Identifying '76-'77 BS38's vs '78-79 BS38's

Rexxis

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Just by looking, how does a guy tell whether he has a set of '76-'77 BS38's or a set of '78-79 BS38's? Are there differences in the carb bodies or is it just in the jets?
 
The '76-'77 carb set and the '78-'79 carb set are as different as night and day. '78 was a "big change" year for the BS38s. They got that new style slide that retains the needle with a snap ring and all different jetting. Overflow tube in the float bowl was eliminated along with it's outlet nipple on the bowl bottom. External vents for the float bowl area were moved to inside around the bell mouth.

Yep, I've definitely got a set from '77-'78 then. You can see, in this pic of my carbs, the float bowl vents, overflow outlet nipple, and, yes, I have the overflow tubes in my float bowls.
56fbbdd2.jpg


In 5twins chart here, it says the '77-'78 carbs use an older style pilot, a BS30/96 style pilot.
CarbSpecsReducedSize.jpg


But here, in this pic from Mikes, it says those type of pilots were only used up to '75 and then again starting '80 with the 34's. Mike's lists the VM22/210 as the only style of pilot for the '77-'78 BS38's. What's up with that?

Ive been running the 22/210 style pilots in my carbs b/c I thought my carbs were from '78-'79. Could this cause a problem? The 22/210 pilots thread into my carbs just fine..

Mikuni_Jets.gif
 
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Your '76-'77 carbs use the VM22/210 pilots. Note the asterisk next to the pilot jet number in the chart and the subsequent reference to it in the "Misc." column. It is also mentioned in the notes below the chart. It was difficult to lay out all the changes in chart form and I did the best I could. Sorry for the confusion. The size should also be a "tell" for you. All pilots in the 20s are VM22/210 type, all in the 40s are BS30/96 type.
 
At a glance 76' & 77' BS-38's are the "584" type with vent outlets external to the carburetors.

The 78' & 79' "2FO" type vented to the front intake side of the carbs internal to the carburetors.

The most obvious distinguishing appearance differences are the existence of external vent tubes with tubing of the 584 versus the additional vent tube outlet holes on the 2FO intake face.
 

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