Machine work on SU for roller bearings

[billgtp]

                                                         Carb. bodies returned today.   picture of sealed needle bearing     

                                   Bearings on throttle shaft. You can see the support with needle bearings                                  Bearing in carb. body                                 

 

Edited May 24 by billgtp

[billgtp]

1 minute ago, billgtp said:

                                                         Carb. bodies returned today.   picture of sealed needle bearing     

                                   Bearings on throttle shaft. You can see the support with needle bearings                                  Bearing in carb. body                                 

 

 

[Captain Obvious]

Neat modification.

I don't think the seals on those bearings are rated for vacuum or pressure though. I think the seals are only intended to keep grease in and dust out. That said, I wonder if the ensuing leak would be any more or less than the original sleeve bearings.

I'm also pretty sure the chrome plating on the shafts would not be recommended by the bearing manufacturer. And if the chrome plating has already been worn off in spots exposing the soft brass underneath (as is so common with used shafts), there's no way it would be recommended for those rollers. However, with another "that said" here...  At low speeds you will see in this application, would the rollers still be better than the original sleeves running on the soft brass?

I'm no bearing expert.  

[Patcon]

So is the throttle shaft a custom part too?

[Captain Obvious]

9 hours ago, Patcon said:

So is the throttle shaft a custom part too?

It looks like they "thinned" the web on the original throttle shafts. You can see the underlying brass where they cut the shaft down.

You know.... For higher performance because it reduces air resistance at WOT. 

[Captain Obvious]

Thinking about this a little... Most of those drawn cup needle roller bearings are available in a configuration where one side is closed off. Totally blind. If one finds that the vacuum leak past the bearings is objectionable, they could use that closed end variety on the outboard ends of the carbs.

That would completely eliminate two of the four potential leak locations.  

[billgtp]

Throttle was milled from 10mm to 8mm. Its something they liked to do when he worked for electramotive.  The picture , shining light up throttle shaft so you can see no light. So I feel the bearings are sealed for air leaks. I did move light around

[w3wilkes]

ZTherapy replaces the bushings with roller bearings. Including me I'm sure there's plenty of folks around here that are very happy with our roller bearing carbs. I'd guess you'll be happy with your bearing mod.

[zKars]

Anyone brave enough to reveal a source for said 10mm ID sealed bearings?  

[Captain Obvious]

I don't know about your side of the border, but on the US side, I'd get 'em from McMaster.

Here's the through version with seals on both sides https://www.mcmaster.com/5905K586/

 

[AK260]

Interesting thread! I too am looking for sealed bearings as I embark on totally messing up a set of spare carbs that are worn anyway.

Not sure why the site won't let me link to my other thread: https://zclub.net/community/index.php?threads/hitachi-su-carbs-the-david-vizard-modifications.30868/

 

I agree that these won't be vacuum sealed but the sleeve bearings aren't fully air tight either - right? 

 

 

Edited May 29 by AK260

[Jeff Berk]

On 5/25/2024 at 7:58 AM, Captain Obvious said:

It looks like they "thinned" the web on the original throttle shafts. You can see the underlying brass where they cut the shaft down.

You know.... For higher performance because it reduces air resistance at WOT. 

At first I thought CO was joking, but after reading the zclub thread, I'm not too sure.