Killed the MS880 while milling

[Kicker_92]

Was going good last night, then started surging while in the cut after it had warmed up. Woudl go from screaming then bog to the point of stalling.

Seems like an air leak. I' forgotted to tighten up the rubber boot fromt eh carb to cylinder, so will try that and see how it tests.

 

[BobL]

I use the same Wixey gauge as Bob, we actually have them here at work for measuring angles on parts.

I think it'd be around equivalent to 0.040" raker depth on a new chain at 8°.

8• is equivalent to 0.035 on a new 3/8 chain

Was going good last night, then started surging while in the cut after it had warmed up. Woudl go from screaming then bog to the point of stalling.

Is that while milling or just by itself?

Seems like an air leak. I' forgotted to tighten up the rubber boot fromt eh carb to cylinder, so will try that and see how it tests.

If is is an air leak you need to vac&press test the whole thing.

One more thing, when using the WIXEY DAF the rounded corners and inset magnets limit the contact area over which the angle measurements can be made.

This diagram shows on the left a side cross section of the DAF, The two arrows show the contact area that should be used. If a cutter or raker encroached into the inset magnet spots or rounded corner areas an incorrect angle reading will be made.

To facilitate this the right hand side diagram shows how I clamp a rebated wood block to the blade to ensure only the small contact area is used.

 

[Kicker_92]

Is that while milling or just by itself?

If is is an air leak you need to vac&press test the whole thing.

It was doing it when in the cut, which would make sense since it's developing vacuum. There's a good chance it was just from missing the hose clamp on the carb to cylinder connection. The only other item would be a leak at the base gasket. Will check that after if it still has the issue.

Searching through the archives, you had something similar on you 076?

 

[Brmorgan]

8• is equivalent to 0.035 on a new 3/8 chain



Is that while milling or just by itself?




If is is an air leak you need to vac&press test the whole thing.

One more thing, when using the WIXEY DAF the rounded corners and inset magnets limit the contact area over which the angle measurements can be made.

This diagram shows on the left a side cross section of the DAF, The two arrows show the contact area that should be used. If a cutter or raker encroached into the inset magnet spots or rounded corner areas an incorrect angle reading will be made.

To facilitate this the right hand side diagram shows how I clamp a rebated wood block to the blade to ensure only the small contact area is used.

Translation for North Americans: Rebated = Rabetted over here. In North America, "Rebate" is a term used to describe a legal way for companies to rip people off via the postal service.


I guess maybe I should take the time to get my milling chains dialed in once in a while like you do, but for the amount (and relative softness) of wood I mill, I'm just not sure the cut time I might save would offset the extra time spent. And as far as firewood chains go, I don't use a gauge of any sort. Just use a flat guide for the round file, and eyeball pretty much everything incl. cutter length, angle, and raker depth. If I really rock a chain or need to even everything up for some reason, I use the clamp-on Oregon file guide which works well enough for what I need. I could probably do a bit better but my firewood chains still seem to cut like a raped ape; I can't say I ever notice much performance falloff between brand-new and after being filed half a dozen times. And my milling times and speeds seem to be comparable to others' experiences here who have similar setups and encounter similar woods, such as Mtngun.

Kicker, I hope you get that suspected air leak sorted out pretty quickly, or you'll be right back to square one in short order.

 

[BobL]

Translation for North Americans: Rebated = Rabetted over here. In North America, "Rebate" is a term used to describe a legal way for companies to rip people off via the postal service.

Thanks for the clarification.

I guess maybe I should take the time to get my milling chains dialed in once in a while like you do, but for the amount (and relative softness) of wood I mill, I'm just not sure the cut time I might save would offset the extra time spent.

I agree.

And as far as firewood chains go, I don't use a gauge of any sort. Just use a flat guide for the round file, and eyeball pretty much everything incl. cutter length, angle, and raker depth. If I really rock a chain or need to even everything up for some reason, I use the clamp-on Oregon file guide which works well enough for what I need. I could probably do a bit better but my firewood chains still seem to cut like a raped ape; I can't say I ever notice much performance falloff between brand-new and after being filed half a dozen times. And my milling times and speeds seem to be comparable to others' experiences here who have similar setups and encounter similar woods, such as Mtngun.

