Dellorto on a '17 125 TXT?

Discussion in 'Trials' started by SammyD, Oct 19, 2020.

  1. SammyD

    SammyD Adventurer

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    Howdy, I just moved from a '14 Raga 300 to a 125 :). Something about me likes small bore engines - how they run smoother, less lumpy, quieter etc. I ride Advanced and haven't competed yet but from what I can tell I don't think it'll be a disadvantage, and bike is really fun to ride. I was always too scared to hold the 300 wide open for a clutch dump but the 125 is making me feel braver. I've done a few, a wow, it really makes the bike fly up obstacles! I had my first taste on a Schoolboy 125 a friend bought for his wife and I fell in love with it.

    Anyway... bike came to me with a Dellorto. Owner put one in at the recommendation of the good folks at Lewisport as he was have a bogging issue with the Keihin that they couldn't fix. I should point out that when I got the bike the air filter was dripping with oil, not sure if that may have played a part.

    Bike had a 50 pilot jet and 118 Main. Does not run as cleanly off the bottom as my friend's Schoolboy with the Keihin. The fuel screw was best at 1.5 turns out, apparently they are supposed to be 3.5 turns out to be optimal. I just put in a 45 and it was better. Any jetting suggestions out there? I'm in San Diego, it's 80 degrees, sea level.

    I noticed with the fuel screw that the more you wind it in (leaner) the revs will eventually start to climb. Do I go out a way, then go in until this starts to happen, and that's the magic spot?
    #1
  2. lineaway

    lineaway Long timer

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    I would try a 40 pilot to bring it closer to stock. It will never run lik
    e your friends.
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  3. motobene

    motobene Motoing for 49 years Supporter

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    A 50 pilot in a Dell'Orto shows jetting savvy for a 125, but may be a touch big, even in a 125. A 40 pilot is considered on the richer side for 250s and 300s, but not necessarily for 125s, or your particular 125. The 45 sounds like it could be righter in your particular bike to get your fuel screw to clean running with 1-1/5 to 2-1/2 turns out (my favored target range).

    Don't forget about the needle clip for fine tuning the low-mid response. If the clip is close to the middle to begin with, I optimize first with jets then fine tune the needle clip to get the best wick-open response from just above idle to the mid-high rpms.

    Now one tack to pursue would be to revert back to the 50 pilot and a more closed fuel screw, but lower needle to clean up the medium-fast slide opening response.

    Fortunately Dell'Ortos on trials multiple jetting iterations are easy and fast. It always takes me about a month to nail the jetting on a bike, however, as I try different things when I think of them, and find out more about a bike while riding in different density altitude and traction conditions.

    When you get the jetting right, the only thing you should have to change is the main jet and idle setting to ride in higher altitudes, and that's convenient on Dell'Ortos because the main jet is in the float bowl bolt.
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  4. SammyD

    SammyD Adventurer

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    Thank you both. I really like the serviceability of this carb, one bolt to drop the float bowl as you say, floats stay in the bowl, and no extra vent tubes to thread back through. I'll try a 40 and will also try the needle with the different sizes. Cheers!
    #4
  5. SammyD

    SammyD Adventurer

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    The 40 pilot really helped, as did taking the pipe off and standing it in a bucket in the sun and having half a liter of think black sludge came out of it.

    My remaining problem is the bike being blubbery on steep climbs with lots of revs. I have to hold her wide open to clear her out first otherwise she feels clogged up and sputters. She has a 115 main in right now. Not sure if should go lower, or if this 'cleaning out' process is something you are just supposed to do regularly on these small bikes?
    #5
  6. jonnyc21

    jonnyc21 Trials Ninja

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    If you get them jetted and adjusted correctly they need little to no cleaning out. I still need a little more adjusting on my daughters 08 Gas Gas 125, but for the most part I don't have to do that at all on it. After I upped the pilot and lowering the needle one position helped a lot with that on her bike a lot. I know the starting (choke) is still to lean and it feels a bit rich in the lower mid range where the needle might help (might need one clip lower than I did?).

    At any rate its way better and she seems to be fine on it so... Good luck.
    #6
  7. Yinzer Moto

    Yinzer Moto Sloppy 300 rider Supporter

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    How much oil are you running in the gas?
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  8. PSchrauber

    PSchrauber Long timer

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    Dellortos are very nice carbs and can be adjusted very well. Indeed there are so many things you can miunt alternatves too that there adjustment is sometimes a challenging.

    To the fuel screw, is it a fuel or an air screw you have? The fuel screw is located between slide and intake, the air screw is located between airfilter and slide.

    (I believe you have a fuel screw)

    The air ir fuel screw should be adjusted to the highest rew that you can gain while adjusting it.

