660 clone port timing numbers for milling (torque)

[huramentzefix]

yes the BB piston is strangely short and I will have to see if I can lift it far enough to stop freeporting.
but even then it is questionable if there will be sufficient sealing?
We will see, it's only a few dollars.

The timing of almost all aftermarket cylinders seems to be garbage. BB even worse... The intake is simply far to low and the pistons to short.

you listed two different 395xp pistons with different dimensions?
I was looking for alternative pistons but thought the husky had a larger pin?
Machining the piston and the squish might be an option if the rings don't run over the plating on top of the cylinder.
Would be interesting to know what your exhaust numbers will be?

Looks like you got duration. But at what degree is your exhaust opening? Transfers clearing the top of the piston? and Bottom of the piston skirt closing the intake port at?

Divide the numbers.
"100+ E 122-124 T 78-79 I" translates to 200°+E 244°T 158°I. same thing.
Transfers I have not taken yet because I need to drop the cylinder and just have filled the intake with pegatanke.
I have never done it that way before but will see.
No it is free-porting. I need to lift it a little bit.

But I will rather lift it, close the free-porting gap and live with lower numbers.

piston dropped in all the way in from skirt to base: 39.62mm
exhaust window closed 38,70mm ~ 38,74mm
that would translate to 0.88mm (0.0346) squish.
(but I have taken ~ 0.3mm off of the base to get the exhaust numbers up)
I will sacrifice some of my beer cans and lift the cylinder to close my free-porting and just run with less exhaust and less squish.
She pulled good with the original holzfforma cylinder and E164° (82°) I158° (79°).

taking 0.3mm off of the base brought the total exhaust up by 3°, I am at 192° right now.
so with a 0.88mm beer can lift I might be at 183° ~ 185° with the exhaust, no idea what my current squish is at the moment, but judging by the piston gap in the exhaust, close to nothing.

 

[thompsoncustom]

But I will rather lift it, close the free-porting gap and live with lower numbers.

why would you do that exactly? I want to know your reasoning behind it as everyone on here will tell you that its guaranteed to make the saw run worse not better.

Randy from Mastermind work saws said the strongest 660 he ever ran free ported .030

it's your saw so build it whichever way you like but I think you should look around this forum and others a little and see what you come up with.

 

[rola]

Sorry the longer piston is a 394. The pin is 13mm, pretty sure the husqvarna bearing is the same OD as the stihl.
I have welded to the skirt of some pistons to make longer but haven't had enough run time to know if it will break.
I also check the height from the bottom of the transfers to the bottom of the exhaust, they should be level but vary considerably.
I am surprised at how far out the factory 660 port timing is, yet it still performs very well. I understand the 064 saw a lot better but have yet to check and compare.

 

[huramentzefix]

raised by 2 cardboard gaskets to close the free-porting.
squish 1.18mm (0.0465)
total E187° (93.5° bBDC / 86.5 aTDC)
total I203° (78.5° aBDC / 101.5 bTDC)
after closing intake and grinding:
total I185° (92.5° aBDC / 87.5 bTDC
total T114° (57° bBDC / 123 aTDC)
Transfers open 21.5° after exhaust

I think I was getting confused by the numbers here? I was used to always doing it in total duration in the past.
the numbers 100+ E 122-124 T 78-79 I is after TDC and not 1/2 of the duration when opened...
100+ E 122-124 T 78-79 I would translate to total duration: 160-E 116-112T 156-158I

looks like I need to deck it and use a piston with a longer skirt.

my timing figures in the previous posts are probably not accurate according to what is being used here...

 

[huramentzefix]

I have put my large chainsaw in the shed for a while, after being frustrated with the bad quality of aftermarket cylinders. (big bore and non-Farmertec cylinder)
I have now a new Farmertec Cylinder, that I am happy with, with an DUKE'S Performance Coated POP UP Piston.

Now I am looking for your guys help again in getting the timing right. I was getting pretty confused last time because of my digital level that I am using, which counts down from 90° when I go over 90°. So I had to deduct the reading from 90° to get the actual reading, if that makes sense now?

My compression is without gasket at 125 (not broken in yet). There is no room to lower the cylinder without cutting squish.
My idea is to get the timing as per you guys suggested specs and then break it in and check compression again before cutting squish.
The compression that I am aiming for is around 190?

I was setting the piston to port opening and then zeroed the digital level and went till it closed again.
So I was calculating total time.
From what I understand you guys talk in 50% exhaust time, 50% intake but full transfer timing?

Exhaust I was getting 186° total which is 93° correct? I have to raise the exhaust to 100° opening before BDC?
The Transfer I am getting 118-120 total time, those should be raised to 122-124°?
The Intake I was reading at 160° total or 80°. If I remove the gasket I should come down with this number?

Thanks to all of you for your patience and insight.

