Sold / Found / Inactive - Keihin PWK 32mm carbs

[scott s]

I have a couple of Keihin PWK carbs that would be a good start for a budget build. One is missing the float (available for about $12). You would need a throttle cable and air filters; possibly manifolds, depending on your set up. They both have the choke knob on the same side.
How does $50 plus shipping sound? OBO

 

[scott s]

Bump.
Found a set of pods that fit, too. I'll include those.

 

[JonW]

What would be the ideal application for these carbs as far as Yamaha XS650s are concerned?

 

[scott s]

Do you mean jetting?
I have no idea.

 

[JonW]

Do you mean jetting?
I have no idea.

No, I mean what particular years, would these 32mm carbs be suitable for, as far as the XS650s are concerned? When XS Performance sold these particular carburetors, they must have been specified for a particular application. What was the application?

 

[scott s]

Withdrawn from sale.

 

[JesseeS]

No, I mean what particular years, would these 32mm carbs be suitable for, as far as the XS650s are concerned? When XS Performance sold these particular carburetors, they must have been specified for a particular application. What was the application?

FWIW you can just buy these carbs anywhere. He didn’t say these were from xs performance in particular. That said, they will work with any xs650 given they are jetted correctly and you have the boots for them, the year of the motor does not matter

 

[JonW]

FWIW you can just buy these carbs anywhere. He didn’t say these were from xs performance in particular. That said, they will work with any xs650 given they are jetted correctly and you have the boots for them, the year of the motor does not matter

Thanks. The reason I mentioned XS Performance is that XS Performance is engraved on the carb bodies. That being said, my '71 specifies 38mm carbs and my '80 specifies 34mm carbs. But, if I can use these 32's, I'm all for it.

 

[JesseeS]

Thanks. The reason I mentioned XS Performance is that XS Performance is engraved on the carb bodies. That being said, my '71 specifies 38mm carbs and my '80 specifies 34mm carbs. But, if I can use these 32's, I'm all for it.

Well I’m blind as hell because I didn’t even see that lol. Those are the carbs they came with, but you can swap 38s for 34s and vise versa. They don’t need to stay that way. As far as running the 32 I don’t know much on that. But grizld and 5twins are the ultra pros on anything carbs. I’d inquire with them

 

[bosco659]

I have new carb to head rubber adaptors if anyone needs them.

 

[Team Junk]

Thanks. The reason I mentioned XS Performance is that XS Performance is engraved on the carb bodies. That being said, my '71 specifies 38mm carbs and my '80 specifies 34mm carbs. But, if I can use these 32's, I'm all for it.

32,34,38

Carb throat bore is like mega pixels in camera. A 40 megapixel cell phone camera makes very different images than my 36 megapixel full frame camera..

There are a lot more variables in carb design than throat diameter that affect how much flow the carb can provide.

 

[JonW]

32,34,38

Carb throat bore is like mega pixels in camera. A 40 megapixel cell phone camera makes very different images than my 36 megapixel full frame camera..

There are a lot more variables in carb design than throat diameter that affect how much flow the carb can provide.

Undoubtedly so. This particular set is no longer for sale but looks like some research is in order. Thanks.

 

[grizld1]

I didn't want to post anything negative on a member's sale thread, but since it's inactive now and since I've been asked, here's my advice. Before you even think about those PWK knockoffs, read mrriggs' fine thread in which he details just what needs to be done to make those things viable. A fast search will take you right to it. It's a long step by step account, with no bias. IMO the PWK knockoffs are junk, but don't take my word for it. Read what an expert tuner wrote and draw your own conclusions.

As far as venturi size is concerned, a 32 mm. open throat carburetor has more unobstructed area than a 34 mm. vacuum diaphragm carburetor with the venturi obstructed by the throttle plate and shaft. A 34 mm. open throat carburetor has as much unobstructed venturi area as a 38 mm. vacuum diaphragm carb and maybe a little more. A carb that's too big for the motor will make for unruly behavior at low rpm. A carb that's too small won't let the motor breathe as well as it should. But for the street, the sweet spot is pretty large; guys make too much of a fuss over a couple of millimeters of venturi.

For a stock XS650 motor, a 32 mm. open throat carb is a good choice, and the cheapest viable open throat carb that I know of is the Mikuni VM32. I don't know why it isn't more popular. The VM34 is the most common choice. It's widely used on 750 short track and TT race motors. 36 mm open throat carbs are a decent choice for performance modified big bore street bikes and for racing on faster tracks. Fast track race setups use carbs as large as 38 mm., but on street bikes they'll be touchy at low speeds--not much fun in traffic. On my cammed and ported 700 motor I'm currently using Mikuni 33 mm. 4-stroke flat slide pumpers. They're smooth as silk down low. Up high they move the machine with 17/32 gearing to 118 mph at 7K rpm in 5th, with throttle left. I haven't run the motor out all the way with them; too old and nervous, my bike has gotten faster than I am. Fuel mileage runs in the high 50's/gallon on 91 octane straight gasoline, mid 50's on premium 10% ethanol.

 

[JesseeS]

I didn't want to post anything negative on a member's sale thread, but since it's inactive now and since I've been asked, here's my advice. Before you even think about those PWK knockoffs, read mrriggs' fine thread in which he details just what needs to be done to make those things viable. A fast search will take you right to it. It's a long step by step account, with no bias. IMO the PWK knockoffs are junk, but don't take my word for it. Read what an expert tuner wrote and draw your own conclusions.

