Stihl 4-MIX

[Paul001]

yup, the reason why customers are told to run ultra mix.

+1

 

[Stihl088stock]

Yup, the reason why customers are told to run Ultra mix.

Yeah, but you can't fix stupid! No one believes me until $#(^ happens,

Our local stealership recommends hp super and most are too lazy to drive out of town...

I had to pay $10.95 for the decarbonizer, five bucks over out of town (unfortunately they were out)

 

[2000ssm6]

Yeah, but you can't fix stupid! No one believes me until $#(^ happens,

Our local stealership recommends hp super and most are too lazy to drive out of town...

I had to pay $10.95 for the decarbonizer, five bucks over out of town (unfortunately they were out)

Oh yeah, I hear ya loud and clear. It is one thing to not be told what to run but when you are told and mess up the engine, that is for sure stupid.

Your local guy doesn't sell HP Ultra?

 

[marcogal]

Hi,

Yup, the reason why customers are told to run Ultra mix.

I wonder: can I use Husqvarna XP mix (synthetic) with 4-MIX engines ?

http://www.husqvarna.com/us/forest/accessories/other-accessories/lubricants/xp-professional-peformance-2-cycle-oil/

Is it good enough for 4-MIX engine ?

 

[Stihl088stock]

Oh yeah, I hear ya loud and clear. It is one thing to not be told what to run but when you are told and mess up the engine, that is for sure stupid.

Your local guy doesn't sell HP Ultra?

closest stealership, 10 miles, no ultra $2.49 for Super (6.4oz)

Best dealership, 25 miles ultra for $3.33 same size.

I only have one 4-mix on a BR600 from 2006, I started with HP super because no one had ultra yet. Been using ultra lately. Switching to Bailey's synthetic since the original HP Super left deposits from the first five gallons anyway. Maybe if I have to clean out my engine I will then go back to ultra? Just to keep'er clean.

 

[MrGiggles]

Have any of you guys ever tried running a bit of seafoam in with the mix?

 

[Stihl088stock]

There is some piting on the crankcase, I'm not sure what caused it.

Oddly, the top of the intake vavle guide shows a jagged surface, but everything else looks ok.

Uh-oh! This FS90 came back to haunt me! These two "unexplained" items I can now account for...

The engine was bogging down again at high rpms... had some crud on the exhaust valve again, even though it was running on synthetic mix. I didn't use Dirko last time, so I thought perhaps whatever I used wasn't fuelproof. I cleaned everything out again, got some dirko, and put it all back together.

It was running "better," I tached it, but I couldn't get it over 8-9k rpms and not steady. I also noticed some rattling noise when it was running. Nothing seemed worse for the wear, so I tried cutting some stuff with it...

Clunk! shimmer-shimmer...dead!

Pulled the valve cover off again to find the intake valve guide broken, along with the spring retainer! :censored::censored::censored:

Pulled the rest apart to find the cam gear severely worn and the front mainbearing missing a few chunks.

In hindsight it all makes sense now... the bearing was providing a ton of resistance because it was damaged all along. I was cleaning the valve, raising compression slightly and the extra power was forcing the bearing to turn. Finally the bearing gave up throwing metal up into the cam and valve area.

I guess it adds to "anything can happen" and I missed it last summer

 

[bass_on_tap]

I had a 4-mix with a bad coil. Read somewhere there was a recall on coils from Stihl. Unit was about 3 years old. Dealer replaced it for free. Didn't even buy it from them. Runs fine now.

Also, both my 4-mix engines are really finiky about fresh fuel.

 

[Brmorgan]

Uh-oh! This FS90 came back to haunt me! These two "unexplained" items I can now account for...

The engine was bogging down again at high rpms... had some crud on the exhaust valve again, even though it was running on synthetic mix. I didn't use Dirko last time, so I thought perhaps whatever I used wasn't fuelproof. I cleaned everything out again, got some dirko, and put it all back together.

It was running "better," I tached it, but I couldn't get it over 8-9k rpms and not steady. I also noticed some rattling noise when it was running. Nothing seemed worse for the wear, so I tried cutting some stuff with it...

Clunk! shimmer-shimmer...dead!

