Stihl 028AV siezed up, then later spins ok?

[Okie]

This thread started out here as a want to buy, but 028AV saw now spinning free???

http://www.arboristsite.com/community/threads/stihl-028av-or-equal.290273/#post-5663977


Got throwed a curve.
Need advice?
Went to shop to take the 028av apart and it's now turning over freely after sitting overnight. Yesterday it seized up in a cut!
Like I said looking thru the piston port looks ok, no sign of scratches, gouges or piston scraping on the skirt, etc, and cylinder looks ok.
Yesterday before I started using this saw and one other saw I had mixed new 1 gallon batch of Super Tech, 2 cycle oil at closer to 40:1 instead of 50:1 and ran a tank of gas thru the other saw first and about 3/4 tank thru the 028 before it seized. It was in a full bar cut and it was cutting strong when it seized. (when it seized it acted like it just ran out of gas all at once) I did notice that the top of the saws plastic cowling was hot to the touch when I sit it down to pull the rope to test for turnover. This saw does not have a chainbrake it only has the plastic handguard, the oil pump gears were ok and not seized. The spark plug was orange colored maybe indicating a lean running carb mix. The saw had been cutting strong for about 30 minuites into some kinda heavy cuts.
Like I said the muffler last year was coming loose and I was concerned that the saw was sucking or had sucked some dust/dirt during the cut into the muffler port before I noticed that the muffler was loose with no gasket. I got the muffler tightened (with only one mounting screw, other one is broke off in the casting) and the saw was running great. I've owned the saw for several years and tried to maintain it well. (new in 1980)
I did check the compression awhile back while testing a new actron compression gauge and the compression was 125 but the saw still started easy and ran strong even thou the compression checked low.
The same siezing issue will most likely return if I just start it up for a re-go???

The number on the block is 5284XXX if that means anything!

Need some advice, thoughts, etc, before I re-ignite the powerhead????
waiting on replies?

 

[pioneerguy600]

Pull the cylinder off and check the piston rings, also check out the radial bearings and the con rod big end needle bearings. If you keep running it something will break.

 

[Okie]

Well it's back together and starts and runs just like nothing ever happened.

Suspect you are correct, it's going to fly apart. If it is a crankshaft needle bearing or rod bearing things are most likely chewed on real good anyway?
Probably keep a eye open for another Stihl saw or another powerhead for this one. It has real good 16 inch roller nose bar and chain, carb, etc.
Could not believe it freed up by itself?????????????
I seen a 4 cycle ATV lose crankcase oil once due to a broke oil cooler line (single cylinder) and it locked up while idling and cured itself after engine cooled down and new oil added and that was 3,000 miles ago and it's still running good.

This saw kinda acted same as the ATV engine (expanded hot piston symptom) only it was running full throttle in a full bar cut with a heavy load when it seized.

 

[pioneerguy600]

Best of luck, hope it doesn`t seize again. Seen a saw with a slightly worn big end on the rod and the needles would bunch and jam but if the flywheel was rocked backward it would clear up and run again.

 

[Guido Salvage]

Once was given a free Craftsman handheld blower that seized up. I got it going again and then it seized up again. I just threw it away.

 

[Duane(Pa)]

Hey Okie! Are you up to speed on air leaks and carb adjustment? You may have been lucky, but I suspect this problem will rare up again unless you can find out what caused it....

 

[Okie]

Hey Okie! Are you up to speed on air leaks and carb adjustment? You may have been lucky, but I suspect this problem will rare up again unless you can find out what caused it....

You asked! Are you up to speed on air leaks and carb adjustment?

