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Carb idle jet oring?

Posted: Mon Feb 04, 2019 9:54 am
by JimmyC
I am sorting out a misfiring cylinder on my truck and suspect it is fuel mixture related. I removed the jet cover and pulled the jets. The slow-running jets (1-40-28, 700.1.08.405.1/60) had o-rings in their seats. The drawing in the parts book does not show an o-ring here.

Does anyone know if there are suppose to be o-rings here?

Thanks!!

Re: Carb idle jet oring?

Posted: Mon Feb 04, 2019 10:47 am
by rmel
Going though some Carb tweaks and fixes myself on my 712 project.
O-rings on the Injectors as they would experience fuel under positive
pressure from the accelerator pump. No O-rings or washers for the Idle
jets they operate under a vacuum. So your right they don't belong there.

Re: Carb idle jet oring?

Posted: Mon Feb 04, 2019 6:33 pm
by boeing7873
As far as I remember, there are two types of idle jets. Old type and new type. Only the new ones have the o-ring. Check these pictures on Ebay.

https://www.ebay.com/itm/ZENITH-NDIX-CA ... :rk:8:pf:0

https://www.ebay.com/itm/ZENITH-NDIX-CA ... Sw7NNUIrbI

Re: Carb idle jet oring?

Posted: Mon Feb 04, 2019 7:48 pm
by rmel
Thanks for posting that link! Interesting, well my idle jets are definitely the older style
as per the Pinz doc's. The telltale is there's a seat for an O-ring with thee newer ones.
Kind'a not necessary though, as far as a fuel leak, always under a vacuum -- one could
argue though there could be a very minor vacuum leak.

Re: Carb idle jet oring?

Posted: Tue Feb 05, 2019 12:58 pm
by Hotzenplotz
Gentlemen
don't get confused

Image
items 20 and 21 on tis pic are the main jet and the idle jet underneath the lid. neither of these jets has an o-ring, but the pump jets 36 do

Image

The idle mixture screw here in the throttle assemby number 11 does have an o-ring number 12
these pics show version 2 and 3 of the carbs. version 1 has the idle adjuster screw with the larger head

Re: Carb idle jet oring?

Posted: Tue Feb 05, 2019 1:41 pm
by rmel
Hmmm, interesting, well it is confusing, especially if your reference
is the standard hard copy Ersatzteilkatalog, Group 1 40. Which is far
more cluttered with breakouts than your images and shows no reference
to O-rings for the Idle valves #62 and #63 (spring). I guess one should
always double check both the hard copy against the www.Puch.at
site for discrepancies. They must be more up to date than something
that was printed in 1985 (or older) :?

Re: Carb idle jet oring?

Posted: Wed Feb 06, 2019 9:26 am
by JimmyC
Thanks for all the help. So mine had o-rings on the idle jet and has run fine until recently. I have taken them off. The o-rings onthe idle mixture screw (small type) are missing. I will put some there.

My front is small screw and my back is large screw. I don't have a good picture of the large screw type. Does it have an O-ring on the mixture adjustment screw?

And finally the idle cut-off valve. It doesn't have a gasket or a soft washer and it is not tapered threads. It seems like it would leak. Do people put it on dry or use pipedope or hydraulic sealant?

Re: Carb idle jet oring?

Posted: Wed Feb 06, 2019 9:33 am
by pcolette
JimmyC wrote:
Wed Feb 06, 2019 9:26 am

And finally the idle cut-off valve. It doesn't have a gasket or a soft washer and it is not tapered threads. It seems like it would leak. Do people put it on dry or use pipedope or hydraulic sealant?
Dry.

Re: Carb idle jet oring?

Posted: Wed Feb 06, 2019 10:36 pm
by edzz
Assume you have looked at Jim's excellent Pinz carb pages :D
http://www.goatwerks.com/carbarticle.htm
http://www.goatwerks.com/carb.htm

Re: Carb idle jet oring?

Posted: Thu Feb 07, 2019 5:34 pm
by JimmyC
My carb is back together and I will try it in the morning. Except for the extra orings on the idle jets, there was no obvious problem.
JIm L's instructions were great. I would only add one thing: Until you get your float level right, use the old top gasket; save your good gasket until you have the float adjusted, then check it again with the new gasket.

It would be smart to have a spare top gasket or two in case you have trouble with the float level when you put the new gasket on. Evidently not all gaskets are the same thickness.

Re: Carb idle jet oring?

Posted: Thu Feb 21, 2019 8:19 pm
by JimmyC
Runs great with clean carb. Must have been something in it.