 

[Ted Jenkins]

I'm ready start selling those in AM or OE just built for milling.
My 660 will pull a 60 but prefers the 36, 40 or something lesser. Anyway you can't get to where they need to be without heavy machine work. I figure 150 a jug should be about right for AM ones ready to mill. Doing a new stock one will be 110 machining and port work only. They need much less work as you can clearly see. Go here. 100+ E 122-124 T 78-9 I
The rest you can figure out. Just remember every crumb you take out increases case volume you can't get back without extra work. Your intake will need extensive work on any jug AM, OE, ect. If your not all in it isn't worth the trouble to bother imho. You will never find a solution without compression and timing being correct. Polishing is for turds. Your on your own with squish but I run 0.018 So... the peanut gallery will be along shortly to discredit that.
Enjoy

I smoked my cylinder on my 660 clone while milling by having the high adjustment too lean.
Now I am holding a new 36$ knock off cylinder in my hand and have just ordered a degree wheel to check timing.
By just measunring with the calipers I can tell that this cylinder is way off compared to the other one.

The upper edge of the exhaust is 3.2 mm lower than the stock holzfforma!
It's about the same for the lower edge. The entire exhaust port has moved down by 3.2 mm.
The transfers are 1.64 mm lower
The Intake is 2.6 mm lower
piston from top ring to Crown -0.5mm
from piston pin to crown -0.5mm
Blowdown is 3.8 mm instead of 2.05 mm (so there might be room to correct all this mess hopefully)

What squish and port numbers should I look for for a milling saw? I am looking for torque and don't want to breed a race-horse.
What I am after is a wide band, not a narrow high-power spike. I was happy with the power as it was (even without muffler mod) before I cooked it.
I will check timings once I receive my degree wheel.

What are good timings for a milling 660 and what squish? and how to achieve torque gain, polishing, widening?

The 660 saws are fantastic saws but not a great choice for milling. The 070 or 070 with the 090 cylinder is a much better choice. The 070 responds very well with a little modification such as muffler work. the 070 is a slow reving bigger bore saw that is quite sturdy. Much easier to manage heat dissipation and such. The 070 and 660 are very similar in power but the 070 and 090 are heavier which should not be a concern for milling. What most people do is fall into a trap of making mods looking for easy power when working with the 660 but then have problems not knowing what the heck they did. I built race motors for many years for a living actually starting sixty years ago. A perfect tune takes into consideration of the designed flow of the muffler or make modifications. The port timing and port volume flow are all equally matched so that each port can be efficient at the designated RPM. Finally the compression ratio along with the skirt specifications are all properly matched. Last heat management can then be well addressed. Even the sprocket and the way the chain is set up will effect performance. Some would want the chain fast others would want it to slow down. Thanks

 

[Bjorn T]

The best sulution for you is to bye a wiseco piston, longer skirt and then you will get much better timing numbers to start with.

 

[huramentzefix]

I have put my large chainsaw in the shed for a while, after being frustrated with the bad quality of aftermarket cylinders. (big bore and non-Farmertec cylinder)
I have now a new Farmertec Cylinder, that I am happy with, with an DUKE'S Performance Coated POP UP Piston.

Now I am looking for your guys help again in getting the timing right. I was getting pretty confused last time because of my digital level that I am using, which counts down from 90° when I go over 90°. So I had to deduct the reading from 90° to get the actual reading, if that makes sense now?

My compression is without gasket at 125 (not broken in yet). There is no room to lower the cylinder without cutting squish.
My idea is to get the timing as per you guys suggested specs and then break it in and check compression again before cutting squish.
The compression that I am aiming for is around 190?

I was setting the piston to port opening and then zeroed the digital level and went till it closed again.
So I was calculating total time.
From what I understand you guys talk in 50% exhaust time, 50% intake but full transfer timing?

Exhaust I was getting 186° total which is 93° correct? I have to raise the exhaust to 100° opening before BDC?
The Transfer I am getting 118-120 total time, those should be raised to 122-124°?
The Intake I was reading at 160° total or 80°. If I remove the gasket I should come down with this number?

Thanks to all of you for your patience and insight.

This is what I have and I have to work with.
Please stay with this and don't go off-topic.
Thanks.

 

[huramentzefix]

Here a more specific question:
100° exhaust. ist that BBDC or ATDC? Are you talking about an exhaust duration of 160° open or 200° open?
My exhaust duration ist currently 173° open. would be 160° more favourable?
Why is mine so high stock?

 

[huramentzefix]

just watching Tinman's. Numbers here are ATDC???
And it should be 100° to 98° max (exhaust closed, why closed numbers?). So my 173° open is higher than favourable 160° (open) = (100°x2 closed???)

 

[thompsoncustom]

Your using a digital level? Post a link or picture or what your using to get your timing numbers.

Also you can't port the saw and then have the cylinder base and band cut as that will affect all of your port timing numbers because everything is physically lower now except the timing between the exhaust opening and the transfers open.