I'm the same for firewood and bucking - especially if I'm cutting in dirty conditions.

The cutting angle approach to setting rakers is about understanding what is going on and comes into its own on big hardwood slabs and short cutters when I clearly see the difference between dust and chip generation. Old timers never worried about specific raker depths/angles, they just kept on filing rakers until they started making chips again.

 

[rxe]

I like the temperature measurements upthread. Anything to stop the paranoia about whether I've got the mixture rich enough or whether the saw is acting "funny"...

I'm going to get a couple of these:

http://www.omega.co.uk/ppt/pptsc.asp?ref=WT&Nav=tema03

...and bolt them to the exhaust stud of my 070 and 090 milling saws. They're just Type K thermocouples, and I happen to have a meter to read them. The meter can read two at a time, so out of interest I might bolt another to the base of the cylinder head as well.

 

[Kicker_92]

Update:

Well, the vacuum / pressure test didn't reveal anything useful. I managed to get the cylinder bolts cranked another 1/8th turn though. There's no way of pressure testing when it's hot, so we'll have to see if that does it.

Our excavator blew a head gasket, so the sawing will be on hold a couple week while we try to fix that. Will update if I figure out the problem.

 

[mtngun]

Well, the vacuum / pressure test didn't reveal anything useful. I managed to get the cylinder bolts cranked another 1/8th turn though.

At least you ruled that out.

Surging sounds like a fuel problem, as you suggested earlier. Keep us posted.

 

[Kicker_92]

At least you ruled that out.

Surging sounds like a fuel problem, as you suggested earlier. Keep us posted.

Haven't rules an air leak out entirely, but it tests well when cold. I would assume any leak major enough to cause a drastic surging like this would be significant enough to not only occur when hot.

Waiting for the headgasket to come in for our machine, so we cut up another 13"x16"x14ft post tonight. Put in a new plug just to rule that out. It went well until about halfway through, when it started surging again.

The interesting part is that is I kep the throttle at about half, the rpms stayed a little bit lower but it continued to cut normally, just with less power. As soon as I opened the throttle too much, it would start surging.

This really leads me to believe that something is going on with the carb. I tried to cover the "dirty air filter" port, but the tape would't stick and stay in place. Will bring something along next time to block it off and see what happens.

I love the way this saw pulls though the wood now. Top end hasn't changed much, but it's got a lot more grunt down low. Ripping through a 16" wide cut was like butter, at least until it started surging.

 

[Andrew96]

Is you fuel tank vent clean? You could be pulling a vacuum on your tank. Next test..when it starts surging...reach over a pop the fuel cap open.

 

[BobL]

Haven't rules an air leak out entirely, but it tests well when cold. I would assume any leak major enough to cause a drastic surging like this would be significant enough to not only occur when hot.

Waiting for the headgasket to come in for our machine, so we cut up another 13"x16"x14ft post tonight. Put in a new plug just to rule that out. It went well until about halfway through, when it started surging again.

The interesting part is that is I kep the throttle at about half, the rpms stayed a little bit lower but it continued to cut normally, just with less power. As soon as I opened the throttle too much, it would start surging.

This really leads me to believe that something is going on with the carb. I tried to cover the "dirty air filter" port, but the tape would't stick and stay in place. Will bring something along next time to block it off and see what happens.

It does sound like the carby, Have you pressure tested the carby?

BTW it is possible do a hot or at least a warm pressure tests. Set up the pressure testing gear and then use a hot air gun to heat the cylinder on the head and the exhaust side. Then do the pressure and vacuum tests. I presume you did both? To get the cylinder hot enough you need a way to blank off the exhaust port other than rubber, telflon sheet is one possibility.

 

[mtngun]

Carbs can be a pain to troubleshoot. In the ideal world, you'd swap carbs with your buddy's 880 and see if that fixes the problem. Then you would know for sure that you need to dig into the carb.

I don't remember if you did a carb kit and welch plug job during this rebuild ? Ditto fuel lines and fuel filter ?

Sounds like its going to be an awesome milling saw once the demons are exorcised.

 

[Kicker_92]

You could be pulling a vacuum on your tank.

That was actually one of the first things I tried, unfortunatly no change with the tank open or closed.

It does sound like the carby, Have you pressure tested the carby?

