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Discussion Starter #1
I know there is a carb tuning post from qwerty and I have read it.

I have TONS of dirt bikes and have modified lots of carbs...pumpers, vacuum, etc.

Usually the kits have you drilling out a cap that covers the mixer screw, drilling a hole in the slide...most kits come with an assortment of jets (pilot and main), a needle, shims, and some come with a spring...like the Dynojet kit.

Keep in mind that I don't actually have my TW yet...just put a deposit on it. I just want to have things ready when it arrives.

I know you can buy individual jets, but by the time you purchase individual jets and pay shipping, you might as well get the kit and have the assortment.

I usually purchase the JD kits, but I see they don't make one for the TW. Dynojet does though...and of course Procycle sells something that they call a kit, but there's not much to theirs.

Just curious as to what most of you guys are doing.

Thanks,
Russ
 

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I'd skip the kits.

As said just yank the cap that covers the idle mix screw and set it to about 2.5 turns (stock is like 1.5).
Stock pilot jet is fine. 31 is stock, some people put a 34 in, IMO unnecessary. The stock jet can deliver plenty of fuel with the mix screw further open.
Swap the main with a #130 (stock is 126)
Send it

That's for a typical, under 3k elevation bike. Higher altitudes often find the stock jetting is close to ideal. You can drill out the CV slide or cut the spring down if you want, ehh, I'm not really convinced either has much effect. This is a mild mannered motor, it's never going to have the "snap" response of a modern 250 motocross bike or anything. Some people also mess around with shimming the needle, again, I'm not convinced this has any performance merit and hits MPG/range.

Feel free to add a slip on down the road, really no changes will be needed. I even did the Wiseco piston and stage 1 cam, and still the jetting seemed pretty much bang on. Just minor adjustment to the idle mix.

It's a Teikei carb, which uses the name numbering system as Keihin (so if you have a Keihin #130 hanging around thats perfectly fine). Dynojet and Mikuni jets are not interchangeable (number for number at least although physically they fit fine).
 

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I can recommend just getting the jet numbers form the tech stickies and if you have a dealer nearby ordering by phone and picking up no shipping that way. Depends on which carb you have later carb has 31 pilot stock and 34 will let you start without choke but use more gas as will shimming as mentioned. I noticed a big improvement in throttle response with shimmering, but I had an after market pipe. Also I needed a bigger main jet with that. I never tried drilling the slide.
 

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If it aint broke why bother even fixing it? TWs come from the factory with just about ideal jetting for most regions and certainly right for PA. Just set the pilot screw after removing the plug and go ride your bike. I bet you could not see a damn bit of difference by changing jets, shimming the needle and disturbing what the bike originally came with. Keep in mind, for every action there is an equal and opposite reaction. A stock TW carb that is adjusted properly is about as good as you can get. I have found that running the TW on 91 octane real gas with no ethanol is about as good as it gets.

GaryL
 

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Discussion Starter #6
Thanks guys. I guess I'm just so used to having bikes that just absolutely need carb work the minute you get them home because they come so choked off from the factory. They have ALL been lean...especially the Harleys. Then there's all the WR's that had to be de-smogged, jetted, and a heavier pumper spring. The list goes on. At the recommendation of so many of you, I'll just start with yanking the cap off the mixture screw only and go from there!

Thanks,
Russ
 

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Thanks guys. I guess I'm just so used to having bikes that just absolutely need carb work the minute you get them home because they come so choked off from the factory. They have ALL been lean...especially the Harleys. Then there's all the WR's that had to be de-smogged, jetted, and a heavier pumper spring. The list goes on. At the recommendation of so many of you, I'll just start with yanking the cap off the mixture screw only and go from there!

Thanks,
Russ
Good plan Russ! There is just so much juice you can squeeze out of this 12 HP single lung monster and unless you plan on riding in the clouds at well over 5,000 feet I think Yamaha has the carb about as good as it will get. Lean factory setting are merely to get them to meet emission standards and the plug over the adjustment screw is probably mandated by the Gov.
Sit around some evening reading the thousands of discussion about those who tried to upgrade the exhausts, re-jet and shim the carbs and done all sorts of other tweaking only to still have a 12 HP Mule. We did used to have a member here who claimed he had his TW running at 90 MPH with gobs of power to spare but none of us ever saw the bike and I think he rode it into a phase shift and onto another universe.

