Carburetor Butterfly Seals - Throttle Plate Shaft Seals

[Rikugun]

I would think symptoms may be most noticeable at low engine speeds. An erratic or surging idle perhaps. Mixture screw adjustment outside the normal range. These things could be indicative of dirty carbs too so don't jump to conclusions.

You could check while idling by directing some carb cleaner spray at the throttle shaft ends. If the engine speed changes briefly the seals may be leaking. Different spray chemicals can be used i.e starting fluid, brake clean, contact cleaner etc. Each has a different effect and may cause the engine to briefly race or stall. You're just looking for something different to happen as the chemical is drawn into the inlet tract through bad seals.

If your bike runs well, idles smoothly etc. I wouldn't give it a second thought.

[Cdnlouie]

You know QBS it is possible for a person who uses their bike regularly to still have good seals. What kills the seals is long term storage and no fuel getting to the seals to keep them supple. Additives in the fuel actually preserves the rubber. Over time the bikes in storage will cause the seals to dry out and shrink and thereby not seal properly. New seals will no doubt improve starting and idling as that is where the bike is most sensitive when there is a vacuum leak. In very hot weather it may be prone to stalling as well.

I suppose it would also show up when you do a carb sync and the level of vacuum that registers at idle. Better seals would no doubt produce better and more regular idling vacuum. It would be a lot harder to sync the carbs with poor butterfly seals as the settings would be prone to change a lot.

If your seals fall in and out of the throttle body they are toast or when you try to squeeze them between your fingers they are hard.  New ones push in with noticeable resistant as the outside edge pushes out against the throttle body.

Make sure you clean corrosion out of the throttle body as well when putting new seals back in. Nice clean metal and new seals are going to be a treat for your Vision.  A little coat of silicone grease is not a bad idea either.

Cheers 8)

[jasonm.]

I would not be surprised if the noted ~4500rpm stumble is from bad shaft seals. AKA lean condition. At idle you can adjust the low speed screws for this. But the more rpm the leaner it will run. Then when you get past 4500 the mains come on line. AND maybe the stumble as you give it a twist at that 4500 RPM.

[QBS]

Facinating stuff jasonm.  Perhaps richening the low speed circuit would help the overal performance down low and help with the stumble as well?

[vadasz1]

Man does my V ever sound fantastic.  Just installed the "SUPER V CARBS" that Cdnlouie had just rebuilt with the shaft seals.  She gave a few puffs of smoke out the MACS on the first few attempts but then once I got the enricher turned on she started with a great RRRROOOOOAAAARRRR!!!!.

This weekend I will hopefully have my spare tank finished and then it will be completely ready for the riding season which is just starting.  Hope that no more snow will fall.

Once the bike is used for a few days I think I will get her synced to the NINES!!!!!

Thanks Cecil and I hope you cleaned these carbs with some Holy Water as well so as to fight off any gremlins.....

[Night Vision]

I would not be surprised if the noted ~4500rpm stumble is from bad shaft seals. AKA lean condition. At idle you can adjust the low speed screws for this. But the more rpm the leaner it will run. Then when you get past 4500 the mains come on line. AND maybe the stumble as you give it a twist at that 4500 RPM.

I had more of a surging in the 4.5 -5k range... larger mains solved it for me... could be weak seals,

but bigger mains is a lot easier to do than the butterfly seals

[Lucky]

but bigger mains is a lot easier to do than the butterfly seals

if it ain't worth doing it the hard way....
it ain't worth doing it at all - Man Law
;D

[raub]

Cdnlouie, I always thought if you are parking the bike for a while you should drain the carbs to avoid gunk buildup normal in car gasoline. What can you pour in the carbs to keep rubber parts happy but the jets and ports gunk free?

[Cdnlouie]

Fuel stablilizer seems to be the best way to try and keep the fuel from breaking down when in short-term storage.  If you are going long term (more than an over wintering) it may well be the best idea to drain the carbs.

For some bikes with fuel pumps draining the carbs creates a real nasty start-up problem, my neighbor has a Honda Interceptor 1000R that made that mistake and we had to prime the cylinders manually before it would pick up the fuel again.

Starting the bike up for short periods in the winter refreshes the fuel in the carbs and keeps the system in its best working order. The small amounts of fuel in the float bowl actually deteriorate faster because of the smaller volume (according to the fuel gurus anyway), so refilling the float bowls is a good idea too by periodic start-ups.

[Lucky]

for winter, I suggest draining the carbs AND the tank, removing them & fogging them with stabil. here's why:

most modern fuels contain ethanol. ethanol can contribute to several problems.  it attacks older rubber, it seperates from fuel but most importaintly, it absorbs water.

that last part is causing all sorts of 2stroke problems, i see it every day...

last thing we need is water in our fuel systems...

