Prepping For Nationals - Bike, Mind, & Kit

Discussion in 'Trials' started by motobene, Mar 22, 2018.

  1. motobene

    motobene Motoing for 46 years

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    National events are a bigger deal to me and worthy if some additional bike and other prep.

    Thinking about such things as tires, for example, with this ongoing thread:

    http://advrider.com/index.php?threads/michelin-versus-dunlop.1287224/page-6#post-34612455

    My 2017 Sherco 250 Factory with modified Ohlins shock has proven to be a precision dream tool, so I have been reluctant to make changes. But I've had a little time to pick away at a few experiments, which I will document further here.

    I would love to hear how you all work up to nationals as well.
    #1
  2. motobene

    motobene Motoing for 46 years

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    One quick experiment, which has proven successful is fitting aluminum S3 aftermarket air and idle screws to my PWK28 Keihin carburetor.

    I normally avoid this sort of bling. I trust the profile of the OE screw tips more than after market. The S3 fuel screws tips for Dell'Orto were long made with the wrong shape, for example, and would mess up low-speed metering. And generally speaking, after the long and patient process if fine tuning jetting on an individual bike, I rarely had to adjust most bikes much.

    These aftermarket aluminum screws are old hat for most of you, but this being my first set in 35 years I thought I'd review them. I find myself needing an easier way to fiddle with the low-speed mixture on my most recent rides.

    On the last two 250 Sherco bikes, I've found the air screw setting is more sensitive than on previous Keihin bikes.

    My '17, for example, has a window width between bogging and blubbering that is only around 1/2 turn. I think part of that is the '17 has been quirky to jet. I've had to adopt goofy compromise settings to get the best performance. Lower float setting, smaller than usual low speed jet, and the needle all the way up. Also the odd need to be close to bogging when warming up to run spot on when warmed up. It's what this particular bike 'asked for', so that's what I gave it.

    On this bike, I have to fiddle once with the air screw at the start of every event day, to stay spot on the jetting. Once right it stays rock solid for the day.

    The stock brass air screw requires a skinny screwdriver. I'd find myself forgetting to bring one and begging around to do my morning tweak. It finally sunk in that I could instead fit aftermarket bling.

    Here's what the two bits look like in situ:

    IMG_20180322_090633.jpg
    Between all that Sherco stuff around the fuel cock AND my left side brake master cylinder, there's not much access for the red bits.

    Results so far?

    The air screw works well. Same turns out as the stock screw, so they got the taper and step at the tip very close to stock.

    The idle screw isn't so useful, but I rarely touch it anyway. It's on that sharp down angle, leaving little room for my dog-chew-toy-size fingers.
    It screws in a gazillion turns and really mashes the spring, making it tight and hard to turn. I had to use some small needle nose pliers to turn it. Maybe it will free up over time?

    I greased both threads of course, for sealing and lubrication.

    One reason there are so many turns on the idle screw, and I think why Keihin uses a plastic screw that fits a little tight, is to prevent a hunting idle rpm due to air leaks (I had that happen when I made a custom idle screw - from an M5 Phillips case screw I think it was - for a 300 GasGas). That one sure turned easily, but rpm would vary just enough to be mental.

    Will give longer term feedback as it develops.
    #2
  3. lineaway

    lineaway Long timer

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    Roswell will be a long loop. So co2 for air will be in my bag of tricks. Dog turds and a few small tools. Colorado will be a short loop So I will be using a smaller kit gor that event. Remember once out on the loop you cannot back track.
    #3
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  4. heffergm

    heffergm Long timer

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    No issue with the quick adjust idle screw on mine. Although I can't recall if I'm using the Jitsie screw or the S3... I think it's a Jitsie, because I'm not running their air screw, which I found didn't equate in turns out to the stock screw. I can't go without the quick adjust idle screw, as the bike gets hot at events I'm constantly playing with the idle. I've had it do the same with the stock idle screw, so I don't really think there's an air leak issue with the aftermarket screw. I did originally grease it putting it in, but then got worried about the grease migrating into the carb, so I don't bother now.

    If you find the S3 air screw is same as the stock I may try one...
    #4
  5. motobene

    motobene Motoing for 46 years

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    Thanks for the backtrack warning. Didn't know that rule.

    I will buy a CO2 setup, if I can find something simple and slick. Just fir airing up though. Work on tires on a loop means a mess of tools.

    I normally carry zero tools in events, having believed instead in great bike prep before leaving for an event. I remember guys from the lots if stopping and hopping era that always carried an extensive array of tools in a fanny pack. They'd light off in a cacaphony of kitchen cutlery noises when they started hopping around. The ridiculousness of the display helped push me to minimalism in tools.
    #5
  6. motobene

    motobene Motoing for 46 years

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    My Sherco thankfully has a very stable idle. I run it a little high for stall protection, but it's not 'nervously' high in neutral.