GaryL
 

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No doubt Elime you have had plenty of experience with these carbs and the link is probably just what the OP was seeking.

I guess the question now goes to the basics I was attempting to point out. On a brand new 2018 TW with a brand new carb that is hopefully running right once he adjusts the pilot screw, Would you even bother messing with changing jets and screwing around with the inner carb stuff? My personal opinion is I would not touch it until it started developing an issue.

GaryL
 

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No doubt Elime you have had plenty of experience with these carbs and the link is probably just what the OP was seeking.

I guess the question now goes to the basics I was attempting to point out. On a brand new 2018 TW with a brand new carb that is hopefully running right once he adjusts the pilot screw, Would you even bother messing with changing jets and screwing around with the inner carb stuff? My personal opinion is I would not touch it until it started developing an issue.

GaryL

I agree with you wholeheartedly !!! First adjust the idle mixture screw and if things are good then you are basically done.
 

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on my 2019 (california model) i installed a TTR header and a FMF can on it and it would lean pop i have since bought 2 OEM main jets for it a 128 and 130 on amazon $11 each shipped i ordered shims for the needle for $16 shipped on amazon (still waiting for the shims) i deleted the vapor canister (yes i know it wont make a bit of difference but i didnt like how it looks) BTW in all my research i have read a few times that California models came with a different main jet then the 49 state models but my research said different and today i verified it when i pulled the float bowl off and it was a 126 jet not a 128 as people have said i also removed the cap blocking the mixture screw and set it at 2 turns out as it was about 1.5 turns out from the factory this weekend i will get it running again and we will see if i can get it running the way it should be at my elevation.. hopefully it will solve the cold start issues also
 

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on my 2019 (california model) i installed a TTR header and a FMF can on it and it would lean pop i have since bought 2 OEM main jets for it a 128 and 130 on amazon $11 each shipped i ordered shims for the needle for $16 shipped on amazon (still waiting for the shims) i deleted the vapor canister (yes i know it wont make a bit of difference but i didnt like how it looks) BTW in all my research i have read a few times that California models came with a different main jet then the 49 state models but my research said different and today i verified it when i pulled the float bowl off and it was a 126 jet not a 128 as people have said i also removed the cap blocking the mixture screw and set it at 2 turns out as it was about 1.5 turns out from the factory this weekend i will get it running again and we will see if i can get it running the way it should be at my elevation.. hopefully it will solve the cold start issues also
All just "Farkles" IMHO! After you get it all dialed in and running right with the new FMF, correct jetting and adjusted to the optimum performance you will still have a TW capable of going from zero to 65 in about 3 minutes and a standard completely stock well tuned TW will keep right up with you. As long as the changes you make make you happy I say go for it but we have seen all of this here many times and never yet heard of much improvement in the end.

GaryL
 

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Sorry GaryL but I strongly (and respectfully) disagree with you. You know people improve all sorts of things on the TW from the foot pegs to the tail lights but you seem think the engine is perfect with no room for improvement? My new 2017 was running very lean with engine surging and paint burned of the header pipe after about 200 miles! I started out with about 2 1/2 turns out on the mixture screw - definitely helped. Followed up with 3 shims on the needle and a 130 main jet - big improvement in performance and I live in the same region as the OP. I and many others enjoy tinkering with our bikes trying to get a little bit more out of them. If you don't, that's fine.

I know I'm not going to convince you but i wanted to share my experience with those who are interested.
 

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Discussion Starter #14
All good information. So I think that, IF I DO decide that the bike might benefit from richer jetting, I'm certainly not going to order just one jet or a couple of shims. Doing it that way, you run into the problem that Wildhorse1966 ran into...order...wait...try...repeat. I think I'd rather just get a kit with a jet assortment, needle, etc. and then try one thing at a time so you know what changed what. This way, you have everything at your disposal. And speaking of disposal...yeah, that's what you usually do with most parts of a jet kit, because unless you move around in extreme altitudes or possibly temperatures, the remainder of the kit just sits in the container once you find out what works.
 

