Topic: Carb Vacuum Balance Port Repair Suggestions Please

[Scootch]

1970 CB 750 K0
So I have discovered that the vacuum port on one of my carbs seems to have the threads bunged up. I'd appreciate suggestions regarding how you would handle this.  TIA

[david 750f]

Try a longer screw as the factory ones are very short. Gently run a tap through (5mm). I'm guessing it's just the first few threads that are buggered up.

[BenelliSEI]

I’ve thought about this in the past. Lots of bikes have permanent nipples, covered by a rubber cap when not in use. Next set of carbs I do, I’m going to find brass pipe the correct OD and thread one end to fit those holes. Cut them off short and red loctite them in place. Cover the ends with rubber, push on caps. When you need them, it takes seconds to install your hoses!

Clean out your buggered threads, make a small nipple, and permanently stick it in place. With a rubber cap, or course.

[Scootch]

I’ve thought about this in the past. Lots of bikes have permanent nipples, covered by a rubber cap when not in use. Next set of carbs I do, I’m going to find brass pipe the correct OD and thread one end to fit those holes. Cut them off short and red loctite them in place. Cover the ends with rubber, push on caps. When you need them, it takes seconds to install your hoses!

Clean out your buggered threads, make a small nipple, and permanently stick it in place. With a rubber cap, or course.

This is exactly what I was thinking!

[Stev-o]

Lots of bikes have permanent nipples, covered by a rubber cap when not in use.

Yes, my Kawasaki [w/Mikuni carbs] has this setup.  Handy...

[david 750f]

Motion Pro makes those permanent adaptors.

https://www.motionpro.com/product/08-0218

[Scootch]

Motion Pro makes those permanent adaptors.

https://www.motionpro.com/product/08-0218

Thank you very much for this !!  👍

[Stev-o]

Motion Pro makes those permanent adaptors.

https://www.motionpro.com/product/08-0218

Out of stock there but available here...

https://www.motosport.com/product/?cc=us&gclid=Cj0KCQjw5ZSWBhCVARIsALERCvyYYaAC870ayNcmEuB8Hn_pEEefHZrPli89faEd4rs8DvNtTxFf_mUaAvvJEALw_wcB&gclsrc=aw.ds&key=Motion-Pro-Brass-Vacuum-Adapter-With-Cap&pssource=true&segment=badger&utm_medium=pla&utm_source=google&variant[MOP008H]=MOP008H-X001-Y001

[MauiK3]

Rubber caps are on all post 1973 Z1 Kawasakis.

[Scootch]

Motion Pro makes those permanent adaptors.

https://www.motionpro.com/product/08-0218

Out of stock there but available here...

https://www.motosport.com/product/?cc=us&gclid=Cj0KCQjw5ZSWBhCVARIsALERCvyYYaAC870ayNcmEuB8Hn_pEEefHZrPli89faEd4rs8DvNtTxFf_mUaAvvJEALw_wcB&gclsrc=aw.ds&key=Motion-Pro-Brass-Vacuum-Adapter-With-Cap&pssource=true&segment=badger&utm_medium=pla&utm_source=google&variant[MOP008H]=MOP008H-X001-Y001

Yep. That's funny cuz that's where I had ordered them from...

[BenelliSEI]

Motion Pro makes those permanent adaptors.

https://www.motionpro.com/product/08-0218

Out of stock there but available here...

https://www.motosport.com/product/?cc=us&gclid=Cj0KCQjw5ZSWBhCVARIsALERCvyYYaAC870ayNcmEuB8Hn_pEEefHZrPli89faEd4rs8DvNtTxFf_mUaAvvJEALw_wcB&gclsrc=aw.ds&key=Motion-Pro-Brass-Vacuum-Adapter-With-Cap&pssource=true&segment=badger&utm_medium=pla&utm_source=google&variant[MOP008H]=MOP008H-X001-Y001

I ordered a set with refill liquid for my sync tool and another set of “straws”. Will report back.

[Rookster]

I had the motion pro adapters with the rubber caps but I was never happy with the sealing washers.  They are a paper/fiber sealing washer.  I took them off and used the stock screws with the aluminum sealing washers the last time I did a sync a month or so ago.  I think the motion pro adapters allow air to leak past them.  They were convenient though.  The rubber caps would get really stuck on as well after a month or so. 

Scott

[Scootch]

I had the motion pro adapters with the rubber caps but I was never happy with the sealing washers.  They are a paper/fiber sealing washer.  I took them off and used the stock screws with the aluminum sealing washers the last time I did a sync a month or so ago.  I think the motion pro adapters allow air to leak past them.  They were convenient though.  The rubber caps would get really stuck on as well after a month or so. 

Scott

Thank you for that info about the caps! I haven't received them yet but did notice that the fiber washers didn't seem like a good idea.