Step by step porting

[little possum]

I know Wiggs, now off to get me some chicken.

Mr Ultra, Id like to give that one a spin Is that the one with the pipe? A 2 piece head could easy be handled, after I get a grip on porting. haha

Thanks for the pics!

 

[04ultra]

I know Wiggs, now off to get me some chicken.

Mr Ultra, Id like to give that one a spin Is that the one with the pipe? A 2 piece head could easy be handled, after I get a grip on porting. haha

Thanks for the pics!

It runs on pipe ........Really nice............



.

 

[AUSSIE1]

Someone can stomp on me if I'm doing it all wrong, but I've been assembling the cylinder on the saw with the piston, tracing my port shape on the piston, and then calculating how much I can widen each side of the port.....Then I stick a strip of masking tape on the inside of the cylinder bore beside the port, the distance that I can widen the port and use that as my guide......That seems simple and less calculating for me.....But I'm errr "simple".

This is the first one I did, and I learned a lot (I've only ported three saws so far)........I'm a hands on learner too, so just jump in and give it a shot. You can see a bit of my original tracing on the piston in the pic......This saw rips, so I didn't do too bad!

Great job JD. You can go a little squarer in the sides/corners for more port area if you like.

 

[little possum]

Awesome Steve, just simply awesome.

 

[04ultra]

Awesome Steve, just simply awesome.

Looks like I wont be running it any time soon ................It sure is a fun play saw...






.

 

[smilin possum]

if he gets it right youll be after him to do your saws

Yes if he does a real good job and don't mess his up I'll make him do mine too. There's about 70 of um and that should keep him out of my hair for awhile. He don't listen to me no how he's supposed to be bushhogging but no he's out there playing with his saws. Kids ya gotta love um.
Joe

 

[Arrowhead]

Just an FYI... you don't want to go any wider than 65% the bore on your port openings. Some say 60% on a work saw. Keep the pics coming.

 

[Tzed250]

Looks like I wont be running it any time soon ................It sure is a fun play saw...

.

Hi Steve!!!

 

[little possum]

Just an FYI... you don't want to go any wider than 65% the bore on your port openings. Some say 60% on a work saw. Keep the pics coming.

So if the bore is 51mm dont want to go but 30.6?(60%)

 

[pops21]

Good luck zach. My 288 only has 5 min of run time after my rebuild/port job. The intake can't be widened too much. I was afraid of grinding into the bolt holes. I used a soda can for my base gasket. Compression is a 185. It sucks not having a decomp. The good thing is the saw is heavy enough to drop start.

 

[srcarr52]

Zach, if you are going to widen your ports, you might as well do your transfers. Open up the lowers as per heaps of photo's of saws with this type of port system. The uppers can be opened toward the back and is one of the easiest mods to do with a stone/cutter in a dremel.

In case you want to compare to other numbers posted around the site this was measured with a custom dial caliper and then I used equations from Bells book to get it to durations. I think it's more accurate then a degree wheel. Plus I can check my progress as I'm porting.

Stock port timing 288xp
Exhaust: 151
Transfer intake side: 115
Transfer exhaust side: 111
Intake: 137

Don't get too high on the exhaust port or you'll loose that 281/288 grunt but returning it to stock after dropping the cylinder is good practice.

I think this the mod AUSSIE1 is referring to for the transfer lowers. This is from a 272xp I did... same design almost identical timing numbers.

 

[little possum]

Thanks.

Guess I need to find the degree wheel I favorited to somewhere
And start learning that too.

 

[Arrowhead]

So if the bore is 51mm dont want to go but 30.6?(60%)

Correct, that's at 60%. I go 65% on mine, I never had any problems. Just make sure you bevel the edges of the ports. Not beveling or going too wide increases the chances of the ring catching on the port... then it's grenade time. Some race saws go 70% or larger. In fact my 98cc Pioneers are 69-70% on the exhaust from the factory. It's up to you if you go 60% or 65%. Maybe someone else will chime in with their advice.

 

[pioneerguy600]

You need a bevel but nowhere as big a one as some OEM ones and definitely not like the aftermarket ones I have used . The exhaust only needs a bevel approx .005-.0010 wide and the intake can be done with sandpaper/ emory paper on the ends of your fingers as the rings don`t cross the intake port.
Pioneerguy600

 

[AUSSIE1]

Zach, if you feel using a degree wheel etc is too daunting for the moment, just do your widening and transfers. You can always go back in.

 

[little possum]

Zach, if you feel using a degree wheel etc is too daunting for the moment, just do your widening and transfers. You can always go back in.

May go that route, and do a few timed comparisons over the extent of the porting. From stock to finished

 

[mdavlee]

I've been taking all the ones I did to 65-70% and haven't had any problems with them. Some have been freehand milling 6 ft or so in oak without stopping so I would imagine if they would have a problem that would bring it out.

 

[Jacob J.]

Correct, that's at 60%. I go 65% on mine, I never had any problems. Just make sure you bevel the edges of the ports. Not beveling or going too wide increases the chances of the ring catching on the port... then it's grenade time. Some race saws go 70% or larger. In fact my 98cc Pioneers are 69-70% on the exhaust from the factory. It's up to you if you go 60% or 65%. Maybe someone else will chime in with their advice.

That's why the Pioneers are such good runners stock. The engineers went whole hog on the port designs and Gilardoni did a great job manufacturing the cylinders.

You need a bevel but nowhere as big a one as some OEM ones and definitely not like the aftermarket ones I have used . The exhaust only needs a bevel approx .005-.0010 wide and the intake can be done with sandpaper/ emory paper on the ends of your fingers as the rings don`t cross the intake port.
Pioneerguy600

I usually just sand my ports (intake and transfers) and put a tiny bevel on the exhaust (same dimensions Jerry points out.) I like to keep the port timing as crisp as possible. A large chamfer makes things all sloppy and you can hear it when the saw is running.

 

[rms61moparman]

I go 70% on the curve if the skirt will allow.


Mike

 

[nmurph]

the first 346 i did is pretty close to 70% without problems. thanks JJ for the tip on bevels. i will have to pull mine sometime and let everyone have a look. i may have put too much bevel on them in the interest of ring safety.