Throttle Shaft Seals/Bad

retiredgentleman said:
I agree with gggGary................OEM is the way to go with these. I tried Mikesxs and they leaked air. Bought some from my local Yamaha dealer and they work just fine.
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You happen to know a part number for the seals on the BS38? Same as what is mentioned above for the BS34?

I need some for my BS38's and I want to get the right ones.
 
Dogbunny-
The choke enrichener with the three screws that you were referring to-- is this on the right side carb (in the shape of a dog) just behind the throttle plate on the BS38's. I always thought the "chirping" was just the way it is and now you got me thinking. I know this piece doesn't have any gasket or any sealant on mine and this part isn't shown on any part fish that I can find as well. So I'm wondering if I'm missing a gasket.
 
DanW said:
Dogbunny-
The choke enrichener with the three screws that you were referring to-- is this on the right side carb (in the shape of a dog) just behind the throttle plate on the BS38's. I always thought the "chirping" was just the way it is and now you got me thinking. I know this piece doesn't have any gasket or any sealant on mine and this part isn't shown on any part fish that I can find as well. So I'm wondering if I'm missing a gasket.
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What year is your carb set?
The gasket first appears in a drawing for the 1976 carb set, it is part # 29 in the following drawing:
http://www.biker.net/74-76_650_parts/engine/650C_carb.pdf
The earlier drawings don't even show the cover or the three screws that hold it on, which is strange.
And, there are two covers, not one as you wrote. If you have a pre-1976 carb set, then the left carb has the cover-with-plunger, and the right carb just has a cover. The plunger is the enrichener, and it enrichens the right carb through a connecting tube. After 1975, both covers have plungers, and there is no enrichener connecting tube.
I took a look at some of my pre-1976 carb sets, and as you say, some don't seem to have gaskets or sealant. However, a gasket from a later carb set will fit.
If I had chirping, I would find or make gaskets for both covers. As I wrote, those covers are the classic cause of chirping. You should be able to verify that with a mechanic's stethoscope.
 
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I have a '72 XS2 that has "chirped" ever since I got her running a year ago. You're the first person on this site to ever mention this unusual sound and the cure. I'll be tearing both carbs off today and making gaskets. Thanks for getting back to me and all your info.
 
Mharrington said:
This sucks! I JUST ordered (April 17th) some parts from MikesXS and the shaft seals were part of the order!
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That's OK they aren't installed yet and they aren't that expensive. Just get the right ones and throw those out. There's a good chance you can just stop by the local Yamaha dealer and buy em.
It would suck if you had the carbs back together and THEN you found they were junk! (like Bill)
 
gggGary said:
That's OK they aren't installed yet.....
It would suck if you had the carbs back together and THEN you found they were junk! (like Bill)
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like Bill and many others as well....myself included.

GGG gives good advice re these critical precision molded rubber parts made all the more critical with the advent of ethanol containing gasoline fuels. Technical pecification compounds, processes and tooling are very important! Unfortunately, a lot has gone by the wayside re material and process controls since OEM parts were being supplied. Caveat emptor....there are a lot of junk molded rubber parts on the market supposedly made for vintage bikes. Footpegs, handgrips, gators, diaphraghms, manifolds, o-rings, tubing etal Some good ones but; a lot very poorly made and without recourse.

It's important to share the good news and the bad....GGG is a peach! So are many others on this forum and elsewhere
 
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So I took my XS to a local mechanic because I didn't have time to deal with the Carb issues I was having. After messing with my XS for a few days, the mechanic told me that my butterfly valves weren't closing and needed to be replaced. Just got off the phone with him, and he said that he couldn't find the butterfly shaft seals anywhere, and he was re-jetting the carbs to compensate... I sent him a link to the part referenced in this thread. Is it just me, or does that sound a bit rediculous to anyone else?
 
Yeah that guy is a no-good-nik for sure. Get your carbs and run, hope it's not too late for you.
 
