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    Here is the play from the worn plastic bushings in the video, this caused an unsteady idle.

    IMG_20190416_103441913.jpg
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    IMG_20190414_165041951.jpg
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    Here is the manifold rebuilt with the oilight bushings and trimmed butterfly screws installed. When locking down the butterfly placement you MUST preload the butterfly shaft with the spring and throttle cable wheel or the butterfly will not be aligned correctly and drag once completely assembled on the bike.

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    Senior Member lowkey's Avatar
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    The OD bore for the bushings measured .381 on the throttle cable wheel side and .379 on the TPS side. ID is 8mm for the shaft.

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    Senior Member lowkey's Avatar
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    IMG_20190408_183108579.jpg

    I originally planned to run these sealed bearings instead of the bushings and also picked up shaft seals rated to hold 10PSI but the Machinist I used didn't want to touch the bore of the manifold ends and the shaft seals X2 would have added maybe to much drag for the throttle return spring to overcome. I also thought of running just one shaft seal and having him cut a recess for an O-ring on the TPS side like the 08+ TPS uses but machine work is extremely expensive apparently from what he quoted me for all that... still RTV and the oilight bushings cheaply got me close to the original plan.

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    Good info, thanks for posting.



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