066 Mag H/L Jet Adjust Post Muffler Mod...

[SandMan]

Read a lot about 066's and muffler mods but didn't see anything to answer my specific questions. Here goes...

Bought and fixed up an 066 Mag for pretty cheap, $260 including $20 in parts from a member of this site (thanks!). Compression was good and the piston and bore look great. I assume this is the later model as it had the puny 3/8" muffler outlet. Due to a small leak and the restrictive outlet, the plastic parts near the chain brake links had cooked, including the hand guard bearing boss. Being the lowly weekend warrior, fixing the chain brake was a must for me- no telling what may lurk in the old farm trees I get for firewood, particularly from fence-high level to stump.

After getting everything fixed, I cut out the goofy muffler 'catalytic' box and opened up the outlet to approx 3/4". When checking the H/L screws, they will only open 7/8 turn for the high and 3/4 for low. The shop manual and (I think) a few posts on this board recommend starting out at 1 full turn open. Putting aside the screw issue, Stihl recommends for the 066 12,000 rpm max with bar and chain. A Madsen's article I read recommends 13,000 rpm max w/o bar & chain.

But what about post muffler mod? Should I adjust for a higher max rpm? I would assume so- but what is my target rpm after the mod? I have a tach, so checking this won't be a problem. With the H screw all the way out (rich), I do get a little burbling at full throttle. I should have checked the pre-muffler mod rpms as post-mod it sounds much higher at full throttle.

Hopefully I can make the adjustments I need with the limited screw travel on the carb adjustments. I had not heard/read about stops on 066 screws- so I don't know what's up with that. Thanks in advance for your help, great site here.

 

[Gypo Logger]

As long as it's not running too lean you shouldn't have a problem. As added insurance I'd be using 32:1 with the saw set at factory rpm.
John

 

[SandMan]

32:1 sounds like a safe bet. Me being of simple mind, the whole 'turn out one full turn' when it will only turn 3/4-7/8 turn had me confused. I'll get out the tach and see what I can do tomorrow. Thanks for the reply and suggestions.

 

[Lakeside53]

Not sure everyone knows this, but you don't have to "open up" the muffler on the 066 Mag... just get the factory "dual port" cover, and it will be just as they came from the factory in 1995 before OSHA told Stihl it was "too loud"... and in making the saw "quieter", derated the HP. Stihl kept the dual port front available as a "spare part". About $45 list price, and you get a dual ported muffler with both spark screens (important in some areas of the country, and if you want to avoid a big fine from the Forest Service..).

 

[Lakeside53]

32:1 sounds like a safe bet. Me being of simple mind, the whole 'turn out one full turn' when it will only turn 3/4-7/8 turn had me confused. I'll get out the tach and see what I can do tomorrow. Thanks for the reply and suggestions.

You obviously have the later version with limiter caps. The "one-turn-out" is only meaningful without the caps installed. I assume it's a WJ-69. This carb has a main jet of .64mm, which is the same size jet as the "pre-osha" dual port muffler version and allows plenty of gas to flow with a moded muffler. You must put back the limiter caps after any adjustment as there is no spring on the screws to hold them in place. Stihl recommends new limiter caps as they tend to get damaged when you take them off, and the last thing you need is for the H screw to vibrate out of adjustment. Only about 50c each...

If you want your saw to last, don't set it for higher than "factory" under no load; there's plenty of threads on AS about torque and RPM, but in short, a higher "no-load" won't necessarily translate to a faster cut. My Stihl data shows 13,000 with bar and chain, and after the break-in period, that's where I set them. I'm not going to argue about 32.1 or whatever, but I run 50:1 and so does everyone else I know, with no problems.

 

[rbtree]

Lakeside, again, I beg to differ with ya. Case in point, the 440 I just got from Madsen's for Ekka. Even with the dual front cover, the total port opening was way too small. I'd say it was only a little larger than the area of the old single port, which was appx 9/16th. So, I opened the main port to almost that size and enlarged the front cover port by 60%, so that, combined, the ports were a bit larger than the eexhaust port opening at the cylinder wall, which had been enlarged by Madsen's. ( based on the 1 to 1.25 ratio recommended by a few saw builders.) Result: the saw came alive, and how!! Only trouble was, it was turning over 15k, and I had to call your shop for instructions as to r and r the caps. It may have been Bob who answered, as Steve was off, and Bob doesn't much like me, as I seldom buy much of anything there, so he was no help. I had called Madsen's once, and then called them back, and they told me how to get the cap off. Anyhow, the saw was almost on a par for performance with my ehp 372 and PP7900, if not their equal...and it only had one tank idled through it.

Do you know, or should I talk to Steve, to find out how to open up the 200T high speed jet, if it is possible, as it needs to be richened up some, in order to allow for more muffler porting? Sorry 'bout the run on sentences.....

