[AT] Spark Plug to Compression Tester adapter

Wed Nov 18 11:20:32 PST 2020

I stand corrected

Thanks
Dennis

Sent from my iPad

On Nov 18, 2020, at 11:19 PM, Stephen Offiler <soffiler at gmail.com> wrote:

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<mailto: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<mailto: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<mailto: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<mailto: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<mailto:md31043 at msn.com>>
> To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com<mailto: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<mailto:md31043 at msn.com>
>
> ________________________________
> From: AT <at-bounces at lists.antique-tractor.com<mailto:at-bounces at lists.antique-tractor.com>> on behalf of Dean VP <deanvp at att.net<mailto:deanvp at att.net>>
> Sent: Sunday, November 15, 2020 11:31 PM
> To: 'Antique Tractor Email Discussion Group' <at at lists.antique-tractor.com<mailto: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.
>
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>
>
> 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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