XS2 carb question

T

tmikeyb

XS650 Addict
Messages
130
Reaction score
105
Points
43
Location
47mb49ab2?
I hooked up a temporary fuel tank to my XS2 project, preparing for an initial startup of a bike that's been sitting for who knows how long. I am completely unfamiliar with these carburetors, so I'm looking for a little info. As soon as I open the petcock, fuel runs out of a tube on each carburetor, which I assume is the overflow tube. I assume that either the valve in the carbs are stuck open, or the floats are stuck in a lower position, or the valve seats have some crap in them keeping the valve from seating. I tried shaking the bike a little, and some light tapping on the bowls with a light hammer. Neither of these changed anything. I guess I need to pull the carbs and clean and inspect. Is there anything else I should try short of removing them?
 
In these photos, some of the hoses are different colors, but you can see the layout. There is a u shaped hose that connects the two carburetors to balance fuel levels, the clear hoses are vent tubes, and on the bottom of the bowls you see small plastic hose barbs, that is your fuel bowl overflow ( if your floats are stuck, that’s where you will see fuel running out ) hope these help.
IMG_1577.jpeg
IMG_6727.jpeg
IMG_7841.jpeg
 
tmikeyb said:
I hooked up a temporary fuel tank to my XS2 project, preparing for an initial startup of a bike that's been sitting for who knows how long. I am completely unfamiliar with these carburetors, so I'm looking for a little info. As soon as I open the petcock, fuel runs out of a tube on each carburetor, which I assume is the overflow tube. I assume that either the valve in the carbs are stuck open, or the floats are stuck in a lower position, or the valve seats have some crap in them keeping the valve from seating. I tried shaking the bike a little, and some light tapping on the bowls with a light hammer. Neither of these changed anything. I guess I need to pull the carbs and clean and inspect. Is there anything else I should try short of removing them?
Click to expand...
For me personally, a most basic initial prep prior to trying to fire an engine that has been sitting would be a disassembly and clean of carbs. God knows what you may find lurking in there!
 
In this particular picture, the clear tubes that are slightly above the fuel inlet fittings are the tubes on my bike that have fuel pouring from them.
1721319734963.png
 
Yeah, there should not be gas coming from those tubes. They are just vent tubes, I’m trying to remember the internal, passageways of the BS38’s, I’m having trouble remembering exactly where those lines vent to.
atom4488 said:
For me personally, a most basic initial prep prior to trying to fire an engine that has been sitting would be a disassembly and clean of carbs. God knows what you may find lurking in there!
Click to expand...

He’s right, they really need to be cleaned and sorted. There really is no substitute for getting in there and seeing how it all works to help you understand your carburetors. I also strongly suggest you make use of the tech section, there is a ton of necessary information in there.

https://www.xs650.com/threads/carbs-carburetors.43/

The more you learn and the more you get. “ hands on “ the easier it gets.
Good luck to you 😉
 
Last edited:
tmikeyb said:
OK, I have a set of Mike's carb kits here for my carbs anyway, so I'll go ahead and pull the carbs and go thru them. I'm not at all familiar with them, but I have worked on many other carbs over the years, so I dont anticipate any problem.
Click to expand...
The general consensus here is that most, if not all XS carb kits suck. They use Chinese knockoff brass and usually don't include the correct parts. You'd be better off in the long run getting genuine Mikuni brass.

At the least though, be sure and compare the old against the new bits and make sure they're the correct part number.
 
tmikeyb said:
In this particular picture, the clear tubes that are slightly above the fuel inlet fittings are the tubes on my bike that have fuel pouring from them. View attachment 331227
Click to expand...
Fuel coming out the clear tubes is almost incomprehensible.

IMG_6727 (1).jpeg
You should get fuel coming out of the white nylon overflow elbows or out of the emulsion tube (needle jet, above) long before. Both of those would have to be completely clogged, on both carbs, which is almost incomprehensible.
 
Jim said:
The general consensus here is that most, if not all XS carb kits suck. They use Chinese knockoff brass and usually don't include the correct parts. You'd be better off in the long run getting genuine Mikuni brass.

At the least though, be sure and compare the old against the new bits and make sure they're the correct part number.
Click to expand...
Thanks for that info. I had no idea. Where are some good places to buy genuine Mikuni parts and / or kits?
 
Well, that is where it was coming from. I checked several times just to be sure. It was dripping from the right side carb, and literally pouring from the left side.
 

Similar threads

M
Right carb crossover issue
Replies
8
Views
469
Mervmaster
M
T
XS2 carb questions
Replies
2
Views
234
tmikeyb
T
T
carb install, XS2
Replies
0
Views
125
tmikeyb
T
T
attempt to start after long term storage
Replies
2
Views
358
tmikeyb
T
H
91 octane or 87 octane for 1972 XS2 with Mikuni carb conversion??
Replies
5
Views
795
Signal
Signal
Back
Top