Something is off with my MS 660 when I am cutting stumps.

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dontbthatguy

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Shoreline, CT
Today I went to take on a large 4 foot diameter stump with my MS 660 I purchased last year.


I started cutting but once my entire bar is in the work, the saw bogs down and the motor won't turn the chain. I back off and run it full idle but once I put a load on it it just bogs down again. It has happened in the past which I blamed on dull chains or hitting something in the stump, but something has to be wrong. I am positive I was using a sharp chain.

I finally gave up and took it to the tailgate. Everything, the bar, chain, nuts, and cover were hot to the touch. I had to put gloves on the handle it. The clutch cover was hot as well. I threw on my 25 inch bar because the saw always seemed under power with the 32 and the same thing happened.

Here is a link to a couple pictures. The first one the dark spot by the muffler was where a little smoke was coming from. The second shows how dirty it was after only a min or two of cutting.

http://imgur.com/a/sr21Y

The saw also leaks a decent amount of bar oil when ever I finish using it. More than just a few drops. I looks like it might come from the bottom of the clutch plate.

I recently cleaned the clutch cover as it was getting all gummed up which seemed to give it new life. But after today its like being back to square one.

I am an amateur when it comes to flushing stumps. I bought the saw specifically for this and ever since I had it last year it seems to lack power when cutting big stumps.

Hopefully someone out there can help me.
 
stumping is hard on a saw, just being a big saw isn't enough to do it efficiently, clean it frequently including under the clutch cover and air filter, let the saw back off a little mid cut to clear chips, if you see dust instead of chips your chain is too dull
also good to make a low cut but not flush first to remove most of the weight of the stump before you lay the saw down on the ground where it will get super hot to make the flush cut of the customer is paying for that
also using the larger sprocket isn't giving the saw all the mechanical advantage it would like in a long hot cut
Dave
 
Thanks for the replies so far. I switched to the larger sprocket after I was having a hard time getting good tension on the 32 inch bar.

Ill take a look this weekend with the muffler off. What would I be looking for?

Also any ideas on the oil leak?
 
An 8 pin sprocket is definitely not the right sprocket to have for stumping. It gives you more chain speed but not nearly enough torque. you will want the 7 pin sprocket. When you take a look in the cylinder, check for any streaks or scratches on the piston and the cylinder walls. Take some pictures of the cylinder and piston to share! :)
 
running a skip tooth chain on that length of bar is advisable as well if you aren't already.

Around here if you cut lower than 1' off the ground you're bound to hit dirt in the wood, if I had to do it frequently (I NEVER do at all) and the chains were dulling too quickly I'd probably go with a semi chisel chain.. doesn't cut as fast sharp, but cuts better than full chisel when it's hit dirt.
 
Is the saw oiling good? With the bar heating up and the oiler leaking abnormally it might not be pumping good enough to cool the bar and that is hard on a sharp chain.
 
dont b thatguy, do you know how to adjust your carburetor?
+1

At least for me, and on a MM066, the saw boatloads more torque tuned richer. It was around 1500 rpm less than what the tune sound to be correct out of wood.

I was using a 28" with a 7pin and .404 with the rakers at .040. In the 36" stump of sugar maple, I was able to bog the saw out easily. It was clear something was wrong. Richened it up, a lot. Saw was able to cut like a champ.

I'd check your piston. Look for any vertical lines or rubs in the horizontal machining lines the piston originally has. Then do a compression test. Then tune her fat and cut wood. Start to lean out the H side by 1/16 turn just until the saw stops 4 stroking with light pressure.

Make sure you clear your oiling tube. Both wher it comes out of the saw, and where the hole in the bar is. You may be clogged and not oiling right. If the bar is clogged, the oil will ooze out all over but not oil the bar groove. May explain all the heat as well. Friction.

Check your muffler screen for carbon build up.

If your saw has a good piston and compression, I bet the above steps fix the problem.
 
try the simple most obvious things first. You say the chain is sharp so that could be excluded, the next thing is the bar, if the rails are not square or the groove has been worn wider than spec the chain won't cut straight, bind in the cut, rob power & produce heat like you described. the state of tune shouldn't have to be touched unless mix ratios have been changed or your elevation or you have a faulty saw.
fangst
 
I'll plus one the possibility of oil clog keeping maximum amount of oil from reaching the chain... along with sprocket issue
 
You guys are better than web MD!

It could be any one of the issues mentioned and I am comfortable trying to fix any of them except retuning the saw.

Also how do I diagnose an oil clog? I can youtube it, but if anyone wants to chime in with a tip that would be great.

Lastly I have read of guys switching to the high output oiler. Should I make that upgrade seeing how much stumps beat on the bar and chain?

I should be able to take it apart tomorrow and will update with pictures.
 
If everything with the power head checks out, proper tune of the carb, good compression, clean air filter, no carbon build up on the exhaust screen and the spark plug looks good with the proper gap the problem has to be with either the bar and or chain.

Double check that your chain is sharp and your rakers are set properly. Check your chain adjustment. To tight is as bad as to loose. When you pull up on the chain it should lift off the bar rails but the drive tang should stay just inside the rail grove.

Clean out the bar rails. Make sure they aren't full of saw dust and wood chips. Make sure the oil holes in the bar are clear. Check the bar rails for wear. If you can feel a burr along the sides of the rails you need to dresss/service the bar. Simply use a flat file and file the burrs off. There are YouTube videos that show the proper way to do this.

Make sure your oil pickup inside the oil tank isn't plugged. Make sure your oil pump is turned up to the max. If you still need more oil you can either get the parts to turn your current oil pump into the high volume pump, buy the high volume pump complete and install it or modify your current pump to output more oil. Do a search on AS. There are threads that cover this mod really well.

Personally when I'm going to be stumping or felling a tree I always make sure my oil tank is completely full. When you hold the saw sideways(oil/fuel cap up) the oil pickup is also pointing up and when the oil tank gets below half full the pickup is no longer submerged in the oil. Thus no oil flow to the bar and chain.
 
Regarding the "oil clog", just make sure the oil holes in the bar are cleared of debris and the bar tip is spraying oil. I think 660's definitely benefit from the HO oiler. Tuning is simple. You need to get comfortable with it in order to protect u'r saws. Or buy a saw with a self-adjusting carb.
 
From the pictures it appears that you don't have the dual port muffler. I would recommend getting the dual port front cover for you muffler. This allows the saw to "breath" better. It also lets the saw run a little cooler and helps to increase power and rpms. If you do decide to put the dual port cover on be sure to have the carb retuned before you use the saw again. The saw will need to be tuned a bit richer. If you don't retune the saw it will likely run lean and destroy your piston and cylinder. If you don't feel comfortable retuning your saw I'm sure your local dealer will be glad to do this for you especially if you buy the dual port cover from them.
 
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