I know, I know...660 tuning and mix for milling with 36" bar and dual port etc...

[Agoraphobia]

I have read lots of threads on this but can't decide how I want to balance everything given the specifics. I need to tune my 660 for the DP muffler I just installed and the new jet (a .74, it was a .62 for High Altitude here on the seashore???). The hardest thing I'll mill is Yellow Cedar or maybe the very occasional alder. I have a 36" bar and a 28" bar with 3 or 4 ripping chains for each. I have the 36" mill, am not maxing it out for most of what I want to do (8"x8" beams from max 24" diameter wood).

The only reason I ask after reading for countless hours, is that I suspect that everything should be balanced. If I detune to say 10,000 and run very rich with a very oil heavy mix say 30:1, I suspect I'll run into problems. Also I've not seen anything address how much rpms the dp should add if any and how that should factor into tuning for milling.

I want to run 36-40:1 Stihl Ultra with 100LL, I have a good proper tach and the limiters are trimmed. With the dual port and the new jet where should I start my tune? 1 turn out exactly? richer? And with the DP and jet at 40:1 where should my peak rpms be or should I just tune to keep the 4-stroking/burble and forget the rpms until I run it enough to esatblish a set point for a given set-up and use.

Anyone care to answer the most asked question again for me? Sorry and thanks!

 

[mdavlee]

I would guess you'll be right around 1 turn out on the H with the larger jet. I would tune around 12.5k for milling and run a good synthetic oil at 40:1.

 

[Agoraphobia]

12,500 seems kind of fast. I was thinking more like 11,500, based upon what I have read. I know factory is 12.5-13K without the DP and the jet (which shouldn't matter). I don't mean to sound like a prick, but why 12,5? Better cooling? The DP muffler (I got the whole muffler so the side outlet is larger too)?

 

[mtngun]

If it is too rich, it won't make any power and you won't be able to cut with it. It'll take longer to make the cut and the saw will have to work harder, defeating the purpose.

I tune to 12,500.

 

[mdavlee]

He hit it on the head. Too rich will just leave you with a blubbering, slow cutting, fuel hog. My 066 I kept tuned to around 13.8k and it was ported with an extra opening in the muffler.

 

[Agoraphobia]

Awesome, thanks a million!

 

[Agoraphobia]

I've seen cylinder head data for lower rpms from like 6000-8500rpms where the higher rpms lowered the temp by approximately 200 degrees. Does anyone have temperature data for higher rpms while milling?

 

[BobL]

I've seen cylinder head data for lower rpms from like 6000-8500rpms where the higher rpms lowered the temp by approximately 200 degrees. Does anyone have temperature data for higher rpms while milling?

Most cylinder head temp data is not reliable because the temp reading is so sensitive to temp sensor placement. However, I have observed the temp increasing with lower RPMS because the saw was being loaded and of course the fan is not able to turn as fast to provide the extra cooling. However if the saw is not being loaded (ie lower RPM is cause by less fuel) then the temperature is not as high as at higher RPM

 

[Agoraphobia]

BobL, What have you noticed comparing mid range milling rpm temps to upper end milling rpm temps in the wood? I understand that one persons data would not be applicable to another straight across, but comparing your set-up to your set-up should tell us a lot.

 

[BobL]

BobL, What have you noticed comparing mid range milling rpm temps to upper end milling rpm temps in the wood? I understand that one persons data would not be applicable to another straight across, but comparing your set-up to your set-up should tell us a lot.

Exactly what I said above. " I have observed the temp increasing with lower RPMS because the saw was being loaded and of course the fan is not able to turn as fast to provide the extra cooling. However, if the saw is not being loaded (ie if lower RPM is caused by less fuel) then the temperature is not as high as at higher RPM"

 

[Agoraphobia]

I seriously don't want to sound like a jerk, but your refernce to high rpms was in refernce to "if the saw is not being loaded," that's the only reason I asked about milling temps under load comparing high and low rpms milling. Just looking for clarity to understand things better.

Thanks again for this and the whole corpus of everything else on here you've done.