Plastic cap on air mix screw ???? BS-38's

[timbeck]

A friend brought what appear to be 78-79 BS-38 carbs over to try them on my XS as a test. He had spent some time cleaning them and adjusting the floats etc. The bike fired up pretty quick with a couple of backfires when going from high idle to half throttle. I went to adjust the air mix screw and found that it was covered with a white plastic cap. there was a slot that you could adjust perhaps a half a turn. I have never seen these caps before on 78-79 BS-38's . Have you ????

tim

 

[gggGary]

Yeah that's how they came, easily, and near universally removed. They got serious about it when the BS34's came out, the EPA death march had started.

 

[timbeck]

Gary---Thanks for the reply. I have had perhaps six sets of 78-79 carbs and the caps must have all been removed before they fell into my hands. So they can just be pulled or snapped off ??

tim

 

[gggGary]

Yep if you are careful you can remove, adjust, replace. I got one I removed from a Honda Reflex wandering around on my bench right now.

 

[5twins]

Yes, you can just pry them off. I wouldn't replace them, they'll just hamper adjustments in the future. Since they have never been off, that means the mix screws have never been removed. They've never had their sealing o-rings inspected and replaced if need be. The '78-'79 BS38s are the only BS38 carb set used on the 650 that had an o-ring on the mix screw. Through some trial and error, we've figured out the original size used to be 1.3mm x 2.5mm .....