How do you pressure test the carb? Do you have a link or a manual for this?

I don't remember if you did a carb kit and welch plug job during this rebuild ? Ditto fuel lines and fuel filter ?

Didn't touch any of them, only pulled the piston / cylinder. Thats why I'm leaning toward it being a problem with the increased airflow.

 

[mtngun]

Didn't touch any of them, only pulled the piston / cylinder. Thats why I'm leaning toward it being a problem with the increased airflow.

Sounds like you are figuring things out.

Sometimes an internal passageway in the carb gets obstructed, or a check valve gets gummy, and it can drive you crazy trying to figure it out. The carb kit/welch plug route may make a noticeable improvement. I did one on my 066 and it fixed a mysterious idle problem, even though I didn't find anything out of the ordinary inside the carb.

I was thinking to order one of those ultrasonic cleaners that they are talking about on the chainsaw forum because I've had my share of stubborn carb troubles over the years.

I had a saw that liked to stumble and die in mid cut. I'd wait a few minutes and restart it, and it would run for a few seconds or a few minutes until the process repeated itself. Turned out to be a dirty fuel filter. I just blew the filter out with compressed air and that fixed the problem.

 

[Andrew96]

I was thinking to order one of those ultrasonic cleaners that they are talking about on the chainsaw forum because I've had my share of stubborn carb troubles over the years.

Mtngun.....go for it. Once you get one...you'll wonder how you ever fixed anything before. I've had one for years. Just don't tell anyone you have one...soon you'll be doing all kinds of old carbs and anything else that has any sort of crazy shape to clean up. Get the biggest one you think you'll ever need. Big enough to put a monster 4bbl in..or some giant throttle body. Does wonders cleaning aluminum prior to welding, etc. Yamaha makes a carb cleaner that is magic with an ultrasonic cleaner...best stuff I've ever found. All kinds of dirt shows up after a good cleaning even on things that were working seemingly fine.

 

[BobL]

How do you pressure test the carb? Do you have a link or a manual for this?

I find it hard to imagine trying to sort out this kind of problem without a manual.

I'd start by giving the carby a thorough clean.

Then I'd go the carby kit.

 

[jaycky]

Fuel is the life of the saw.
My buddy has a stash of gas on property and it's been awhile in the jerry cans I will not use it due to cold hot causing condensation aka water build up. He has mentioned he killed a saw in the blink of an eye last time getting wood for town and he thinks it's from screw turning on him I think it's poor fuel. But we could argue about this for ever or I could try his fuel on my saw and see what happens! Not...
Anyways I'm not screwing around with my 880 and when I start milling it gets a simple cheap and easy fix a temp gauge. I don't know why others don't just get one they under 50 bucks and it's like a triple life line...

 

[jaycky]

Oh while running shop in alberta do you have any idea how many issues we had with the dumb asses parking diesel trucks inside for the night after a -40 day it's not a great idea unless you were to top up all tanks which they never did. Within days failures on pumps engines and on and on. Not to say how much diesel fuel anti gel they added? One night equipment developed mega water condensation In fuel tanks after a week things weren't running . People just don't think . But point is fuel left out all day in sun expansion cold contraction it kills fuel so just mix what's needed and keep the main batch in a cool area store it proper and should be golden. I have read big saws over certain cc's should be mixed at 33.1 so if you did 35.1 or even 40.1 saw should be great and back to setting saw up every-time before getting milling! But cheapest insurance is a temp gauge IMO

 

[BobL]

. . . . . when I start milling it gets a simple cheap and easy fix a temp gauge. I don't know why others don't just get one they under 50 bucks and it's like a triple life line...

I wouldn't rely on an external contact temperature gauge to prevent overheating. By the time these gauges register the temp that will overcook a saw the saw will be toast. A better gauge would be an EGT but finding one that will run on a small battery and that is physically robust enough to survive on a powerhead could be tricky. Most EGTs are 12V for motor vehicles and not suitable to locate on a powerhead. I would look into the RC accessory market and if you find a good one let us know.

 

[jaycky]

http://www.trailtech.net/722-et3

What you think if this?


I was more a less thinking tune saw before work and keeping eye on it in mill cut to keep it in the range basically if something starts to move up then double check? Just a cheap insurance on an expensive saw