What to do? - High Speed MS170/180 14.2-15K!

[ChoppyChoppy]

I've classed the 170 and 180 kind of in the Wild Thang category if they come in the shop. Unless it's very minor work, it's simply not worth it to work on them.

~2 years ago had one come in with a broken brake and handle and destroyed bar. Happened to have a parts saw so we fixed it all up. Before getting into it, called the guy to make sure it was ok, would be an hr of labor. He was fine with it, really liked the saw, etc, etc.

Between parts and labor, a new chain, etc it was maybe $150 total.

Well he comes to pick it up and all of a sudden he didn't like the saw and basically threw a fit about spending that kind of money on a $200 saw.

Sooo.. anymore, I just say, throw it out and buy another, gonna cost more to fix. Just cause it's a Stihl doesn't mean it's a good one.

 

[a. palmer jr.]

The 180 I'm working on right now kinda fits in that category, piston and cylinder, oil line, carburetor. Not sure what it's worth but I'll let him have it cheap since I don't have much in it. I already had the cylinder kit, other two were cheap..less than 100 for sure.

 

[SteveSr]

Well, here is the latest update... After searching around I found a difference in the fixed jet that came with the new carburetor versus the original. The new carbs came with a 0.44mm (smaller=leaner) while the old ones had 0.45mm (richer).

I also found a newer IPL for these saws 5/2018 that showed that the -S57G carb which Stihl is now supplying is SUPPOSED to come with a 0.45mm jet. Since it obviously didn't I decided to call Stihl Tech support. I talked to a guy named Mike and learned quite a few interesting things...

1. Mike, who used to work in the durability department, said that they would set this series (170/180) up to run at 14K max and then test them under load and seeing few if any failures during the 200 hour test time. Apparently these saws can take this carburation. He also recommended not going above 14K and stated that they sometimes had to make fixed jet jetting changes to get them to run at this specified max.

2. Mike talked to his carb expert who related that when you buy a replacement carburetor the repair part supply chain is full of the current production part which may or may NOT be suitable for an older version of the saw (like I have)! In other words there may have been intervening small production changes which would allow the current production 170/180 saws to work properly ( <14K ) with the smaller fixed jet. Mike advised changing the jet in the new carbs to 0.45 and see if it brought the saws to or below 14K.

3. We also discussed metering lever adjustments as a way to richen up the mixture. Mike advised against this approach as there was a very fine line you hit where the needle doesn't close and you now have flooding issues i.e. it starts to get real rich with a very small change in lever height. He said that the best way to adjust these carbs was to change the size of the fixed jet.

Also while researching this I went hunting for different sized jets for this carb, a Zama C1Q series. Turns out that they make a bunch of different sizes. I have a attached a comprehensive Zama manual which shows all of the Zama part numbers for all carbs through 2011. For just the jets go to the price list in the back and look at the 00700xx part numbers. Once you find the size that you want search the document for that part number to find the Stihl carbs that us that particular jet. You can then go to that Stihl IPL and get the Stihl part number to order that jet. You may also be able to get these direct from a Zama distributor (for about a quarter of the price!).

So I have transferred the 0.45 jets from the old carbs to the new ones but haven't had a chance to run the saws yet. Should be able to get to this tomorrow in the daylight.

 

[Jasonrkba]

Wouldn't open for me.

 

[SteveSr]

Wouldn't open for me.

I downloaded it directly from my post and it opened fine. Probably need to download it to your PC and then open it from there.

 

[DND 9000]

MS 170 carburetors and max rpms

C1Q-S57A 14.000
C1Q-S57B 14.000
C1Q-S57C 14.000
C1Q-S137A 14.000
C1Q-S237 (2-Mix) 14.000
C1Q-S137 15.500

MS 180 carburetors and max rpms

C1Q-S137 15.500
C1Q-S137A 14.000
C1Q-S152 13.300
C1Q-S286A (2-Mix) 13.000

 

[a. palmer jr.]

MS 170 carburetors and max rpms

C1Q-S57A 14.000
C1Q-S57B 14.000
C1Q-S57C 14.000
C1Q-S137A 14.000
C1Q-S237 (2-Mix) 14.000
C1Q-S137 15.500

MS 180 carburetors and max rpms

C1Q-S137 15.500
C1Q-S137A 14.000
C1Q-S152 13.300
C1Q-S286A (2-Mix) 13.000

Mine has a Walbro on it...

 

[SteveSr]

MS 170 carburetors and max rpms

C1Q-S57A 14.000
C1Q-S57B 14.000
C1Q-S57C 14.000
C1Q-S137A 14.000
C1Q-S237 (2-Mix) 14.000
C1Q-S137 15.500

MS 180 carburetors and max rpms

C1Q-S137 15.500
C1Q-S137A 14.000
C1Q-S152 13.300
C1Q-S286A (2-Mix) 13.000

Got any info on the C1Q-S57G? That is the one that Stihl is now selling as a replacement for these saws.

Also, anyone have access to the newer Stihl Tech Notes that explain the carb changes to get the carb from -57A to -57G?

 

[DND 9000]

No more info ever seen. I think it`s model update, if a batch of carburetors is at the end, they make a new one with slight changes from collected experience and the designation changes to the next letter.

 

[SteveSr]

Well, as a followup I tore the saw apart again and replaced the seals. The new ones hold about 10-15 PSI pressure or vacuum.

I had to wait until today for winter to return to get comparable ambient temperatures with what I had tested before. Today it was about 45F and the saw maxed out at 14.4K with the 0.45 fixed jet. This is still high but it came down about 600+ RPM from before changing the seals. Based on this I am concluding that even though the existing seals held 5-6 PSI pressure and vacuum that they were "weak". It looks like it would take a 0.46 or 0.47 fixed jet to bring it down to Stihl's 14K "recommended" max range.

Next week I am going on a mission trip to help remove damaged trees from Hurricane Florence in New Bern, NC. Hopefully I will get some run time on this saw and get a chance to see how it runs in warmer temperatures which may lower the max RPM some more.