Compression tester issues?

[Okie]

I found these cores at a nearby NAPA. part# 700-9556 (quantity of 5)

Just for giggles and comparison, I once tried the core from a (Chinese) wheelbarrow tube.
IF memory serves me, It cut the compression reading by nearly half!

Good info. Using a standard automotive valve my compression readings went from 150 to 30# if a auto red band
and 50 with the non-modded weaker spring long auto valve with the clear/white band.

I tried to find the snap on MT24DA1,or MT24DB1 that the guy mentioned above and appears they are a discontinued item. I did see a Milton 1251-2 and a Lisle 20100, but not sure of their operation. (and they are pricy)
I've seen more Schrader valves give error reading than I have valves that would give correct readings.

I'll research the Napa Balkamp 700-9556.
My long type modded Automotive clear/white band with 4 turns cut off the little spring are working great for my homemade tester. It is kinda strange that the automotive type will not fit my Actron 7828 and vice versa. (appears that the threads are different, they will not even give a promise of a fittament. (the actron Schrader valves might be metric???)

Have you ever tested to see if the 700-9556 will fit into a standard automotive tire valve core? (my ORM actron 7828 valve will not fit into a standard auto valve core??)and vice versa

Thanks for the Napa valve info.

 

[LegDeLimber]

I haven't tried to swap the 700-9556 into an automotive stem.
Dangit, now I'm curious about that switch out.

 

[torch]

I tried to find the snap on MT24DA1,or MT24DB1 that the guy mentioned above and appears they are a discontinued item.

Really? Wow. I bought 2 of the MT24DB1 just a couple of months ago from the online store.

I wonder if it's a US-Canada thing? I think mine were shipped from Alberta, IIRC.

For fun, I checked the opening force of a couple on a postal scale: 20 - 25 grams of spring pressure required. Then I tried some regular tire valve cores (with red rubber seats): 250 grams. I have an old Equus (cheap Chinese Canadian Tire house brand) compression gauge. I pulled the core from it and found it has a clear seal; it was the lightest of all at 5 grams. If I hold the compression release open on that gauge, I can blow through it by mouth.

 

[Okie]

I haven't tried to swap the 700-9556 into an automotive stem.
Dangit, now I'm curious about that switch out.

Let us know what you find about the swap out????

 

[Okie]

Really? Wow. I bought 2 of the MT24DB1 just a couple of months ago from the online store. Well the MTDB1's showed as available today at the online store @ 3 for $6 (have to register before ordering and shipping to lower USA would probably be out of site, I did not register) but now the NASA 700-9556 is easier for me to acquire if still available in local NAPA store.

I wonder if it's a US-Canada thing? I think mine were shipped from Alberta, IIRC.

For fun, I checked the opening force of a couple on a postal scale: 20 - 25 grams of spring pressure required. Then I tried some regular tire valve cores (with red rubber seats): 250 grams. I have an old Equus (cheap Chinese Canadian Tire house brand) compression gauge. I pulled the core from it and found it has a clear seal; it was the lightest of all at 5 grams. If I hold the compression release open on that gauge, I can blow through it by mouth.

I briefly tried a digital postal scale and a digital reloading scale to check the spring tension opening and could not get a stable reading to ID a exact opening by reading the scale, but placing the valve inside a core and just pushing on the stem with a drift punch I could get a feel for when they are correct pressure and most likely to read correct when installed in the tester.. Main thing is that they re-seat. If too many turns of the spring are removed they won't re-seat (hold back pressure good) and even stretching the spring is temporary fix if too many turns are cut off.
I've used scales to check other type larger springs with good results though.

 

[Okie]

I got 3 of the Napa 700-9556 compression gauge Schrader valves today after the local NAPA ordered from their warehouse. The come 5 in a box and you can buy them each @ approx. $2.20 each. They worked A-ok. One was defective out of it's sealed package, was not spring loaded on back check due to a broken spring, noticed immediately before attempting install for test..

