Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => McCulloch => Topic started by: Al Smith on November 02, 2014, 09:15:19 pm
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This is kind of a repeat I'd done before .I was asked my a member to show it again .
The subject is a Mac 125 the chrome had delaminated .I chose grade 50 grey cast iron for the material for two reasons .It machines easily plus it's the samegrade of cast iron Harley Daividson used on iron cylinders .
I bored the block 70 thou over ,machined the sleeve for a heat shrink fit of 2 -2.5 thou over following the rule of thumb of 1 thou per inch of sleeve on a heat shrink fit .
The sleeve was cored out from a 3" chunk of fine grade cast I got from Mc Master -Carr .
I left it about 2 thou undarsized incase of warpage or distortion and final honed it to a fit of 4.5 thou larger than the piston skirt .
The ports were cut in after the sleeve was pressed by leaving the welch plugs out .That wasn't a big deal nor was the rest .The time was building the holding fixture to hold the block and making the boring bar for the Bridgeport milling machine .
It took me 2 hours to tram the mill in to get it pefectly in alignment to bore the block and about 15 minutes to do the job .
It came out fine ,runs fine .I have not ran that saw even enough to seat the rings since I did the rebuild .
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Good job - The 125 is a beast
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Well thanks very much for that.
I'm not sure if i'm up to that level with the lathe, but thats given me an idea on how to start at least thinking about doing it.
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I might add my method was just one of many options .I also imagine that if a person looked at LA Sleeve company that a ready made spun cast sleeve could be adapted .
Now I've seen rather ingenious holding devices for cylinders used in a lathe .Randy of "mastermind " fame showed one and Dennis Cahoon had another one .The reason I used a device bolted on the side of the cylinder was because to me it appeared to be the most simple method at the time .
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Looks good Al. Thanks for posting that...
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Al, I am having my machine shop do a block for me. It's a 101B block with
removable head so it will be much easier. He has found a sleeve already
so as soon as i get off my but and give him the block i can get it done.
Mine is originally a cast bore but the motors wrist pin moved and out came
the needle bearing for the wrist pin. Made a mess of the bore.
Lee
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L.A. Sleeve will probably has sleeves for about any application, I think they are the largest sleeve manufacture. If not they can make one and I'm sure it would be cheaper than a solid chunk of cast.
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Anyone have thoughts on minimum wall thickness for a hotsaw application?
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Anyone have thoughts on minimum wall thickness for a hotsaw application?
It all depends on the amount and type of supporting material. I've seen sleeves sub of 0.060" if there is ample supporting material. You can also go thinner on steel sleeves than cast.
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I've got a Mac 797 that was already at .070 over when i restored it. Not much cast
left in that saw. Thank god the piston was still in great shape. I've also heard that
back in the day folks were boring 101 kart blocks .100 over. That cast bore was
extremely thin. But anything goe's to win a race.
Lee
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Thank you. May machine down the cooling fins on an 084 cylinder and add some filler to thicken up the wall and use a sleeve on it. Any recommendation on a steel type in lieu of the cast iron?
Thk. Adam
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12L14
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Thank you
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12L14 is a free machining, leaded type steel that you will not have any trouble making (dimension) with. With a hot saw or cookie cutter this should be very acceptable.
If you use something like 4140 chrome moly, you will need to jump though a few hoops to get it made for a good fit. Rough machine, aging, finish machining.
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12l14 looks like it may be hard to find in larger bar stock. I'll keep looking. May use a spun iron sleeve as they are a dime a dozen. I'll have to weld more material around the jug to support the thin sleeve
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Centrifugally cast Meehanite cast iron would be great if you can get it at a good price.
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Looks like the LA Sleeve products is centrifugal cast. Used one on a 2100 Husky project and it was very well made O.D was ground very consistent. Let you know how it goes
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very informative gentlemen, I just watching and learning...
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Me too ........................................
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I'll second LA Sleeve .Coring out a piece of gray iron takes a long time .Spin cast also should be stronger I would think .
In my case with 70 over the wall thickness was around 35 thou give or take .I think you could press a thick sleeve like that and once pressed bore it out some .Too thin I'm about afraid you'd crack it pressing it in .