 

[ross_scott]

Not sure everyone knows this, but you don't have to "open up" the muffler on the 066 Mag... just get the factory "dual port" cover, and it will be just as they came from the factory in 1995 before OSHA told Stihl it was "too loud"... and in making the saw "quieter", derated the HP. Stihl kept the dual port front available as a "spare part". About $45 list price, and you get a dual ported muffler with both spark screens (important in some areas of the country, and if you want to avoid a big fine from the Forest Service..).

are you saying that over there the magnums are being sold without the dual port muffler covers and they come with just a single port???

 

[Lawn Masters]

pretty much, yes.

 

[timberwolf]

I agree with Rbtree, if I jet my oh66 down to 12-13k is spitting fuel and not running right. Much better in the 14-15k range. Even the dual port opening may not be taking full advantage of the engine potential, but a good option for anyone not wanting to hack up a muffler.

I make sure it has lots of high quality oil at 32:1, no problems so far.

 

[SandMan]

This is a low buck 066 Mag- not pretty on the outside but great on the inside, and that's what counts. I tapped out some dings in the muffler cover, so cutting it up was not a problem. The muffler side exhaust outlet can be enlarged quite a bit and still flow 100% through the screen. It blows my mind how Stihl could use such a small opening on the stock muffler.

I'll do some more work on it today and check it with a tach. Good to know about the limiter caps.

Regarding pro vs. non-pro Stihls: I know the power is not even close to comparable, but the 066 with same size bar does not feel much heavier than a 310 I traded away. After getting the 066 parts and selling the 310 on ebay for the same as what I paid (go figure), I came away with a bigger saw and an extra $125 in my pocket. Last winter I had to borrow a 440 to buck some large oaks and liked the muscle to get the job done faster. 310 was AOK, but saving money is a good thing after feeding a house full of Katrina evacuees (inlaw=outlaws ) for many weeks. Anyway, I appreciate the advice from the forum quite a bit.

 

[Lakeside53]

Lakeside, again, I beg to differ with ya. Case in point, the 440 I just got from Madsen's for Ekka. Even with the dual front cover, the total port opening was way too small. I'd say it was only a little larger than the area of the old single port, which was appx 9/16th. So, I opened the main port to almost that size and enlarged the front cover port by 60%, so that, combined, the ports were a bit larger than the eexhaust port opening at the cylinder wall, which had been enlarged by Madsen's. ( based on the 1 to 1.25 ratio recommended by a few saw builders.) Result: the saw came alive, and how!! Only trouble was, it was turning over 15k, and I had to call your shop for instructions as to r and r the caps. It may have been Bob who answered, as Steve was off, and Bob doesn't much like me, as I seldom buy much of anything there, so he was no help. I had called Madsen's once, and then called them back, and they told me how to get the cap off. Anyhow, the saw was almost on a par for performance with my ehp 372 and PP7900, if not their equal...and it only had one tank idled through it.

Do you know, or should I talk to Steve, to find out how to open up the 200T high speed jet, if it is possible, as it needs to be richened up some, in order to allow for more muffler porting? Sorry 'bout the run on sentences.....

I was only talking about the 066 mag (and thre 1995 dual cover); I don't know about the 2004 440 mufflers, but I'll go measure the 066 muffler openings ports. I just add the dual port front to the original muffler back (I'm pretty sure this didn't change prior to 2001), and it pretty much doubles the opening area. I'll need to check the old tech notes, but I think we gain about .6hp to .8hp with just this change (or lost it in 1995). It's not personal - Bob doesn't like anyone fixing anything over the phone... on the other hand, the employees will help anyone and that grinds on the boss a little. Hint, Bob never gets in before 10, so call early

200T: I assume you're not talking about the limiter cap etc, and you saying you run out of rich adjustment with the raw H screw - i.e. the internal jet is too small? Which carb do you have (exact, with variation suffix (A,B,C etc)? In general, the Zama carbs will require drilling with some precision jet drills. It's not as hard as you may think 'cos the H screw compensates (within limits) for excess material removed. The walbro W326 020T carb can be made to fit easily and this carb has removable (screw in) jets. BTW, in case you didn't know, there are a couple of variants in the Zama range - the later units have accelerator pumps, and the earlier did not. If you have a "lag" on accelerate, it's often not the "L" adjustment, but the fact that you don't have a pump.

 

[Lakeside53]

are you saying that over there the magnums are being sold without the dual port muffler covers and they come with just a single port???

yes, since 1995... way before the EPA stepped in about emissions, OSHA limited the noise (and consequently the power) for us - too loud for our poor ears... but the dual cover is available as a "spare".

 

[Lakeside53]

. It blows my mind how Stihl could use such a small opening on the stock muffler.

Stihl (and Husky and others) don't go out of their way to make a small hole just to make us mad They are attempting to limit emissions and noise, and yes, they could make a fancier muffler at more cost, but then what would AS talk about It would be interesting to have AS members from other countries send in the muffler opening sizes and serial numbers to compare the effect or USA regs verses say Europe, NZ/AUS, CA and Brazil (don't even have fire screens in most Brazil mufflers!).