The NAPA Balkamp 700-9556 have the white band and the spring is very weak and wimpy. My long type automotive with 3 turns cuts off the spring worked just as good in the homemade tester using the automotive valve stem in the spark plug adapter.

I was wrong about the Actron 7828 valves being a different size than standard automotive Schrader valve threads and size fittament..
I was just being too careful with the only actron low pressure OEM core that I had as it was not starting easily into the auto valve core looked different and the automotive was not dropping down into the actron adapter normally.

 

[Okie]

I will say that I am by NO means saying you shouldn't use a compression tester, I am just saying sometimes all is well even if you get a low reading....

Yes: (about compression tests)
I've got a couple of small Homelites that read a weak 80psi that run, start and cut good. Normally anything less than 100-125 is reject.
I seen a little Stihl MS170 that would just fall to the end of the pull rope with very weak compression felt on the rope. It would always start and run good with lots of power. I could not believe what I was seeing. Wish I had tested the compression out of curiosity but I just accepted such and let it do it's thing. A Guy had brought it too me for a minor repair.
Also do not believe all those high compression reading you see on ebay from sellers of saws. Those reading can be from a air compressor, not the saw.

 

[JP56]

I found these cores at a nearby NAPA. part# 700-9556 (quantity of 5)

Just for giggles and comparison, I once tried the core from a (Chinese) wheelbarrow tube.
IF memory serves me, It cut the compression reading by nearly half!

WOW! Only 3 years after this post, and NAPA no longer has this part number or anything even close to these cores. WTF?

 

[a. palmer jr.]

I will say that I am by NO means saying you shouldn't use a compression tester, I am just saying sometimes all is well even if you get a low reading....

Yes: (about compression tests)
I've got a couple of small Homelites that read a weak 80psi that run, start and cut good. Normally anything less than 100-125 is reject.
I seen a little Stihl MS170 that would just fall to the end of the pull rope with very weak compression felt on the rope. It would always start and run good with lots of power. I could not believe what I was seeing. Wish I had tested the compression out of curiosity but I just accepted such and let it do it's thing. A Guy had brought it too me for a minor repair.
Also do not believe all those high compression reading you see on ebay from sellers of saws. Those reading can be from a air compressor, not the saw.

Many of the older saws have a reed valve and as such can get by with lower compression readings. Something like a newer Stihl use a piston ported engine and no reed valve and have to have over 100 to run, preferably higher.

 

[Okie]

WOW! Only 3 years after this post, and NAPA no longer has this part number or anything even close to these cores. WTF?

Yes, seems strange. That they are NLA from Napa. You can find some notes where I removed some coils from the spring on some of the long type Automobile schrader valves and made them work ok. I did this mod when I seen the inflated price of the special low pressure types and I happen to have a bunch of the automobile type in my flat fixing stuff.

Here is some info I happen to have on file about small engine compression testers and schrader valves.

https://www.arboristsite.com/community/threads/compression-tester.336165/

Watch in the upper right hand corner of the video for the Amazon link to his tester. (or here is the link)https://www.amazon.com/gp/product/B...pa-20&linkId=cdbd6f22890e891c57a50a4c630c7756
It is a Actron CP7828A. I bought one just to get the adapters. It worked ok, but only comes with the one low pressure special valve. If the valve gets to where it don't backcheck (hold pressure) trying gently cleaning. Usually a small piece of carbon.


3 /2018
Napa #700 9556 is obsolete.

Here is a special low pressure schrader valve for compression gauges Milton and Lisle part number's and I seen them on flea bay as still available.

Milton 1251-2 @ about $5 each

Lisle 20100 @ about $7

 

[Okie]

Just because a schrader valve has a white band does not indicate that it is actually a low pressure valve. I've seen them different colors. A regular schrader tire valve will result in a low reading.

Here is an example.
https://www.ebay.com/itm/121040848441

I have two compression testers for small cc engines. If one reads low I confirm such with the other. One is homemade.