Any way to put a tunable carb on a 661?

So there is a non mtronic 661 over there?

 

Unfortunately not so, IME. Adjusting "H" lean can boost unloaded rpm, but decrease rpm under load. Just the way AFR varies with flow-rate with typical diaphragm carb- no air-correction. With high airflow-rate unloaded @WOT AFR may be suited to extreme rpm, but with lower airflow-rate under load AFR may be leaner than optimum, thus lower rpm than if adjustment were optimum for peak power. And of course, not good for piston longevity. ("AFR"-air/fuel ratio)
If anything, what matters is maximizing rpm under load. Exactly what AutoTune does. I've found that "experts" attempting to adjust carbs on a couple of my saws ended up setting them stinky pig-rich under load, causing me (and others) to totally discount "tach setting" of mixture unloaded @WOT.
OTOH, if someone adjusted properly for peak power and then noted rpm unloaded @WOT, that's a totally different story.

 

You NEED the Mtronic carb solenoid and coil connected to the main coil for the saw to run. So if something with your mtron system fails it most likely will not run with an adjustable carb.

I had a Wj69 on my 661 for abit. It did gain in the wood but as stated earlier the Mtron works just fine even with heavy mods.

 

Yeah a lot of the countries without emissions as strict as ours here have them.

 

Moparmyway

 

Yes you have mtronic and no mtronic in europe market , but the most customers prefer the mtronic , then they change and want the no mtronic
you see how good is the stihl to the brainwash ???

 

I sent him coil from the no mtronic , now i am looking to sent him and a carb from 661 no mtronic , just for see the results

 

Thanks for the info, I am glad that people on this site are so knowledgeable about saws. I know some stuff but are lost on a lot of it! It really helps out and put things into perspective when someone else knows what they are talking about.

 

Thanks mastermech. I just wanted the ability if need be to apply any mods that I may want to in the future if need be a tunable carb, ported muffler etc. And I wasn't sure if the mtronics would allow me to do that or not.

 

The earlier coils run leaner and a little higher unloaded rpm as well. Certain applications like milling may want the fully adjustable to run extra fuel to cool it.

 

That was some of the stuff that I had concern for because I would like eventually get a milling setup for it to mill some lumber

 

One guy said he preferred a 395 for milling that has a 661 or 2. Shawn curry has one he used some for milling.

 

So mdavelee your saying that the newer coils may run a little richer?

 

I agree 100% I swapped a Wj69 after I ported mine for the sole purpose of seeing if I could gain. Which it did but it wasnt a large enough difference over the mtron to leave it. If I were racing the saw heck yeah but then again it would probably be a larger carb.

 

The 4700 coil is a replacable warrenty item has a leaner fuel curve than the current 4701.

 

Thanks for the unfo!