    The fuel or air screw is controlling 0 - 1/8 of throttle movement or gas.

    To the pilot/idle jet, which is too responsible for 0 - 1/4 of throttle 40 sounds good. The main sound big to me.

    In which altitude do you ride and what carb model and duameter do you use,
    too what slide is mounted (there are to some Dell'Ortis different models available with much different cutaways), what needle and what is the position.

    I strongly believe your bike is running far too fat thereor blubbering.

    As a comparison I run my 276cc SWM with a 50 pilot and a 90 main, a 60 slide and a X1 needle with 2nd notch from aboveat around 50m above sea level, this combo is suficient up to 1000m.

    What you should do too is clean the airfilter very well and onky slightly oil him just a thin layer is needed, you should squeeze out all exessive oil by after you have put new oik on the cleaned filter the kned the filter in a plastic bag so the oil is really everywhere.
    Then wrap the filter in kitchen towels and kned out exessive oil, this provides best prorection and best air flow.

    Then change the exhaust dampening material and clean the exhaust, messy but worth it.

    Then check timing.

    To the gas oil mixture I use a mix of 75ml oil to 5l of gas which is 1:66.7 that worked well so far to all bikes when used with high octan fuel with as less bioalcohol as possible. To oil recommend an oil with low burning temperatur.

    Modern triak riding means 50% ideling to 1/4 throtteling around, 30-40% 1/4 - 1/2 throttle and 10 - 20% 1/2 to full throttle.

    To this I believe we have to adjust your carb.
    #8
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  9. motobene

    motobene Motoing for 49 years Supporter

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    Sound advice, PSchaube!

    Only point of disagreement regards filter oiling: "...wrap the filter in kitchen towels and knead out excessive oil, this provides best protection and best air flow."

    Best filtration? Filtration of fine particles that accelerate engine wear is the responsibility of the oil, so minimal is best? I don't agree.

    Best performance? My half century butt dyno testing has found no direct correlation between performance no filter, dusty dry filter, lightly oiled filter, heavily oiled filter, and very dirt loaded filter. This has lead me to the assumption of over capacity of flow relative to our engine displacements.

    Thus I err on the side of protection and advocate for Maxima FFT, soaked and squeezed out once, and getting away from having multiple filters and/or doing frequent swaps/maintenance.

    But that's me. The engineer in me want to find test data, like ISO 5011 results for small motorcycle foam filters with varying amounts of Maxima FFT oil and dust loadings. So far have failed, and it's automotive data that abounds.

    I'm left combining empirical evidence with interpolating relative sensitivities on power to oil loading and dust loading.

    Here's one relative sensitivity, for example, to heavy dust loading on a paper filter at a very high flow rate. I see a flat curve well up into dust loading:

    K&N Capacity Test.JPG

    Here's a fun calculator (non-SI units):
    https://www.ajdesigner.com/phpengine/engine_equations_air_flow_rate.php

    To each his own analities!:beer
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  10. lineaway

    lineaway Long timer

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    We have dust. Fine dust, light dust, heavy dust, dust storms, dust devils and lots of wind. Also we rarely have rain or any kind of moisture. A whole lot of reason to properly keep a filter and intake system well oiled and sealed.
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  11. PSchrauber

    PSchrauber Long timer

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    Nope here I disagree and thst is why:

    Take your lungs also filled with bubbkes these are bubbles too to enhance the area, the area of one lung is as big as a complete football field.

    Why that?

    Because of oxygene transfer, if you smoke your lung bubbles get glued up thus providing less area thus you can get Pneumea or short breathe.

    Collecting oxygene is like collecting dust as bigger the area as better it works.

    To trap the dust you need glue but not too much like tar while smoking instead a thin layer that is provided by an air filter oil with solvents that will make the oil thin and then evaporate,
    Thus you have to kned the filter, once applied you want to empty the filled cavaties thus a wrap of kitchen oil to soak up pressed out oil. That the surface of the filter might then dry is completly OK there are enough surfaces by the bubbles of the foam where fine stuff might be trapped and it is also wise to trap the groove stuff first and the finer stuff later.

    I can get into math if you want but biology and smoker lungs are explaining it much better I think.

    And of course are paper filters nit as good for dirty environments, best filters for dirty environments are centrifugal filters with attached oil sump filters, that what all heavy equipment for landscaping or desert working have, it all about the trap.
    #11
  12. UstaKood

    UstaKood Been here awhile

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    I think ...

    It’s gonna be a long winter.

    :fpalm
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  13. PSchrauber

    PSchrauber Long timer

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    I' m done so far and during winter and now oartly lock down will do enhancememts to the bikes and keep fit if not even try to get even fitter.