You can get precision tubing in about any size which is very strong but like 4140 steel it doesn't machine that well I suppose it could be honed to size but it would take a month of Sundays to do it .
How thick,good question I think under combustion pressures can reach 800 PSI .If it had enough "meat" to back it it up and could transfer the heat maybe 10-12 thou ,just a guess .
Now on a Mac it's fairly easy because you can go right through the ports to cut in the ports .Some like a Stihl or a quad port Husqvarna you's about have to make a port map template and do every thing inside which would be a chore .If you tried to cut the ports in first you'd first of all have to be right on the money plus the ports being cut in ahead of time would probably cause the sleeve to crack while being pressed in .
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The way to cut ports is to press the sleeve in the cylinder without any ports , give it a good bath in acid , take it out and voila . This process is called port etching .
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Explain to me how does one pull out a heat shrunk pressed in sleeve other than bore it out .These are not slip fit sleeves .
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Sure worth the read , some pretty cool projects , even some chainsaw related !
http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop/page4
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That is ingenious but it is an open cylinder with a head .With a blind end cylinder like a saw engine once you pressed the liner you have no way to pull it back out .With a heat shrink fit it's almost as rigid as if the liner were die cast into the block like a modern aluminum block automobile engine .
Plus the fact on that M/C engine there's enough room to use a thick walled flanged sleeve .Now what a person might be able to do is port map it and cut the ports undersized and press it home then finish cut the ports .It's only speculation on my part if it would work or not or just be an exercise in futility .
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cool link 604f1.
the acid idea is interesting. wonder if just making a port map on paper, then wrapping it around the new liner to scribe port outlines would be similar? either way, it would seem difficult to get port angles correct.
Al, think you nailed it.
do you think there is enough room to counterbore the jug flange for locating pins for the liner after mapping?
just trying to pick up the scraps you guys are dropping to learn.
-joe
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Unless it had a head you'd have to pin it at the bottom .Then you have the problem of hitting the pins .You've got to remember that motorcycle cylinder is huge compaired to a chainsaw.That guy in the vid claimed it swelled 10 thou from the heat .You never get that much on a saw cylinder .I only heated my cylinder up at 350 in an old oven .Heaven forbid I do it the wifes oven .
Even at that with around 2-3 thou interference fit and a frozen cylinder it took some pressure the get the sleeve in .
About the only thing I've seen flanged sleeves was on wet sleeve cylinders like tractor engines .Usually on a dry sleeve they just cut from the top down and leave about 1/2-3/4 inch uncut at the bottom of the cylinder .Press the sleeve and mill the top off flush with the head deck .Almost nobody dry sleeves an engine any more for repairs other than some very rare engine .
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Now I have a very vivid imagination so bear with me .An idea which may or may not work .It's only theory and conjecture that it might .Application would be a race engine .Much ado about boost ports ,finger ports ,external ports and the like .
They all do about the same thing only use different methods .So what would happen if say a stock cylinder were bored 15 thou over ,finger ports ,shallow cut in the cylinder wall .Could be two,could be 4 terminating right above the intake advanced 3-4 degrees ahead of the main transfers ,press in the sleeve .Cut the sleeve further down to ID size with port mapped template and do the ports .You'd probably have to stay fairly close to stock bore to save the cylinder wall strength .
What you could get might be better than externals ,that much advance before the main transfer would really boost the velocity .You would not need to reverse the piston or move the ring pins or worry about snagging a ring .Cut the extra ports with a hard upward angle to sweep above the intake but enough not to short circuit right out the exhaust .Who knows might work .It also might give you enough extra sweep you could leave the exhaust port long and really hang on to the torque .
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Now I have a very vivid imagination so bear with me .An idea which may or may not work .It's only theory and conjecture that it might .Application would be a race engine .Much ado about boost ports ,finger ports ,external ports and the like .
They all do about the same thing only use different methods .So what would happen if say a stock cylinder were bored 15 thou over ,finger ports ,shallow cut in the cylinder wall .Could be two,could be 4 terminating right above the intake advanced 3-4 degrees ahead of the main transfers ,press in the sleeve .Cut the sleeve further down to ID size with port mapped template and do the ports .You'd probably have to stay fairly close to stock bore to save the cylinder wall strength .
