77'BS38's with push in main nozzle??

[ChopperRobb]

Hey, it's been a really long time since ive been here but...
anywho, ive been reading all the carb literature and whatnot and still need some questions answered, if anyone can...
I have a set of early 1977 BS38's...i am of the understanding that they had the screw in main nozzle (that the needle goes through before it gets to the main jet)...mine has the push-in kind with the o-ring...can someone help me out here? id much appreciate it...i mainly need to know the proper rebuild kit for the carbs and to make sure i get the right main, pilot, needle, etc for the carbs i have.
robb

 

[650Skull]

76-77 Carbs main nozzle is a push in.

Z8-Z6 Type

Pic by 5T

 

[5twins]

All the BS38 650 carbs use a push-in needle jet sealed with an o-ring. Not sure where your "understanding" came from. There are no suitable rebuild kits for your carbs. They all contain incorrect parts. Half the stuff in there may be correct and work, if you're lucky. It's best just to buy the parts you need individually.

 

[ChopperRobb]

thanks fellas...my understanding is not as great as yours...my bad, man, but i appreciate your help. i figured i need the main 122.5 (and maybe one lower and one higher), the pilot is a 27.5 (i think, but the ones in them now are 25...and maybe one higher for tuning also), clean and blowout all the passages, set bowl height, new gaskets, new hoses and clamps and button em' up. also have the needle set on ring 3 (i think?)....ive only had the motor bored to the 4th oversize, stock cam, rephased goodies, open pipes, and uni air filters....thinking of getting some of those JBM carb holders (if they work as they say)...

 

[5twins]

Here's a chart I made up showing the stock 650 carb specs. If you study it, you'll notice your '77 carbs came with the smallest main used in any of the sets. While 1 or 2 up on the mains may work on some of the other sets for mods like yours, I think you will need a bit more for your carb set .....

I would suggest starting with mains in the low 130s (130 or 132.5), one up on the pilots (to a 27.5), and with the needles leaned one step (slot #2 from the top). I ran a '77 carb set on my bike for a while. I have the UNI pods and a freer flowing Commando exhaust. My final jetting was one up on the pilots (27.5), 4 up on the mains (132.5), and the needles leaned a step. Your open pipes could flow even more and might require an even bigger main.

 

[ChopperRobb]

Thanx 5twins!. yeah, ive read and re-read (and will again when it comes time for tuning and setup) your carb guide and remember seeing that the 77' had the smallest jets. Thanks for the advice on a good starting point baseline. im excited to finally get this thing on the road soon.

 

[justifiedman]

I have a 1975 XS, everything is stock. I am rebuilding the carbs. I removed the Needle Jet (aka Main Nozzle, I think) and found the o-rings to be in bad shape. I acquired the Chemical-Resistant Viton Fluoroelastomer O-Ring from McMaster-Carr 1 mm Wide, 4 mm ID, from and having difficulty getting the Main nozzle to seat (getting the o-rig to compress enough to slide in. I have cleaned the groove thoroughly, used 0000 steel wool in its home and red grease on the o-rings prior to insertion. I have pushed, twisted and lightly tapped. Should I lightly press them in in my vice? Thanks for your advice.

 

[5twins]

The o-ring groove on your Z-6 needle jet is very close to the shoulder that stops the jet from pushing in. It's pretty common for the o-ring not to want to slip into the hole. I would lube it up real good and temporarily install the float bowl. Let it sit overnight. When you mount the float bowl, it pushes the needle jet in fully and holds it there. Hopefully, after sitting overnight with pressure on it, the o-ring will have worked it's way into the hole and seated. And even if it doesn't, I'd assembly the carbs anyway and not worry about it, because it will seat into the hole eventually.

 

[justifiedman]

Understand. I'll let you know. And thanks!