    On the ~2,000 feet of vertical of the Sipapu loop. I figure out on loop one where to set the idle at the high point of the loop. That makes idle a little high at the bottom of the loop, but a higher idle is vastly preferred to a too-low idle producing a sloppy/tired clutch stall five.

    Thankfully the GasGas-type clutch I my newer Sherco drags less than those on my former GasGas bikes (my 2014 Replica excepted). I don't have to the unloaded idle as high on the Sherco to compensate for clutch drag.
    #6
  7. heffergm

    heffergm Long timer

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    Yeah, I do get a decent bit of drag... weirdly not enough to move the bike a lot, but enough to bring the idle down quite a bit so that the difference between in gear and in neutral is rather big.
    #7
  8. wheelieman14

    wheelieman14 Adventurer

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    I usually set air screw for conditions in the morning and don't mess with idle screw. Not having much for elevation changes at my events in the North East, I'm fine with a slightly faster idle to help prevent stalling and happy with profile of Beta Remote cable adjuster air screw, that lets me adjust from open right side of carb. The Jitsie A/S was a shorter taper than the stock PWK Keihin Air screw on my GasGas, so I just carried a small flat blade screwdriver for that bike and used the stock air screw. I do however, check air pressure after each loop back in pits, since the pressure tends to rise with temperatures.
    #8
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  9. 2whlrcr

    2whlrcr gooligan

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    [​IMG]
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  10. lineaway

    lineaway Long timer

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    Yep, Better pull that thing apart lube and antisieze and a little loktite here and ttere. Check the ring gap too.
    #10
  11. motobene

    motobene Motoing for 46 years

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    What thing? The TRS?
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  12. Norman Foley

    Norman Foley Devotee of the Husqvarna

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    Your Sherco isn't a "Freshie" anymore....
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  13. lineaway

    lineaway Long timer

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    Yeah I was ribbing the as new guy.
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  14. motobene

    motobene Motoing for 46 years

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    I've been mentally preparing. I kept thinking I need to get some more rigorous aerobic exercise as well, but doggone this getting older stuff! Ranch, construction, and cows put rest higher up in the priority list.

    The older body is so SLOW to recover from a string of high activity days. The over night full recovery, wake up fresh feeling of youth is a very distant memory!

    Planning and finger crossing is essential to not arriving at events being already depleted.
    #14
  15. 2whlrcr

    2whlrcr gooligan

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    I've been busy trying to track down my coolant leak, changing oils to get a clutch feel to my liking, changing gearing, looking at the gas all over engine cases, wondering if I should lower the floats, etc...
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  16. motobene

    motobene Motoing for 46 years

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    I lowered my Keihin floats a while back from 20 to 23mm as seen on my float bowl). The division character means 'to' in Yurp. That change helped clean up the bottom end and got rid of jostle enrichment.
    #16
  17. lineaway

    lineaway Long timer

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    New sprockets, Wheel bearings, tires and chains today. And a little Team Bling. Both sides of the sprocket for that warm FIM rule feeling.

    Attached Files:

    #17
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  18. motobene

    motobene Motoing for 46 years

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    For me, a new chain and an experiment adding a ? brand half link to the D.I.D chain to work with the oddball Sherco swing arm length.

    Oh and a new front sprocket. The dinky 9-tooth front sprockets on the new-clutch Sherco are required due to the faster primary, and they wear faster than the usual 10-tooth sprocket.

    I did find some water in the wheel bearings. It's only been a year since they were packed full of grease. I think what did it was I drove a long way through rain to get to one event. A 'fat' rain seems to be able to eventually get into anything.

    Not to worry. I just pop the seal off, add oil to the grease, then blow it all out with air pressure. Re pack fully and voila! New bearings again.
    #18
  19. motobene

    motobene Motoing for 46 years

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    Now I've started into more practice rides. Had a great one yesterday!
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  20. motobene

    motobene Motoing for 46 years

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    So this morning I'm still in bed at 9 and enjoying this forum. Lots if nationals prep has been done, as seen in other posts, but I'm beat up in a bid to keep wife happy.

    The garden is now surrounded by t posts with cattle panels (field fence and chicken wire to follow), and gate posts welded up and set in concrete.

    A touch of tennis elbow and general malaise later....

    Note again to self: Do not play out the body before nationals!

    Tomorrow is all day with cattle, so I need to get my ass out of bed and continue organizing things. The last thing I want is the usual mad scramble at the end.
    #20
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