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Discussion Starter #1 (Edited)
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.
 

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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.
 

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Discussion Starter #3
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.
 

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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.
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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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.
 

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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!
 

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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.
 

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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
 

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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-main-jet-9-99-and-free-shipping-Off-road-motorcycle-carburetor-engine-TK-JOG/32261782626.html?spm=2114.13010608.0.0.iCMGef

https://www.aliexpress.com/item/12-pilot-jet-10-9-free-shipping-Off-road-motorcycle-YBR-carburetor-vice-injectors-TK/32261696051.html?spm=2114.13010608.0.0.iCMGef
 

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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.
 

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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!
A while back I installed a #34 pilot and opened the fuel screw (you called it an air screw) to 2 1/2 turns out on my 2016 tw. I'm really glad I did, the bike runs much better and you can really tell the difference. I highly recommend this to everyone, these new tw's come pretty lean. I've ridden up to 6,600 ft so far and it still runs perfect. Like tweaker says, make sure you buy the #34 Yamaha pilot though.
 

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Thanks everyone!! My Tdub isnt quite as cold blooded as welders. Popping on decel, long warm up times. I want it to run optimally though. Thankfully we have non-ethanol gas around.(premium at $3.75). I have been running the bowl dry after every outing and keep a splash of Seafoam or Lucas in the fuel.
No official bike dealer in my town, so its online or a 1 hour drive.
 

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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
I'd go larger on the jet. After all, you have a screw to set the fuel flow. Maybe instead of 1 1/2 to 2 turns out, you'll only need 1 to 1 1/2 turns out, but the flow will be the same. At worst, all the larger jet will do is use slightly more fuel and affect MPG. It won't blubber from too rich unless you misadjust the screw.
 

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Alright then...34 is the one to try first. Chaparral had them? I have used them before. Must be nice to be able to walk into the real store. Looks huge!

chaparral doesn't stock them but can order one in for you. From what I've been told by it's supposedly the largest cycle sports store/dealer in the world. But no way to confirm that.


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Discussion Starter #17
Do the 2017 models have the same carbs (TK) as the previous bikes? I thought I read that the new TWs are coming equipped with Mikunis? If so the jet sizing is almost certainly different.

On my wife's 2015 TW I have the idle fuel screw turned out about 2.5 turns with the stock jet and it runs pretty well, though still requiring a pretty long warm up time (5-10 miles) before it really runs its best, but it still has the gnarly detonation KNOCK!!! on start up sometimes. I know this can't be good for the engine. So I will put a 34 in it too.
 

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at near sea level I found the 34 pilot to rich although the bike starts great it's flubbery and I went back to the stock pilot just making sure it's a clean stock pilot I believe they are the perfect size if clean

If I didn't mind cracking the throttle to clear the rich mixture the 34 was ok but that got annoying

btw I buy pilots buy the bag I think I still have like 50 of those 34's ordered from XT250's parts list on Partzilla

btw I picked up a 2015 from Brothers Yamaha in Bremerton WA with 3.7 miles on it and the pilot was already dirty exhibiting most of the issues the op mentioned
 
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