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Dipping Carbs - Throttle Plate removal?

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Guest

Guest
Hello,

I posted a message in an old forum but thought I should probably start a new thread instead.

Anyway, I pulled the carbs off the 82 GS550M i recently purchased as part of the rebuild and was following the rebuild guide from BikeCliffs website. That guide does not say to remove the throttle plate shaft. But, I was pretty certain that the shaft is sealed with o-rings based on other carbs I've worked on. Anyway, I went ahead and removed the throttle plate and shaft on the #3 carb and sure enough, there is a unique o-ring on each side of the shaft, just under each actuation arm. I don't know about you guys, but putting anything rubber in that dip destroys it. And of that o-ring is not sealing, I got to believe that air is leaking past the shaft and leaning the mixture. I have attached a pic of the o-ring.

What has been you experience? Do you dip with these in place or do you remove them? Are replacements available?

Here's the shaft with one of the o-rings. There's one an each end.
ThrottlePlateShaft.JPG


And here's the o-ring. It's not a true o-ring in that it has a groove in the center. This side faces out.
ThrottlePlateShaftOring.JPG

Thanks,
Sci85
 
I have dipped and rebuilt MULTIPLE racks of carbs and have not removed throttle plates, ever.
noway.gif


Not saying it's not a good idea, but I have not had any problems.
shrug2.gif


Because the screws that hold the throttle plates are swadged into place, I would be more worried about making sure they stay in place than anything else. If that screw falls out, there's only one place it can go. :oops:

.
 
Agreed Steve but that's what locktite red is for. I can't believe that those o-rings have survived being dipped in Berryman's. There's just no way. The question is, will air make it through the shaft and into the bore with a bad o-ring. And I'm also wondering how many mysterious carbs issues are the result...
 
Most here report fine results with leaving those seals in place. Maybe the lack of noticeable damage is related to the more eco friendly carb dip these days? Regardless, I don't think there is any problem with removing the throttle plates, but I'd get new screws and use that red loctite as already alluded.

Good luck
 
Thanks for the link hampshirehog. Looks like this was discussed a bit already. I gotta get better using good search terms:confused:

Anyway, that guys was leaking so it's certainly possible.

Maybe because there's enough richness to cover up any minimal leaking around these seals. these BS32's have a fairly tight fit in the carb body so maybe it's not enough to have a noticeable impact.

I wonder if there's a way to test for leakage after a good dipping, especially on really older carbs. I don't have access to any kind of vacuum machine but maybe some kind of rubber safe liquid would be sufficient? Anyone got any good ideas?

Sci85
 
I have re-kitted, overhauled, and actually rebuild hundreds of carbs. over my career in the trades and advise you strongly to avoid removing choke plates or throttle plates.

The screws are staked in almost 100% of the cases which requires grinding away of the staked portion of the screw or you are likely to spread the holes such that new screws will not hold properly. An additional problem is to realign the plates and shafts so that they do not bind but this can be more difficult than one may expect.

The only reason for which we removed throttle or choke plates was if the carb. needed to be re-bushed because of throttle shaft or shaft bearing surface wear.

The most popular means of identifying air leakage around the throttle shafts (other than the obvious check for excessive side movement) is to spray a combustible aerosol around the exterior of the shaft bearings while engine is idling to check for engine reaction.
 
I've rebuilt more than a dozen and less than 20 racks of carbs over the last four or five years and never once removed the throttle plates. Never had any problems either. I have however seen evidence on carbs where that Oring has apparently leaked fuel vapor (and by that point in the system it would be vapor/atomized pretty well) and discoloured the cap. Those bikes ran just fine however, so I don't suspect that, even with bad Orings, they're sucking much air around that seal. If so, maybe they'd be set a little richer than perhaps they originally would have been from the factory, but personally I simply wouldn't fret about it that much. Obviously now that you're to that point you'll want to take care of it, but for the next set ya do, or even the next carb, I'd leave it be. The possibility of greater damage occurring should your red thread lock fail and the plate come loose outweighs any ill running characteristics of not stripping those apart to that point. Just my .02
 
I will say this for ya though, compared to most new members who want to half ass everything and think some spray shots of choke clearner constitute "cleaning the carbs" you definitely deserve the "Overcheiver of the Month" award :D
 
On some of the Keihins you have to pull the throttle plates if you want to split the carbs. It slows the whole job down as those dinky screws are fiddly but it's not a biggy.
 
Sci85...its an urban myth that berrymans will liquify the orings...it wont. We say take the orings out and replace them when rebuilding so the oring grooves will get cleaned and to be sure the rings are supple and reseal properly.
 
Well if you guys say it's not a problem, then that's good enough for me then. Thanks for all the input on this. Now, off to the garage!

Sci85
 
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