Stihl 090 vs 088 questions

[Metallichg]

Today I ran my 090 for the first time. I also have an 088 that I bought new years ago. My first question is regarding starting the engine. the 088 takes muscle to start, without the compression release, I would not be able to turn the engine over fast enough to start it. With the 090 it turns over super easy with the compression release, and I can start it from cold without using the compression release at all. Is this normal for an 090? It started up on the 2nd pull, 088 always takes about 6 pulls from cold. Today I ripped against the grain with full engagement on a 36' bar (no skip chain) and 30 degree teeth. the 090 was working hard, but did not bog down. If I did this with the 088, I would have had to go easy on the pressure or it would have bogged down. What are the first symptoms of needing a piston and cylinder replacement on a 090. Are the things I mentioned normal for a 090? I the 090 to start harder and with more muscle on the rope than the 088, not less. Does this sound normal, or should I make plans for an 090 rebuild? I don't know what normal is for a good 090 so I am asking. Last question, does anyone know what the recommended oil/gas mix is for the 090? I used 50:1 pre mixed 92 to octane and added an extra splash of stihl oil in the saw's tank. I use 50:1 pre mixed gas in the 088. is this ok in the 090 as well? thanks very much for any imput on this-Joe

 

[sawfun]

Your 090 should be able to be leaned on a good deal more than the 088. Aftermarket 090 cylinders can be easier to pull over than OEM. With a Baileys 090 piston/cylinder, I never needed the decomp and it still ran strong. See if you have an OEM or aftermarket top end. Either way, new rings are easy and cheap to install.

 

[hseII]

So you're saying the 090 is pulling better than the 088, & you are worried there might be issues with your 090?

1. Do a Vacuum test to verify you don't have any leaks.
2. Check the compression, & if it's within the range for your altitude, I wouldn't fret over it.

CHANGE YOUR OIL RATIO FOR BOTH SAWS.

I'm no Miller, but my 090 & MS880 will never see less than 40:1 oil & probably will run on 36 or 32:1 oil.

Oil is cheap, Pistons & Cylinders are not.

 

[William Balaska]

Mine is two pulls max before having to engage the decomp when cold.

 

[Metallichg]

I'm really glad I asked the questions, thanks for the help. I will change to 40:1. oddly, the dealer that sold me the 088 years ago told me to use 50:1. I thought that 50:1 had more oil than 40:1, obviously I was wrong on that. I will get a compression Guage and check it. I hope the 090 is ok, because it runs and starts great, but I want to find out if I am getting reasonable power from it, or poor power and not knowing any better. It will be interesting to see what the compression is. Maybe by 080 would turn over easier with more oil in the gas? I will find out and let you guys know.

 

[mdavlee]

50:1 and ripping will end up with a blown crank after a while unless you're tuned real rich.

 

[hseII]

50:1 and ripping will end up with a blown crank after a while unless you're tuned real rich.

Mike,

What do you recommend for milling on with these saws?

@Quietfly

 

[mdavlee]

25-32:1.

 

[Cease232]

I have both of these saws and run 32:1


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[Metallichg]

Today I pulled the muffler. It looks like my saw had a "rustoleum rebuild". The saw is stamped 1258376. I did not yet receive my compression Guage, but I can see scoring on the piston (concentrated in the area of the exhaust port. the scoring does not look real deep to me, but I am not sure what normal looks like. the cylinder says " MAHLE W6 58ZN4. does anybody know if this is a stock or a replacement cylinder? Can anybody tell the year of the saw based on the saw number? I need to get a technical manual for this 090, can they be downloaded or is buying a disk off Ebay the way to go? thanks very much-Joe

 

[Cease232]

Yes stock cylinder.
Pistons are real cheap for these for some reason. Like $45 from any stihl dealer.
Several methods to salvage a scored cylinder. Research it here.
I'll PM you the repair manual.



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[chainsaw-57]

58zn4 would be oem 070 cylinder.

 

[bulletpruf]

58zn4 would be oem 070 cylinder.

Ruh roh...

 

[hseII]

58mm is the bore for an 070, as mentioned above.

An 090 is obviously larger, 66mm I believe. ( I haven't had mine apart.)

Call Stihl tech services, give them your serial number, & let them tell you what they know.

Their records are hit & miss prior to the mid 1980s, but they should be able to tell you something of use, especially if the paperwork was ever filed on that saw.

It sounds like you're the owner of an 070, which isn't necessarily a bad thing.

Post some pictures of it, & the Cylinder & Piston.

 

[Cease232]

58zn4 would be oem 070 cylinder.

Totally overlooked the number. That sucks. Still a big saws though.



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[ML12]

I've got an 090AV here, and if you don't use the decomp when its cold your asking for trouble, when its warm you can start it without using the decomp, but you've got to be committed.

 

[d45]

You could have a 090g saw they came with a 58mm bore. The regular 090's came with a 66mm bore I believe.

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[Metallichg]

can I just bolt an OEM 66mm Piston and cylinder on the saw and leave the crank and Rod alone? And use the same exhaust, carb and everything else? Thanks guys

 

[Metallichg]

I have an 090G, and this saw does not have a gear box. a previous owner could have used the smaller piston and cylinder on it, I suppose?

 

[Cease232]

G stands for gear drive so can't be an 090G unless I'm missing something. Differences between the 070 and 090 are the cylinder and clutch so Yes you can bolt on a 66mm cylinder with no other modification. Any way you can post up pictures?


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