I thought about that (running lean) and I have the original manual for this 1980 028AV and owners manual indicated normally as a start 1 1/4 turns out on each jet as a start and too adjust the jets out in rich condition as far as possible when adjusting. The NGK spark plug looked like a lean run maybe, not hardly any orange and hard crust buildup. Carb has not had any adjustment or even checked in several years because saw running great. I checked the H jet at 1 1/4 out and the low was set a 1 1/8 out and did not actually check them with the saw running yesterday.
Another indicator that the saw may be running lean or too good is it will rev real high in rpms real fast when lifted from a cut and will cut really strong and fast with no bogging using a new aggressive chain using the full length of a 16 inch bar into green oak logs.
I'll check the H jet and see if I can enrichen the setting.(back off or out on the H adjustment little bit)
I'll also pay closer attention to the heat I mentioned at the top of the cowling when I set the saw down for a re-start.
I checked the muffler, spark arrestor screen, and air filter and all were very clean.
I'm now suspecting an overheat condition probably due to running lean under full load of the powerhead? I don't think a bad bearing would free up and be as smooth with no felt roughness as easily as this power head freed itself overnight.
I was into a full length 16 inch bar cut of a big log and cutting strong and using a aggressive cut chain and cutting fast with chips flying with no bogging, just a good heavy load on the engine when she seized and I had been continuously cutting other firewood logs just previously and have to back off on the throttle and throttle the rpms down really soon as the bar load lightened to keep the saw from over revving. In past I normally did not cut this large of a log for extended period of time into a cut and normally did not use a full bar load cut when cutting firewood.
I had installed a new kit in the carb about 15 years ago and not changed any carb setting since! (saw may have age crept into a lean carb setting)

I would think that a air leak causing a lean condition would cause some erratic running issues??

 

[Kenskip1]

I would look at the sides of the cylinder for a lack of air circulating around the cylinder,Just a thought, Ken

 

[Okie]

I would look at the sides of the cylinder for a lack of air circulating around the cylinder,Just a thought, Ken

Checked the cooling fins and the flywheel fins first and they were real clean!

I did find a Briggs and Stratton lawn tractor engine few days ago that had a valve seat popped out of the head and the cooling fins were severely clogged due to owner neglect. The owner was not even aware that the engine had cooling fins.
I also found the air filter clogged so bad I could not believe the engine would even run due to the clogged air filter and the oil looked like 90W. I casually told him he should change the air filter, oil and clean the cooling fins at least every mowing season and not use ethanol type gas. (I suspect was wasting my breath)
The Briggs sure had it's tongue hanging out when being used! (he rode it hard and put it away wet)
I re-staked the valve seat and changed all and she ran great!

If it had been and horse or cow I would have had to put er down. (too sick for rehabilitation)

 

[AKDoug]

There are lots of reasons for lean seizes. Reading spark plugs does virtually nothing on a chainsaw. Of the dozens of lean seized saws I've looked at in the last year, I can't recall a plug that was white like you get on a dirtbike or snowmobile seizure. Have you pulled the muffler and looked at the piston?

 

[Wood Doctor]

When the 028 bar and chain get hot, the saw's engine will stall out and try to save itself. The saw is trying to talk to you. The operator can actually make this happen by (1) forgetting to add enough bar oil, (2) using lousy bar oil, or (3) forcing the saw too hard and through a long cut. Occasionally, the bar oiler temporarily gets clogged up and that can cause it also.

Check all four of these possibilities. I have found that the saw sometimes has more brains than the guy pulling on the trigger. Occasionally that has included me. Letting the saw rest for 15 minutes cools it off, and it will start right up again, doing the best it can to satisfy its owner.

 

[Okie]

There are lots of reasons for lean seizes. Reading spark plugs does virtually nothing on a chainsaw. Of the dozens of lean seized saws I've looked at in the last year, I can't recall a plug that was white like you get on a dirtbike or snowmobile seizure. Have you pulled the muffler and looked at the piston?

Yes piston and cylinder looked normal and very clean, not even a scratch!

 

[AKDoug]

Yes piston and cylinder looked normal and very clean, not even a scratch!

Sorry, I missed that in the first post.

 

[Wood Doctor]

Sorry, I missed that in the first post.

So, perhaps that brings us back to post #11.

 

[AKDoug]

So, perhaps that brings us back to post #11.

Possibly. I have seen them seize where you can't see it through the exhaust, but it's extremely rare.

 

[Okie]

Wood Doc:
Yes, the 028AV talked to me and said it is old and got tired and don't won't to work that hard anymore, even thou I've been really nice to it for 35 years and its served me well! I don't like slackers and freeloaders of any kind thou! If it can't cut the mustard anymore it will get replaced fast.

