Butterfly and other carb questions...

[corey]

Its been a while for me, but now that its spring, I'm back at it....

I was rebuilding my carbs, due to leaky buttefly shaft seals, and came upon a few questions...

1) The buttefly seals from MikesXS fit all BS34 carbs, no? I have a 79SF, but I do believe the carbs are off a 80 or 81 (they are BS34III, judging by the four holes on the inlet mouth). The MikesXS part number for what I'm looking at is 48-5021.

2) I dropped the little bearing for the choke slide that rests in the number 4 carb body. Anyone know where I can get one or what would be a good substitute?

3) One of the screws on the butteflies was rendered inoperable by my screwdriver, thus I drilled it out. Anyone know where I can get a replacement screw? I was thinking about riveting and/or otherwise fixing the plate to the shaft also. Any suggestions here? Surely one screw will not do the job.... will it?

4) Finally, I was working on the carbs upside down, assuming that everything was fixed in place. However, two very tiny springs (smaller than, say, the mixture screw springs) fell out from an unknown location. Any idea where they might go? I figured I might run across their previous locale, but no such luck yet.

I guess that covers my inquiries for now. Any help, as always, is GREATLY appreciated!

[John]

Well, I think the springs may have fallen out of the choke detents, They hold pressure against the little ball bearing that you lost. If I remember correctly, Randy Rago has used the shaft seals from Mikes XS and says they were a good fit. Another good source for all things carb related is: motorcyclecarbs.com. They stock a lot of OEM Mikuni parts.

[underdog57]

I bought oem yamaha shaft seals from my local dealer $5.00 ea.
You can get screws from bolt depot , can look up the size .
Would recomend using loctite for the butterfly screws as they were peened originally. Be carefull and make sure the butterfly
are fully seated closed before you tighten the screws . They can be misaligned and cause a problem closing fully ...

Getting parts from the yamaha dealer is hit and miss , some stuff is very extinct or expensive , but I've found them to be a great source ...
Bob

[skids]

Re: Butterfly and other carb questions...

I think I might have an extra screw. Contact me off list
sidhansen @ comcast.net

Originally posted by corey

3) One of the screws on the butteflies was rendered inoperable by my screwdriver, thus I drilled it out. Anyone know where I can get a replacement screw? I was thinking about riveting and/or otherwise fixing the plate to the shaft also. Any suggestions here? Surely one screw will not do the job.... will it?

[Brian_D]

1) yes the shaft seals from MikesXS are a perfect fit and priced cheaper than *most* all other sources.

2) John is correct - this would be one of two ball bearings and springs for the choke detent. can't find the thread right now, but should be a few that discuss a suitable replacement. I bought replacements from bikebandit - they lived up to their name on this item

3) since the factory screws are peened over, and their integrity was compromised on removal, I replaced all of them during my last carb rebuild. other than being slightly longer, I used original Mikuni Super BN Throttle Plate Screws from Parker Yamaha. also ordered the Yamabond (to *paint* the diaphrams) from them as well.

4) see #2. again, there should be 2 ball bearings and 2 springs. without these in place, the choke lever WILL spring back to 'off' position as soon as you remove your hand from the choke lever.

[Yamaniac]

Off topic, but Skids, did you change websites? I can't access anything on the earthlink site you listed. thanks

[randy]

The detent ball(s) is a plain old 1/8" diameter ball bearing.

[Yamaniac]

wow, for the ball, $.47, for which I'm thankful, I seem to have lost both for the '80 . Glad I have that springs, though.... $4.52 for each of them.

(To no one specifically, just an observation) Try getting your balls back from your OL. I bet it'll cost you more than 94 cents!!!!

[underdog57]

on the balls , you can buy a caged ball bearing and seperate it.
plenty of extras then and I'd guess the bearing would be cheap
from a bearing house ....
good luck

Bob

[randy]

McMaster-Carr has the balls:

9528K11
E52100 Alloy Steel Ball 1/8" Diameter, Grade 25
In stock at $2.75 per Pack
This product is sold in Packs of 100


And you'd never worry about losing one again!

[underdog57]

Originally posted by randy
McMaster-Carr has the balls:

9528K11
E52100 Alloy Steel Ball 1/8" Diameter, Grade 25
In stock at $2.75 per Pack
This product is sold in Packs of 100


And you'd never worry about losing one again!

At 3 cents each he could corner the market on throttle lever balls...

Bob

[fredintoon]

losing a ball

One of my carb choke detent balls went pit-a-pat across the garage floor and disappeared. Lucky me saw the teensy spring trying to follow it and caught it before it escaped. I went to Bearing & Transmission, reluctantly willing to buy a 100-pack of the things. When the counter-child heard my sad story and that I only needed one, he gave me one as a freebie. Perhaps that only works if you are a white haired old guy with a Brit accent but bless the lad anyway.
Fred Hill, S'toon.