Compression is 120 psi on Jonsered 2165; too low?

[Kenora]

Jonsered 2165 turbo

I have a 16" bar and was hoping to get a 20" bar for this saw, but it sometimes bogs down going through tough stuff with the 16" so I thought I would do a compression test. I started it up and warmed it up good and check it 3 times...every time it was 120(ish).

Is that too low?

If so does that mean a new piston and ring(s) or a new cylinder too?

Thanks.

 

[HUSKYMAN]

Pull the muffler and have a look at the piston on the exhaust side, check for scoring.

While that sounds low have you tried adjusting the carb to eliminate the bog?

Some compression gauges read lower than others. Before you tear the saw down you should do a leak down test which will give you a better idea of the condition of the cylinder.

 

[huskydave]

120 is low it will need honing and new rings soon maybe a piston only one way to find out. New should be 170psi midlife145psi end of its life 120psi.

 

[taplinhill]

A 2165 should not bog in anything with a 16" bar.

 

[Kenora]

Wow! That was quick, thanks for the info.

The saw is new to me, the only thing I've done is run some decarb through it (I have 2 stroke outboards!), this made no difference.

I haven't touched the carb but it runs well, just doesn't have the jam I think it should. Should I try something else before I buy some rings ( I saw some advertised on fleabay)?

 

[HUSKYMAN]

Try adjusting the "H" screw on the carb 1/8 turn either way and see if it helps. If the saw is too lean or too rich it will not have the power it should.

If adjusting the carb does not help you may need rings.

 

[Kenora]

OK!

At the risk of asking for too much..................................well hell I've bugged you this much so here goes..

Do I need to buy oversize piston/ring?
or just a ring?
How do I know?

Its still cold out there and my heavy cutting won't be for at least 6 weeks so this is the time to tear into it, what should I do? I know with a car a guy would never just replace the rings, I always went .010 oversize or so and needed a new piston, rings and the bore machined. Is that not the case here. If not would I just replace the worn ring and deglaze the bore?

I know I asked the same question a few different ways, I don't want to screw up now that I'm gonna buy parts. I see piston/ring and wrist pin on fleabay for $29.99, sounds good to me...or should I buy from a Jonsered dealer?

Thanks and thanks again

 

[huskydave]

I would go with oem piston. You just need a light hone and install the new piston arrow toward exhaust port and install a new basegasket and your good to go if your cylinder isn't scored.

 

[Kenora]

Excellent, I'll pull off that muffler and see what it looks like!

 

[Ray Bennett]

I would try just rings first. Maybe a gasket if that gets torn up in disassembly. Maybe Im lucky but If my piston and cylinder show no scoring I have always had good luck with just replacing the rings. Just did my 044 and it was running ok with 120ish compression but with new rings and impulse line it is near 160 and not broke back in yeat. Now if you have scoring you are gona need a lot more parts.

 

[Kenora]

I'll pull the jug tomorrow and post a picture and let you guys determine where I go from here.

 

[andrethegiant70]

Heck, even at 120lbs that saw shouldn't bog with a 16in bar. If the piston looks ok I'd be givin' that thing a good tune. I've got a few saws that run really nicely at 120. Maybe I've got low standards or something.

 

[HUSKYMAN]

I think he has his mind set on tearing that thing apart no matter what

 

[volks-man]

hey fellas.
i'm learning here but i thought you did a comp test cold. or at least it yeilds higher readings cold, right?
he tested after warming up.

 

[Kenora]

Hi again; NO I absolutely not set on tearing into it, I thought it was a forgone conclusion that I HAD to.

If a tune up will bring back some power I am all ears (well eyes.... since reading is a visual experience).

What should I try first?

I am willing to read and learn, heck I've learned a ton already; for instance I didn't know the compression test should be done cold.

That seems counter intuitive to me but if thats the case I will repeat it in the am when its good and cold, its gonna be -20c(ish) tonight (thats about -5f) and its in the detached, uninsulated garage.

 

[andrethegiant70]

Yes, Andy (I think it was Andy) is right, compression testers are not always the be-all, end-all judges of compression that you might think. Definitely look hard at the piston and bore, make sure your air filter is clean, make sure your muffler isn't full of carbon or sludge, use fresh mix, make sure your intake stack is snugged up, and put a good tune on the carb before you take the thing apart. The other questions I'd ask are, is the chain sharp and how far down have you taken the rakers? That's a big, strong saw...even if the compression has sagged to 120, the symptoms seem extreme.

If you're looking for a good project, that's a different story.... have at it. If you're just trying to find out why your saw is down on power, you have a few other things you can check before it gets expensive.

Just my 2 cents.

Oh, and make sure you're running the right plug.... I've done THAT one before...

 

[HUSKYMAN]

Hi again; NO I absolutely not set on tearing into it, I thought it was a forgone conclusion that I HAD to.

If a tune up will bring back some power I am all ears (well eyes.... since reading is a visual experience).

What should I try first?

I am willing to read and learn, heck I've learned a ton already; for instance I didn't know the compression test should be done cold.

That seems counter intuitive to me but if thats the case I will repeat it in the am when its good and cold, its gonna be -20c(ish) tonight (thats about -5f) and its in the detached, uninsulated garage.

You have everything in this thread. First thing is to pull the muffler and look at the piston. If there are grooves going up and down on the piston you are done, tear it apart. If not start adjusting the carb slightly on the high speed screw and see if it improves your bog.

Get out there and let us know what you find

 

[Ray Bennett]

I have found compression guages to be as much as 10 lbs low on 2 stroke engines. Im figure your true compression is between 120 and 130 which means you will want rings soon. In my opinion it is no rush. Another real good compression test is to start your saw warm it up, shut it off and see if you can pick it up off the floor with the pull cord. If it works its way down the cord you are definatly getting near the end. This is a really good test for saws in the 60 to 80 cc range with mid size bars. Hope that helps.

 

[Ray Bennett]

One more thing, very important. If you are low on power due to low compression and rings getting worn. Do not Lean the saw for more power. If you do you will burn that saw down and need more than just rings.

 

[Kenora]

Hi again...

I just came in from the garage (its about -10c in there).

Cold compression is about 120 psi.

When it wouldn't start on the 3rd pull I got worried and sure enough had forgot to put it in RUN, next pull it started right up.

I let it idle for 10 minutes then ran it at 1/2 throttle or so in bursts then 1/2 sec bursts of full throttle a few times, I don't want it to blow up

I shut it down and then tried the "hold it by the T grip handle and let it go test"

each time it dropped smoothly about 3 inches then a small chug, then a wait of about 2 seconds for a big chug,

then dropped about 3 inches again and repeat, in all it took about 7-9 seconds to go to the bottom of the cord.

I still haven't taken the muffler off...

Ray; I was able to find the two carb adjustments ( L and H)... I assume that I want to back the H screw OUT to richen it up??????