Well, I had my butt handed to me on a platter with this 48mm cylinder. I literally have thousands of hours experience porting outboard motors and automobile cylinder heads and all the equipment anyone could want, including dyno and 1200cfm flow bench. I can spend 100 hours porting one V6 Johnson or a set of cylinder heads, so I though a few hours on this one cylinder would be a piece of cake. That was until I found out getting tools in that little bitty transfer port in that dinky 48mm cylinder was not quite the same as getting them in 3.5" to 4" bore cylinders.
Since I have gotten out of the business because of medical problems, I'm not really into buying another $400 grinder to do one chainsaw so I did what I think will give me the most bang for my buck with what I had and would like some opinions and suggestions.
Since I couldn't do anything with the transfers, I didn't change any port heights. Research had indicated 103, 120, 80 were good numbers and that's what I was going to do.
I opened the intake port, not the so much the opening in the cylinder, but the runners going in. The port opening was already much wider than the intake runners so I managed to get them out to where I have a 1 degree tapered funnel going in. I did not take any off the roof at the cylinder and left most of the metal in the roof but did a blend so the was not a wall for the charge to hit starting in.
I've also ordered a ms361 intake boot. I looks like it's a lot more open than that useless thing on the 360. I've also order a slightly larger carb I think I can modify and make it fit. Won't know until it arrives.
For the exhaust, I widened them approx. .045" on each side (left .030" on each side to overlap the piston skirt) and put a 1 degree taper out toward the muffler. Again, did not change anything in the port opening other than width.
I had mixed emotions about not raising the exhaust port about .020" because I've replaced the stock cylinder gasket with a .005" copper shim I made.
Leaving the cylinder gasket out, gave me a .016" squish and I decided not to do any machine work since I can't do the transfers. Research showed I should run a .020 squish so with copper shim I have .021".
I cleaned up the piston's ports and dropped the bottom of the lower transfer to take that sharp edge off, but not drastically. I think the stuffing would be more valuable than the nickel's worth of gain it might produce
The, muffler has been opened to match the exhaust port, and I will be installing the two 5/8" openings and deflectors.
Any comments or suggestions on things I should change when I replace this cylinder will be appreciated. If anyone want's to do just the top transfers in my new cylinder, talk to me.
All the porting was done on the OEM cylinder and piston. I had to replace the crankshaft in it and I do have a new cylinder set I haven't messed with I ordered with the crank.
I put it back together today and was going to see how it ran (since I've never heard it run) with the stock carb, intake boot and muffler but the thing has a bad coil. That's probably why I ended up with it. I found it laying in the woods and you could tell it had been there for several months so I know nothing about how the thing ran in stock form. I have a 029 Super Farm Boss, so I'm thinking it should at least be an upgrade from that. I looked at stealing the coil out of the 029 but you have to rip the thing all apart to get the plug wire out so I decided I will just wait.
Since I have gotten out of the business because of medical problems, I'm not really into buying another $400 grinder to do one chainsaw so I did what I think will give me the most bang for my buck with what I had and would like some opinions and suggestions.
Since I couldn't do anything with the transfers, I didn't change any port heights. Research had indicated 103, 120, 80 were good numbers and that's what I was going to do.
I opened the intake port, not the so much the opening in the cylinder, but the runners going in. The port opening was already much wider than the intake runners so I managed to get them out to where I have a 1 degree tapered funnel going in. I did not take any off the roof at the cylinder and left most of the metal in the roof but did a blend so the was not a wall for the charge to hit starting in.
I've also ordered a ms361 intake boot. I looks like it's a lot more open than that useless thing on the 360. I've also order a slightly larger carb I think I can modify and make it fit. Won't know until it arrives.
For the exhaust, I widened them approx. .045" on each side (left .030" on each side to overlap the piston skirt) and put a 1 degree taper out toward the muffler. Again, did not change anything in the port opening other than width.
I had mixed emotions about not raising the exhaust port about .020" because I've replaced the stock cylinder gasket with a .005" copper shim I made.
Leaving the cylinder gasket out, gave me a .016" squish and I decided not to do any machine work since I can't do the transfers. Research showed I should run a .020 squish so with copper shim I have .021".
I cleaned up the piston's ports and dropped the bottom of the lower transfer to take that sharp edge off, but not drastically. I think the stuffing would be more valuable than the nickel's worth of gain it might produce
The, muffler has been opened to match the exhaust port, and I will be installing the two 5/8" openings and deflectors.
Any comments or suggestions on things I should change when I replace this cylinder will be appreciated. If anyone want's to do just the top transfers in my new cylinder, talk to me.
All the porting was done on the OEM cylinder and piston. I had to replace the crankshaft in it and I do have a new cylinder set I haven't messed with I ordered with the crank.
I put it back together today and was going to see how it ran (since I've never heard it run) with the stock carb, intake boot and muffler but the thing has a bad coil. That's probably why I ended up with it. I found it laying in the woods and you could tell it had been there for several months so I know nothing about how the thing ran in stock form. I have a 029 Super Farm Boss, so I'm thinking it should at least be an upgrade from that. I looked at stealing the coil out of the 029 but you have to rip the thing all apart to get the plug wire out so I decided I will just wait.
