Mikuni BST40 slide guide

KTM 640LC4 with under 20K miles (32,187 km) (claimed). The depressions in the bottom corners/concentric to the bore (normally found in the area bounded by the red circles) as well as the four circular depressions are worn completely away. The plastic is worn completely through adjacent to the bore at 10 and 2 o'clock (when viewed in the installed position). Maximum wear measures 0.085" (2.16 mm), which works out to .0042"/1K miles (.07mm/1K km) (!). Emulsion tube wear ensues rapidly when the slide guide has worn beyond ~0.010" (0.25 mm). This carburetor had drilled slide lift holes, which accelerate the wear pattern.

end view

new

slide, used

slide, new

emulsion tubes, new and used

jet needles, new and used

New BST40 slide guides can be purchased here.

Applications list:

Aprilia Moto 6.5 '95-'02
Cagiva Canyon 600 '96-'97
Cagiva Canyon 500 '97-'07
Husqvarna SM610S '03-'04
KTM 400 LC4-E '01
KTM 400 LS-E/mil '04-'05
KTM 400SXC '00
KTM 625SXC '03 (USA only)
KTM 640 Duke II '00-'07
KTM 640LC4 '98-'99 & '02
KTM 640LC4 Adventure R '99-'07
KTM 640LC4-E '00-'01
KTM 640LC4-E/mil '98
KTM 640LC4 Enduro '03-'05
KTM 640LC4 Supermoto '01-'05
KTM 640LS-E/mil '00
Suzuki SG350 Goose '91-'99
Suzuki DR650 '90-'16
Suzuki GSX-R750RK '89
Suzuki GSX-R1100 '91-'98 (non-USA)

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