(BS series) Throttle Seals: Who's done 'em, who needs to?

Sounds like you're good to go with a local Buna-N quad seal as an offset to OEM.

Remember...as Jfinnan reminds us, that the OEM Yamaha part #256-14997-00-00 can still be ordered through your local dealer or online Yamaha parts supplier.
 
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re: still available OEM parts.

And like yamaman once mentioned in a thread about swingarm bushings.
Are the resin/fiber originals really that bad? They lasted 20-30 years, are half the cost of brass and still a stocked item. Dollars to donuts 85% of the riders on here couldn't tell the difference in handling.
Likewise the difference between the/a seal. It's sealing and doesn't need fixed or it isn't and does. The originals in my 79 are working fine. I was having some climbing idle problems on a 83 when it warmed up, checking the seals found one with a pinched outside lip most likely done at the factory. It made me wonder what the 3 previous owners had done to try and fix it(the idle climb).
 
Maybe this pdf is something of useful reference. Thanks to 5twins for much of it.

Touche' weekendrider. Points well taken.
My interest and concerns in this matter are actually driven by ethanol compatibility in general and the search for Viton R and/or other offsets of improved resistance for those who need and want them. A growing list it seems. Blue
~~~~~~~~~~~~~~
 
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Put the "square section" o-rings in a set of 38s last week backed em with a thin section o-ring to "fill the space". Doped em with silicone lube too. OK, a little brag here.

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Just ordered enough Yamaha 256-14997-00-00 to do 5 sets of carbs Boats.net has em for 2.75 each. Now to find the best deal on stainless steel socket head bolt sets WITH the 4 to bolt the carbs to the angle iron. Next a Caswells nickel plating kit (maybe)
 
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I source my stainless Allens in quantity from McMaster Carr as well. They make a special lock washer for Allens called a "high collar". It is a little thicker and has a slightly smaller O.D. so it fits better under the smaller diameter Allen head. I recommend using them with Allen bolts. For your 38s you'll want .....

M5 x 14 & 16 for the tops
M4 x 12 for the bowls (with the thicker "high collar" washers, a 13 actually works best - I cut down 16s)
M5 x 16 for the manifold clamps

For the 34s you'll need .....

M5 x 12 & 14 (w/lock washers) for the tops
M5 x 16 for the bowls

M6 x 20 - manifold bolts for all models

The beauty of stainless is you can just buy the longer size and cut them down to make shorter ones.
 
So this may be a little redundant but this topic really helped me out.

My bike: 1977 xs650D, bs38 carbs.

PROBLEM:

My bike hesitates to come back to a normal idle after hitting the throttle and sometimes the idle will stay high, forcing me to constantly adjust the idle screw. I determined that the throttle shaft seals went bad(sprayed a little carb cleaner at them with the bike running and the idle went crazy)

SOLUTION:

Replace the throttle shaft seals(4) and also the screws(4) holding the plates to the throttle shafts.

From McMaster Carr I ordered:

A pack of 50: Double-seal Viton(r) Fluoroelastomer O-ring (1/16" x 5/16" x 7/16" AS568A-011) which is part number 6540K121 on their website.

And

A pack of 100: 18-8 Stainless steel Metric Oval Head Phillip Machine Screw, M3 Size, 8mm Length, .5mm Pitch (part number 90258A178)

I have read that the OEM part is the only way to go with these seals but McMaster is located nearby and if it works out i'll be riding with a normal idle in a couple of days. I will relay the results by this weekend (5-12-12).

The o-rings from McMaster, as you've probably already read, are an offset to the Yamaha OEM part # 256-14997-00-00. It took a lot of searching for me to find this information so I just wanted to try to sum it up for anyone else looking for this solution.

As i've stated, I have a very large quantity of these parts now and would be more than happy to share with anyone in need of them!
 
Just a tip on removing the butterflys. I don't have any JIS bits but I found that using a #2 Pozidriv bit works excellent. (PZ2) Seems like every bit set I've ever bought comes with them and I never use them, but they worked really well on these screws. A dab of Kroil penetrating oil and good downward pressure and a slight turn and "pop" you hear them break loose and good to go.
 
Yeah, unfortunately I didn't read anything on how to remove those screws so I just went at them with a regular phillips and needless to say i stripped a couple of them.
 
So the seals didn't solve the problem :banghead:

The plastic spacers that sit against the seals are worn, maybe those need replaced? Maybe I just need the OEM seal?

Pretty sure I'm just going to end up getting some VM34's and be done with it. These carbs are a pain.
 
Sandy: What seals did you use? Other members have reported the MikesXS seals as useless or worse. Are the throttle shafts snug in the bodies, not sloppy? Sometimes the shaft/ body fit has worn so badly that the carbs are beyond repair. Not so common here in the midwest but in dry dusty/sandy country or with lots of miles it happens.
 
gggGary, I used the Viton(r) Fluoroelastomer O-ring (1/16" x 5/16" x 7/16" AS568A-011) from McMaster Carr.

It turns out that one of the stock seals was actually missing from the throttle shaft which was weird because I'm pretty sure it had never been taken apart(the plate screws were still cross cut at the end so i assume they were probably the originals). Maybe it just crumbled and fell out? But the others were in decent shape.

But to answer your question, yeah the shaft seems like it's a bit worn because it gives a small amount when I wiggle it. Like I said, I'm probably just going to order the VM34 kit from 650central, it's $399 and comes with the carbs, uni air filters, throttle cable, manifold mounts, and jets. I don't feel like taking these things apart any more lol.
 
I just thought of something. If I get those vm34's will my sidecovers still fit on the bike? not too concerned, just wondering.
 
Doing the throttle shaft seals on a set of stock BS38. Got the 4 seals from 650central.
Couple of questions.

1)
Butterflies came off but now I can't get the shafts out. They should slide out away from the sync screw? ( see photo ). Any ideas?? I started to hammer the inside end with a drift but it was making dings against brass part.

2)
Also when butterflies are closed should they clear the two plates behind the the plate? (see second photo )
 

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You need to disconnect the two carbs from the bridge that connects the two on top and from the mounting rail (angle arm as well as loosen and pull out the connecting rod.

After that, the direction of removal of the throttle shafts will both be to the left as per your first picture.

I don't understand your second question? Blue

DISCONNECT...SEPARATE.... THE CARBS THEN YOU CAN REMOVE THE THROTTLE SHAFTS
 
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