Not true , ALL XT / TT 350, ALL XT/TT 550 , 600, 660 up to 2003 all have TK double carbs , and are all very alike.

The "new" 660 engien in the XTR and XTX 660 from 2004-today and also used in the XTZ from 2008-today are single trothle body injection

As for jets and carbs the 2kf model XT 600 has a slitgly different, bigger tk 27 , the same that is used in the 660 tenere from 92-99 and the TT600 , also
the later TT 600 R also has a different one with a diferent jets

you could try ato get a more recent carb from a european model and maybe be easier to get jets for that

also some models in europe were power limited to local licence limitaitons , theses had different jetting also , if you can hget these you could just drill them out

also check the swiss spec bikes that had different carb setiting (generally leaner)

The Y26PV found on approximately 1991 & newer XT600s uses the same style primary carburetor main jets & pilot jets as the older Y27PV carbs found on approximately 1989 & older XT600s. The jet orifice sizes may change from year to year or model to model or country to country but the actual jet style does not change for the primary main or pilot jets. The secondary main jets are not the same style between the two carbs though. The 1989 & older Y27PV secondary jets are no longer available. The newer Y26PV secondary main jets are still available thru Yamaha & a company called Kedo out of Germany. The selection of these Y26PV secondary main jets sold new is limited & some are very expensive. Because the selection is so limited & costly swapping to these newer TK YDIS carbs is not really that much of an advantage. The chart of jets I put together on page one of this thread shows the Y26PV secondary main jets Yamaha sells #100, #106 & #125. Kedo sells #110 #120 #125 very high prices. If another source for these secondary jets for the Y26PV could be found or if a person hunted up obsolete Yamaha secondary jets then maybe it may make more sense.

Just to be sure everyone reading this is on the same page I would also like to note that the Teikei model numbers of these carbs is confusing if you are unaware of these carb's specifications. The 1989 & older Y27PV is a 27mm carburetor & the 1991-2003 Y26PV carburetor is a 28mm carburetor. Why the second generation of the carb wasn't call a Y28PV I do not know. At any rate a Y27PV is a 27mm carb & a Y26PV is a 28mm carb.

One other thing I would like to note is that in America since the 1990-1995 XT600e was still sold & had a Y26PV carburetor it is not necessary to buy such a carb from Europe per say as they are often available in America used. Ebay has them for sale sometimes as do motorcycle salvage yards. Europe over all probably has more for sale at any given time though the shipping can be cost prohibitive for them to be bought by someone in the US.

Here is a link to a chart showing specifications on XT600s from 1984 - 2003 including when the change in carb models occurred. Wartungsdaten XT600-Modelle

Here is a link to 1984 XT600 specs showing a 27mm carb Yamaha XT600

Here is a link to 1989 XT600 specs showing a 27mm carb Yamaha XT 600

Here is a link to 1990 XT600e specs showing a 28mm carb Y26PV Motorcycle Specs

Here is a link to 2003 XT600e specs showing a 28mm carb Y26PV Yamaha XT 600E

Here is a link to Kedo's page KEDO - Performance Products

Hey check this out. I did some research on main jets that can fit in the Teikei YDIS carbs. I found that the Keihin 393 series of main jets will fit as main jets. Both jets are 5mm x .8 thread. The jet numbering system is a little different for the Keihin jets. Its just that the jet #s themselves don't swap straight over between brands. Teikei jet #s are in mm and the Keihins are a little smaller per jet #. The shape & design effects flow probably too between brands. However once tuned in with Keihin jets the jet numbering will work as normal, smaller # is leaner, bigger # is richer ect. The initial tune will just take a little guess work.

Converting over to Keihin will take a shot in the dark to get started on the tune. I would suggest getting Keihin jet #s larger then what you would need in a Teikei jet # & see how the bike runs to begin to tune with Keihin. Keihins seem to run smaller then Teikei on the jet orifice comparison charts I have seen. So basically pick some Keihin jets a little larger then the Teikei jet already in the carb to get started on the jet brand transition. Then let that bike tell you which way to go either richer or leaner in Keihin jet # and BAM! The Teikei carb will tune as normal with the Keihin jet #s.

What would be nice about converting to Keihin is that pretty much any motorcycle shop will have the jets for around $5. They are available all over the place on line too. I picked one up at a motorcycle accessories store in town today for $5 & it sure beat hunting down & getting ripped off for old OEM Yamaha jets on FleaBay. Below are pictures of the Keihin jet I got today compared to the OEM Yamaha jet as well as pics of the two different jets mounted in a TK YDIS.

Keihin 393 series main jet specifications & for sale Mick Hone - Factorypro KEIHIN 393 SERIES MAIN JET size 210 (JET FTC-393F-210)

More Keihin 393 series main jet specifications & for sale http://www.factorypro.com/products/Jets ... %20buy.htm

Jets R Us Keihin 393 series main jet specifications & for sale http://www.jetsrus.com/a_jets_by_carbur ... 28-xxx.htm

Here are the pics of the OEM Yamaha/Teikei Main Jet vs the Keihin 393 Main Jet I picked up today.

http://s29.postimg.org/rsobgpn6f/oem_vs_keihin.jpg

http://s17.postimg.org/hbt5g6k0t/tk_keihin_ydis.jpg

The worst part is I need the pilot jet and needles, main jets are good (correct mixture) on mine, I'm just un-godly rich at idle.