Mark_Skyland

The video to you tube doesn't seem to be showing for some reason. Try searching this Stihl MS 170 Oil system repair. Changing Oil pump, worm gear, oil line, service.

I didn't the first time and had to strip another saw down to check as I didn't have the stihl tool! This video suggests that you just push the pump all the way down, it might be correct but I couldn't say for sure.

I measure the depth the depth of the pump before I remove it, I think its around 5mm.

I haven't has a chance to rebuild the round tube pole saw but I've done two square tube ones this week, a lot easier by far!

Ill find a workshop manual and send it to you. Those pumps need to be inserted quite specifically or they wont work. The pump needs to be set to the right depth and it needs to be facing a certain way. If I get a saw in with those pumps and the pipe or filter isn't blocked I just replace the pump, its not worth cleaning it and putting it back in as it never works.

You're a better man than me. I've always struggled to rebuild these things. I did one a month or so ago and I've got another one to try and sort out this week. Half of the problem is that the bearings break down so a lot of the parts have moved and arent in the right place. There is a good video on you tube somewhere, ill try and dig it our for the OP. You need to make sure that you have the right bearings as there are two types, they are installed the correct way, the springs are installed correctly and that you have the splined shaft installed correctly as it has a circlip that makes sure it moves when you extend the pole. IIRC! I think one of the issues is that the stihl diagrams are misleading and they don't show how its properly put together. Ill try to take some photos when I put the next one back together.

TBH I havent worked on any machines that have had a big end failure. Do you mean the main bearings?

If you cant get your hands on a 2nd hand saw before buying it then its a bit of a lottery IMO. On a big saw like the 661 you can get away with a few issues, even a knackered engine if its cheap enough. I wouldn't pay more than 500 maybe 600 for a second hand one unless you know the operator or can try it before you buy. Don't forget, on big saws bars and chains aren't cheap, you need to factor that in when comparing 2nd prices to new.

It might not be causing the issue. As I said the vid looks like its oiling as it should. If the chain isn't constantly getting slack and the chain doesn't look dry then its probably ok. I would still expect some splatter of oil off the end of the bar though.

I have customers that do have to swap from mineral to bio oil. It doesnt usually clog up but then I do advise them to drain the tank before filling up. I think its more likely to go rancid when its left for some time in the tank then you fill up with mineral oil. Do you have three saws that now have oiling issues?

If the carb is leaking once you fire it up it will pour out smoke and run really rough for a bit. A 15 euro carb is definitely not genuine and its hit and miss if they are any good. Worth it for a last ditch attempt before binning a machine though. Its around £100 for a new carb over here.

Try Micks advise first and scrape out the bar groove. The amount of oil coming out looks fine but is it consistent if you run it for a minute or two? The Pump on those machines is only small, its the same one fitted to a lot of the old home owner machines like the 017, 018 etc they can fail in that they pump some oil but not enough, you sometimes see air bubbles or the oil just stops for a bit. If the oil filter is the same setup then you usually cant remove it from the oil tank you have to strip a few bits off on the sprocket side and take the oil pipe out that way to get at the filter. It may be different on your machine but I haven't had to strip one down so I cant say for sure. The pump is lubricated by the chain oil and bio oil can coagulate when mixed with mineral oil and cause a few problems. You could try emptying the oil and flushing it out with petrol. You need to put some fuel in, really shake it up, pour out and repeat a few times. All that will do it clean the filter a bit at best. That sometimes works but tbh its more of an out on the field last chance saloon attempt at a quick fix.

Is it the c be version with the easy start? If so check the starter mechanism, its a bit more complicated than standard starters and it might be causing the issue that you have.

Yes, they use the same drive shaft and drive tube. Just undo the pinch bolt and swap the whole thing over including the guard.

Ive seen the same issue with the impulse pipe on the 026, I put it down to worn av rubbers causing too much movement. As you have said forceps plus time, patience, lots of swearing and glasses for me.