Pulled the valve cover off again to find the intake valve guide broken, along with the spring retainer! :censored::censored::censored:

Pulled the rest apart to find the cam gear severely worn and the front mainbearing missing a few chunks.

In hindsight it all makes sense now... the bearing was providing a ton of resistance because it was damaged all along. I was cleaning the valve, raising compression slightly and the extra power was forcing the bearing to turn. Finally the bearing gave up throwing metal up into the cam and valve area.

I guess it adds to "anything can happen" and I missed it last summer

Very interesting... I just serviced my brother's FS90 and it's been having some of the same symptoms. It's much better than it was though - I pulled the plug and was amazed it would fire at all. The electrode was pretty much buried in black carbon buildup, and a big chunk also fell down into the cylinder on top of the piston when I pulled the plug out. I cleaned the plug and it's like a whole new machine. It does occasionally feel like it's bogging out easier than it should at higher RPMs as well though, and the shaft will occasionally shake a bit as if the drive cable is loading up on itself and twisting. I know the cutterhead bearing is good and well lubed though. Hopefully the engine is fine.

 

[lwn9186]

Uh-oh! This FS90 came back to haunt me! These two "unexplained" items I can now account for...

The engine was bogging down again at high rpms... had some crud on the exhaust valve again, even though it was running on synthetic mix. I didn't use Dirko last time, so I thought perhaps whatever I used wasn't fuelproof. I cleaned everything out again, got some dirko, and put it all back together.

It was running "better," I tached it, but I couldn't get it over 8-9k rpms and not steady. I also noticed some rattling noise when it was running. Nothing seemed worse for the wear, so I tried cutting some stuff with it...

Clunk! shimmer-shimmer...dead!

Pulled the valve cover off again to find the intake valve guide broken, along with the spring retainer! :censored::censored::censored:

Pulled the rest apart to find the cam gear severely worn and the front mainbearing missing a few chunks.

In hindsight it all makes sense now... the bearing was providing a ton of resistance because it was damaged all along. I was cleaning the valve, raising compression slightly and the extra power was forcing the bearing to turn. Finally the bearing gave up throwing metal up into the cam and valve area.

I guess it adds to "anything can happen" and I missed it last summer

4 Mix engines have a limiting coil of about 10,500 rpms. I have chucked a Dremel to the valves while they were in the head with a little lapping compound to get them to seat, also check for cracks around the exhaust seat.

 

[paladin]

My fs 110 had the same problem,it was the ignition mod. Also replaced one on a ht 101 but that one acted up while running.

 

[lwn9186]

When the modules go bad you can chase air leaks, valve timing, carb problems all kinds of funky stuff before thinking the module is bad.

 

[fishercat]

sorry,

I am not sure about the gum up part. Mine never sits long enough.

I meant carbon not gum.

 

[Stihl088stock]

Very interesting... I just serviced my brother's FS90 and it's been having some of the same symptoms. It's much better than it was though - I pulled the plug and was amazed it would fire at all. The electrode was pretty much buried in black carbon buildup, and a big chunk also fell down into the cylinder on top of the piston when I pulled the plug out. I cleaned the plug and it's like a whole new machine. It does occasionally feel like it's bogging out easier than it should at higher RPMs as well though, and the shaft will occasionally shake a bit as if the drive cable is loading up on itself and twisting. I know the cutterhead bearing is good and well lubed though. Hopefully the engine is fine.

Do you happen to know what oil he's been running in it?

 

[Brmorgan]

Just regular Stihl premium, not the Ultra or another synthetic. It's all I normally run in my saws and does fine, but you guys make it sound like these 4-mix engines are a bit more picky. I'm not even sure our dealer in town ever carries the Ultra. I asked once a couple years back and they didn't have any then, said the loggers wouldn't pay the extra so they never sold any, and I would have had to order an entire case if I wanted some.

I should point out that the FS90 is the one that gets used the most for the yard care business, and probably gets about 4-5 hours' use per day on average, five days a week from April through to early October, so after two seasons it's probably WELL past its intended hour-use expectancy anyway. Overall I've been really impressed with it though. Loads of torque to power through thick or tough weeds. I do believe he's planning on getting another trimmer this year, since the FS85 that used to be his main unit and is now the backup is becoming less and less reliable every time we go to start it. I've tried twice this spring without tearing it apart and can't get it to even sputter.