The bar and chain were not hot and oiling ok. I use Stihl bar oil, the blue jug during very cold weather (winter blend) and the Stihl orange jug this day.
I took the saw too the shop and was around the saw, depressed and inspecting for over an hour and it was still seized when I went for a rest and to ask some questions to the pro's on this site and posted question about current replacement models in the want to buy section. I also thought it might cool off in little bit and I tried the WD40 on the piston and into the spark plug hole and still same afterwards.


When I went to shop to take it apart next morning thinking I would start by pulling the flywheel and taking a look and then maybe the piston jug. I was surprised to find it healed itself overnight.

The spark plug condition was very dry and very hard crusty orange buildup with some white, no soot or oil color at all.
Yep, it talked to me, said it was tired and wanted to quit for the day and get some rest.

Rain is quitting today!
I'll carefully put the 028 back to woodpile in day or two after checking the setting of the H jet and make sure it's not too far in towards the lean setting while the saw is running.

Another thought and question?
I have a very accurate 3M infrared thermometer that I use around automotive to test block temps and to compare cylinder temps of automotive engines, bearing temps and air conditioning temps! I can check the block temps while it's being used easily.
Does anyone know what would be the normal running temp of a chainsaw saw block around the jug area and what temperatures to watch out for as being too hot or starting to get out of range? (has anyone ever tried checking the block temp of a chainsaw with a infrared thermometer to detect a lean condition or detect overheating conditions?)

 

[Wood Doctor]

35 years and this is the first time this has happened? Truly amazing. Just open up the hi-speed screw a quarter turn. It may four stroke s little and then jump to two-stroking. That's usually music to my ears with all four of my 028's. Seems like a lean fuel mixture is involved here. Carb may not be letting in enough fuel and too much air.

Give that a shot when the rain finally quits. We got about 3" of water around here but no white stuff. Might dry out Wednesday. Good luck, Okie. That 028 is worth saving.

 

[Okie]

I took the 028AV and two other Homelite saws to the wood pile and the infrared thermometer.

Tested the Homelites first into a big green 16-18 inch pine log with full bar cuts. The piston jug averaged about 200 degrees idling after warmed up and around 360-380 heating gradually as the two homelites were cutting full bar and the engine loaded heavly but not overrevving, (engine bogging due to the full bar cuts)

The 028AV with 16 inch bar and new aggressive cutting chain started heating fast with the engine bogging into a full cut and reached 380 and was still going when I backed out of the cut due to the temp rising fast as compared too the two other saws. I let the saw cool down idling and then backed out the H jet another 1/2 turn (1 3/4 total) and back too the cut. The saw saw kinda 4 cycled little bit (gurgled) then loaded up great with good power and the temp stabilized at around 360-380 and did not rise real fast like when the H jet was at 1 1/4 out. Indicates to me the saw was adjusted too lean (needed less air and more fuel/oil) and was the reason for the seizing after the saw was used in heavy cuts with no rest between cuts.

The saw was headed for another overheat condition and the thermometer detected such before it happened.
I also use the infrared to check bearing temps, automotive individual cylinder temps and overheat conditions of water cooled engines block and radiator temps. Air conditioning temps, instant read. Can take temps from several feet away if desired. This one is by 3M.

This Stihl saw does not have a winter/ hot/cool air flow switch on the cowling it's full cool air flow all time.

 

[Wood Doctor]

I think you have it solved. My 026 PRO and my favorite 028AV are also adjusted about the same way. When it kicks out of the 4-stroke and into the 2-stroke under load, it's music to my ears. Run it this way for awhile. Remember that you are working with an older horse, and they tend to be temperamental and tire a little faster when coming down the home stretch.

 

[Okie]

Thanks: I'm going to eventually get a tachometer for use on my saws. I have several lesser quality saws, homelite, Polan, craftsman, McCullouch that I have to work on this was one that I very seldom had to touch, my go to saw.

T
What I like about using the thermometer is their was no guessing about if it was going to overheat, it detected such and I was able to shut it down before it got too hot even if it had been something else causing the issue other than lean condition. What I'm saying is the saw was not overreving and causing the overheat it was lean on lubricant, too much air. Heck Ronnie Milsap could hear and detect that the saw was not overreving in the cut when it started overheating the engine was bogging and carrying a heavy load.