28mm carb swap to 35mm? Worth it?

Discussion specific to KDX models not sold in the USA
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Tokyotim
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Posts: 40
Joined: 10:42 pm Aug 26 2023
Country: Japan

28mm carb swap to 35mm? Worth it?

Post by Tokyotim »

User @kdxdazz mentioned jetting the 28mm carb will be a real pain when I change pipe etc so I am wondering should I alleviate this issue early and swap to a carb everyone has experience with? Are there a lot of small parts to hunt down for the swap? I am about to place a large order of parts from the USA so just trying to gather it all in bulk. Will it make my life easier in the future to do this swap and get it out of the way
kdxdazz
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Joined: 07:51 am Dec 28 2017
Country: thailand
Location: Thailand

Re: 28mm carb swap to 35mm? Worth it?

Post by kdxdazz »

short answer is absolutely not, long answer is you have slightly misunderstood what i said, the 28mm carb is no more difficult to jet than any other carb its just that you won't be able to ask for jetting advice on here, if you swap to a 35mm carb it also doesn't mean the jetting advice on here will be correct as you are in a different country with a different enviroment,granted japan probably has a more similar environment to the US than thailand does to the US, as an example with the jetting advice i was given on here my bike wouldn't even idle it was so rich becuase of the heat,humidity and air density near the equator

you already have the most user friendly carb that ever came out on a dirtbike and your plan is to use it as commuter to the places to ride right? you will also lose your oil pump feature, you will lose the smooth torque of the smaller carb, if it was me this is what i would do, order your fmf gnarly pipe, have it fitted up and see how it runs, if it feels a little lean you can change the pilot jet and/or main jet to suit its just you won't have the correct needle, you can order the correct needle but you will need to work out the factory needle code and then go one step richer on the straight diameter and possibly the taper, if all this sounds complicated its because it absolutely is as a beginner thats why i recommended to not change things.
another option if the bike feels lean is make sure to run non ethanol fuel as this burns much richer

the guy that previously owned my kdx220sr tried converting it to a large carb and made such a mess of it he gave up and sold it to me now i inhertited his mess lol, what i wouldn't give to have the small carb and oil pump
1999 KDX220SR (KDX220-B5)
Tokyotim
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Posts: 40
Joined: 10:42 pm Aug 26 2023
Country: Japan

Re: 28mm carb swap to 35mm? Worth it?

Post by Tokyotim »

Ok thank you sir I absolutely will not change the carb and just try to have a mechanic here help me with the getting once my pipe/reeds arrive
Tokyotim
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Posts: 40
Joined: 10:42 pm Aug 26 2023
Country: Japan

Re: 28mm carb swap to 35mm? Worth it?

Post by Tokyotim »

Do you happen to know if Jeff Fredette is still running his website? I have called and emailed all week with no reply, and his website would not let me check out with items when I press the checkout button nothing happened. Now today when I go to the website, I just see a giant error message and it won’t load the website at all
Tokyotim
Member
Posts: 40
Joined: 10:42 pm Aug 26 2023
Country: Japan

Re: 28mm carb swap to 35mm? Worth it?

Post by Tokyotim »

kdxdazz wrote: 08:30 pm Nov 08 2023 short answer is absolutely not, long answer is you have slightly misunderstood what i said, the 28mm carb is no more difficult to jet than any other carb its just that you won't be able to ask for jetting advice on here, if you swap to a 35mm carb it also doesn't mean the jetting advice on here will be correct as you are in a different country with a different enviroment,granted japan probably has a more similar environment to the US than thailand does to the US, as an example with the jetting advice i was given on here my bike wouldn't even idle it was so rich becuase of the heat,humidity and air density near the equator

you already have the most user friendly carb that ever came out on a dirtbike and your plan is to use it as commuter to the places to ride right? you will also lose your oil pump feature, you will lose the smooth torque of the smaller carb, if it was me this is what i would do, order your fmf gnarly pipe, have it fitted up and see how it runs, if it feels a little lean you can change the pilot jet and/or main jet to suit its just you won't have the correct needle, you can order the correct needle but you will need to work out the factory needle code and then go one step richer on the straight diameter and possibly the taper, if all this sounds complicated its because it absolutely is as a beginner thats why i recommended to not change things.
another option if the bike feels lean is make sure to run non ethanol fuel as this burns much richer

the guy that previously owned my kdx220sr tried converting it to a large carb and made such a mess of it he gave up and sold it to me now i inhertited his mess lol, what i wouldn't give to have the small carb and oil pump
JDjetting told me to order this kit for the 28mm carb I will give it a shot https://jdjetting.com/product/jdy018-yamaha-yz85-19-23/
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