660 rebuild

[woodworkingboy]

Specs at max 13000 rpm.

 

[sawinredneck]

13,000 is supposed to be max, 12,500 is supposed to be the sweet spot un modded, but we all know how that goes

 

[Al Smith]

I've seen modded ones tick it over at close to 15 thou .

No sense tuning one to run some speed like a model airplane engine when it likely will be 10-11 thou if that in the wood .

 

[wiley_p]

Al, those are some great pictures of plug colors. So clear, and the lighting is perfect.

 

[Al Smith]

Alright already ,I gotsta get a better camera .

 

[Peter]

Just spotted this old thread, I am happy to report that the 660 is going strong after a year or so. Time for a muffler mod methinks!

 

[SkwerI]

Should have done that before you fired it up the first time.

 

[Al Smith]

You can do a lot by just reworking a muffler .To make it run it has to breathe .To breathe it has to get out before it gets in .Seems back assward but that's just the way it works .

 

[Peter]

Would you remove the internal baffle thingy altogether or just drill some more holes in it?

 

[MasterBlaster]

I'd remove it.

 

[woodworkingboy]

Sometimes removing an entire baffle can give idling problems, if you open up the exit too. Not enough back pressure, the saw won't idle at a low enough rpm for the chain not to spin without the engine dying. You'll be wishing you didn't remove it.

 

[Al Smith]

You can completely gut them if you want .They might idle a tad rich and bog on accelleration though .They can get a little fussy about the carb settings but that's just something you have to deal with .More times than not it's merely a tweek an eighth of a turn or less on the screw .

Idling has more to do with the size of the exit hole(s) rather than the baffles .Of the half dozen or so modded saws I have nary a one has a baffle in it .


The intent of a baffle is to bounce the sound waves hither and yon .When they bounce back into each other the sound is attenuated beings that opposing forces tend to cancel one another .Fine and dandy but this stops or hinders the exhaust flow which robs power .

 

[Cobleskill]

WHATT?? It reminds me of the old Super XL Homies my Dad used to run. I learned on 'em too.

 

[Al Smith]

Those old horizontal cylindered saws with a side exhaust would "wake up " if you debaffled them .They got loud enough to raise the dead when you did so though .

I installed a better muffler on my old Mac 650 geardrive that was running open exhaust.The damned thing doesn't like it . It prefers to be a fire belching loud mouth . That one would set the slopes ablaze in the piney wood hills of the PNW .

 

[woodworkingboy]

My caution about removing the baffle is based upon an 038, a saw that I know Al has a lot of experience with. Opened up the exhaust exit to 3/4" and removed the baffle plate, that just slips out when you take off the muffler cover. No way I could get it to idle without the chain moving at whatever carb setting. Stuck the baffle back in and it idled fine.

No doubt that the external hole was too big, but the problem was definitely in combination with the removed baffle.

 

[Al Smith]

Yes it's a combination of both .

Both my 038's are souped,Mag and AV and both are baffleless .Both have duel port,one factory,one I did .I think the outlet is around 80 percent ex port size .The Av runs a nice brown plug,the Mag a tad rich but it spins over at 14,600 rpm .

I think the problem could be too large of a hole on an unmodded saw with stock port sizes ,less transfer and resulting less volume of exhaust gasses .Better to just take the hole out a tad bit at a time and check it .

 

[Al Smith]

Oh BTW the Mag will idle but very rich .The work on the upper transfers doesn't kick in until at speed then it really boogies .It 's just the stuff you get when you change the port scheming on a saw .Just don't make a practice of letting them idle too much .