Yes 190 compression is the sweet spot but a little more say 210 is fine after that your gonna just be adding heat with this saw. I already posted the ideal timing numbers on page 1 so refer to post #7

 

[Lightning Performance]

The 660 saws are fantastic saws but not a great choice for milling. The 070 or 070 with the 090 cylinder is a much better choice. The 070 responds very well with a little modification such as muffler work. the 070 is a slow reving bigger bore saw that is quite sturdy. Much easier to manage heat dissipation and such. The 070 and 660 are very similar in power but the 070 and 090 are heavier which should not be a concern for milling. What most people do is fall into a trap of making mods looking for easy power when working with the 660 but then have problems not knowing what the heck they did. I built race motors for many years for a living actually starting sixty years ago. A perfect tune takes into consideration of the designed flow of the muffler or make modifications. The port timing and port volume flow are all equally matched so that each port can be efficient at the designated RPM. Finally the compression ratio along with the skirt specifications are all properly matched. Last heat management can then be well addressed. Even the sprocket and the way the chain is set up will effect performance. Some would want the chain fast others would want it to slow down. Thanks

So where does volumetric efficiency occur in a 660 cylinder?

That should be an easy question answer with all your building experience.

 

[Lightning Performance]

"But I will rather lift it, close the free-porting gap and live with lower numbers."

But you just settled for less and that will never be a winning combination.

 

[Lightning Performance]

The 660 saws are fantastic saws but not a great choice for milling. The 070 or 070 with the 090 cylinder is a much better choice. The 070 responds very well with a little modification such as muffler work. the 070 is a slow reving bigger bore saw that is quite sturdy. Much easier to manage heat dissipation and such. The 070 and 660 are very similar in power but the 070 and 090 are heavier which should not be a concern for milling. What most people do is fall into a trap of making mods looking for easy power when working with the 660 but then have problems not knowing what the heck they did. I built race motors for many years for a living actually starting sixty years ago. A perfect tune takes into consideration of the designed flow of the muffler or make modifications. The port timing and port volume flow are all equally matched so that each port can be efficient at the designated RPM. Finally the compression ratio along with the skirt specifications are all properly matched. Last heat management can then be well addressed. Even the sprocket and the way the chain is set up will effect performance. Some would want the chain fast others would want it to slow down. Thanks

The 070 only hangs with a 660 because of crank weight nothing more. Bigger clutch and crank gives more inertia to pull more chain. They have the same stroke.

Please explain how the 070 cylinder is a better offering to make torque?

 

[Lightning Performance]

It seems that you don't like peanuts?

Good Idea to sell those jugs for milling on amazon.

Well thank you so far I will have to wait for my degree wheel to see where I am at, and then see how much I would have to take off to get to your numbers.
What extensive machine work are you referring to?
I will possibly put it into the lathe to get my squish to where I want it to be.
What else is there to do?

And remember, I want a saw with a wide band for milling. No crazy screaming competition disc cutting machine that has a pointy narrow band. And I don't need to screw around to get the last % of power either. This saw has plenty for what I am doing already.

I think 100+ E 122-124 T 78-9 I is pretty much 661 stock?

It's said that the Meteor are the best, is that true? Does anyone here have the timing numbers of a meteor here?

I just stuck the cylinder on as is so that I have a running saw till I get the degree wheel. It runs and revs OK, just haven't tested it yet to see how it pulls.

Your funny comparing a 660 to 661 on timing numbers. They stroke changed so your thinking is flawed substantially.

 

[Lightning Performance]

I concur with these timing numbers in a milling saw, although I do prefer a bit wider squish.

Why?

This will an intelligent answer imho.

 

[Lightning Performance]

OK thank you guys so far.

it seems that most of the pros don't like the 56 mm bore kits because they supposedly don't make good power.
I have read that many of them have freeporting issues.
The 56 mm cylinder kit I can get for 23$, the 54 mm is 25$ I still ordered the smaller one.

What is wrong with those big bore kits for the 660's?

The transfer ports are shaped poorly for good flow and are too small in the 56mm big bore 660 cylinders. You can't fix the missing short side or increase the area enough to run well in milling operation.

 

[Lightning Performance]

Hello all,my first message on here, have tried these BB kits and are currently working on a few idea's.
I suggest looking at using a MS661 or husq 395 piston and clearancing the case etc to make it work.Problem with the BB is they shortened the piston 2mm so it didn't hit the case, this caused all sorts of issues with port timing.
Have just made a hybrid ms361 clone with 440 crank and 460 cylinder and carb, 272 piston and ms360 flywheel. Still needs some fine tuning. But very pleased with the result.

Pics?

 

[Bjorn T]

This is what I have and I have to work with.
Please stay with this and don't go off-topic.
Thanks.

This is very far from going off-tonic. That piston Will give very good porting numbers to start with. And no free porting.

But use what you like. you can Always use jb Welld
But not in the exhaust, it will break. Longer skirt will solve the problem with free port and reduce the high intake Numbers.

 

[Ted Jenkins]

The 070 only hangs with a 660 because of crank weight nothing more. Bigger clutch and crank gives more inertia to pull more chain. They have the same stroke.

Please explain how the 070 cylinder is a better offering to make torque?

I do not believe the stroke on either motor is relevant. However which engine revs higher. I believe more than once there is no substitute for displacement. an 090 will produce a substantial amount of torque period. It is not up to me what saw you use or build. My experience by far found the the slower revving engine produced a longer lasting chain and just plain lived longer. I love my 660 for limbing and all around use but only minor use for milling. Thanks