What you could get might be better than externals ,that much advance before the main transfer would really boost the velocity .You would not need to reverse the piston or move the ring pins or worry about snagging a ring .Cut the extra ports with a hard upward angle to sweep above the intake but enough not to short circuit right out the exhaust .Who knows might work .It also might give you enough extra sweep you could leave the exhaust port long and really hang on to the torque .
+1 lots of potential there. with a sleeve, think the possibility of lowering the exh roof would also be available for a torque style build.
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Al, how did you mark and cut the ports on the Mac you re-sleeved?
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I tried to find a picture but I have no idea where they went .Any way it goes like this .
The reed valve Macs area all built about the same way .Carb on top of a reed valve so no actual intake port expect the manifold which holds the reeds .Transfers top and bottom ,exhaust out the side ,horizontal engine .Bottom transfers are bottom tunneled ,three ports ,top kind of open three ports ,non windowed piston .Bottom tranfers are plugged with welch plugs .
The sleeve or liner only extents to below the bottom transfer tunnel .Leaving the welch plugs out all the ports can be cut right through the old ports left in the block and of course reinstalling the plugs once that's complete .The trick is chamfering the dang things without a right angle die grinder which I don't own .
Because the liner is cast iron they can be ground using a long shank tool .However working with a mirror every thing is backwards with regard to movement of the die grinder .It's not that difficult just tedious but then again any port work is tedious no matter what engine it is .If you aren't in the mood what until you are .Lotta work there to screw it up with a temper tantrum . ;)
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+1 lots of potential there. with a sleeve, think the possibility of lowering the exh roof would also be available for a torque style build.
On that and in reference to a removable cylinder like a Stihl it's normally done by cutting the cylinder base .I had thought about building a "slugged" partly blind end cylinder liner for the 125 Mac but changed my mind because it's a fairly rare saw .All I wanted it to do was run as good as a stocker which it does .
Slugging a cylinder is making a tapered top open in the middle removable spacer done on old John Deere two cylinders running "hot farm stock" to raise the compression but that is in no way connected with chainsaws .
There's lots of old ideas that have been around for decades most people never heard of from days high compession pistons were not even thought of yet .But then again a 50 year old farm tractor and a chainsaw engine really don't have much in common .
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Al, thanks for the expalnation...
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+1 lots of potential there. with a sleeve, think the possibility of lowering the exh roof would also be available for a torque style build.
On that and in reference to a removable cylinder like a Stihl it's normally done by cutting the cylinder base .I had thought about building a "slugged" partly blind end cylinder liner for the 125 Mac but changed my mind because it's a fairly rare saw .All I wanted it to do was run as good as a stocker which it does .
Slugging a cylinder is making a tapered top open in the middle removable spacer done on old John Deere two cylinders running "hot farm stock" to raise the compression but that is in no way connected with chainsaws .
There's lots of old ideas that have been around for decades most people never heard of from days high compession pistons were not even thought of yet .But then again a 50 year old farm tractor and a chainsaw engine really don't have much in common .
didn't elaborate enough on my reply. aware of "dropping the jug." when the need to drop the jug, for whatever reason, you are limited by just how much, due to the freeport dilemma. could see where the exotic pistons would be of help with this. the other ports are not a big deal to correct.
if i was going to go through the time/expense to do any of this, would put the exh roof where i wanted it to begin with.
the only replaceable liners i have personally seen were in a box. for a ford tractor motor in pieces. my ex-father in law never finished this project even all the pieces were there.
thanks for taking the time to explain these things, Al. like learning new things.
regards
-joe
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On just the general topic of sleeves for example a John -Deere model D is a 6 3/4" bore .They would use honed steel tubing which you can buy .Bored from top to bottom leaving about 3/4 to one inch at the bottom of the cylinder uncut .Cold press the sleeve and like the old flat head Fords mill off the excess flush with the block head deck .
That's just talking engine cylinder sleeves.Another is sleeving the brake cylinders on old Corvettes that sat all winter .The brake fluid used to eat up the cylinder walls on old cast iron brake components .That was the fix,sleeve them with stainless steel .