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Thread: Low Quality Cast Aluminum...

  1. #1
    apriliaforum expert angrybob's Avatar
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    Jul 2003

    Low Quality Cast Aluminum...

    on the throttle bodies. I noticed some small voids in the t/b before I sent them off to be machined, but upon return WOW. The porosity of the t/b casting is terrible for a production part.

    I am very familiar with castings and the casting process. I worked for a brake system supplier for 7+ years and if we ever had that kind of porosity in our rotors/calipers/wheel cylinders/etc. we would have been desourced! Granted most of our products were cast iron but a small amount were aluminum.

    I also understand that the further away from the surface, the more prone the area is to voids forming. It may be expected a little by machining 1.5mm of material depth, but I am surprised.

    I am sure its not a functional problem as the T/B's really don't see any stress, but its the point of it. I always had this image of Italian quality when it came to motorcycles.

    AB the anti-post-whore
    '06 YZ450F

    "You say that it is your custom to burn widows. Very well. We also have a custom: when men burn a woman alive we tie a rope around their necks and hang them. Build your funeral pyre; beside it, my carpenters will build a gallows. You may follow your custom. And then we will follow ours." - Sir Charles Napier

    "Good people sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf."
    - George Orwell

  2. #2
    apriliaforum expert
    Join Date
    Jul 2003
    Keizer, Oregon USA
    I work as a process engineer at an aluminum foundry and deal w/ porosity all the time. It costs a lot of money in order to make a low porosity aluminum, especially if they are recycling the scrap material. People here give me a hard time about the poor quality of the cast swing arm on my Mille. If it isn't a high stress or fatigue part it makes no sense to send the money to fight porosity. The Mille swing arm is really beefy so the aluminum quality doesn't have to be as good. Just polish it all and nobody will know.

  3. #3
    apriliaforum expert Louge's Avatar
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    Jul 2003


    AB ~

    While you've got the TBs off consider hand polishing the inlets with 400 grit. The front cylinder in the pix has been finished with a little more effort on the floor, a little less on the ceiling. The rear is still au-natural for comparison.

    Leave the bottom half of the TBs unfinished as Ken delivered 'em to promote micro turbulence and keep the air from sticking to the walls.

    The missus' vacuum worked better for getting into the ports than the shop vac. Toilet paper made some good wadding just above the closed valves. A foot long artist's brush freed up the last bits of material for the vacuum. After removing every spec I could see I opened the valves, removed the plugs and went at it some more.
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  4. #4
    apriliaforum newb
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    Aug 2003

    re:inlets polishing

    Louge did you note any improvement after inlets polishing, does it worth for std TB´s?


  5. #5
    apriliaforum expert Louge's Avatar
    Join Date
    Jul 2003

    The various globs of rear inlet material are visible in the pix. What the lower resolution pix doesn't show is the casting surfaces are in the 60 to 100 grit range. My attempt was merely to do a port cleanup. Note the lighter colored area in the middle of the front inlet. That's a slight depression below the floor.

    I spoke with Ken about 54mm TB setup after reassembly. He advised against finishing the inlets to promote microturbulence. Ken has the benefit of running a business and a dyno, I have an oak tree with some shade under it.

    I can't quantify if it made a difference or not. I can say that with mods limited to an Evo race airbox, 54mm TBs, Akra can and time spent dialing the bike in it'll leave lengthy 3rd gear darkies and roll past modded Gixxer 750s down front straights.

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