[AT] Spark Plug to Compression Tester adapter

Wed Nov 18 11:18:21 PST 2020

With all due respect, Dennis, the Cub uses an 18mm threaded plug, not
7/8".  (The HEX on the Cub plug is 7/8" however)

SO

On Wed, Nov 18, 2020 at 1:21 PM Dennis Johnson <moscowengnr at outlook.com>
wrote:

> I have a compression tester that has several fittings that screw onto a
> hose. One of them fits the 7/8” plugs on my Cub. Had it for a while, and do
> not remember brand. Good change I got it at O’Riley or similar store
>
> Dennis
>
> Sent from my iPad
>
> > On Nov 18, 2020, at 10:08 PM, Dean VP <deanvp at att.net> wrote:
> >
> > I'm sure old compression testers used the rubber tip that would work on
> the 7/8" spark plug hole because 7/8" spark plug sizes were more common
> then. Since I kind of abandoned doing engine work for 40 years I don't have
> the luxury of owning one of the old kits. I'm sure one or more has sold at
> an auction I attended over the last 20 years but I didn't have the smarts
> to buy one of them. But.... when testing a hand start tractor one really
> needs one that screws into the spark plug hole.  A Leak Down tester would
> also be useful.
> >
> > Dean VP
> > Apache Junction, AZ
> >
> > -----Original Message-----
> > From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of BRUCE MAHR
> > Sent: Monday, November 16, 2020 8:24 PM
> > To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com
> >
> > Subject: Re: [AT] Spark Plug to Compression Tester adapter
> >
> > I have an old one with a rubber tapered tip that's fits the 7/8s too
> >
> > Bruce Mahr
> >
> > ----- Original Message -----
> > From: Mitchell Daly <md31043 at msn.com>
> > To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com
> >
> > Sent: Mon, 16 Nov 2020 16:15:32 -0500 (EST)
> > Subject: Re: [AT] Spark Plug to Compression Tester adapter
> >
> > Keep us up to date on your project.
> >
> > Mitch
> > md31043 at msn.com
> >
> > ________________________________
> > From: AT <at-bounces at lists.antique-tractor.com> on behalf of Dean VP <
> deanvp at att.net>
> > Sent: Sunday, November 15, 2020 11:31 PM
> > To: 'Antique Tractor Email Discussion Group' <
> at at lists.antique-tractor.com>
> > Subject: [AT] Spark Plug to Compression Tester adapter
> >
> >
> > For those of you who have tractors with 7/8” 18 TPI spark plugs and
> would like to do a compression test with the low cost compression testers
> kits sold today  you are SOL.  All the threaded as well as rubber stopper
> adapters are too small. The biggest is 18MM. 7/8” is equivalent to just
> over 22mm.  Doing a compression test is impossible on a hand start tractor
> with that set up unless you can buy an adapter from 7/8” to one of the
> metric adapters in the compression tester kit.   I just found a company
> Billman Company that sells a few of those adapters of various sizes
> including one from 7/8” to 14 mm.
> >
> > https://brillman.com/?s=spark+plug+adapter&post_type=product
> >
> >
> >
> > I was thinking I was going to have to make one out of the compression
> kit rubber stopper adapter and braze it into the inside of a gutted
> sparkplug.  This is a better solution in my mind.  When I receive this I
> will be able to test the compression on my Hand start 1935 JD B. Will be
> able to compare cylinders by hand cranking, using a belt on the pulley or
> pulling it in gear.   My current guess is the compression on cylinder # 2
> is about half of #1 by the feel on the flywheel. We will soon find out.
> >
> >
> >
> > I also want to make sure that the manifold isn’t rusted out or leaking
> from the intake side to the exhaust side. So I made an adapter plate that
> fists on the carburetor intake side of the manifold and then drilled and
> tapped a ¼” Pipe thread and installed a quick connect air fitting.  With
> the adapter plate bolted to the carburetor inlet to the manifold I can add
> air pressure to the intake side of the manifold.  If things were perfect I
> should get no air leakage into the exhaust side but the intake valves may
> open slightly and allow air pressure into the combustion chamber.  With the
> flywheel at TDC on #! Cylinder all the valves should be closed.  If I get a
> bunch of air pressure into the exhaust I know I have a manifold problem. If
> that passes then if  the intake valves open  and I get no leakage out of
> the exhaust side than I know I have a good manifold and two good exhaust
> valves.  If I get some leakage out the exhaust then I probably have exhaust
> valve problems.
> >
> >
> >
> >
> >
> > Have to get the B out of winter storage here and start doing these
> tests. I brought 4 restored DLTX-10 Carburetors and 4 Magneto’s along so I
> can isolate if either one of those are causing me problems.   I hope I
> don’t have to pull the head on this tractor but my gut tells me that will
> be what happens as a result of the tests. Pulling manifolds on one of these
> old tractors is an exercise that usually ends up with 4 broken off studs in
> the head.  Broken off bolts don’t scare me like they used to but it takes a
> whole bunch of time and frustration to get everything cleaned up again
> ready for new studs. .  Maybe for once I will get lucky and not have to do
> major surgery.
> >
> >
> >
> >
> >
> >
> >
> > Dean VP
> >
> > Apache Junction, AZ
> >
> >
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