Rebuilding BS34 - Carb Passage Plugs black goo

[DTs]

I got a 2nd set of carbs for my 81 XS650 Bobber.
The carbs have been sitting a while, slides are stuck, I am slowly carefully taking them apart.
The passage plugs are just black goo, is that from 'reg unleaded' gas or ?
Going to replace gaskets, clean passages, check jets, etc.
I imagine I should replace shaft seals while got them apart ?
I am running Uni Pods and straight pipes w/ 6" baffle inserts.
Any recommended jet combo for this setup for a starting point.

 

[jpdevol]

Personally, I'd forego the throttle shaft seals until proven needed.

The slides could use some PB Blaster and gentle heat from heat gun/ hairdryer

I'm guessing ethanol and age on the pilot jet plugs

I like to err a little rich to start, so with stock US Needle/needle jet combo:
45 pilot, 142 Main with one spare either direction on the pilot and two spare leaner, one richer on the main

 

[5twins]

For the stuck slides, the important thing is the heat (but not too hot). You don't even need a penetrating oil like PB Blaster, something mild like WD40 will do, easier on the rubber diaphragms too.

JP's jetting tips look good but don't forget about the air jet. With it you can fine tune the idle circuit. It doesn't have as big an effect as changing a pilot jet size so can be used to achieve richness levels in between pilot sizes. For instance, if one size up (to a #45) isn't rich enough but two up (to a #47.5) is too rich, you can get a richness level in between the two by running the 45 and reducing the air jet a size or two.

 

[DTs]

Ok, I got them disassembled, the slides were mostly being held in place by the varnish on needle in the Emulsion tube.
This is what I have currently, i have a set of 140 Mains (I pulled 135's out of it) mains, the Pilot Jets are 45,
and the other (are these the 'Air' jets?) jets are marked 135.
Once thoroughly cleaned, I will reassemble with these jets, while I order add'l jets thinking: ( 42.5 & 47.5 Pilots) , (137.5, 142.5, & 145 Mains)
What size Air(?) jets should I get, and is there a recommended vendor y'all get jets from ?

 

[5twins]

Yes, the 135's are the air jets. I would recommend getting 132.5's and 130's. They are actually a main jet, same as the type used in the BS38's, just used to flow air in this case .....

 

[Jim]

and is there a recommended vendor y'all get jets from ?

https://www.jetsrus.com/index.html

http://www.nichecycle.com/ncs/

 

[Vincenthdfan]

Ok, I got them disassembled, the slides were mostly being held in place by the varnish on needle in the Emulsion tube.
This is what I have currently, i have a set of 140 Mains (I pulled 135's out of it) mains, the Pilot Jets are 45,
and the other (are these the 'Air' jets?) jets are marked 135.
Once thoroughly cleaned, I will reassemble with these jets, while I order add'l jets thinking: ( 42.5 & 47.5 Pilots) , (137.5, 142.5, & 145 Mains)
What size Air(?) jets should I get, and is there a recommended vendor y'all get jets from ?

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Acetone will make quick work of cleaning up that black, congealed fuel.

I've had a couple of dirt bike plastic fuel tanks that had that black/brown goo in them from non-ethanol fuel drying in them.

Nothing and I mean nothing solvent wise would touch that stuff except acetone....it dissolved it all immediately.

 

[jpdevol]

I don't know if your needle jet and needle were (are) gummed or otherwise needing replacement (perhaps the needle jet should be removed and cleaned), but I found that the Non-US 51X11 needle and 336 Y-0 needle jet run much better than the fixed stock US needle/NJ. If you decide to go that route, the pilot and main will need leaned some vs what was suggested above (still in the range discussed).

 

[DTs]

Thx jp, they def were gummed up, I removed them and cleaned them of all gum/varnish. soaked them in acetone overnight, used my dandy pin poker set to ensure all hole were clear, as far as the needle itself goes iirc it is a MikeXS Dyno tune needle with the clip set in the 3rd from top (1 see 2 slot above the clip).
But was able to get it all cleaned up. Pretty sure I still have the original needle I took out of it (years ago), if I need to go back.

 

[jpdevol]

Yep, that appears to be the Dyna Tune (?) needle and the original NJ. I've actually had that set-up run well too with pods and straight pipes. IIRC it was used with 145 main and 45 pilot.

L to R: Dyna, Stock (5HX12), 51X11

 

[DTs]

Great, when I get the new jets, I should be fairly close, and have the options on hand to dial it in.

 

[Paul Sutton]

Sorry for the intrusion, but is a 45 jet 0.45mm or do Mikuni numbers refer to the time for a set volume of fuel to pass?

Thank you.

 

[Jim]

Sorry for the intrusion, but is a 45 jet 0.45mm or do Mikuni numbers refer to the time for a set volume of fuel to pass?

Thank you.

Fuel volume.