So throttle shaft seals may leak at idle?

Norton7d

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So after recently starting a bike that had sat for a few years, I thoroughtly cleaned the carbs although I did not mess with the throttle shaft.
While running with indications of at least 1 vacuum leak, and not understanding why it sounded like a bird was in the garage with a chirping noise, I tried to diagnose.
After reading the volumes of leaky throttle shaft posts and vacuum leaks including post discussing chirping noises, I come upon the notion that throttle shaft seals may not seal at idle...thus spraying starting fluid at idle may produce negative results? Wow...now I'm really scratching my head.

I can squirt at all four seal ends, all produce higher RPM's while at idle.
I can squirt at the right side choke body gasket, and it produces higher RPM's at idle (didn't check left side yet as it's somewhat hidden).
I can squirt at the right side carb where it enters the rubber boot / manifold, increases revs slightly although this may be the result of old rubber boot and lack of air box to provide proper carb support.

I will try to secure the choke body gaskets better to see if that helps matters.
Do most who have properly running BS38's acknowledge the possibility they leak air at the seals during idle RPM, or is this situation rare but acceptable?

Thanks.
 
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Do most who have properly running BS38's acknowledge the possibility they leak air at the seals during idle RPM, or is this situation rare but acceptable?
Pics ? Your low mileage, low corrosion, but long time dry carb set would expectedly seal up?
I’m wondering if it is common for vacuum to suck past the seals, perhaps a little thick oil or even grease on the shaft would be enough ?
:umm:
 
Pics ? Your low mileage, low corrosion, but long time dry carb set would expectedly seal up?
I’m wondering if it is common for vacuum to suck past the seals, perhaps a little thick oil or even grease on the shaft would be enough ?
:umm:[/QUOTE

I will work on other vacuum leaks fist, then attempt some sort of grease / seal but knowing how many people on here have complained about leaky seals, I assume grease isn't a probable cure and likely will be forced to change the seals, although Mikes is currently out. other / better sources?
I see some just run a really close match O ring.
 
I’ve come to the same conclusion myself only recently. After I replaced the seals in my own carbs and it not curing my air leak at idle I concluded that the bore must be worn, so I purchased another set of carbs and another set of seals.

The results were the exact same there is still a small air leak at idle. It was then with the carbs on the bench that I looked at the action of the butterfly shafts and noticed that they squeeze the seals as they open so maybe the carb isn’t ever totally sealed at idle??

It will be interesting to see what the opinion of some of the senior members is.
 
I will work on other vacuum leaks fist, then attempt some sort of grease / seal but knowing how many people on here have complained about leaky seals, I assume grease isn't a probable cure and likely will be forced to change the seals, although Mikes is currently out. other / better sources?
I see some just run a really close match O ring.
see the great seals and o-rings thread.
http://www.xs650.com/threads/the-gr...ut-bolt-sizes-used-on-the-xs650-thread.51957/
 
The seals work on vacuum. As the speed of air through the carb increases, they get sucked in tighter and seal better. So yes, it's very possible they don't seal 100% at idle. Old ones that have hardened have even less chance of doing so. This is an all rubber seal with no spring or metal band in it. It is very soft and flexible when new.

I think I read here that chirping is usually the choke leaking.

The last set of butterfly seals I installed got packed full of red rubber grease. They are working fine so far. DO NOT buy the MikesXS seals. Chances are they are aftermarket and the quality probably isn't as good. Besides, genuine seals are actually cheaper than Mike's, and better yet are Suzuki seals, same part but a dollar cheaper than Yamaha .....

https://www.partzilla.com/product/suzuki/13651-51010
 
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