TOPIC:

Thanks for the validation and advice Scotch. You're correct on the terminology regarding the Choke supply tube. In my haste to post my findings I got carried away with the words. The old brain is thinking about what to say and not so much about how to say it. We need to all speak the same language. I'll try to get it right in the future.

I agree with you about not tearing down the throttle plates and shaft. There's no gain to doing that, BUT I have a concern. Looking at the exploded view of the carb, I see that on the outboard end of the throttle plate shaft there is what Kawasaki refers to as a "oil seal" part number 92093-1027. I haven't looked at it yet but I'm assuming it's a lip seal to keep atmospheric air from leaking past the throttle shaft/ bushing. Won't soaking it in lacquer thinner destroy the elastomer seal? Or is the lacquer thinner not toxic enough to damage the seal. I'm also wondering if the o-rings are nitrile (buna- N) based. I believe you're in the UK and not sure about your fuel over there. When they pulled the Tetraethyl lead out of our fuel they replaced it with Ethanol. 5% for regular fuel, 10% for midgrade and 15% for premium. I know on my 1980 Porsche 928 I had to upgrade all the "rubber" components in the fuel system because the "new fuels" were destroying the elastomers. (Oh, and if you didn't the pressurized fuel system would burst and engine compartment fires were common)

Would appreciate hearing your thoughts on this matter.

You've asked a valid question to which ....wait for it ...............

"I don't have a definitive answer".

The boilings and soakings I have put my '80 set through and the recent '79 set rebuild, do not appear to have had any adverse affect on either set. I say this purely on the ability to get them sync'd and for that synchronization to hold.

I have never had the throttle shafts out of either so I have not had that seal in my hand to test it for incompatibility to fluids such as lacquer thinner.

Having said that:

1) I live in British Columbia Canada

2) Anyone out there actually had that seal out for replacement? Any formal comments ?

3) Certainly there is a concern here for you so reduce the soaking time to 30 minutes per side. The syringe flow-test will confirm the results. Repeat the 30 minute per side soaking as often as required to get the transition porting to stream fully and equally.

4) Odds are that the seal is offering minimal sealing capability anyway, now. I say this based on the '79 carbs "factory original" idle-air screw O-rings (presumably made from the same material) having shrunk slightly and not providing a seal for the idle screws.

5)Hypothetically one could also suggest that carbs having sat for many years would have the seals stuck to the shaft or shaft-bore which could damage the seal surfaces the first time the shafts are rotated.

6)Bottom-line: I have never concerned myself with this issue because the primary objective was to clean the carbs so they could operate as correctly as possible. The need to replace the shaft seals would then be of concern if the carbs couldn't be sync'd and were not holding that adjustment.

Again: A very GOOD question !

It is sometimes difficult to remember the objective was to drain the pond, when you're up to your ass in alligators !

scotch

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This is an excerpt from the Parker O-ring handbook which would explain what Scotch was describing as shrinkage of the orings noted on the air bleed screws after cleaning.

3.9.4 Fuel System
Gasoline and diesel fuels are used in normal commercial
vehicles. Fuels are more aggressive than mineral oils and
cause higher swelling of the elastomer which increases with
temperature. Swelling of an elastomer in fuel is, however,
generally reversible when the absorbed fuel vaporizes completely.
When parts of a compound are dissolved or leached
out of the elastomer however, shrinkage takes place which is
permanent. If a nitrile-based compound is required, a compound
must be selected which contains minimum amounts
of plasticisers, anti-aging or anti-ozone additives. By careful
selection of the seal compound, the tendency to shrinkage or
cold brittleness is avoided.
Figure 3-6: O-ring Linear vs. Volume Change Relationship

I believe too, IMHO, that because the "seal" referred too is not in flow/circulation nor being physically handled (scrubbed) but rather just being "wet" by the solvent - the damage concern is of little or no significance. Again: its' age probably has more detrimental affect.

An omission on my part and something worth mentioning is the drop of a light machine-oil placed on the throttle-shafts where they pass through the venturi. 4 points per carb. This is more to lube the metal to metal contact but the seal might benefit also.

None of the throttle shafts on the 3 '79 carbs would rotate without significant force when first received. The boiling in water/lemon-juice freed them noticeably and the soaking in lacquer-thinner freed them completely. The drop of oil seemed obvious - maybe why I didn't mention it.

Wow, having just read and digested all of the information I think I will stop trying to get the bike running and just remove the carbs and start from scratch - thinners, tooth picks etc etc. You guys really know your stuff.

Thank you all.

For the record, I did a little experiment yesterday with a cut o-ring from the carb bowl drain screw. I dropped it in a teaspoon of lacquer thinner for 20 minutes. First I checked the diameter with my vernier at .064" and after 20 minutes it had swelled to .075" and was as soft as butter and I literally wrote my name in my hand with it.

The 1980 carbs I'm doing now will be stripped of all the O-rings and cleaned, flow checked and rebuilt with new O-rings. I'm going to put a call in to Parker O-ring technical on Monday and see what the latest o-ring material they suggest for gasoline which has an ethanol blend. Just looking through their catalog and I see a least 5 elastomer materials that could be used.

I can't justify buying carb kits when all you really need are the O-rings and a bowl gasket. I'll just buy bulk gasket material and cut the three gaskets, pick up the O-rings from Parker and do the carbs. At some point I'll post the o-ring part numbers so that others can just buy the O-rings.