The only thing my old 660 had on my 372 was weight. Big heavy turd in stock form. Sell it to some stihlhead and get a 395XP
Being a fairly new 660 owner, I'd say you have an issue. I've run the 372 and the 660, both bone stock....for me the 660 is a noticeable difference.
Like this? Those are aftermarket filters. I don't have any exp. with that particular one. That's just it. The 660 suffers from being modified to meet emissions standards that are much tighter now than when the design debuted with the 064/066. Take a good look at it and notice the baffle inside the muffler and the ridiculously tiny exhaust outlet. Twin transfer port engines on a Stihl like to breathe. Which is why the MS440/460/660 all respond very well to muffler mods. (Note: the 440 has a larger exhaust outlet than either of it big brothers. ) Other's know more than me about this saw but I gather there are some pretty significant differences in the cylinder port timing over the years as well.
I wonder if this bog is why the guy got rid of it? I would pull the muffler and check the piston or check the compression.
Have you ran a 660? Not being rude but it sounds like most of the people responding here Havent, or don't have much experience running one other than reading about them. There are minor porting differences over the years but there are no major light saber models over the run. They are no slouches stock. It is probably the worlds largest selling big stump saw with a 36" bar. The late poly 066's are the same as the 660's. They all have baffles. The dual port cover hasn't came on one since 1990-something. 96?97? They've all had small outlets since. But the dual port covers have still been available. They are still strong saws, and have such a huge following because they have great power and weigh a ton less than the same sized husky. Most tree services have at least one or two. It's had a 20-25+ year run because it flat out works and works well. Short of a few hundred people on a few chainsaw sites, no one modifies them and they get used everyday by tree people. We get too caught up in porting because that's what we do. It isn't required. I'm not saying porting doesn't help them significantly, but so does porting an old 066, old 044, old 046, and old 371xp or 372, and old 262xp, heck even a 51/55 husky that's been around since 1980 before EPA took over. What I'm saying is there is something wrong with the saw if it's bogging. A clogged air filter won't make it bog, an 8t won't make it bog. It has an intellicarb to compensate for a plugged air filter. The new aftermarket filters are still light years ahead of the crappy HD filter that stihl had used since what, 1989? The carb set to lean could have scored the piston enough that it still runs, or crank seals that has started aluminum transfer but hasn't stuck the ring yet. A carb set too fat will not bog, it will still run, just at a way lower than peak rpm. Guys that mill with stock 660's set them fat to bring the r's down, keep extra oil in it to keep it from melting down. A stock 660 with a single muffler outlet or a dual port can be stood on with a 20" and a clogged air filter. Anyone that has milled with one knows how packed the filters get and it still keeps chugging with much longer bars and literally pushing/standing with all your weight. So, I'll say it again, pull the four T27 bolts that hold the muffler cover and look at the piston.
I'll admit I don't have a LOT of run time with the 660 but that's mostly because I've run one enough to know I don't like it stock. I agree that it should cut with a bicycle chain on that 20" bar but in smallish wood it does not surprise me that the OP's 372 is right there with it. I have an 066 in a box that I've contemplated throwing together but it just needs too much to make it worth the time/$$. The OP has stated he didn't feel there was a real mechanical issue with the saw, just that it's performance wasn't what he expected. He might see a bigger difference in bigger wood too.
I have personally had a MS 360 with an intellicarb that would bog under load. Had an OEM filter and several seen it run at the GTG at Swags in May. Revved like a mad man. But once in wood? It lost all power. Took me a month of testing to figure it out. I put almost $600 in that saw and racked my head over what was wrong Had new Everything.. Except the air filter. The filter had been blown out, but after years of fines, it was just "plugged" up.
Mill with an old hd filter. Compressed air barely blows the dust out its so packed. I'm talking about the 660/066 here, not a 036
That is a different animal. Yes.. But some have not upgraded to that system and an Original HD filter with Prefilter can and will "pack" the same as a flock filter. And these Chinese White pleated filters are even worse than the original flock filters. Having ran one side by side? I pulled it.. And will ship it someone for free.
that;s not the same filter that mech posted. mechs is like a white K&N or a stihl HD#whatevernumber now. I still run the old HD filters. the second gen ones, like your pic above. most have probably never seen the first gen HD filters, looks strangely like the latest, but was metal instead of plastic. anyway, I run the last gen filters that have worked for 18-20 years. Why?, because they work, and I have '8-10 of them. 50 bucks is much better spent these days. I'm talking about abuse here, not regular cleaning out of filters. Milled some serious sized lumber, like 2 tanks per cut and an air cleaning because its so packed. I thought I had seen "dirty" filters on my 046/440/044/066/660's in the past, but nuthing and I mean nuthin' like one 10' long 28" wide mill cut. Point is, so packed, the saw still ran with every ounce of body weight to advance the saw down the board. I highly doubt a line trimmer or hedge trimmer that used it all day, every day would let the filter get clogged up, because he has to rely on it. not saying it isn't possible at all, but I also know what Ive seen and experienced. Amish loggers don't change filters. The saws run and run and run until at some point they adjust the carb and melt it down. a stock 066/660 in 20" wood won't be "impressive" but it should not bog. The op doesn't know if it is supposed to or not. They shine in bigger wood, but in 20" wood, any of the 60-80cc saws would likely be the same. Maybe he was wrecnchin on it with all his weight, and you can bog any saw doing that. Maybe he was reading all the old 660 is god threads on AS and thought it was supposed to be a light saber. That is not. It is heavy, and too heavy for 20" bar material, that is 372 territory.
I've run every version of 066/660 and the very early ones run like it's ported compared to the newest versions hamstrung by epa standards. If it's a newer version I can see the disappointment in it. I bought a new one and was the same after running it with some older 066s.
wow I'm overwhelmed with the responses and ideas. I'm charging my GoPro camera right now and will have videos up later. I've got a friend that has a compression tester, I'll pull the muffler off and get some pics of everything I can. I think I said it earlier, I'm a Husky man that has no problems with Stihl. My 372XP will cut anything I'll ever encounter around here. But the 660 is legendary that I couldn't pass this deal up.
I think you will be more than happy once you get it running as it should be. I have had mine about 3 years now and love it. Bought it new with a 3ft bar. It is kinda heavy but lets be real here. It's a log saw, not a trimmer. I limb up with another saw and do the 20 and up with the 660 and let her rip. I'm running a full house RSC chain and it cuts great for me. I cut more than the average guys large diameter wood and it's just plain fun doing so now. My only complaint with it was the air filtration system as mentioned before. From this quote you say the saw is a year old? To clarify, we are talking about a MS 660 Magnum correct?
