MS 650. Fix it or sell it?

[Monkey_With_A_Chainsaw]

I recently did some work for a friend in return for an MS 650 magnum he got from someone else that he was never able to get to run. Took it to a shop and its not getting enough compression and they recommend replacing the top. Original owner probably ran a bad mix or used gas with ethanol. Questions: Should I spend the money to fix it or sell it as is? If I sell it as is, how much should I ask for it?

 

[Brent Nowell]

Yes I would fix it. What a loaded question!!!

 

[Ryan'smilling]

Not enough info to call it. Welcome aboard, by the way. There's tons of folks on here who can get you started fixing it if you want to go that way. First thing would be to do a pressure/vacuum test to see if it's leaking air, which would cause the damage to begin with. After that, you can pull the cylinder off and see how bad the damage is. Often, you can clean up the cylinder with some sandpaper, pop in a new piston, and get back to cutting. That would be a lot cheaper than a whole new top end. Finding the cause of the original problem is very important though, because if you reassemble, but don't fix an air leak, you can be right back where you are now, except having spent a decent chunk of time and money.

 

[Mad Professor]

1) how does it spin over, what is compression? Make sure decomp valve closes, or plug it

2) pull muffler , what does piston look like?

3) pres/vac test. Air leaks?

If saw looks good besides P/C , it's worth fixing.

If OEM cylinder cleans up just get a piston, fix leaks found in #3. If needs a cylinder, look for a good OEM still 066/660 cylinder and get piston, or new 066/660 stihl or meteor P/C. Fix leaks

Why 066/660? Bolt on and 2mm bigger bore. Also more plentiful used OEM.

You could go chi-com with piston or cyl parts, and save $$$. But quality is all over the place.

Results of 3# will tell what leaks need fixing. A OEM gasket set will have a set of seals included

 

[Monkey_With_A_Chainsaw]

Thanks for the info and the welcome guys!

The shop said it was getting 78% when they did the compression test and it needed 95+ to run. That’s why he recommended replacing the top end. I don’t have any mechanical experience but have felt the need to start learning it if I’m going to keep doing tree work as a side job. Hopefully this site and YouTube will keep me from making a box of parts.

 

[cuinrearview]

One more vote for fix it. You don't need mechanical skill to fix one.

 

[Brent Nowell]

Thanks for the info and the welcome guys!

The shop said it was getting 78% when they did the compression test and it needed 95+ to run. That’s why he recommended replacing the top end. I don’t have any mechanical experience but have felt the need to start learning it if I’m going to keep doing tree work as a side job. Hopefully this site and YouTube will keep me from making a box of parts.

I think fixing saws and maintaining them is fun, that’s just me though. If your not mechanically inclined you can learn if you want to.
I would start with a factory service manual, it will walk you through the steps of rebuild and testing tolerances etc.. this will take time to learn but we will help.
Goto “beg for manuals” thread, search for it and request the service manual for your saw. Within a day someone will send you the manual in your inbox.

The service manual will also tell you what tools you should have, and another resource is YouTube. This may not be the right way to do it, but watching disssembly and rebuild videos on that saw will show you how it is done. And yes there is a process.

Good luck

 

[Wood Doctor]

One of the first saws I ever added a new top end to was a Stihl MS650. I upgraded it to an MS660 and the owner was ecstatic. He still uses it today as a logger, often pulling a 36" bar for big cottonwood trees.

 

[Mad Professor]

Thanks for the info and the welcome guys!

The shop said it was getting 78% when they did the compression test and it needed 95+ to run. That’s why he recommended replacing the top end. I don’t have any mechanical experience but have felt the need to start learning it if I’m going to keep doing tree work as a side job. Hopefully this site and YouTube will keep me from making a box of parts.

Pull off the muffler and post a picture of the piston. That will tell a lot.

 

[Wood Doctor]

Attached is the MS650/660 service manual. BTW, compression is usually measured in psi, not %. If you were quoted a percentage, I would have to ask % of what?

 

[Monkey_With_A_Chainsaw]

Now that you mention it, he probably said psi. I’m going to get started on it the week after next (family vacation) and will take and post pics as I go along.

 

[Gord404]

Someone mentioned it and I think it is a really important step on any troubled saw is a leak down test to see what happened in the first place before tearing it down and one more after work is done...takes a lot of guesswork out of the job at hand, - highly disappointing when you sink money and time into a saw and your right back where you started. My 100$ mityvac is one of the most useful tools I have.

 

[Monkey_With_A_Chainsaw]

Here are some pics. The one closest to the exhaust port shows the back of the cylinder. Couldn’t get it to focus any better. Pretty sure neither should be as scratched up, lol. My finger nail catches on the ones I can touch.

 

[pioneerguy600]

The piston is toast, only cleanup will tell if the cylinder can be saved.

 

[Wood Doctor]

The piston is toast, only cleanup will tell if the cylinder can be saved.

I tried three times to buy a piston and ring kit only and add them to a honed down cylinder. One was successful, but the other two were not. After that, I bought both at the same time -- P/C kits. These have always worked.

 

[pioneerguy600]

It can go either way of course but in my rebuilds I have had at least a 90% success rate maybe a bit higher. Cylinder condition is the variable and knowing what will or not work well is the deciding factor.

 

[Monkey_With_A_Chainsaw]

Pull off the muffler and post a picture of the piston. That will tell a lot.

Posted some pictures

It can go either way of course but in my rebuilds I have had at least a 90% success rate maybe a bit higher. Cylinder condition is the variable and knowing what will or not work well is the deciding factor.

I can see that the cylinder has scratches too. I don’t know what I’m doing with sanding/clean up. I can try to sand it smooth again but I wouldn’t be able to tell if I’ve just rounded a spot out for air to leak. At my amateur experience level I think it would be best to do a whole kit.

 

[Monkey_With_A_Chainsaw]

1) how does it spin over, what is compression? Make sure decomp valve closes, or plug it

2) pull muffler , what does piston look like?

3) pres/vac test. Air leaks?

If saw looks good besides P/C , it's worth fixing.

If OEM cylinder cleans up just get a piston, fix leaks found in #3. If needs a cylinder, look for a good OEM still 066/660 cylinder and get piston, or new 066/660 stihl or meteor P/C. Fix leaks

Why 066/660? Bolt on and 2mm bigger bore. Also more plentiful used OEM.

You could go chi-com with piston or cyl parts, and save $$$. But quality is all over the place.

Results of 3# will tell what leaks need fixing. A OEM gasket set will have a set of seals included

Got any recommendations on where to go online to get OEM cylinder kit?

 

[pioneerguy600]

OEM Stihl parts are mostly dealer only but there are times OEM parts come up on fleaBay but for me they always cost me more by the time I pay taxes and shipping.

 

[rupedoggy]

How about a new meteor kit from CCC that is a sponsor here? You can get the 660 kit. Mike