SU Mod: Sealing worn throttle bushings

[240260280z]

A plastic cap (screw cover) from ACE hardware's parts bin and sealant/goo/glue seal the outside bushing nicely.

Installed

A thin washer and an o-ring seal the inside bushing with negligible effect on the throttle return.

[Zforce]

You just demonstrated the difference between a parts changer and a mechanic

[240260280z]

Nah, I defined thrifty canuck eh?

Lets hope the engine heat does not loosen the glue or it will be RTV time.

[Jeff G 78]

You rock Blue! Nice work.

[Captain Obvious]

Neat ideas Blue.

Are you sure that you didn't preload the position of the butterfly plate towards the O-ring?

By that, I mean... When the butterfly is completely closed, the side-to-side movement of the throttle shaft is restricted because the butterfly is a tight fit in the carb bore. But when the butterfly is opened, the throttle shaft can move back and forth a bunch before either the butterfly or the linkage bits hit the carb body.

If your O-ring is compressed when the throttle is closed, then it will pull the butterfly towards that side of the bore, but when the throttle is opened it may wear the butterfly plate or bore prematurely in that location from the constant scraping every time you open or close the throttle.

Not saying it's a big problem. Just a thought.

Edited August 9, 2011 by Captain Obvious

[240260280z]

Excellent point!

Presently the side force on the shaft is minimal as the O-ring is very low in height. As well, I am guessing that a leak would suck the washer in closer, especially at idle.

I could put a thinner washer there to completely unload the butterfly valve but I did not have one here in NJ.

Maybe I should just drill out another plastic screw cap, sand it to the correct height then glue it on... yes I think that would be even better! At $0.20 each it is not a risky venture.

Thanks for your insight! Another set of eyes and brain is great!

[Oiluj]

Nice idea. Many years ago I did something similar with teflon o-rings. Difference is I turned a slot in the shaft andsipped the o-rings onto the shaft where they sealed against the bore of the carb. Worked fine, but my machining skills were not the best and it could have been better...

[Captain Obvious]

Don't get me wrong... I wouldn't get all worried that you're cutting huge chips off the inside of your carbs at any great rate. It's just that I've seen some carbs from other applications that were wallowed out to the point where the butterfly's wouldn't seal anymore and getting them to idle and come off idle without issues was impossible.

How long would it take for you to get to that point? Probably years.

Another thought is that I've seen some other carbs that had actual seals on the shafts from the factory, and they didn't use O-rings. They used non-round cross section seals with the lip direction such that the vacuum would suck in the direction that would increase the effectiveness of the seal. I'm no seal expert, but it makes me wonder if O-rings are the correct choice for vacuum application. Maybe it's a tradeoff between seal effectiveness and friction? But... Any seal will be more effective than "none".

Lastly, I'll cut you some grooves in your shafts if you would like to try putting some O-rings on the shafts to seal inside the bushings in the carb bodies like what Oiluj suggested.:bulb: I've even got a bag of "X" cross section (non) O-rings laying around here somewhere that might be close to size.

[ConchZ]

Blue, were you happy with this fix? Did it last?

Matt

[240260280z]

Worked fine. But CO's mod is the right way to go.

[Captain Obvious]

Butter smooth. No leaks.

[ConchZ]

That's awesome. Might have to try it. Wonder if my grandpa's old shopsmith can be used to turn that.