As far as venturi size is concerned, a 32 mm. open throat carburetor has more unobstructed area than a 34 mm. vacuum diaphragm carburetor with the venturi obstructed by the throttle plate and shaft. A 34 mm. open throat carburetor has as much unobstructed venturi area as a 38 mm. vacuum diaphragm carb and maybe a little more. A carb that's too big for the motor will make for unruly behavior at low rpm. A carb that's too small won't let the motor breathe as well as it should. But for the street, the sweet spot is pretty large; guys make too much of a fuss over a couple of millimeters of venturi.

For a stock XS650 motor, a 32 mm. open throat carb is a good choice, and the cheapest viable open throat carb that I know of is the Mikuni VM32. I don't know why it isn't more popular. The VM34 is the most common choice. It's widely used on 750 short track and TT race motors. 36 mm open throat carbs are a decent choice for performance modified big bore street bikes and for racing on faster tracks. Fast track race setups use carbs as large as 38 mm., but on street bikes they'll be touchy at low speeds--not much fun in traffic. On my cammed and ported 700 motor I'm currently using Mikuni 33 mm. 4-stroke flat slide pumpers. They're smooth as silk down low. Up high they move the machine with 17/32 gearing to 118 mph at 7K rpm in 5th, with throttle left. I haven't run the motor out all the way with them; too old and nervous, my bike has gotten faster than I am. Fuel mileage runs in the high 50's/gallon on 91 octane straight gasoline, mid 50's on premium 10% ethanol.

I’d love to hear more about these carbs. Do you have a write up or mind a PM?

 

[grizld1]

I'll take some pics and send them to you in a PM, but these carbs are pure unobtainium. I bought two sets cheap years ago on fleabay just for the hell of it. One set was a bank of 4, the other a bank of 2, and neither the sellers nor the techs at Sudco could tell me what machines they had been configured for. Neither set was configured for 120 mm. centers, so I had to mod a throttle shaft, choke actuator, and bracket. They're the same design group as the current TM33/8012 pumpers, but with differences in the bodies and air horns. It would probably be more trouble than it's worth to bank two TM33/8012 pumpers. You'd have to fabricate a throttle shaft, machine a hole one side of the right hand carbie to let the throttle shaft pass through (line boring highly recommended), and figure out a way to tie the choke actuators together. If you want flat slide pumpers you'd probably be money ahead to order a TM34/B120 kit from Topham Mikuni in Germany or from one of the British vendors. (Mikuni America doesn't import them. May their bean counters rot in Hell.) The kits have gotten fine reviews from a couple of our members; you might send member arcticXS a PM. One of our British members bought the kit as well, can't recall who off hand. The only touchy part is carb boots. The TM34/B120 has the same 40 mm. spigot OD as the VM34. The OE BS34 has a 42 mm. spigot OD. It's been claimed that the sealing ring in the BS34 boot won't line up with the groove in the VM34 spigot. I've tested that claim and it just ain't so; the VM carbs snap right into place. If you remove the OE clamp and replace it with a quality hose clamp, the OE BS34 boot will draw down and seal on any 40 mm. Mikuni spigot. I used those boots for a couple of seasons with my 33 mm. pumpers, which also have 40 mm. spigots, before I switched to a pair of extended aluminum mounts from 650 Central. Not much seat of the pants performance difference, but I had to fabricate spacers and cut a second pair of gaskets with the boots to let the carbs clear the valve covers, so the extended mounts present fewer opportunities for vacuum leaks.

I'll try to get pics to you tomorrow.

 

[JesseeS]

I'll take some pics and send them to you in a PM, but these carbs are pure unobtainium. I bought two sets cheap years ago on fleabay just for the hell of it. One set was a bank of 4, the other a bank of 2, and neither the sellers nor the techs at Sudco could tell me what machines they had been configured for. Neither set was configured for 120 mm. centers, so I had to mod a throttle shaft, choke actuator, and bracket. They're the same design group as the current TM33/8012 pumpers, but with differences in the bodies and air horns. It would probably be more trouble than it's worth to bank two TM33/8012 pumpers. You'd have to fabricate a throttle shaft, machine a hole one side of the right hand carbie to let the throttle shaft pass through (line boring highly recommended), and figure out a way to tie the choke actuators together. If you want flat slide pumpers you'd probably be money ahead to order a TM34/B120 kit from Topham Mikuni in Germany or from one of the British vendors. (Mikuni America doesn't import them. May their bean counters rot in Hell.) The kits have gotten fine reviews from a couple of our members; you might send member arcticXS a PM. One of our British members bought the kit as well, can't recall who off hand. The only touchy part is carb boots. The TM34/B120 has the same 40 mm. spigot OD as the VM34. The OE BS34 has a 42 mm. spigot OD. It's been claimed that the sealing ring in the BS34 boot won't line up with the groove in the VM34 spigot. I've tested that claim and it just ain't so; the VM carbs snap right into place. If you remove the OE clamp and replace it with a quality hose clamp, the OE BS34 boot will draw down and seal on any 40 mm. Mikuni spigot. I used those boots for a couple of seasons with my 33 mm. pumpers, which also have 40 mm. spigots, before I switched to a pair of extended aluminum mounts from 650 Central. Not much seat of the pants performance difference, but I had to fabricate spacers and cut a second pair of gaskets with the boots to let the carbs clear the valve covers, so the extended mounts present fewer opportunities for vacuum leaks.

I'll try to get pics to you tomorrow.

Thank you I really appreciate it!