I have a box full of Mikuni 38mm carb parts and don't know how to match up parts for a complete carb set. I can get everything right except for the float bowls. For instance, the "E" and "H" bowls have different ways to flow fuel through the pilot jets. How can you know which bowl works with which body? I seem to run way too rich at idle with "E" bowls installed. Should the "H" or any other bowl make a difference?
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Too many carbs and too little know-how!!
- Thread starter igya
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The "H" bowl fits 74-75 model carbs. The tell on these carbs is the choke system: only one carb has a choke valve, and a hose from it feeds enriched mixture to the other side. This bowl takes BS30/96 type pilot jets (metering hole in barb end of jet).
The "E" bowls are for 78-79 carbs. The tell here, in addition to the stamp, is the absence of a vent pipe in the float bowl; the float chamber vents through two holes in the carb body that exit through the intake bell. Use type VM22/210 pilot jets (metering hole in thread end of jet).
The "E" bowls are for 78-79 carbs. The tell here, in addition to the stamp, is the absence of a vent pipe in the float bowl; the float chamber vents through two holes in the carb body that exit through the intake bell. Use type VM22/210 pilot jets (metering hole in thread end of jet).
Thanks for the kind words, Bill. I'm writing a carburetor manual for the Yamaha 650 Society to be printed in the Society News the old-fashioned way, in serial form. The first bit of it, which includes the carb ID section, was just finished today, so everything was at my fingertips. The manual will run 25-30 pages, and $25 for a year's dues will buy the whole series and more. Anyone interested can go to 650 Central and follow the link to the Society site.
Read the carb guide. The bowl differences are explained there, also what type bowl goes with what year carb set. You've noticed the difference in the 2 bowl types. What you saw was the air passages. Air is delivered differently to the 2 pilot jet types. You must use the correct type of pilot with the correct bowl that was designed for it. Even though the 2 pilot types will physically interchange, they won't flow right if used in the wrong bowl.
That's 10-4, thanks! That Mr. Griz is the MAN!! Shoot, I'm lovin' these ol' 650s more and more. I've had 8, still have 4, wish I had another! Can't get enough of these things. I've got to redo my '78 ring job because it used 1-1/2 qts of oil in 400 miles. I'm pretty sure I forgot to stagger the gaps on the oil ring rails. The top of both pistons are wet with oil, even though smoke isn't visible out the exhaust. Bummer!! Oh well, just another day shot. Hum-m-m-m....I wonder if I could get away with using the base and head gaskets again with a light coat of Copper-Coat sealer. My wallet says "yes", my brain says "NO" you idiot!
Just for yucks, here are all the bowl stamps, year-by-year.
70-71: Plain boss, no marking. 72-73: A. 74-75: H. 76-77: O. 78-79: E. 80-83: A (marked on bottom of choke reservoir casting, does not interchange with BS38 A bowls).
igya, I feel your pain.
70-71: Plain boss, no marking. 72-73: A. 74-75: H. 76-77: O. 78-79: E. 80-83: A (marked on bottom of choke reservoir casting, does not interchange with BS38 A bowls).
igya, I feel your pain.
I have a set of what I was told are '72 carbs. They have one choke on the left carb only, plastic nipples on the float bowl overflows, but the bowls are stamped "F"? It is the older bowl style that's all cut out around the main jet tower.
Wow, that's a weird one!. All the 72-73 carb sets I've seen had two choke valves, and that bowl stamp isn't anything I recognize. Do the carb tops have Solex markings? Are the venturi floors raised or round?
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Yes, tops are marked "Solex" and they have the raised floors. According to the exploded parts diagrams, '72-'73 carbs had only one choke, just like the '74-'75 sets .....
http://www.boats.net/parts/search/Yamaha/Motorcycle/1972/XS2/CARBURETOR (XS2) (TX650)/parts.html
http://www.boats.net/parts/search/Yamaha/Motorcycle/1972/XS2/CARBURETOR (XS2) (TX650)/parts.html
Right you are! That one trips my memory up every time--the 2-choke setup with the flat strap actuator got dropped after 71. My mind's eye keeps wanting to see it on everything with a Solex top, but it ain't so. BS38's, Solex stamps, ramped venturis,1 choke feeding both carbs--they pretty much have to be 72-73 XS650 carbs.
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