Mikes carb throttle shaft seals, problems and fixes?

[XS650D]

I finally got around to installing used choke side carb body I purchased of EBAY last fall.
To hopefully fix the original unit I never could get to idle /run correctly.Yes we tried everything, something internal was the problem (probably someone screwed the fuel screw in to tight, just a guess, I read this was an issue on the 76/77 38 mil carbs.
The company I purchased from sells rebuilt/refurbed units that are totally gone thru, repainted, new seals hardware ect.The unit looked new to me .It was only the carb body so I proceeded to take everything off my old unit and reinstall. It already came with the throttle shaft, seals and hardware for shaft installed on carb body. I did not
believe there was any need to pull apart. Fast forward, got it on the bike and set up.Good news, was actually able to set the fuel screw to 1.5 turns out and it ran great, no farting ,uneven running ectI used to have my old carb at 3 turns out just to get it to run at all and it still wasn't right! I ended up after balancing the carbs and tweaking the fuel screws both sides are now within 1/4 turn of the stock setting of 1.5 +/- half turn.
Bike is running much better BUT not perfect, still a lil stumbling in the idle.I decided to do a starting fluid test on the carbs and seals.Yep u guessed it, seals not sealing properly, called company that I got carb from just to inquire if they were indeed changed and yes but with aftermarket seals, probably Mikes.I could pull it all apart again and get some Yamaha original units which are available but I decided to try an old trick of swelling the seals with some brake fluid applied to them (I just squirted it on best I could) I did this on an old Chrysler tranny years ago that was slipping (lots a miles) added some brake fluid to tranny. Woked great rite up until I sold it a year later, no more slipping tranny. Has anyone tried something like this on a bike shaft seal.I read that it can swell seal up to 15%.I figure if it docent work then $20 for new Yama seals is worst case sceniro.Just not looking forward to pulling it all apart again! Sorry long winded.

 

[TwoManyXS1Bs]

Closest I've come to that is packing the seals with silicone grease.
After replacing the throttle shaft bushings.

http://www.xs650.com/threads/1971-xs1b-bs38-carbs-throttle-shaft-bushings.43326/

 

[XS650D]

Great info Twomany! The throttle shaft bores may be slightly worn on this rebuild carb I purchased,no way to know
how many miles on it. Thats a fairly extensive project replacing the bushings. whats your thoughts on just replacing
seals with o-rings with a more snug fit.Im not sure how long it takes for seals to swell but I will advise if this works for a quick fix.
I fired the bike up this morn and running smooth .I dont think the seals would swell that fast so its most likely the brake fluid
has filled the voids slightly similar to adding grease as mentioned.I have used Teflon Brake slide grease on seals before and
it worked great until it washed or wore off. I do have the old carb (original) and may swap the shaft but I think the issue may be the bushings as u stated

 

[5twins]

I don't think the later carbs have bushings, just the carb body is all. Last set I installed I packed with red rubber grease. They are working but I can't say how long the grease will stay in there. It's rubber friendly stuff so I figured it couldn't hurt. Although I haven't tried it yet, I've thought about adding a skinny o-ring that would fit inside the seal and possibly force it against the shaft more. It would take some searching and experimenting to find just the right size. Too big and it would bind the shaft up.

 

[XS650D]

You like that Red grease eh 5T ,Lol!
Noticed u use it on many applications, have a similar affair with the KleenFlo EZ slide brake grease, rubber friendly and I think it contains
Teflon to aid in keeping things moving easily ie: brake slides, Also designed not to wash off easily ,wont brake down with extreme heat.
Your correct ,no bushings just the Aluminum body on the 77 I have. Going to add a few more drops of brake fluid DOT3 with an eye dropper and swell those puppies up bit more.Might just work, snake oil fix!

 

[XS650D]

Update: seems the brake fluid swelled the seals enough to cause no air leaks!
I have had the bike out twice and its idling smooth, no hiccups or hesitations at all, never ran this this before.
Hopefully the fix will hold up,i will advise if it docent. Looks like brake fluid does swell seals!
Also upon closer inspection it appears that at least on my 77 that there is definitely a brass bushing
on either side of the carbs wear the throttle shaft slides or pivots.FYI on the 77 model year.

 

[grizld1]

Yep, there are throttle shaft bushings in BS38 carburetors up to 78 (I'm unsure about the 78-79 version). Unlike 2M's early carbs, bushings in later carbs are splined brass, so the only way to get the slop out of the bushings is to bore the originals for inserts.

 

[XS650D]

Thx Griz