Need help from the experienced guys

Discussion in 'Trials' started by PMK, Sep 2, 2018.

  1. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    My 2005 Scorpa SY250r has kind of a poorly thought out airbox and airfilter design, I think.

    Skipping the buy a newer bike comments, or duct tape everything, curious, how important is the large volume still airbox setup.

    The SY250r air filter is like a bathtub shape. This is placed at the top opening of the airbox. Any water that gets into the filter area, kind of settles into the foam and is drawn through an oiled air filter. The airbox has no drain. Once water passes through the foam, it is either pooled into the bottom of the airbox, or ingested into engine / carb. In some cases, the water winds up in the bottom of tne float bowl.

    Curious, again how important is the still airbox, but more importantly, if a pod filter with water shield were installed down inside the airbox, similar to the more modern bikes, any ideas on if the performance would change?

    So, thinking, do not run the oem bathtub filter, make an adapter to install a reasonably sized pod filter with water shield, and add a drain to the airbox.

    Open to hear opinions
    #1
  2. Hoss Cartright

    Hoss Cartright Been here awhile

    Joined:
    Oct 23, 2016
    Oddometer:
    594
    Location:
    Earl Park Indiana
    I'm not familiar with this design... but a small water drain hole in the box should always be before the filter. As this seems to be a filter on top of the box design (many bikes are like this) you need to work on finding a solution to water entering the filter area. Shield or redesign the top lid above the filter.

    And absolutely. I did this test in the early 1990s.
    Water ( often with sand and earthen materials suspended in an imulsion) goes onto the filter.
    1) the foam expands and this allows larger particles to pass through.
    2) the water almost eliminates the sticky filter oil's ability to capture particulates.

    If you don't believe me. Simply place a clean and well-oiled cone filter over a clear jar. Mix some sand and water into suspension and pour it down into the filter cone and you will see that the sand passes right through.
    #2
    Dirt Dud, Norman Foley and jonnyc21 like this.
  3. Huzband

    Huzband Team Dirt

    Joined:
    Oct 4, 2006
    Oddometer:
    7,906
    Location:
    Cowford, Fl.
    I installed pod filters inside the air box on my 1190R, and drilled 2 small drain holes in said box. I'm not shy when it comes to water crossings & have yet to find any evidence of ingestion. So I think your plan is a good one.
    #3
    Dirt Dud and Hoss Cartright like this.
  4. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Agree, and a major part of why I am keen to modify the oem setup.
    #4
  5. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    C2E8A991-48B5-4E52-AF9E-92FF35E0DC80.jpeg
    View of the top of the airbox with the rear fender removed. The fender is not a good seal to the subframe, or airbox to keep water out. As you can see, any water, settles to the bottom of the filter, and is drawn through. Since all the air inside the airbox must pass through the filter, adding drain will allow unfiltered air to enter.
    #5
    Hoss Cartright likes this.
  6. Hoss Cartright

    Hoss Cartright Been here awhile

    Joined:
    Oct 23, 2016
    Oddometer:
    594
    Location:
    Earl Park Indiana
    Maybe you just need to add a front breathing lid on top? Some of the years of GG were like that. This is from the 1994/95 GG parts book.

    20180902_220457.jpg
    #6
    jonnyc21 likes this.
  7. Norman Foley

    Norman Foley Devotee of the Husqvarna

    Joined:
    Mar 20, 2004
    Oddometer:
    2,186
    Location:
    New York... The Finger Lakes
    You might want to check with Mike Komer and Nigel Birkett. A lot of these bikes were run in very wet conditions in eastern USA and UK. They might have a solution, from back then?
    #7
    Hoss Cartright likes this.
  8. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Pretty much what I keep reading is to ensure the duct tape effectively seals the airbox to prevent water from entering the sides or back.
    #8
  9. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Have been considering making a lid similar to item 2. As I get motivated to make the tool to mold a carbon fibre lid, I just think should I simply convert to a pod filter inside the airbox.

