PWK carb adaptors splitting

[bosco659]

On my ‘76, the PWK carb adaptors crack or split within a couple of hundred miles from new. The adaptors are supporting the weight of the carb and pod filter but are under no other stresses. Is this a common occurrence? I can’t keep buying replacements as they are costly. Is there a better solution? It appears in photos that the new PWK kit uses a machined or welded flange and a short section of reinforced hose. Can that be purchased separately?
Photos to follow. Thx

 

[bosco659]

split or crack can be seen by the mounting bolt in the lower left of the second image.

 

[5twins]

On the stock set-up, the rubber manifold is covered with a tin shroud. This adds much needed support and the manifold can split rather quickly without it, as you've discovered .....

There were 2 different sizes used, one for the BS38 manifolds and one for the BS34 manifolds. I'm not sure which, or if either, would fit your PWK manifolds. If I had to guess, I'd think the BS34 ones might.

I've been running my BS38s on my '78 with pods and unsupported for a good dozen years now, and I've had no splitting manifold issues.

 

[bosco659]

Thanks 5twins. That would definitely help. My carbs are also set back with a 35mm aluminum spacer. Any idea why the po may have installed these? I’ve seen thinner spacers for sale but not these thick ones. I’m thinking the further the carbs stick out from the head, the greater the vibration would be, and perhaps more strain on the adaptors. If there’s no significant advantage to leaving them on, maybe I should remove them. It would also give me more room for the air filters. Right now the pods are crammed in beside the rectifier / regulator.

I’m going to look for a set of the metal shrouds. Should I post in the classified section? Thx for your help

 

[gggGary]

Devise a simple support strap frame top tube to carbs.

 

[arcticXS]

Thanks 5twins. That would definitely help. My carbs are also set back with a 35mm aluminum spacer. Any idea why the po may have installed these? I’ve seen thinner spacers for sale but not these thick ones. I’m thinking the further the carbs stick out from the head, the greater the vibration would be, and perhaps more strain on the adaptors. If there’s no significant advantage to leaving them on, maybe I should remove them. It would also give me more room for the air filters. Right now the pods are crammed in beside the rectifier / regulator.

I’m going to look for a set of the metal shrouds. Should I post in the classified section? Thx for your help

Most likely, the spacer is there to increase the intake length, and hopefully increase mid range power and torque . They may also create a smoother transition from carb diameter to port diameter.

 

[650trader]

Aluminum Spacers make a significant difference in throttle responce.

 

[bosco659]

I’ll look at making up a support bracket. Need something, my newest adaptor is nearly in two pieces. Still would like to try the metal shrouds. Can someone help with a part number for the BS34 shrouds ( a members has BS38 shrouds but they are too big (ID).