Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Dolmar Makita => Topic started by: dolmar on September 13, 2014, 10:26:42 pm

Title: 5100s air leak
Post by: dolmar on September 13, 2014, 10:26:42 pm
what is the best way to find a air leak on my 5100s, saw run great last year but now I got a air leak somewhere any help would be great thanks.
Title: Re: 5100s air leak
Post by: 660magnum on September 13, 2014, 10:42:29 pm
You can do a close examination but likely the only way you will find it is with a pressure vacuum test.
Title: Re: 5100s air leak
Post by: 660magnum on September 13, 2014, 10:55:48 pm
Sources of air leaks . . .

Seals around the crankshaft bearings on either the chain or flywheel side or both sides.

Carburetor intake rubber boot

Compression relief valve but I don't think the 5100s has one?

Impulse line if it has one.

- - - - - - -

The test involves blocking off the carburetor and muffler exits. Pump up the engine with 7 lbs of air pressure and check for leaks with soapy water? If you find the seals leaking at the crankshaft on either side, you have found the problem and no need to do the vacuum test.

And then draw 15" vacuum on the crankcase and see if it still has 10" vacuum after 30 seconds. The vacuum test is to check for bad seals on the crankshaft ends. The vacuum test will show the seals bad where the pressure test did not.

If it fails, you try some heavy oil on the seals and see if it changes the leak rate any.
Title: Re: 5100s air leak
Post by: Nathaniel Vansickle on September 14, 2014, 06:34:14 pm
+1 and no decomp on a 5100
Title: Re: 5100s air leak
Post by: 660magnum on September 14, 2014, 06:39:11 pm
I have a 5105 with no decompression but didn't know about the 5100.
Title: Re: 5100s air leak
Post by: dolmar on September 20, 2014, 08:20:55 pm
still cant find the air leak checked everything I could think of any of you guys had this problem with your dolmar
Title: Re: 5100s air leak
Post by: 660magnum on September 20, 2014, 08:27:21 pm
I have a 2009 5105 but never any trouble with it.

I've seen a couple 5100's with the clutch side bearing spinning.
Title: Re: 5100s air leak
Post by: farmboy on September 20, 2014, 10:05:57 pm
+1 and no decomp on a 5100
I put a  decomp on one of my 5100's won't do that again  pops it out every pull.  It is pulling 205 psi w/base gasket tho.  Checked it w/2 guages.
Shep
Title: Re: 5100s air leak
Post by: jmester on September 21, 2014, 07:01:21 am
Not real familiar with the Dolmar saws. But may be worth a try to check the cylinder base screws for tightness. Have seen them come loose on some 50cc husky saws. Has the saw sat since this time last year? If so you may need to look for a fuel issue more so than a air leak.
Title: Re: 5100s air leak
Post by: aclarke on September 21, 2014, 11:29:19 pm
As Jmester mentioned, i'd look into fuel flow issue. Perhaps pull the carb apart and clean/inspect
Title: Re: 5100s air leak
Post by: dolmar on September 22, 2014, 08:02:02 pm
what makes you guys think it might be a fuel problem it was running just fine as soon as I pulled it up to cut again I noticed it was starting to rev way up I shut it down and started to check things out it was fueled up with fresh gas I work on all of my stuff it sounded like it just got leaned out right now
Title: Re: 5100s air leak
Post by: brokenbudget on September 22, 2014, 08:25:38 pm
if the little screen in the carb is getting blocked (either from a passing fuel filter or fuel gumming) it will act somewhat like an air leak.
best to check the easy and most obvious first.
Title: Re: 5100s air leak
Post by: jmester on September 23, 2014, 05:54:44 am
saw run great last year but now I got a air leak somewhere any help would be great thanks.

This is where I was thinking maybe a fuel issue. Saw ran great last year but now I have an air leak. Witch I assumed that you have not run the saw since last year.
Title: Re: 5100s air leak
Post by: aclarke on September 23, 2014, 12:25:25 pm
Run away motor is gonna be lack of fuel or too much air.  If it has been running great and the issue is spontaneous I would look first at a torn fuel line, pulse line, intake boot.
 In my experience that particular carb in the 5100 runs really lean and any small amount of crap under the Welch plug or low speed metering circuit can compound that issue and burn up a motor quickly.  Check the basics, like the above items as well as loose cylinder bolts and make sure the piston isn't damaged from the lean out.  Granted, everything else checks out, I would suspect dirty low speed circuit on the carb or worst case crank seals...
Title: Re: 5100s air leak
Post by: 660magnum on September 23, 2014, 01:08:37 pm
5100's were kind of known to get this way.
Title: Re: 5100s air leak
Post by: jmester on September 23, 2014, 04:21:39 pm
Did you try and richen up the high speed?
Title: Re: 5100s air leak
Post by: woodplayer on January 10, 2015, 11:46:55 am
what makes you guys think it might be a fuel problem it was running just fine as soon as I pulled it up to cut again I noticed it was starting to rev way up I shut it down and started to check things out it was fueled up with fresh gas I work on all of my stuff it sounded like it just got leaned out right now

Mine would run well on an upcut but lean out when cutting normally.  I found that the fuel lines on the early models were a little soft and too long and would sometimes kink and restrict the fuel.

Here is a link to dating back a few years to someone else who had the same problem, as well on the 2nd page of the thread I had included a link to my original problem.
http://www.arboristsite.com/community/threads/my-dolmar-5100-wont-run.106668/page-2

I might have some photos kicking around if you need them.
Title: Re: 5100s air leak
Post by: 7sleeper on January 13, 2015, 03:38:06 am
+1 and no decomp on a 5100
Here in europe they had the Makita 5001(I forgot what the exact Dolmar counterpart was) which came standard with a decomp. I know because I had one.

7
Title: Re: 5100s air leak
Post by: Nathaniel Vansickle on January 14, 2015, 10:46:11 am
i was doing a bit of research on the 5100-5105 and ran across this. So it is possible that you will see one with a decomp.
Title: Re: 5100s air leak
Post by: 660magnum on January 14, 2015, 11:24:59 am
My 5105 is the hardest to pull over saw I have.

However it fires if you can get it past Top dead center and has never back fired or kicked back.
Title: Re: 5100s air leak
Post by: farmboy on January 14, 2015, 01:28:14 pm
I installed one on one of my 5100's won't do it again it pops it out every pull. 
Shep
Title: Re: 5100s air leak
Post by: dolmarfan on January 16, 2015, 04:12:20 am
My dolmar 5000 the european version of 5100 has decompresion valve.