First time porting

[2broke2ride]

I posted this in the "hot saw" forum as well but figured I'd try here. I have never done any porting beyond just cleaning up what was already there and some lower transfer work. That said, I've finally collected what i need to give i a go. I picked up a Frankenstein Husqvarna, it has 272 cases with a open port 61 Rancher topend. I'm Looking for advice on which way to go for my first time. Should I just port the 48mm cylinder or buy a cheap 50 or 52mm topend to grind on for my first attempt in case i screw it up? My knee jerk reaction is to do a 50mm topend so it fits under the 61 top cover. I just am not excited about the open port cylinder.
I already have a degree wheel, piston stop, and a grinder setup plus I've studied on this for literally years so I feel like I'm as prepared as I can be. lol

 

[huskydave]

If the 61 top end is good I would run it. If the crank bearings/seals are suspect change them. Ditch the base gasket and use high temp gasket maker, be careful around the crankcase impulse hole, you don't want to block that, set squish to .020 thou. Measure in 3 places around the piston, (Solder through spark plug hole) set the exhaust ATDC First ray of light - 102 (156 duration) Transfers ATDC - 124 Blow down - 22 Intake opens ABDC - 110 or 70 ATDC, 140 degrees of Intake duration. Eyebrow the transfers towards the intake side in the cylinder. chamfer the ports on the inside of the cylinder slightly. I built some like that, 200+PSI compression and ran like snot with a ported muffler. I use a magnetic pocket digital angle indicator instead of a degree wheel. Stick it on the end of the crank and zero it at TDC. Set ring gap .008-.010 thou, you can clean up the casting marks on the bottom of the piston on the pin bosses if you want but don't take a lot of material off, just blend the flashing. Do a leakdown test after the work is done (pressure/vac). Build that and it will put a smile on your face.

 

[huskydave]

You can widen the ports a little but be careful, less is more sometimes. I like to taper the intake and exhaust into a bell mouth and match the gaskets. Be careful who you listen to, lots of disinformation around. You don't need a fancy grinder, basic die grinder or a dremmel will work with some flap wheels and carbide burrs of different shapes, ball on the end, ball-nose, tapered, straight etc... take your time and be careful not to hit the cylinder bore, the material comes off quick you don't need a lot of pressure, 2 hands on the grinder if you can. once you start grinding you will get it into the zone. Worst case scenario you mess that cylinder up but then you can bolt a big bore 52mm kit on that saw and play with that. I am here to help and there is a lot of good people on here, some of them do port work. Just think about flow, you want it to flow!

 

[NSEric]

I put a cheap after market 52mm 272 top end on a 61 and ported it. It's a very strong saw now, it out cuts a stock 365 special. You will never get that much power out of the 48mm open port top end.

I widened the intake and lowered it to 76, dont go past 78, you need lots of case compression in these saws.
The transfers were at 123 out of the box so I just aimed them towards the intake side a bit and widened the lowers a bit. Dont go full width/as big as possible on the lowers, it hurts case compression.
The exhaust is widened and raised to 102, these are short stroke saws dont go higher than 100.
I opened the windows up in the piston too.

 

[huskydave]

I will run a lot stronger with the BB kit, no doubt. No replacement for displacement. If you want to run 32 inch bars get the BB kit.

 

[2broke2ride]

Well guys, I ended up ordering an inexpensive 52mm topend as well as a full gasket set and new crank bearings and wrist pin bearing. I will try my hand at porting and if I screw up I still have the 48mm topend. Thanks for the advice. @huskydave, what are some good numbers to shoot for with the 52mm topend? I plan on going no base gasket but I have no other way to lower the cylinder.

 

[NSEric]

The one I built has .025 squish with the paper thin base gasket.
It was .016 with no gasket, I ran it for a bit like that but it was a bear to start.
9/10 of these saws do not need the cylinder lowered more than removing the gasket lowers it IMO.
That's why first time porters have at em lol.

 

[2broke2ride]

The one I built has .025 squish with the paper thin base gasket.
It was .016 with no gasket, I ran it for a bit like that but it was a bear to start.
9/10 of these saws do not need the cylinder lowered more than removing the gasket lowers it IMO.
That's why first time porters have at em lol.

Its interesting you say that, I just rebuilt a 162SE and it came in at .037 with no base gasket, OE cylinder and aftermarket piston. I've done about a half dozen saws and none of them have come in under .040

 

[huskydave]

EX 102 TR 122 IN 78 .Set squish around .020. Tune it around 14kRPM or a bit less with a tach. If you set the squish below .030 thou you should pull the topend and de-carbon it from time to time imho, having 200-220PSI compression is worth it though. 2x 3/4 inch ports in the muffler. That saw will run with or beat a stock 066 if you did a good job.

 

[huskydave]

They burn more fuel with the BB top end 15-20 minutes to a tank. I do this part time but someone like Donny Walker is a good person to listen to and ask questions. He ports a lot of saws and he builds them similar to what I do for a work saw that will last a good while. After 1000hrs re-ring it. I don't like going past 14200RPM on a worksaw. Good Luck, take your time and do it right. When your done take some time and sharpen your chains like a razor, this will help a lot. I like using OEM top-ends if I can help it to be honest, if the piston still has horizontal machining lines in it then it wasn't run much.