Zenith 32NDIX stripped thread

[Simon Whittley]

Hello,
Any suggestions for fixing a stripped thread on the carb body (caused by the throttle return spring pulling the screw out of line)

IMG_7542.JPG (2.49 MiB) Viewed 2093 times

[Dave Wildrick]

The only information I have on this is from 2002, but may help you:
[Subject: Zenith covers
From: "Walter E. Grube, Jr." <wegrubejr@talon.net>
Date: Sun, 25 Jun 2000 16:17:39 -0400

In my local hwe store yesterday I spied taps and dies in 5mm x 0.8
and 5mm x 0.9 , made by Vermont American tool company.
In addition the the request for what is a cheesehead bolt, how about
also carriage bolts, stove bolts, machine bolts, ad infinitum. On rainy
days, just walk thru your local big hardware store, like Lowe's, home
Depot, etc, and windowshop the fastener collections.
Mike R., or somebody, I forgot what they called those countersunk
bolts that hold plowshares on.
Walt.

Subject: Re: Zenith carb screws
From: Steve & Barbara Proctor <stp356@theriver.com>
Date: Thu, 07 Mar 2002 19:53:36 -0700
>Yes, just repaired a carb top last month with a helicoil. The screw that
>normally causes the problem is the one that holds the return spring
>bracket. The thread engagement is diminished on this screw. I have used
>the M5 x 0.8 helicoils for this application since the 1980s. The last one
>was actually done with the carb on the car and it worked great. Now the
>screw will take LOTS of torque.

STP

Subject: Zenith helicoils
From: calsspeedster@webtv.net (Cal Ensor)
Date: Sat, 9 Mar 2002 09:19:16 -0700 (MST)

I understand Kendall Krieg sells 2 sizes ,
5x.9 for original bolts and 5x.8 for the more common replacement.He can
be reached at KKrieg4643@aol.com,no affiliation but a satisfied
customer.
He also has a large assortment of cabriolet components.
Cal

R.C.(Cal)Ensor
7230 S.Prince St.
Littleton,Co.80120
Speedster 80613
Registry Member #1316

[Simon Whittley]

that's very helpful, thanks Dave

[Jacques Lefriant]

BTW you should have used the stock longer bolt. CFI I been told has the correct thread repair kit. Carb Rescue's repairs are marginal.
j

[Vic Skirmants]

I have never seen a longer bolt in that location on a Zenith; Solex, yes; Zenith, no.

[Dick Weiss]

There are 2-versions that I do to repair the hole in the zenith body for the return spring -hook.

1. I undercut the OEM 5x.9mm screw so the 'lengthened threads (20mm) will reach what's left of some
threads not stripped out from the bottom of the hole.
2. OR--I use a 6x1.0x20mm bolt and modify the hex head to look like an OEM hex head, adding the slot,
and the carb's body will be tapped for the threads.
As mentioned, 1-of-8 top cover screws on Solex carbs is longer for the hook's thickness; Zenith's don't.

I also repair stripped banjo bolt threads in the zenith's top cover w/a threaded/bonded bronze insert;
I don't use Heli-coils. I have several covers for exchange or sale during Hershey/Stoddard swap meets.

[Martin Benade]

Is that bronze insert something that you make or buy?

[Al Zim]

If you want something that works but do not mind if it does not look like the other bolts, you can use a standard thread bolt and tap the hole for the larger bolt. it is better to use a fine thread bolt. I have used a lot when people were price conscious and do not remember any failures. al zim

[Dick Weiss]

I make the special insert, Martin.

[Dick Weiss]

I make the special insert, Martin.

[Dan Kalinski]

Get the part from Dick, or you can do this where you only need an end-mill and a lathe:

https://video.search.yahoo.com/yhs/sear ... ction=view

[Ron LaDow]

I do not know if any of the current repair folks are offering this, and if not, why not, but it is neither expensive nor difficult to get a helicoil of the correct pitch in a stripped hole.
Any good cutter-sharpening outfit can make you a tap which matches the standard m5 diameters and has the correct pitch; mine cost ~$80 some time back and adding two more put it to $100 (the extras are gone).
You'll have to grind relief on the installation tool to keep it from forcing the wire into the wrong pitch, but other than that, hey, you're golden. If you do more than one set of carbs, you're probably right-side-up on buying the tap and an M5 helicoil kit.

[Martin Benade]

Ron, is the $80 tap what you use to prep the hole for a helicoil, allowing the almost-correct-pitch helicoil to be installed as the correct pitch thread? The exactly right setup is not available?

[Ron LaDow]

Ron, is the $80 tap what you use to prep the hole for a helicoil, allowing the almost-correct-pitch helicoil to be installed as the correct pitch thread? The exactly right setup is not available?

Martin,
The exactly right setup is available.
A good tool-grinding shop can deliver a tap which is an *exact* match to the pitch and is an *exact* match to the the helicoil OD and ID tap dimensions. The *EXACT* match; no foolin', and why this is a question is a mystery to me.
I posted this at the time Pre Mat was offering Zenith rebuilds; this is not magic, folks. Call Cliff at Pacific Reamer and order an m5 X? (can't remember the pitch) helicoil tap.
The *exactly-right* tap is available as simply a custom order to whatever cutter-grinder shop you choose.
Why this is yet not widely known is a mystery to me; doing the right fix is probably cheaper than doing two carbs wrong.

[Martin Benade]

Isn’t it then a less expensive off the shelf kit from Helicoil? I don’t understand why you needed a special tap made.