Should Have Started with a Bigger Pilot Jet
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Thread: Should Have Started with a Bigger Pilot Jet

  1. #1
    Senior Member Welder's Avatar
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    Should Have Started with a Bigger Pilot Jet

    I have two 2015 TWs. Both ran lean as heck new from the factory... backing firing on decel, needing choke for the first mile of riding even after a long warm up period or else any throttle would kill the engine, surging at light load and throttle, rough running rolling off a closed throttle, and common single massive detonation events in warm weather with a warm engine during cranking to start up. My bikes are all stock with the 2015 Teikei carbs. I am close to sea level.

    I tried adjusting the idle mixture screws which helped, but not near enough. The only problem it completely eliminated was the back firing on decel. I found opening the screws beyond a certain point, about 1.5 turns, had no further effect on idle speed, and they were still too lean. I tried running with the screw out 2-3 turns but it seemed to make little difference after about 1.5 turns out.

    I just put in a 34 pilot jet and the bike ran instantly better. Started right up, ran way better when cold, ran better when warmed up. It was 36 F out and raining / frozen raining. I will do some experimenting with the idle air screw when time allows, but for right now I notice the same thing as with the stock pilot jets.... after turning the screw out a certain amount, about 1 turn now with bigger pilot, it seems to have little effect on idle speed.

    BTW I also <previously> tried shimming the needle and bigger mains as that seems a popular thing to do. Running both bikes side by side in warm weather, the totally stock bike ran crisper in the mid to full throttle range, and out ran the rejetted bike. I pulled the shims and went back to the stock main jet.

    Anyhow I will experiment more with screw adjustments when it isn't late, dark and raining. But for now I can see I was wasting my time with everything else until the bigger pilot jet went in. It appears to me that should be the place to start when trying to make the TW run right.
    Last edited by Welder; 03-05-2017 at 08:41 PM.

  2. #2
    Senior Member Tweaker's Avatar
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    I only upped the main jets on my bikes because of the aftermarket exhausts called for it. The shims on the needle may improve throttle response depending on the bike. The bigger pilot jet did get rid of cold bloodedness on my bikes.
    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper Bars one with risers, DG oval pipes. rejetted carbs, 130 main jets, 2 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Aserbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

  3. #3
    Senior Member Welder's Avatar
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    52F and not too wet today. I went with 1 1/8 turn on the 34 pilot (other wise 100% stock) and it starts and runs great! Wish I would have done this 2 years ago.

    I still haven't changed the wife's pilot yet, will do soon. Like mine used to, it CRACKS sometimes on turning over. One big detonation event. I have to think that over time this would bust up the ring lands. Seems crazy the bike is delivered like this.
    littletommy, jtstdub, Ken and 1 others like this.

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  5. #4
    Senior Member Deepseadan's Avatar
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    Quote Originally Posted by Tweaker View Post
    I only upped the main jets on my bikes because of the aftermarket exhausts called for it. The shims on the needle may improve throttle response depending on the bike. The bigger pilot jet did get rid of cold bloodedness on my bikes.
    So I'm heading to chaparral tomorrow to pick up a few things and thought it would be a good time to grab a couple jets. Since we live somewhat close and similar elevations, what did you settle on for your carb jetting (just pilot and main)? My 2016 still has the stock 126 and 31 and I want to richer it up just a bit. I know you went up on the pilot a bit, but how about the main? My tw still has the stock exhaust.


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    Ken likes this.
    Current bikes 2016 KTM 500 EXC, 2016 Yamaha TW 200

  6. #5
    Senior Member Tweaker's Avatar
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    Chaparrall may have to order the jets my dealer didn't stock them. Take the numbers with or call them to order then pick up no shipping charge. You could get a #34 pilot to try and a 128 main. I don't know if you need a 130 main jet with a stock exhaust. Also there is #125 jet maybe for high altitude along with the stock #126. I think it might be good to order an extra bowl gasket too.
    Ken likes this.
    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper Bars one with risers, DG oval pipes. rejetted carbs, 130 main jets, 2 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Aserbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

  7. #6
    Member Roseburg's Avatar
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    Welder.....i just picked up a 2017 tw. So you feel good about going to the 34 pilot and fiddling with the air screw? Im in the pnw too on the wet side and am interested in how things are working out for ya!
    Ken likes this.

  8. #7
    Senior Member Ski Pro 3's Avatar
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    For me, my experience was that the pilot jet increase solved the cold blooded starts needing long choke and warm-up times. The needle shims solved a lag just off idle. To test if shims might help your bike, try this;
    After the bike has been thoroughly warmed up and idle speed set, try turning your throttle very slowly from full closed to 1/8th turn. Listen to the RPM's and see if there's a 'flat' spot in the throttle where RPM's don't increase even as the throttle is turned. The flat spot on my throttle was solved with the shims. I've found no advantage to main jet changes. I ride from sea level to over 8,000' and the larger pilot and 2 shims was all that is needed.

    Keep in mind; these are very general recommendations. EVERY bike is different. I don't know why, but you can't put 3 bikes side-by-side and have any two run the same. I do notice a slight performance increase when running non-alcohol gas. Not easy to find in California but I have found quite a few stations that sell it in Oregon.
    Ken, Tweaker and cowboyjeff like this.
    The bear slayer!

  9. #8
    Member Roseburg's Avatar
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    I just checked JetsRus ....they have a 32.5 and then a jump to 35 size.. Do you think 32.5 is enough to cure a cold blooded bike? I dont want it blubbery with a 35.
    Thanks

  10. #9
    Senior Member elime's Avatar
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    I have the old style carburetor and went one size leaner on the main jet and the bike ran great! Spark plug was porcelain was white even after many many miles. Screw was out 3 1/2 turns but I don't think it made much difference after 2 to 2 1/2 turns. I live basically at sea level. And yes, every carburetor is different in how it makes the bike run.

    I don't know about the main jets and pilot jets in the newer carburetors but if they are the same as the older carburetors this is a heck of a deal if you don't mind waiting. I have been using them and they seem to work just fine.

    https://www.aliexpress.com/item/12-m...608.0.0.iCMGef

    https://www.aliexpress.com/item/12-p...608.0.0.iCMGef
    Last edited by elime; 05-16-2017 at 07:37 AM.
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  11. #10
    Senior Member Tweaker's Avatar
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    Roseburg some aftermarket jets are not the same as stock jets. I recomend getting Yamaha jets. Yamaha offers a #31stock and #34 pilot jet. $8-10 a jet. Elime has used the alibaba jets and the price is right you just have to wait longer. The pilot jet gets clogged so easy that having spare pilot jets is a good idea in what ever size you end up using.
    Twin 2014 TW200's made side by side on the assembly line, Moose rear racks, Protaper Bars one with risers, DG oval pipes. rejetted carbs, 130 main jets, 2 -.020 shims on the needles and @ 2 1/2 turns on the pilot screw, #34 pilot jets, Aserbis hand guards, Shinko 241 front tires, modified Krator foot pegs, 14-55t sprockets, Ricochet skid plates and 90 degree fuel filters.

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