    This had me post the topic, and I still wonder, is the large volume airbox important on the trials bike like it can be on other motorcycles?
    #9
  10. Huzband

    Huzband Team Dirt

    Joined:
    Oct 4, 2006
    Oddometer:
    7,906
    Location:
    Cowford, Fl.
    I'm not an airflow engineer, but all my years of reading Kevin Cameron tell me no. Many, if not all, superbikes are to some extent designed around the air box. These are clearly not superbike engines, & I've never seen evidence of emphasis being put on the air box.
    #10
  11. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,241
    Location:
    Wichita Mountains SW Oklahoma
    I suggest being pickly with what and how you oil a filter can be more effective than special covers. As in do the following and don't worry about it.

    Maxima FFT liquid oil in the bottle is by far the best filter oil. This stuff is a liquid that includes aggressive evaporants. It goes in a liquid then gasses off to become very sticky and hydrophobic. Gravity will not bias the oil toward the bottom of the filter anywhere near as fast as with many oils.

    Not using an evaporant-type foam filter oil and under oiling has a lot to do with a filter passing grit-filled water.

    I pour FFT on a filter in a gallon ziplock bag and squeeze the filter until I see that all the foam is completly soaked when squeezed, then I fit the filter. The evaporants are so aggressive you will feel them coming through the bag as you work the filter!

    Been doing filters this way on many bikes for decades. My top ends are 'eternal.'

    I do wonder with filters cupped up using adequate FFT if grit water would pass the Hoss sandy water test well intoitge maintenance cycke after the filter starts loading up with dirt? Water will stand in a freshly cleaned filter treated with FFT like in a bowl.
    #11
  12. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    No doubt about quality filter oil. I have noticed the filter does hold water, but it also allows passing the water through the foam. My suspicion is the filter filled enough that is was not a gravity feed, but rather as the engine was running, the suction pulled the water through the foam until adequate airflow was obtained, and the remaining water sat on the oiled foam.

    Essentially the design is good for dry conditions or if you are faithful to always remove and drain the airbox .

    I need to measure the air intake coupler between the airbox and carb, then see if I can find a worthy adapter to install a pod filter onto, within the airbox.
    #12
  13. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Agree. certainly not a very tuned if at all tuned airbox design. However better to ask as these trials bikes sometimes are quirky. Thanks
    #13
  14. jonnyc21

    jonnyc21 Trials Ninja

    Joined:
    Feb 8, 2011
    Oddometer:
    3,169
    Location:
    Boise aria
    It isn’t a trials bike example but the 80’s Honda CX and GL twin engine bikes require re-jetting when going from a standard air box to pod filters without one. So isn’t just a super bike thing to need to deal with changes in airflow when going away from stock.

    This is just a note so you double check things after fitting the pod if not using the stock air box as it could at the very least need a slight re-jet. Heck, double check even if you keep the stock box.

    Good luck! :thumb
    #14
  15. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    8,631
    Location:
    nm
    Most POD type filters went backwards with less air flow. You have to have more surface area to have more flow. 90% of these did not work. (Better) Even a lot of the newer after market filters actually flow less than the paper elements. Just drives me crazy. Trying to improve a stock air box is quite difficult. Silicone and foam in the right places is much more effective. Try reading Scottish Six Day Preparation for idea`s.
    #15
    jonnyc21, North ride and Brewtus like this.
  16. Huzband

    Huzband Team Dirt

    Joined:
    Oct 4, 2006
    Oddometer:
    7,906
    Location:
    Cowford, Fl.
    Much of what you say is true. But difficulty in improving on a trials bike air box? C'mon, the air box is just a work-around of the necessary parts that make a trials bike. I'm not saying a pod filter is an improvement, but I doubt it's a hindrance either.
    #16
  17. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    8,631
    Location:
    nm
    Funny. The shop I worked in invented K&N before it was K&N. Not that I had anything to do with it. Just used them before most knew what or how it worked. Pods on multi cylinder engines were a joke as sold to the masses.
    #17
  18. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    As a followup, via some internet searches I found and read SSDT prep guides for Betas, Gas Gas, and Scorpas. Honestly quite amazed, but also realize the intensity of the event, at how ill prepared the current Betas and Gas Gas bikes are. Granted it is a grueling event and their prep guide is complete, but the certainly advise main mods and preps. Birketts prep guide for the modern Scorpa was very general, but did touch on the same general topics as the other brands, however Birketts had very few bike specific concerns. Possibly this was intended to be more general or maybe not needed.

