272xp Rebuild and Port

[Magic_Man]

Did you degree the ports before you tore it down? I find it helpful in analyzing what I want to change. If you intend to delete the gasket then raise everything back to where it was having the pre-tear down numbers help with that plan too.

I did degree it before, I'm going to degree it again when I get the new bearings in it and the new piston installed. Those two things alone could cause some changes.

 

[XP_Slinger]

I did degree it before, I'm going to degree it again when I get the new bearings in it and the new piston installed. Those two things alone could cause some changes.

Yes they could. Good stuff, I'm still learning also. Looking forward to how this one turns out

 

[jmssaws]

Once you start using a degree wheel all these numbers start to make sense.
More addicting than any drug

 

[Magic_Man]

Once you start using a degree wheel all these numbers start to make sense.
More addicting than any drug

Ive only used one a couple times, now I wanna time the ports on every saw just to see what they are. Lol

 

[jmssaws]

Ive only used one a couple times, now I wanna time the ports on every saw just to see what they are. Lol

I love to degree cylinders.
This is why I love a 066 so much,no two cylinders the same so it's exciting to check them.

 

[PA Dan]

Once you start using a degree wheel all these numbers start to make sense.
More addicting than any drug

That's what I'm excited about and afraid about!

 

[Magic_Man]

Managed to find a little time after dinner tonight to pull the old bearings and drop the new ones in place.

 

[calebng15]

Split my case, and got the bearings off. I don't have the bearings yet, so I'll put them back on later.

Couple pics of my splitter. I should have used stronger metal, I probably wouldn't have had to ad bracing.



Not pretty, I know! But it works! Here it is on the case.



Gets the job done!

 

[merc_man]

Long as it got the job done. Looks good to me.

 

[calebng15]

Looks like it might need them?


I'll use this puller for the bearings. I need to get me one. This is my dad's. It's a little big, but it has to be this long, so...


Takes 'em right off!


Probably time for a new bearing!


Have a little clean up on the cylinder, but really isn't that bad. I would have thought it would have been worse. But then again what do I know! I don't know why, but splitting a crankcase is my favorite part of a rebuild like this. Maybe because the case is pretty well clean, and I can just take my time?

 

[Magic_Man]

Looks like it might need them?
View attachment 18778

I'll use this puller for the bearings. I need to get me one. This is my dad's. It's a little big, but it has to be this long, so...
View attachment 18779

Takes 'em right off!
View attachment 18780

Probably time for a new bearing!
View attachment 18781

Have a little clean up on the cylinder, but really isn't that bad. I would have thought it would have been worse. But then again what do I know! I don't know why, but splitting a crankcase is my favorite part of a rebuild like this. Maybe because the case is pretty well clean, and I can just take my time?

Yikes, your bearings were in real bad shape. Mine were still complete but rough.

 

[Keith Gandy]

Looks like it might need them?
View attachment 18778

I'll use this puller for the bearings. I need to get me one. This is my dad's. It's a little big, but it has to be this long, so...
View attachment 18779

Takes 'em right off!
View attachment 18780

Probably time for a new bearing!
View attachment 18781

Have a little clean up on the cylinder, but really isn't that bad. I would have thought it would have been worse. But then again what do I know! I don't know why, but splitting a crankcase is my favorite part of a rebuild like this. Maybe because the case is pretty well clean, and I can just take my time?

Dang!! Wheres the rest of them?

 

[Magic_Man]

Hoping to put my cases back together tonight. What's the opinion on the case gasket as far as sealer or no sealer ?

 

[Motorhead]

Just my .02 cents,If the gasket is of a good quality,Ample thickness,I clean up the mating surfaces,use the good gasket no sealer,If the gasket looks a bit cheap,Thin,I use sealer.Its much easier to put them together with a good quality gasket and no sealer.

 

[Magic_Man]

Got this new toy, er I mean tool today. Ended up with about $20 in it all. Way more accurate than my old paper print out/magnet wheel.


Couple seconds with a unibit to open the wheel to 1/2" and bam.


No saws will be safe from my port timing curiosity.......

 

[Magic_Man]

Enough tearing stuff up, time to start putting it all back together.

 

[Magic_Man]

Well that was easy enough, made a rookie mistake and didn't have the rod in the right spot when I dropped the crank in the case. Luckily I had it warm enough to tap the crank and bearings back out and drop it in again.

 

[Magic_Man]

I put the top end back on to check squish and timing numbers. Squish was a little tight and inconsistent because of some carbon build up in the chamber. So I used the old piston with some self adhesive 3M sand paper to clean the carbon out and take a few more thousands to put squish at .020 without a gasket.

 

[Magic_Man]

Alright, now is where I need input from you good fellas that replied to my other thread about building this saw. Everybody wanted to see what timing numbers where as stock and here is what I came up with.
Ex: 106
Trans: 128
In: 73

Port widths:
Intake 33mm = 63.46%
Exhaust 30.5mm = 58.65%
Piston Skirt width = 41.25mm

So whatcha think about those @Mastermind @jmssaws @David Young @rattler ? Or anybody else who has some input on timing numbers for a 272xp.
This saw will be run by my old man wearing a 24" bar and Stihl RS chain. If we bleed off a little compression to help with starting that's ok as long as we don't loose too much torque.

 

[jmssaws]

100 120 78 is what I'm using in the one I'm doing