A guy i talked to use's these sandpaper mandrels he just swaps out for a longer shank bolt and uses Emory cloth I haven't tried it but it should work. 2" disc pad holder - Google Search
I probably have one of those laying around in the shop somewhere... That sounds terrible, but with my work schedule, I don't get to spend enough time in my shop to keep track of stuff... The old saying, if you don't use it, you lose it...
Got in touch with my machinist. We need to figure out a time to cut the squish band and the cylinder base. I did order a .006 base gasket so I'll work around that to figure out what I want to cut. Compression will go up, but the main driver in cutting base and squish is dropping the cylinder enough to get the exhaust to hit at 100* atdc after raising it enough to get blowdown to 22* up from 18*. I'm wanting to target intake and exhaust durations at 160* with blowdown at 22* and let compression end up wherever it ends up. I didn't bother checking it yet since the saw wasn't really broken in at all prior to this teardown.
I did some carb work this evening since my 3mm brass screws for the choke and throttle plates came in. I replaced the both plate screws and used locktite. The choke plate screw had different threads than the throttle plate so I had to tap that hole. Had to be careful to line up the choke plate correctly so it's notch clears the Hi jet nozzle in the venturi. The throttle plate notch has to line up with the line of low speed jets in the bore. They are in line with the Hi jet nozzle. I taped off all the fuel passages, pulse hole, jets in the bore, and atmosphere vent on the metering diaphragm side before cutting the metal. Then I thinned the shafts and took out the screw length and flattened the heads some. Should flow better than before... Not a pro job by any stretch, but It'll do for this weekend hack... Being the belt and suspenders kind of guy, I also peened the threaded end of the screw after they were ground off. This along with the locktite should keep these screws in place. I like a saw that eats wood, not carb screws. I put a screwdriver in a vise to support the screw head in the shaft so punching the other end doesn't stress the shaft or carb at all. I tried to get some pix of the punched ends, but my photography skills are rather limited... I'm pretty sure the tape kept all the brass chips from the carbide cutter out of all the places I didn't want them getting into. This should have a little more flow than before. This is what it started with. I know there will also be gains in the throttle settings once the carb is back on the saw. The WOT stop lets the plate go way past center so that will get fixed and also will be checked out to ensure the linkage opens it all the way. Those are easy adjustments on this saw.
Ethan called this morning and said he had time today. He cut .040" from the base and .032" from the squish band. The .006" base gasket will get used for this build so the cuts were based on that and targeting the upper transfers to end up at 121* or 122*. I don't have a right angle tip for my grinder. Then I will be able to grind the exhaust port with the target of widening it to 35mm and raising back up to 100* to get a duration of 160*. I also will adjust the intake timing by removing skirt off of the piston to lighten it as well. Cut cylinder before grinding. I sanded .008" out of the squish band to get through the plating so it wouldn't mess with Ethan's tooling on his lathe. He cut .024 more out. I opened the windows on the piston a little and got rid of casting seams and sharp corners. I marked the intake skirt to match the intake port floor with the timing wheel set for 160* of duration. Then I cut the skirt to match it to get the timing and lighten the piston at the same time. I left the "ears" to help keep the piston rocking to a minimum. I matched the piston top edge to the exhaust port instead of making the port top flatter. I'd rather not hang a ring by getting a wide exhaust port too flat. I had to do some tweaking to this after the picture was taken to get it to match better. This pic is from the first pass. The piston ended up another gram lighter after these modifications.