    As for details specific to the SY250r, there were no remnants of guides if they existed, nothing on Hell Team nor Birketts. RYP has a very good general guide for bike prep overall, yes very good, but I did not see anything SY specific.

    Visiting Trials Central. Pretty easy to find stories of crappy running SY250r that have ingested water and pulled dirt through the filter. Also some have mentioned the pooled water in the bottom of the airbox. Trapped water inside the carb. In some cases dirt lining the rubber airboot, carb bore and more, even inside the float bowl.

    Overall, the easiest solution offered was not to wash the bike or ride in the wet.

    Various homemade attempts to solve the concern involved adding foam weatherstrip to seal partially around the air filter opening, greasing the fender and applying silicone to the airbox followed by fender install, electrical tape.

    Essentially, there is no true solution to resolving the bathtub style foam filter, or stopping any water that accidentally finds its way onto the filter from being pulled through the foam, taking dirt with it, and no means to have a self draining airbox since the entire airbox must remain sealed to prevent entry of dirt.

    Thanks for the input guys, ride safe.
    #18
  19. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Not one to give up, and with no defined plan, I went forward.

    I was very much into the idea of going to the pod style filter. It was hoped I could fabricate and install a short section of curved aluminum tubing to extend the airbox to carb duct very slightly. With airbox removed, and in hand, I spent time assessing if that was viable. Ultimately, primarily on account of limited space, the added tube and pod filter idea was shelved.

    Shifting to building a cover or maybe more correctly called, a “splash guard” of sorts, I fabricated a cover from a small piece of aircraft aluminum. Pretty basic overall, basically flat with one bend. I drilled a hole to allow the cover to share a common fastener with the forward rear fender bolt. Originally, the fender bolt utilized a clip nut. Because this would not allow the cover to sit flat against the aluminum subframe, the clip nut was swapped out for a riveted on platenut.

    On assembly, I installed the fender bolt temporarily to position the new cover. In position, I used strips of duct tape to seal the edges. The tape then kept the position of the cover, until the rear fender and bolt was installed and secured.

    Next will be some riding to validate proper airflow and jetting. Overall, I hope any reduction, if any is small and of no effect. The issue, may be the cover being flat did not follow the rounded profile of the fender, which may or may not alter air entry into the airbox. Overall though, the air opening is almost the same as stock. Plus, I am not a high rpm rider, time will tell.

    If it works, I need to round the corners of the cover and slighly shorten its length, then I will post a photo for your critiques.
    #19
    Junglejeff1 and jonnyc21 like this.
  20. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    299
    Location:
    SoFlo, USA
    Follow up. Air filter was cleaned and oiled, to give a good baseline. Rode the Scorpa to validate the splash guard effect on jetting and how it runs.

    The bike was fired up, warmed up and ridden a bit. From idle to reasonably high rpm it ran well. At wide open throttle, it is running rich with the splash guard installed.

    Took a moment, removed the splash guard, reinstalled the fender and tested again. At wide open throttle, better, but very slighly rich.

    Final test was no fender or splash guard, essentially unrestricted airflow into the filter / airbox. This ran absolutely clean, maybe even a tad lean as the load was not a lot of strain on the engine.

    All the test runs were same time, with same ambient temp, on the same section of yard.

    As a newer rider, and not yet doing those big throttle moves, I will make a jetting change and see how it feels to ride. From past experience jetting bikes, it feels like I need two sizes smaller main jet, just need to see if I got them when I was ordering parts.

    Want to add, with the splash guard installed, and this was never a concern, but there is no intake noise to hear.
    #20
    jonnyc21 likes this.