Teach me how to port a chainsaw

[happysaws]

[QUOTE="drf255, post: 6100962, member: 126014"
100/122/75 is pretty safe for all. Maybe 124 on the transfers for a long bar.
[/QUOTE]

Sorry for my ignorance, but what do these numbers represent?
Thanks

 

[troutfisher]

I'll throw out a number, I'm not scared of getting some **** Dont raise the exhaust over 170* total duration, as a general rule they'll lose bottom end and turn gutless. OK, commence the beating.

 

[Westboastfaller]

Most of them will be logging saws felling timber,a saw that has tourque is preferred so when partway through a cut and sighting up direction of fall ,needs to be able to roll the power on easy when the chain stuck with softwood chips. 440 460 and 660 saws most likely,the guys around here like the older saws still,the 461 and 661 are starting to come around for a few guys.

One word for you; Balance!

I see why some builders go for maximum torque because it takes the ignorance out of the equation doesn't it.

A production falling saw is a multi activity saw and is a colaberation that conjoins theory and methods. It's going to take two educated parties. More relevant with these smaller 70 cc saws. It may be a well balanced build but would have much less room for error If the faller is greener than kermits cum and doesn't compromise methods with filing/sharpening as well techniques considering species/percentage of species. Dude would not reconize it to be satisfactory if he smashed his phucken grill out with the chain brake.

One little trick I use for Hemlock when I'm 'filing' for Cedar to reduce the saw from clutching out is a birdsmouth (pie) undercut. This way you take half the rise from the butt and half from the stump, splitting the grade. A saw that plugs because you slow down to consider aim is a saw filed out of balance for falling. Way too much self-feeding. Apart from some trouble in some Hemlock and Grand Fir /Balsam then you should always be able to use the falling dogs and file specifically for them first in mind

 

[Trx250r180]

[QUOTE="drf255, post: 6100962, member: 126014"
100/122/75 is pretty safe for all. Maybe 124 on the transfers for a long bar.

Sorry for my ignorance, but what do these numbers represent?
Thanks[/QUOTE]
From what i have took in so far ,first # is exh ,middle is transfer port ,and 3rd one is intake #s ,i still have a lot of learning before i do any mods ,port shape also has a role in flow of the air .

 

[happysaws]

From what i have took in so far ,first # is exh ,middle is transfer port ,and 3rd one is intake #s ,i still have a lot of learning before i do any mods ,port shape also has a role in flow of the air .

Okay that helps,
I would assume these numbers are degrees before top dead center, right??

 

[troutfisher]

here's a thread on timing numbers, might help some..........

http://www.arboristsite.com/community/threads/port-timing-questions.113678/#post-1799245

 

[happysaws]

here's a thread on timing numbers, might help some..........

http://www.arboristsite.com/community/threads/port-timing-questions.113678/#post-1799245

THANK YOU!!
It finally makes sense!

 

[drf255]

Shape is important, but be careful there. Make sure your exhaust roof still has an arch to it. I'm realively new to this game as well. Maybe have done 30-40 saws. @jmssaws has been porting for over 20 years. If he gives advice, heed it.

First number is exhaust opening. BTDC or ATDC are the same in a 2 stroke. Making sure these are the same is a way to make sure your wheel is properly positioned at TDC.

Second number upper transfers opening. Both exhaust and transfers read at piston crown.

Third is intake opening. This is the intake floor and measured at the bottom of the skirt.

 

[troutfisher]

"Make sure your exhaust roof has an arch to it"

YES!! if not that'll snag a ring every time.......

 

[troutfisher]

for that "arch"..... look at the thickness of a 4mm alan wrench, the port should be that much higher in the middle than it is at the sides. Gotta help tuck that ring into the groove on the way up.

 

[jmssaws]

I time all the ports from tdc.

There's a lot of ways to do it and it'd really easy to get a decent gain on a lot of saws but without machine work I'd be pretty selective about which saws I'd do.

A 460 is one that makes a good gain without machine work but to run a longer bar you will want a little compression, not a lot but some.

 

[pioneerguy600]

A little bevel on all new cut port edges also so the rings don`t snag a new sharp cut edge. My chamfer/bevel is really quite narrow, something like .010 is plenty, no need of these .025 - .030 ones I see on AM jugs.

 

[Chris-PA]

It's easier to measure port durations - the angle the port is open. Zero the wheel at the point the port starts to open and measure the angle when it closes. All port timing is symmetrical about TDC, so you never have to find TDC at all.

 

[Trx250r180]

Am i thinking wrong about a port map paper,seems like you could use the same map on several jugs and not have to degree wheel them all ?

 

[pioneerguy600]

Am i thinking wrong about a port map paper,seems like you could use the same map on several jugs and not have to degree wheel them all ?

Yes, you can.

 

[jmssaws]

Am i thinking wrong about a port map paper,seems like you could use the same map on several jugs and not have to degree wheel them all ?

I never see 2 the same.
It is a 30 second job to setup a degree wheel and find tdc.

 

[blsnelling]

IMHO, port timing is not where you start. There are successful builders out there that never put a degree wheel to the saw, not that I'm recommending that. There's FAR more things to porting than the numbers. I recommend you start by reading every post you can about porting. There is a FAQ thread in the stickies. In that thread are several links about porting. Study lots of pictures. Port shape is very important…to both performance and longevity. There are lots of does and don'ts. It's not really something than can just be taught in a thread.

 

[Trx250r180]

Yes i have a lot of homework to do before pick up a grinder still.i will check out the stickys ,forgot about those ,seems like a lot of older threads with good info lost some images last i looked though.

 

[93Dakman!]

I never use a degree wheel. I convert measurements from from top of cylinder (mind your squish) to degrees. You can and should use plasti gage on top of the piston any time you mill the cylinder or remove gaskets or base plates. Everyone has a different method.

Sent from my SM-G900V using Tapatalk

 

[93Dakman!]

Replied to wrong thread.