Help with over heating 3120xp milling saw

[watermark]

I am running a 3120xp as a dedicated milling saw with an alaskan mill. I have been running it here and there over the last 3 years when I picked it up used with a 60" mill set up that was unused other than the frame. I also got a 48" cannon bar with it which had been barely used and an ugly 32" bar. The guy I bought it from said it had very little use and saw was real clean and to my untrained eye looked like it was in top shape. I have since found some signs he may have BSed me. Zip tie on throttle cable to secure it on filter cable and missing screen in carb.

The saw was doing great until the last few times I have used it and it is over heating really bad and quickly. The first time it happened was when I was running the 24" bar and chain from my 372xp to mill smaller logs I changed out the rim sprocket to match pitch.

I assumed the smaller bar was the problem but now it happens no matter what bar I run on it. I am using the ripping chain from baileys with out any modification and running fuel mix 50:1 and also using auxiliary oiler.

I have been searching all over for answers and from what I read think it may be A) intermittent oiler B) should be running richer mix C) saw is running lean

Here's why
A) when turning chain by hand on the bar it runs freely for a little then has some resistance back to running freely and back to resistance over and over and same goes with chain off just rotating clutch with my hand.

B) just from what I have read on other threads.

C) same day I milled with smaller bar my friend adjusted carb settings because saw would die out when idling. Also responses to other posts regarding over heating saws

Is the oil pump on it's way out or damaged from over heating caused by another problem?

Any advice on how to figure out whats going on would be awesome. Thanks in advance

 

[smokey7]

What symptoms are you seeing when it overheats. Is the bar getting hot? Did the saw get tuned richer when it was tuned last? The resistance you are feeling could be from a rim not being machined true round. Have you tried going back to old rim to see if the resistance goes away?

 

[cus_deluxe]

Ive never milled or run a 3120 but i know lots of guys, especially with big bars like that will set up an auxiliary oiler on the tip to help keep up. Milling is extremely hard on saws, and so i bet most would tell you to run 40:1 at least. Are you saying that you are turning the clutch by hand or the drum by hand. if turning the clutch by hand and there is binding (other than piston at TDC) then you have a crank issue. if turning the drum and there is binding then you have a clutch bearing and drum that need to be replaced. Also probly time to pull that muffler and have a look inside. If it really is getting hot then you want to check for transfer and clean it up before it is made worse.

 

[sunfish]

Get a band saw mill...

But if you have to mill with a chainsaw, 40:1 or better yet 32:1. Richen up the carb settings. Make sure chain is Sharp.

 

[Marshy]

From your description it was hard to understand if your saw engine is having the overheating issue or if your talking about the bar only...
I have no first hand experience with milling but I use to help my uncle who had a 3120 setup for milling (so I'm qualified right?). I'm pretty sure most here would agree 50:1 is not enough oil for milling application. I personally wouldn't run less oil than 40:1 and if your doing a lot of heavy cutting then just stick with 32:1 (just my opinion). Also, I remember he use to keep his fuel can in the shade or under a pile of brush to keep it as cool as possible. IIRC in the dead of summer he has some issue where the gas was boiling and air locking the carb. If I were you, I would 1) do a compression check, 2) pull the muffler and look for transfer, 3) inspect the clutch bearing, 4) check your crank bearings for smooth rotation. Keep the air filter clean and the chain sharp, most cases bars that were over heated are from dull chain. Once the chain is dull and bar is hot it can act like the bar is getting pinched (ie, feels like the bar is sticking in the cut). Depending on the species, size and cleanness of the wood you might have to file after only a few rips. Lastely, check the nose sprocket is not binding.

 

[Marshy]

Get a band saw mill...

But if you have to mill with a chainsaw, 40:1 or better yet 32:1. Richen up the carb settings. Make sure chain is Sharp.

Most 3120's only have a Low speed adjustment, but valid point. And I let the saw idle after hard cuts to slowly cool. Dont just shut it down after a hard run.

 

[mdavlee]

The jet on those is very easy to ream to a bigger size to richen it up. What coil is on it?

 

[Cj genever]

Would be worth doing pressure and vacuum tests to look for air leaks.

 

[spindrift7mm]

Also check spark screens if you're running them, they can cause some real issues if plugged. Ken

 

[Nitroman]

You can line the inside of the cylinder housing with reflective tape to cut down heat transfer to the carb. Also, remove the housing and clean the cylinder really well, make that REALLY well. Then spray it with flat black header paint so it will radiate more heat into the airstream.

 

[Big_Wood]

i don't believe there ever was a 3120 that ever came with a high speed needle despite the AS myth that there was some. i've scanned all the IPL's ever available on them and could not find any that ever had the high speed adjustment. i'd just get terry to modify it. overheating and 3120 often mean scored. they run insanely lean from the factory for a big saw. a stock 3120 with the green coil is almost worthless and i would run a 395 anyday. put the old ignition/flywheel or 272 coil on a 3120 with an adjustable carb and everything changes.

 

[Justsaws]

It is probably time to take the muffler off and look very carefully at the piston and cylinder. Retuned carb and then overheating problems are usually going to be bad news. That saw should be tuned as rich on the low side as possible with as high an idle RPM with out spinning the chain as possible, while on it's side like it would be mounted to the mill.

I would highly recommend 32:1 mix ratio. Might have to go 24:1 or even to 16:1 depending on what you are experiencing.

Clean the carb carefully, replace the the kit and the fuel filter. Look the the fuel line over or just replace it.

Check the vent system. Has to be in good working order.

In my opinion if the saw has a limited coil it needs to go, it is not because you are operating the saw under load at the coil's limit but because the limited coils in my experience add a variable to the operation of a milling saw that is hard to keep track of. Milling saws get hot, stay hot. Limited coils can do some weird stuff after they have been cooked and while they are being cooked.

That being said the carb is going to limit what you can do so personally I would mount a tach to the saw and keep a close eye on the RPMs under load. Ideally you need to be in the sweet spot not to high and not to low. Here is the rub, that sweet spot needs to be determined by your circumstances. Get a non contact thermometer and mount it up so that you can get a feel for how hot things are getting at what loaded RPM. You do not need the temps to be NASA accurate just enough to give you an indication of what the saw is doing.

If I bog the saw down with a certain type of chain to where the chain is really cutting well the saws temp will go waaaaaaay up however if I reduce the pressure and let the RPMs go up the cutting becomes less effective but the temp of the saw goes back down quickly.

In terms of the oiler, check out the parts replace what is broken. Clutch drum may rub on the clutch but it should not wobble. The oil drive gear should be looked over carefully.

If the clutch is constantly slipping(chain stalling in cut) it needs to be looked at and probably replaced. If it is constantly slipping that will affect oil output and saw temp. It really needs to be working correctly, if not things can get hot fast. Another thing to consider in terms of clutch condition would be the springs and spring mount area if they are sprung or hogged out then the clutch will engage at idle speed and sometimes this can be misdiagnosed as a tuning or carb problem. The chain will want to spin at idle speed and depending on how it is setup sometimes this can cause the saw to stall out at idle.