[VFan]

I would not be surprised if the noted ~4500rpm stumble is from bad shaft seals. AKA lean condition. At idle you can adjust the low speed screws for this. But the more rpm the leaner it will run. Then when you get past 4500 the mains come on line. AND maybe the stumble as you give it a twist at that 4500 RPM.

This is an interesting thought. A couple of years ago I had a ~4500 rpm stumble so I took apart the carburetor, dipped them, with the same result. To mitigate against this stumble I crack the choke lever over just an 1/8 of an inch. Right now my carb is in pieces and I have a set of new seals from Louie. I will probably start riding again in March so I'll report back my experience then.

Naive me, I didn't even know those seals existed. A couple of years ago I dipped both throttle bodies in a can of carb cleaner with the seals still inside. Without this forum, and CDNLouie resurrecting this 2007 thread, I would have NEVER learned about them.

VFan

[Rick G]

Failed butterfly seals will produce difficulty in tuning the carbs and also a wandering idle.

Age  is certainly a factor, but many seals die from the carbs being left in the dip too long. I don't recommend leaving them in longer than 30 min.
I've had the the plates out on a couple of carbs (they were staked and the screws were scarificial)  its very easy to bend the shaft while attempting to remove them.

While working on old bikes in OR. during 2001 -2004, I worked on a XS650 with bad seals . we replaced the outer seals  but had no luck with the inner ones. We ended up with a small O ring , which worked , but I have no information on the long term effects.

[VFan]

for winter, I suggest draining the carbs AND the tank, removing them & fogging them with stabil.

What does "fogging" mean? When I had a PWC, as part of the winterizing it I used to fog the engine by spraying Fog oil into the throttle body for 30 seconds as the engine was running before shutting it off.

I'm assuming Lucky is using the term fogging to mean spraying Stabil Fog through the drain hole after the gas has been drained? Meaning no dis-assembly?

Thanks,
VFan

[Lucky]

To me fogging is a general term that implies getting a protective coating everywhere possable, basicly use whatever you like to coat the inside of the tank (empty) with an oil film. probably best stored upside down because any condensation formation will penatrate oil and attack those lower corners..

for the empty carbs douse them in stabil, shake out the excess and store them in ziplock bags or sealed totes...

[Tiger]

for winter, I suggest draining the cabs AND the tank, removing them & fogging them with stable.

What does "fogging" mean?

Fogging oil comes in a spray can and comes out in a mist/fog like way. It allows you to coat your cabs, cylinder walls, gas tank, etc, with a product that protects the metals from rusting/gumming up, etc, when laying an engine up for a period.

Spray some through the cabs with the engine running, shut the motor down...remove carb drain plugs and spray fogging oil in to the cabs, replace drain plugs.

Remove the spark plugs and spray in to cylinders, replace spark plugs.

You can empty the gas tank of ALL fuel and 'fog' the gas tank, if you wish... :-\

I keep a full gas tank...premium fuel and stabiliser...and fire the 'V' up every two weeks or so, let her get up to working temps, leave her running for a few minutes and shut her down again. This is my regular winter procedure... ;)

                8) ....... TIGER ....... 8)

[Lucky]

Tiger is there ethanol in the gas in Canada?

[Tiger]

Tiger is there ethanol in the gas in Canada?

:( Sure is...

[Rick G]

When I lived in MN. I was given a 1968 CB160. The owner had stored it in heated storage for 26 years. He discarded the battery, drained the tank and ran it out of gas.
When I bought it , I figured I'd have to rebuild the carbs and coat the tank. I was eager to hear it run, so I hooked up a battery charger to the battery wires and put a bit of gas in the tank and jumped the ignition terminals on the back of the switch. (it came with no key)
I pulled the choke on and kicked it over and for the first time in 26 years  it started and immediately settled in to an idle. I was dumbfounded!!  But  it was prepaired for its long sleep.
The 1976 CB100 I acquired about the same time had sat for over 20 years with 1900 miles on it , original tyres chain and sprockets. But it had not been prepaired and need a new gas tank and a carb rebuild.
Preparation for storage is essential.
I much prefer, Seafoam added to gas instead of stabil.

[Jimustanguitar]

Part No. 5598 fits all butterfly shafts of 8mm with housing I.D. of 11.5mm.

I was wondering if we could get a bit of a deal on a few.  In talking to Martin at Keyster he mentioned that Robert at www.motorcyclecarbs.com  (who is one of Martin's Keyster dealers) is stocking them and he just orders what he needs from him.  They are 6.00 US a piece.  Shipping unfortunately increases the price substantially.  It gives us a contact anyway.

Louie  :)

Motorcyclecarbs.com, Inc.
4292 Country Garden Walk NW.
Kennesaw, Ga. 30152 USA.
Office: 770-974-8851
Fax: 770-974-8852

Looks like the part number has been superseded and is now 10904.