    Curious about the data of the Dell'Orto carb to that 125 TXT.
    #13
  14. motobene

    motobene Motoing for 49 years Supporter

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    Someone needs to instrument a test to answer the issue, challenging 'apparent knowledge', yours and mine.

    When I ran an engineering department in a medical company for 13 years, my guys would make assumptions along the lines of "Everyone knows X is the case." I made them confirm through testing and sometimes the result was the opposite of what was assumed.

    You are on the minimally oiled end of the continuum. I'm on the heavier-oiled end. So far no COPD on any of my bikes and none on oxygen. Same for you too. Any differences in resulting wear are impossible to instrument and determine, so to each his own.

    Long winter indeed.
    #14
  15. motobene

    motobene Motoing for 49 years Supporter

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    Indeed! Some of us live in arid places and get heavy dust loadings on filters.

    My dustiest event wasn't in New Mexico, but just a little east, at Sid's wonderful thousands of acres Texas panhandle ranch on the Palo Duro Canyon rim (900 feet of vertical change from his house to the canyon floor). He had put in many roads for access that year. We had a well-attended 2-day event and three long loops of about 8 miles. Lots of soil types, with some areas that just went to powder. By the end of day dust on the loop was in places deep enough for wallow-plowing through. I worried a lower-class rider would injury face plant on one of the long downhill sections.

    No one got hurt. My bike ran great the entire time. I was running jetting for 2,000 feet and the event site was 3,800 feet. No change in power that I noted, even WFO. Monday I did filter maintenance (on the Sherco that means removing the subframe to pressure wash it while the cleaned filter is drying out, and replacing the filter with the subframe off to be able to see it through the air boot). That filter was:yikes ridiculously coated!
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  16. Huzband

    Huzband Team Dirt

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    Evidently we need an air filter oil thread.








    :hide
    #16
  17. lineaway

    lineaway Long timer

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    It`s not Winter yet? Or does this year just suck that much.
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  18. SammyD

    SammyD Adventurer

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    I just found all these newer replies! Thank you!

    Back to my 125...

    I thought I sheered the woodruff key. Bike would start, but refused to rev. Bit the bullet and bought a flywheel puller, my friend fixed the last one.

    Laid the bike on its side to check something in the clutch. After half an hour stood the bike up, gave it one final kick before tear down, lo and behold she started right up and no issues.

    So I have this issue where the bike is occasionally does this. I may fire it up three times a day, two are fine, third it will start and idle but wants to die the second I rev it. I have to lean it over and let fuel drain out and that can fix it. Carb is a year old, floats move fine and they float, level seems right. It’s like the bike sometimes can’t pull enough gas to get the siphon going. I think pilot at a 40 may be small but it runs so smoothly!

    Update: Rode McCain on Sunday. 4000 ft elevation, I ride at home at sea level 80 degrees. 65 degrees at the start. Bike started and ran, blubbed when getting on the main (115). I came in and dropped the needle/ raised clip up one to highest groove. , Bike did the ‘woodruff’ thing again. Went the other way and raised the needle two clips. Ran and rev’d but ran worse. Good lord. Put back to second clip from top and by this point the weather was 15 degrees warmer and ran best it had all day (original setting I started with)...
    #18
  19. jonnyc21

    jonnyc21 Trials Ninja

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    I am in the Boise Idaho aria and at about 3000 ft. My daughters 07 Gas Gas TXT Pro has a Dellorto on it and other than a little hard to start on a cold day it runs well. I think I am running a 42 or 44 pilot and a 105 or 110 main jet, needle clip in the center. (I am not 100% sure on that) It might be a week before I can get to it, I will try and see if I can spare some time to pull the carburetor and double check the jets in it for comparison sake.
    #19
  20. PSchrauber

    PSchrauber Long timer

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    Briggs&Stratton do explain the cleaning and oiling in the same matter and lawn cutter are exposed to very much dirt, see here:
    https://www.briggsandstratton.com/e...-how-to/browse/changing-foam-air-filters.html

    I never had an issue with that procedure, but I had several times issues with too much oil which harmed the foam of the filter, also once with a clogged air filter of a new old acquisition where the previous owner had soaked the filter and too used to dense foam, which resulted in periodical engine failed leading to sooted plugs and also not being powerful at all.

    Another bad experience was to use wrong oil like NoToil green which lead to disintegrated filter foam, corrosion and lumpy gelatinous
    particles on the nozzles and jets of the carb, (It was too over oiled, the bike was a TXR 312).

    We have too dusty trials especially in the Belgian mountains with their distinctive red clay soil, ... so you have your experience I have mine, here is the winter hasn't shown up so far.
    #20