Widened the exhaust port and set it to 100*. Since the jug got dropped I cut about .040 off the intake partition wall. This saw uses a solid intake block as opposed to a flexible rubber boot like a newer design. When the cylinder gets bolted to the case you have to be careful not to crack that plastic block if it hits the partition wall. Also the screws on the bottom of the carb could hit on the intake box floor so I'll make sure those had clearance as well before final assembly. The lower transfers had a sharp lip on the bottom edge. There was also a weird curve to it on the exhaust side. I didn't take much out of the lowers to keep the crankcase volume down but I did get rid of the S-curves and sharp corners so the lowers are more like a velocity stack instead of a box. Before After The upper transfer ports looked pretty good. I didn't touch them after checking for a plating ridge along the top of the ports that I've found in a few saws. I always file those ridges out to allow smooth laminar flow at the top edge of the port. A ridge or lip there will cause drag and eddy currents that slow things down. The plating in this jug was OK and didn't flake at all. I was careful to keep the burr rotation into the wall whenever possible to minimize the possibility of chipping. I finished all the edges and chamfers with some small shaped diamond files. I was able to get started on the muffler but I'll braze the tube in tomorrow if I get to it. I think it was Czed that suggested working on the chain oiler pump so it will last longer. I took it apart and the pump gear that the plastic worm gear drives had very sharp edges and felt like it would eat the plastic worm gears for lunch. So I ran a tiny wire wheel for a dremel tool along all the sharp edges in there to soften up the inner workings. After putting it back together, it was WAY smoother and turned much easier. Of course the oil pump O-ring was crap so I have a couple of those on order. I greased all the guts of the pump well. I'll assemble the whole saw tomorrow after running to the hardware store to get a couple screws for the intake block off plate so I can do a pressure / vacuum test to see if that O-ring will hold or not... I'm very curious to see if that one can be re-used or not. Sorry I didn't get any pix of the oil pump work. I'm glad I tore into it. I'll change the bearings after I get the gasket set, but I'll start it up tomorrow if I get time to vac test it and throw it together. The overall assembly of this saw is pretty easy.
I have a couple of those punches I use for laying out stuff. I never thought of using one of those, although the ones I have probably wouldn't fit down the bore of a carb. They're kinda short and stubby... I did need 3 hands to hold the carb on the backing screwdriver, get the punch where it needed to be, and whack it with the hamroid... I'm used to working alone and some of the Rube-Goldberg set ups I come up with can be entertaining...
I finished the muffler, washed out the filthy crankcase with kerosene, did a vac/pressure test and it revealed a leaky de-comp valve as others have mentioned about these saws (I had a good old one in my tool box that's missing the blue button), did clearance work on the intake box due to the cylinder dropping a total of .053" with the cut and gasket change. final numbers are: exhaust duration 160* intake duration 161* blowdown 21* squish .025" That's right in the zone where I was wanting the numbers to be. I haven't measured compression yet, but I have to push the button to start it. It sounds healthy, but I'll know more once it gets into some wood. It definitely requires ear protection. I did get a few heat cycles on it. I did not change the bearings yet cuz the gaskets aren't here yet. I was surprised the oil pump O-ring still sealed for the vac test, but I'll run it for a bit and change that out when I do the bearings. I'm exited to get to use it, but we will be on the go all day tomorrow. https://www.youtube.com/shorts/tUJymSHEzgc
A few pix. Intake box clearance had to be cut. Not beautiful, but it works. Added a second output. It doesn't look like it in the picture, but it is angled a bit to the left and up.
I was gonna do another heat cycle while checking the wood stove at bedtime... but Sum Ting Wong!!! Probably an easy fix. But still a fix...
Is it a correct assumption that this may be a symptom of the cord being too short? The center hex head cap screw inside had become super tight and wasn't letting things turn properly. Can this screw get tightened when hitting the end stop when the cord is pulled all the way out? I'm not familiar with how these work internally so I'm curious to find out more as to why this happens.
Sounds good Isn’t that the way it goes you rebuild the saw have some success and then something breaks
Happy Easter everyone. I hope you all had a blessed day. We visited several friends and had two different family meals to share fellowship and good food with. I was able to get another heat cycle on the saw this evening when we got home. I'll do a couple more tomorrow and give it a little light duty workout in the evening if the rain holds off.
another heat run in the daylight. https://youtube.com/shorts/e76vxvvWGt4 32:1 mix with red armor. hi jet set for extra blubbering rich for now...
Second tank of mix I started letting it do some work but smaller stuff for most of a tank and then a little bit bigger later. https://youtube.com/shorts/rrgkkcK6Rtc https://youtube.com/shorts/WO_PoJNEph0
