Porting a ms260

[t4driller]

This is the first time for me porting a 260. It has a 44.7mm cylinder that I cleaned up. I talked with drf225 a little to see which way to go with it. THANK YOU..

Without base gasket I came up with .010 for squish. Timing numbers are..
Exhaust. 99.5
Intake. 70
Trans. 121
I widened the exhaust , opened up the intake and squared the port up. but didn't widen the intake much because of where the ring locating pins are. The lower transfers I nipped the heels and smoothed everything out. Still have to get squish set to .018 and advance the timing. But so far so good. Advice and criticism welcomed. Thanks

 

[huskihl]

If you're sanding the squish, in the 026 there's a rim where the wall meets the band. Not sure if the 260 is the same. I got up in there with Diamond bur and cleaned that up. But I also took some off the base. I'd pay attention to the squish measurement at the perimeter to make sure it's not too tight. Grinding looks good. Might get up into the transfers with a cut off wheel and raise them the thickness of the gasket

 

[t4driller]

I am sanding by hand. It doesn't seem like there is a rim there. I was looking at it and trying to feel it with a fine point flat screwdriver and cannot feel it. Hopefully by the end of tomorrow there will be a metal lathe sitting in my garage.

 

[drf256]

There's a rim there like Kevin said. The rim is the tiny Squishband that there saws come with from the factory. Use the old piston with some stick backed sandpaper to remove some for squish setting.

You can widen the intake. Leave .100 on the sides for the skirt to seal. I find squaring it up works the best.

Be careful on the intake roof near the top ring gap. Leave that area a bit rounder. You don't need the bottom ring. The saw will pick up rpm without it.

Did you nip the exhaust floor? Looks like you didn't on the inside pick but you did on the outside port pic.

I'd try to clean up the transfer some more. Sometimes you see a lot more when you actually post a pic than what it looks like on your bench.

 

[drf256]

Here's a pic of a squared 026 intake

Here's a flat cut chamber

Sent from my iPad using Tapatalk

 

[t4driller]

The rim, I thought he meant up the sides of the cylinder wall. I see the rim your talking about. I won't conservative at first, so I don't mess it up. I had lines drawn with a sharp pencil of 1 mm inside the piston skirts to know where to stop the edge of the ports at.
I didn't nip the exhaust floor.
Looking at your pics, it looks I can go much further. That cylinder looks nice.

 

[huskihl]

The being conservative part- the hardest part for me is grinding from the outside while looking at the inside. I usually look at the side where I'm grinding. I've been lucky I haven't ground past a line by not looking at it.

Make it look like Al's ports. He's really good at squaring corners while maintaining symmetry

 

[t4driller]

His work looks top notch. Like to be able to go take some lessons.

 

[Redfin]

Ive takin my ports to within .05 of the skirt Mike. If you want to raise your transfers I have a ra head. You could bring that jug over some time.

 

[t4driller]

Ive takin my ports to within .05 of the skirt Mike. If you want to raise your transfers I have a ra head. You could bring that jug over some time.

I would definitely like to come up sometime just to talk and go over some stuff. Thank you for the offer. I'll give you a text sometime soon and figure out when we could meet up.

I was just out looking at it and drew some new lines closer to the skirt edge. On both the exhaust and intake. Tonight I will square the intake up like the pic posted and work over all the ports again.

 

[Chainsaw Jim]

Another way to get that rim out of the way to get your squish right is to scrape it out with a chisel by hand. The nice part about it is you only need to take it down flush with the surface next to it so it gives you the control to not go too far and as long as you only take it down flush with the rest, it will also be even. That should leave your squish right about .020 when you're done. Sometimes the nickel plating covers that band and the chisel won't work.

 

[t4driller]

Got the intake squared off. Got to touch it up a little and put a chamfer on it. But I'm really liking these new burrs I bought. [emoji4]

 

[t4driller]

Exhaust ruffled in. Lowered a hair and widened.

 

[huskihl]

Once i get it roughed in like that, I use the appropriate sized nail (maybe 10d) with a slit in the end for a dremel mandrel with some 80 grit Emory paper and wd40 to do the polishing. Have to change it a few times, but leaves a pretty smooth surface for the exhaust

 

[t4driller]

Once i get it roughed in like that, I use the appropriate sized nail (maybe 10d) with a slit in the end for a dremel mandrel with some 80 grit Emory paper and wd40 to do the polishing. Have to change it a few times, but leaves a pretty smooth surface for the exhaust

That's what I've been using is nails cut off. Got the squish sanded down and set at .020

 

[huskihl]

I tried thinking of a way to do that for awhile. Didn't figure there was enough width across a nail to put a slit in it and still fit Emory through it. Adirondackstihl showed me that trick. It works really well

 

[drf256]

Intake looks huge.

Numbers?

Did you raise the roof or floor?

Nice grinding btw.

 

[t4driller]

Thank you means alot coming from you. I tried to make it look like yours.

Intake stayed the same for numbers. It does look big, the flat side of intake makes it look off center a little but it's not. I put the cylinder on and checked to make sure the skirts would cover the port, and it does by a little less then 1 mm on each side. Exhaust is right at 1 mm skirt coverage. I took my time getting that close to the skirt edges. Take a little off check it, take a little check it.
I'll have to setup the degree wheel again. Took it off to get flywheel off to advance timing. I shaved .018 off the key and put it back on and tightened up good. Should I raise the upper transfers at all or leave them alone? That's about all I would have to do before reassembly.

need to Polish up the exhaust a little bit yet.

 

[t4driller]

I tried thinking of a way to do that for awhile. Didn't figure there was enough width across a nail to put a slit in it and still fit Emory through it. Adirondackstihl showed me that trick. It works really well

I've been taking a hot glue gun and putting a little on a nail and then wrapping different grit emery cloth around it. I made probably 25 of them all together. I couldn't get a slit cut in a nail to just slide it threw.

 

[t4driller]

Looking threw the exhaust port, the roof of the intake has a descent arch to it. Looking at it from the bottom of jug it looks flat.