 

[Lakeside53]

I agree with Rbtree, if I jet my oh66 down to 12-13k is spitting fuel and not running right. Much better in the 14-15k range. Even the dual port opening may not be taking full advantage of the engine potential, but a good option for anyone not wanting to hack up a muffler.

I make sure it has lots of high quality oil at 32:1, no problems so far.

With the standard muffler (most of what comes in the store) I don't see any problem with the 066's at 13k... I need to err on the conservative side as they are customer saws, so I set them for factory limits. Immediately after a cylinder/piston replacement, they are set to 12k (like the factory) and told to come back after 5-10 tanks and we'll reset them higher. Evey one seems happy... To be clear, the guys are much more worried about a "good performing saw" than a "perfect performance aw", and I always get asked "can't you stop my guys from over reving it, but make it work great for me"?. Need a Boss/Employee key switch I guess...

 

[timberwolf]

Your point is a good one lakeside, no doubt a saw set to run at 12000 rpm should outlast a saw set at 15000 all other things equal, for a customer saw likely a good idea.

If they go out cutting on a -20 day with a high preasure front the mix leans out and the saw revs 13k and change, no big deal. But if the saw is set at 15k and the same is done the saw could be too lean and over rev.

Maybe I have lost some objectivity in just trying to make saws cut fast, But once you have experienced a 066 on pipe at 15k, it is hard to turn it back to 12k.

 

[ross_scott]

yes, since 1995... way before the EPA stepped in about emissions, OSHA limited the noise (and consequently the power) for us - too loud for our poor ears... but the dual cover is available as a "spare".

They are still selling them here in new zealand with the dual port cover as osh doesn't seem to worried as they say we have to wear hearing protection that is grade4 or 85 decibel or better on the noise protection rating and most of all the big saws arent really used in urban areas unless it is an arborist doing a job for someone, The way i see it is government departments just love to be a PITA

 

[Lakeside53]

RBtree -> I was a bit out when I thought adding a Magnum front to an 066 muffler only doubled the area...

The standard muffler on a USA post 1998 066 or MS660 has an exit hole of 0.43 inch diameter. Prior to 1998, this was 0.63 inch. In 1998 they also made changes to the cylinder porting to reduce emissions (not sure what they did).

The USA Magnum muffler front has a internal rectangular hole (with rounded ends) of 1/2 x 1 9/16 inches feeding an external slot of 5/16 x 1 1/2.


So, area of outlet:

Prior 1998 : 0.311 square inches
Post 1998 : 0.145 square inches

Add a Magnum muffler front to either : add 0.469 inches... (and it might be a tad more than this).

Yes, the saw winds up pretty good with a magnum front and you have to remove and reset the limiter caps to richen the carb.

The internal box with all the smaller holes in it is the same for all the 066 mufflers.

That Post 1998 size sure seems puny in comparison to the other numbers!

NOTE: anyone messing with an earlier 066 muffler needs to make sure they have a main carb jet of at least .72mm. The "red eye" 066's had a main jet of .66mm (because the ignition limited the max rpm). Stihl published a tech note to say that using the .66 jet and turning up the rpm will result in piston seizure... as the saw couldn't get enough gas at high rpm.

 

[SandMan]

OK-

Here's the result: 14,270 rpm with the needle out as far as it will go without changing the limiter cap, no B/C mounted, 32:1 mix. At full throttle it is 'breaking up' or burbling just a little.

Opinions? Thanks, Ed

 

[Lakeside53]

Too fast.... but it's your saw...

I'd reset the limiter cap anyhow just so you have adjustment range. Right now your slowest speed is 14,700... I'd hate to think what the highest is.

 

[caretaker791]

066 Muffler cover

I replaced my 1999 model 066 muffler cover to the older open style.(dual port), and noticed a difference- also a obvious increase in noise. However-there are a few differences between my saw and the earlier versions. According to the info I have. The 066, since the beginning had 3 different power ratings. The first versions (with the red light) were 7.4 bhp as I recall. The second versions-from after the red light years to just before the muffler was restricted came in at 7.8 bhp. The final versions come in at 7.0 bhp. After reading all the technical notes I could find on the subject it seems that there were differences in the port timing----also ignition timing, as well as the muffler changes over the years. The older 066 cylinders had a different part number as well reflecting the different port changes( for the worse). The new part number supercedes the old as the old cylinders can only be purchased new if they are leftover. So sorry to ramble on so much, but in conclusion, to get the old power back-it is a combination of finding the old cylinder in good shape or new +open front muffler cover- and proper flywheel to match-yes--there were quite a few various flywheels used on these saws. As stated earlier the carb shouldnt be a hinderence, even with the limiter caps since the old main jet (.64) is the same size as the new main jet. Thanks, sorry for my long windedness,,,thats why I only write once a year to this site--thank God right. Take care,,Thanks