Author Topic: Early 1990's 044 vacuum test question  (Read 108 times)

0 Members and 0 Guests are viewing this topic.

Offline Wood Butcher

  • 3 cube
  • *
  • Posts: 18
  • Karma: 0
Early 1990's 044 vacuum test question
« on: October 24, 2014, 11:55:31 pm »
Hi, inhereted an 044 from a buddy of mine who's too old to use it.  Sat for 5 years.  I rebuilt the zama carb, which made a difference but I still can't seem to get it to really run right.

Performed a pressure test to check manifold and pulse tube, which are air-tight.  Didn't want to check the seals unless it was as a last resort.

I vacuum tested it and it held vacuum fairly well.  Shop manual says it should hold (in psi, which I converted to inches of mercury-Hg) 11.8 Hg for 20 seconds and not rise above 8.7Hg.  I vacuumed it down to 11.8Hg and after 20 seconds it was showing 10.4Hg, which is pretty good for a 20+ year old saw.

So here's my question:

I'd have to do a little more setup to do a quality pressure test with actual values, but I can measure vacuum easily.  So, if a saw holds vacuum, can I assume it's holding pressure?

Share on Facebook Share on Twitter


Offline 660magnum

  • Global Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 6437
  • Karma: 249
  • For The Love Of Chainsaws
  • Location: NCO
Re: Early 1990's 044 vacuum test question
« Reply #1 on: October 25, 2014, 12:07:35 am »
The definitive way to check the seals is the vacuum test. Seals will pass a pressure test but fail a vacuum test. So I would say that your seals are OK. The test vacuum value is 1/2  atmosphere or 15" and the test pressure is also 1/2 atmosphere or 7lbs. With the vacuum test you are to still have 2/3 of your original test value after 30 sec.

There is no need for you to do a pressure test now. The ease of the pressure test is that you can bubble check for leak areas externally.

A friend put a dual port front on the muffler of a early 044 last year and it really made a difference. He gutted the dog house out of the muffler inside also. It certainly was a likable saw after he changed the muffler. He obtained the muffler cover from HLS

Make sure your fuel and impulse lines are in perfect shape.
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
Be all that you can be . . .

Offline Wood Butcher

  • 3 cube
  • *
  • Posts: 18
  • Karma: 0
Re: Early 1990's 044 vacuum test question
« Reply #2 on: October 25, 2014, 10:54:59 am »
Hey 660...thanks for the reply.

I did a pressure test, it just wasn't all that sophisticated.  I pressurized the saw by covering the carb w/ a 1/4" piece of plate steel I drilled holes through and using a rubber gasket.  Muffler was sealed with one of those Stihl triangular things between muffler and cylinder.  Pressurized it to about 10 psi.  The manifold got bigger, so I think I had enough pressure.

I checked the pulse tube and manifold for leaks with a soap solution.  They pass.

I did change the fuel filter, but did not change the fuel line.  I will order one of those.  Will also check cylinder base bolts. 

It feels like a fuel delivery problem to me.  The fuel tank vent on top has two fine screws- one about halfway in the line and another at the end of the line.  I took the line off completely and ran the saw and it didn't make a difference.  Are those screws correct?

Offline 660magnum

  • Global Moderator
  • Nitro Hotsaw
  • *******
  • Posts: 6437
  • Karma: 249
  • For The Love Of Chainsaws
  • Location: NCO
Re: Early 1990's 044 vacuum test question
« Reply #3 on: October 25, 2014, 12:17:29 pm »
Yes the little set screw are correct.

You can make a new vent with a new piece of Tygon and put the two screws in there just like in the old one.

You can check the vent with your vacuum pump to make sure it works.

The block-offs you did were good but next time only use 7 lbs pressure.
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
Be all that you can be . . .

 

Related Topics

  Subject / Started by Replies Last post
17 Replies
613 Views
Last post August 03, 2013, 08:50:20 pm
by Cut4fun .
6 Replies
346 Views
Last post November 10, 2013, 07:13:26 am
by rayvil01
4 Replies
200 Views
Last post January 21, 2014, 04:55:55 am
by 660magnum
Early Stihl 028 AV

Started by KilliansRedLeo « 1 2 ... 5 6 » Stihl

50 Replies
615 Views
Last post March 22, 2014, 10:08:33 am
by KilliansRedLeo
4 Replies
68 Views
Last post June 08, 2014, 10:35:37 am
by Cut4fun .
4 Replies
115 Views
Last post July 14, 2015, 08:53:42 am
by Mnd
early 10-10A

Started by countryhog « 1 2 » McCulloch

14 Replies
659 Views
Last post July 23, 2016, 04:26:36 pm
by Eccentric
1 Replies
365 Views
Last post August 09, 2016, 04:33:12 pm
by Cut4fun .
6 Replies
124 Views
Last post May 19, 2017, 09:37:53 am
by Seldomseen
3 Replies
124 Views
Last post June 07, 2019, 03:03:12 pm
by HolmenTree