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For those interested, here are the shims I used:

https://www.mcmaster.com/99040a310

Be careful removing the needle - that little spring can fly and can be impossible to find! I now keep an extra one just in case. Yamaha part # 5LB-14275-00

And here is the main jet from Partzilla:

288-14343-65-00 JET,MAIN #130 (Yamaha Motor) $4.73
 

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Sorry GaryL but I strongly (and respectfully) disagree with you. You know people improve all sorts of things on the TW from the foot pegs to the tail lights but you seem think the engine is perfect with no room for improvement? My new 2017 was running very lean with engine surging and paint burned of the header pipe after about 200 miles! I started out with about 2 1/2 turns out on the mixture screw - definitely helped. Followed up with 3 shims on the needle and a 130 main jet - big improvement in performance and I live in the same region as the OP. I and many others enjoy tinkering with our bikes trying to get a little bit more out of them. If you don't, that's fine.

I know I'm not going to convince you but i wanted to share my experience with those who are interested.
It is not at all a matter of convincing me or even disagreeing with what I posted. I've seen and rode with a few bikes with the exact same upgrades as you and many other did. Their bikes were running way better with their upgrades according to them and I did not disagree with them or any of the upgrades they did at what ever expense and time invested. My bike was still totally stock in every way except for a Cycle rack and wide foot pegs. From my house it is straight up hill for about a mile and we usually take off full throttle to the top. where it flattens out for another mile. I stay right with them to the top every time and only on the flat section can they pull away but not by much, maybe just 2 MPH more top speed. I just know for my own personal preferences I would never spend a dime to gain another 2 MPH when I find the top speed of around 65 is not much fun to run at any way. I could hit 70 on my way back home down the mile long hill but for what? I do not disagree with anyone attempting to milk every last drop of juice out of their TWs, it is your bike, your money and your time so go for it and if it makes you happy then all is good. I have already done just about all of these changes on one or another of the 7 TW's I have owned. My 1991 first TW with a new OEM carb ran perfect and the 2006 one I had was a tad faster on a flat straight but again, maybe a mile or two per hour faster. With different jetting and the shim deal I did notice the throttle was a little more responsive but the bike was not any faster and I hit the reserve about 10 miles sooner than with stock jetting and no shims. Sprocket changes did the most in my opinion but where you gain on one end you lose on the other. Road style tires also help if the road is where you do most of your riding.
Matador has the right idea if he wants to go that way once he gets his new bike. One change at a time so you can determine if what you did helps.
As far as tinkering with my bikes, there are not too many here who have me on that. I have sold 4 or 5 of my TWs to members right here and not one of them left here if it was not running great and most left with all sorts of "Farkles".

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I'm not sure why anyone would suggest correctly jetting the bike is not a good idea. Especially since it's a pretty cheap proposition on the TW if you just buy a main jet, pilot jet and shim the needle. I'd have to go back and see what I paid for the 2 jets and a couple washers for shims, but it wasn't much.

This is not subjective. These bikes are very lean from the factory. Getting the air/fuel ratio right not only makes the bike more enjoyable to ride but it's easier on the bike as well. These TWs get flogged hard because of their lack of power. Constantly running them hard at air/fuel ratios that are probably 15:1 is a longevity concern.

I will agree that it's not some huge power gain. I doubt the peak power increases more than maybe 1/4 HP, if that. It just makes the bike start and ride so much nicer. I'm very sensitive to driveability/rideability issues. And I think in stock form, near sea level, the stock bike runs poorly with surging, hesitating, etc. Once properly jetted it starts and runs wonderfully.
 

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Well Doc, I am not sure why anyone would suggest the engineers and technicians at Yamaha don't have the TW carb correctly jetted to begin with. I do agree they come to the US leaned out just so they can pass the emissions standards in some states. That is a very simple fix that requires a simple adjustment of the external pilot screw. I will not disagree with you in that you feel the internal changes you made are satisfactory to you. Here at 1400 feet above sea level I was able to cure the hard starting, surging and hesitating by setting the pilot at between 2- 2 1/2 turns out. Once I found the sweet spot the bikes runs perfect. We have lots of members who enjoy doing all sorts of tweaking and lots of others who do not. I say go for it if you enjoy it or just adjust the pilot screw if you are not interested in removing the carb and changing the jets and needle settings. I also always say never fix anything that is not already broken when a simple adjustment can do the trick. YMMV.

GaryL
 

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Well Doc, I am not sure why anyone would suggest the engineers and technicians at Yamaha don't have the TW carb correctly jetted to begin with.
GaryL
Maybe for the same reason that anyone would suggest the engineers and technicians at Yamaha didn't seem to get the seat, suspension, footpegs, gas tank, gearing, headlight, handlebars, or front tire correct to begin with either. But darn, they were spot on with the jetting;)
 
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