Piston question.

Guydreads · November 26, 2020, 12:32:56 PM

Hello! I've been working on my Partner 500 chainsaw, and I decided to take off the cylinder because, I mistakenly thought, I needed to take it off to get to the crank seal. Well, I found out recently that I don't have to. Anyway, that's NOT the question. The question is: there was a decent amount of what looked like carbon build-up on the side of the piston below and above the one ring. Is this normal? I don't know. The cylinder has some scratching but no major grooves. The top of the piston, as usual has plenty of carbon build-up. Thanks! And Happy Thanksgiving by the way

Real1shepherd · November 27, 2020, 09:43:35 AM

Can't say without pics.There are two types of buildup; coke and carbon. Carbon is fairly easy to get off with like a Scotchbrite pad....looks like soot. Coke on the other hand is baked on and crystallized. It's extremely hard and dangerous to even the hard plating. Take care in removing it.

After you get any aluminum transfers off your cylinder plating, run your fingernail across any scratches that are left. If your fingernail 'catches', you have a potential problem in the plating. Depending how deep, you may of may not be able to polish out the scratches.

Depending on the gas itself and the oil mix used, there is normal buildup and excessive buildup. Sometime you can run that expensive canned gas and a 40:1 mix or 50:1 mix with a couple of tankfuls and it will clean up everything inside your cylinder.

Kevin

Al_Smith · November 27, 2020, 10:15:53 AM

Usually if you have pyrolited carbon ( coke ) it's caused by bar lube oil that gets in the crankcase .The Partner model 500 is much like the larger p-85 and p-100 models as it uses an internal oil pump driven by a worm gear on the crankshaft ..
I just went through the same problem on a rebuild of two p-100's .The o-ring seal had degraded from age and it leaked around the shaft and pump housing sucking lube oil .They smoked like they were burning soft coal .It was just a simple matter of removing the pump which is easy and replacing the 0-ring which are inexpensive .The size of the o-ring escapes me but I bought a whole bag full so I can look it up .
I've had the same problem with McCulloch oil pumps that operate on crankcase pressure and vacuum pulsations .Leaking pump diaphragm.

Al_Smith · November 27, 2020, 03:09:15 PM

The o-ring I mentioned is metric 5 by 1.75 .A bag of 25 cost me around 6 bucks, flea bay .

Real1shepherd · November 27, 2020, 03:43:56 PM

Coke buildup is a common problem I've seen inside 2 cycle engines where the owners still insist on 32:1 or 16:1 mix.

Kevin

Al_Smith · November 28, 2020, 01:04:50 AM

On that we might agree to disagree .I've never seen one coke up on heavy oil mix .I have on leaky bar lube oil pumps .Those old marine Evinrude and Mercury outboards ran for decades on 16 to 1 oil ratios .Some are still in operation 50 plus years old .
Now saying that this is not 1965 and there are much better oils these days and thus the oil to gasoline does not need to be so oil rich .--but I still run 32 to one --old school ;) It's part of the never ending always amusing great debate of the oils wars .You have the 100 to 1 Amsoil bunch and the old fuddy duddies like myself .It's great sport 8)

sablatnic · November 28, 2020, 01:13:27 AM

Don't worry about the oilpump, it is external on the 500, located behind the clutch. But Al Smith is dead right about the 85 and 100 having internal oil pump, and so have the 550, 650, 70 and 7000.

Real1shepherd · November 28, 2020, 10:25:00 AM

All you have to do with 32:1 and 16:1 to get coke is run the carb too fat in operation. Seen it done.

Kevin

Al_Smith · November 28, 2020, 10:55:37 AM

In all my stuff I don't have the IPL for the 500 Partner .So I had to refer to the IPL from ChainsawR .It appeared to me the pump was similar to the P-100 /85 .As for the saw Kevin (Cut for fun ) I think used that model to win the 3 cube at one of the national races .Real snappy little saw .West Virginia I think .I ran I think a Partner 50 at Chardin Ohio but didn't set any record although it too was a good little runner .

sablatnic · November 28, 2020, 05:49:36 PM

Al, the Partner 500 is a farmer version of the 5000+, and it is not one of the "cube Partners", which all had internal oil pump.
The 5000+ is the only saw I have had past 21,000rpm unmodified.
Jonsereds, Jobu and I believe Poulan sold the 5000 too, but in different colours.
If you want to see an ipl, just google ipl partner 500

Al_Smith · November 29, 2020, 09:36:48 AM

Actually I did find the IPL on "ChainsawR " .Evidently I misread the parts list because it showed a worm gear drive pump . I do a have a dealers book with a lot of parts lists but the 50 and 500 are not included all though sales posters are .
Partner IPL's are not the easiest to figure out and written in Swedish adds to the confusion .However to be able to compare concrete saw parts to chainsaws has made it easier to find parts .
What I did do was find a reprint for a McCulloch 1000 which is a Partner P-100 .With that using those parts numbers it was a snap to cross reference stuff .Prior to it was like looking for a needle in a hay stack .Like I've said many times restoration work is not for everybody especially the impatient .

sablatnic · November 29, 2020, 04:55:42 PM

No, you are right, restoration work is for people who have the time to wait for the missing parts to appear, some times like magic!
The Partner 50 is a Partner 55 with "stiff" handles. (Without vibration absorbers). If you have a handle from a small cube Partner, (55 - 65 - 70 etc.) you can put it on, and have a way better saw.
And if you feel like it, you can put the cylinder/piston from a Partner 5000 / Jonsereds 490 onto a Husqvarna 50 / 51 / 55.