Carb

[yam-a-ha]

Hi all. i just got an xs650se special. 1978 i reckon. the carb is different slightly from others i seen
the air mix screws ure upright on the intake side of the carb,brass screws,also there are two black rubber plugs above the pilot jets
in the inner of the carb, afe these supposed to be here,the reason i ask is i have cleaned the carbs twice, all jets,float heights done
did my valve clearences ,new plugs that spark, im getting petrol to the bowls spark to the plugs but they are dry, seems im not getting fuel to the cylinders,
compression on both cylinders 150psi. anyone throw some light on this.ignition timing is good also.

 

[jpdevol]

Pics would confirm, but it sounds like a description of BS34 carbs found on 1980 and later XS's

 

[gggGary]

Yup sounds like BS34s
The rubber plugs are correct and needed.
The float bowl has an orifice that feeds the choke circuit. I'll bet dollars to donuts that's where your problem is.
I use a piece of sharpened fine safety wire to open it if spraying carb cleaner from the top isn't enough

If it's REALLY plugged I've dug out gunk with a safety wire hook from the bottom.

 

[5twins]

If they are BS34s then the float height spec will differ from the '78 spec, and also be different depending on whether the floats are brass or plastic. What kind are they and what did you set them to? The two different specs (plastic or brass) are in my chart that Gary posted above, and as you can see, they both differ from the '78 spec.

 

[gggGary]

If they are BS34s then the float height spec will differ from the '78 spec, and also be different depending on whether the floats are brass or plastic. What kind are they and what did you set them to? The two different specs (plastic or brass) are in my chart that Gary posted above, and as you can see, they both differ from the '78 spec.

Hey @5twins can you post up your excellent choke orifice pic?

 

[gggGary]

Plastic float setting.

 

[5twins]

The choke jet is pressed in place so can't be removed for cleaning. You have to blow it clear with compressed air. But, as the drawing in Gary's post shows, the area below the jet can get filled with crap and may need to be cleaned out as he's shown.

 

[JJames]

Welcome new menber. If you need info on the bs34, you've come to the right place and heard from some of the best. I found the rubber plugs baffling the first time I encountered them. Wondered if you removed pilot screws as well as washer, spring and o-ring underneath and clean out those passages.

 

[650Skull]

Welcome from Ireland. Determining weather your bike is a 78SE would also mean to determine if it is a Euro spec bike or import

Euro spec Specials 80/8182 (US Custom), were also marketed as SE's.

Post, pics of your bike and all will b reveled by the experts

 

[yam-a-ha]

If they are BS34s then the float height spec will differ from the '78 spec, and also be different depending on whether the floats are brass or plastic. What kind are they and what did you set them to? The two different specs (plastic or brass) are in my chart that Gary posted above, and as you can see, they both differ from the '78 spec.

Thanks. i set to 22mm. brass floats.

 

[yam-a-ha]

View attachment 251170

View attachment 251171

The choke jet is pressed in place so can't be removed for cleaning. You have to blow it clear with compressed air. But, as the drawing in Gary's post shows, the area below the jet can get filled with crap and may need to be cleaned out as he's shown.

my float bowls don't look at all like those. they just have the drain plug hole at the bottom, no passage ways like in the pic. the choke is the pull button type on the left of the carb. i must post pics.

 

[yam-a-ha]

If they are BS34s then the float height spec will differ from the '78 spec, and also be different depending on whether the floats are brass or plastic. What kind are they and what did you set them to? The two different specs (plastic or brass) are in my chart that Gary posted above, and as you can see, they both differ from the '78 spec.

Thanks, i came across a schematics pic of the carbs like mine. it was for the xs650G, seems for japan market??

 

[5twins]

OK, first off, 22mm is wrong for the brass floats, that's the plastic float spec. The brass float spec is 27.3 ± .5mm. Set at 22mm, the floats and fuel level will be way too high, and the bike will probably run rich, maybe leak fuel from the bowls too.

My pics are of other Mikuni carbs but the principal is the same. Your bowls probably look more like the one in the 1st pic in post #3.

 

[jpdevol]

i must post pics.

 

[yam-a-ha]

OK, first off, 22mm is wrong for the brass floats, that's the plastic float spec. The brass float spec is 27.3 ± .5mm. Set at 22mm, the floats and fuel level will be way too high, and the bike will probably run rich, maybe leak fuel from the bowls too.

My pics are of other Mikuni carbs but the principal is the same. Your bowls probably look more like the one in the 1st pic in post #3.

Thanks

 

[650Skull]

Your on a US based site, from a Euro country that had different set up's for there XS's and talking about a Japanese set up when the Japanese had completely different model set up' from the US and Europe. Carb bowls on the early BS34' change between countries/continent' on that specific model, (80G/SG). pecoal models from 78-81/3 from Europe to japan and Oceana and the US all have different renditions of the ame model. 78 Japan got an Alloy spoke wheel model the US got in 79 that Oceania and Europe never got. he U and Japan got an 80 model that looked like the 78/78 model but the US got poke wheel on it and japan got mag wheels.

Pics have been asked for. Any information you have on the Japanese carb semantic, (post the semantic), or link to any variables you have found will help any one who is being asked to help.

PIC'S

 

[gggGary]

This should be your float bowl. Brass float 1980 BS34

 

[5twins]

Well, almost. I think he'll have drain bolts like the BS38 bowls instead of the drain screw your pic shows. Your pic is of an '81 or newer bowl like this .....

This is the '80 bowl with the drain bolt .....

 

[650Skull]

Well, almost. I think he'll have drain bolts like the BS38 bowls instead of the drain screw your pic shows. Your pic is of an '81 or newer bowl like this .....

View attachment 251285

This is the '80 bowl with the drain bolt .....

View attachment 251286

But my 80 bowls, (Oceania 80SG), has bowls that are the same as the first pic.

Keep guessing everyone. Should we run a Sweep??

 

[yam-a-ha]

Your on a US based site, from a Euro country that had different set up's for there XS's and talking about a Japanese set up when the Japanese had completely different model set up' from the US and Europe. Carb bowls on the early BS34' change between countries/continent' on that specific model, (80G/SG). pecoal models from 78-81/3 from Europe to japan and Oceana and the US all have different renditions of the ame model. 78 Japan got an Alloy spoke wheel model the US got in 79 that Oceania and Europe never got. he U and Japan got an 80 model that looked like the 78/78 model but the US got poke wheel on it and japan got mag wheels.

Pics have been asked for. Any information you have on the Japanese carb semantic, (post the semantic), or link to any variables you have found will help any one who is being asked to help.

PIC'S