Rx7man
Cattle Rubbing Post
Well, I've been lurking around here a while, read all 18 pages of the porting thread by Pepsifreak, and got a lot of information from it, so I decided to tackle one of my old Husky L65's.. They're just about 40 years old, I have 2 runners and a parts saw, and know of another parts saw my neighbor has. The parts saw wasn't running worth a darn, which is why it started getting robbed of parts, so i figured I might as well have some fun with the jug and piston. Both our running saws have 24" bars.
I'm not a newcomer to porting, I've done a lot of it from Cummins Diesels to (of course) Rx7's, and especially in the rotary engines the power gains are AWESOME. My last one with Weber carbs started to really wake up around 5500 RPM and was immensely fun on dirt roads
I measured the squish first, with no gasket it was a .022", on one machine, and about -.010" on another (wouldn't turn over), luckily for me that was the parts crankcase so I didn't worry about it.
I hogged out the exhaust port a fair bit in width, probably was able to get 5mm extra, didn't mess with the port timing at all, and haven't port matched the muffler yet. Transfer port runners I port matched to the crankcase and cleaned up pretty nicely, then ran a little strip of emery cloth through them. Intake port I got rid of the stud bosses that really protruded into the intake runner, and widened them a fair bit, the ring never comes into the intake port so I wasn't too concerned there, and I blended it all in nicely with the intake. I ordered 2 new piston rings (while I can still get them!), one for each saw, but since it'll be a week or two before I see them, I couldn't resist putting it back together and firing it up. The ring on the parts saw had nearly .080" end gap, and the one that I had apart had about .050" end gap.. I'm certain that's FAR too much.. The cylinder of the parts saw also had a little score mark, but not bad, that's the one I tested my porting skills on, and that's the one I put on, saving the other jug for the next porting attempt, it's in mint condition, and so is the piston (maybe a little much ring clearance for the anally retentive).
So I fired it up and I certainly notice an increase in power, It was rated at 3.8hp, I figure it was down to 3.5 from the worn ring (that's still in there), but i think I'm probably back to 'new' or better. I took the saw apart that had the least compression of the 2 runners, and the more worn one definitely revs much better (probably +2000 rpm). Once the new rings are in and I don't have .050" end gap, I think those saws will be restored to their former glory and then some.. Makes me actually look forward to cutting firewood again. I was thinking of getting a new saw, but perhaps these will do for another 40 years Once I get onto a real internet connection, I'll try and upload some picture.. they ain't pretty saws anymore though.
I'm not a newcomer to porting, I've done a lot of it from Cummins Diesels to (of course) Rx7's, and especially in the rotary engines the power gains are AWESOME. My last one with Weber carbs started to really wake up around 5500 RPM and was immensely fun on dirt roads
I measured the squish first, with no gasket it was a .022", on one machine, and about -.010" on another (wouldn't turn over), luckily for me that was the parts crankcase so I didn't worry about it.
I hogged out the exhaust port a fair bit in width, probably was able to get 5mm extra, didn't mess with the port timing at all, and haven't port matched the muffler yet. Transfer port runners I port matched to the crankcase and cleaned up pretty nicely, then ran a little strip of emery cloth through them. Intake port I got rid of the stud bosses that really protruded into the intake runner, and widened them a fair bit, the ring never comes into the intake port so I wasn't too concerned there, and I blended it all in nicely with the intake. I ordered 2 new piston rings (while I can still get them!), one for each saw, but since it'll be a week or two before I see them, I couldn't resist putting it back together and firing it up. The ring on the parts saw had nearly .080" end gap, and the one that I had apart had about .050" end gap.. I'm certain that's FAR too much.. The cylinder of the parts saw also had a little score mark, but not bad, that's the one I tested my porting skills on, and that's the one I put on, saving the other jug for the next porting attempt, it's in mint condition, and so is the piston (maybe a little much ring clearance for the anally retentive).
So I fired it up and I certainly notice an increase in power, It was rated at 3.8hp, I figure it was down to 3.5 from the worn ring (that's still in there), but i think I'm probably back to 'new' or better. I took the saw apart that had the least compression of the 2 runners, and the more worn one definitely revs much better (probably +2000 rpm). Once the new rings are in and I don't have .050" end gap, I think those saws will be restored to their former glory and then some.. Makes me actually look forward to cutting firewood again. I was thinking of getting a new saw, but perhaps these will do for another 40 years
Once I get onto a real internet connection, I'll try and upload some picture.. they ain't pretty saws anymore though.