The seals are still a fairly current part, used in various Yamaha models right up to almost the present day. Time to find a new mechanic I think. That guy may know some stuff about other bikes but he's not much up on Yamaha 650s. Here's a link to the seal listing. It's used on more Yamahas than I can count, all the way up to 2011 .....

http://www.boats.net/parts/detail/yamaha/Y-256-14997-00-00.html
 
So I'm assuming that there wasn't anything wrong with the valves, and it was running lean because of the worn seals... All I know is... the valves he machined had better not be shit... and he better still have the old ones.

How the F do these people stay in business.
 
If you mean the butterfly plates, Yamaha never sold that part individually. Scrounging them from another carb set is the usual routine. I scrounged a set for some BS34s from XS400 carbs. Same part and number (135) and they worked fine. This is a precision part with the top and bottom edges beveled to seal properly in the bore. If that guy made a set, my hat's off to him. But since he can't order a simple readily available seal, I doubt he can make butterfly plates, lol.

To get the plates to operate properly, you need to center them in the bore when mounting. That may have been the problem to begin with and he just didn't know the proper mounting technique. A guy in another recent thread swore up and down he mounted his plates correctly but when he checked them, he found out he didn't. He fooled with them but couldn't get things right so I think he flipped them. Due to those beveled edges, you can't do that - but I'm not telling him, lol. Let him learn "through experience".
 
Yeah... his competence is definitely in question... Luckily, he said he hung onto the stock ones. Searching the forums now to figure out how to center the plates once I get the bike back from him (and take out whatever Frankenstein crap he put in there). Now I just have to convince him that I'll gladly pay for the "work" he did... Just not the time he spent being a moron. :banghead:
 
I'm about to replace my throttle seals on BS34's too. I love to hear any tips on proper mounting technique for the plates before I plough on in...
 
Yes, the proper plate mounting technique probably should be outlined in a thread like this that pertains to the seals. Install the plates with their mounting screws just snug. Then assemble the rest of the components onto the shafts - spacers, washers, nut, and most importantly, the return spring. Now open the butterfly plate (rotate the shaft by hand) and let it snap shut. Do this several times and then tighten the plate mount screws.

When the return spring is installed, it pulls the shaft towards it slightly. If you have the butterfly plate screws tight already, the plate will be pulled against the spring side wall of the main bore and bind. The more you open the plate, the less contact there is between it and the bore walls so binding is minimal at these larger openings. The problem is most pronounced at small plate openings when it is nearly closed. This is what causes the hanging or high idle.
 
5twins said:
Yes, the proper plate mounting technique probably should be outlined in a thread like this that pertains to the seals. Install the plates with their mounting screws just snug. Then assemble the rest of the components onto the shafts - spacers, washers, nut, and most importantly, the return spring. Now open the butterfly plate (rotate the shaft by hand) and let it snap shut. Do this several times and then tighten the plate mount screws.

When the return spring is installed, it pulls the shaft towards it slightly. If you have the butterfly plate screws tight already, the plate will be pulled against the spring side wall of the main bore and bind. The more you open the plate, the less contact there is between it and the bore walls so binding is minimal at these larger openings. The problem is most pronounced at small plate openings when it is nearly closed. This is what causes the hanging or high idle.
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Legend:thumbsup:
 
Well I got the bike back from that moron "Mechanic", and it died on the road 4 days later... Since I was out with no tools, I ended up having to get a tow. Luckily, the wait for a tow truck wasn't entirely unproductive... I got to write a very honest review of my experience while I waited. Thank you smart phone.

Once I got home, I pulled the plugs, and they were extreemely carbon fouled. I'm gonna pull my carbs tonight to see what the heck this guy did to my bike, but wanted to see if you guys had any suggestions. My thought is that he probably did a crappy job of mounting the plates, and tuned the bike a little rich from the get go. After some riding, the plates probably settled in a bit more, leaving the bike running even richer.

I also plan to check to make sure my air filter isn't preventing air flow or anything... Any other thoughts?
 

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