New Project, Small Husqvarna Limbing saw.

weimedog · January 13, 2011, 10:41:59 AM

Got a box of junk...parts of a Husqvarna 42 and parts of a 238. Neither complete and in running condition, but between the two can either have a (almost..have to buy a few bits & pieces) running 42 or with more work, enough for a running 238..the 238 needs a piston & rings & the cylinder salvaged from a blowup. Its got a bit of aluminum wiped in the standard location for such things..around the exhaust port. Not terrible but will never be like new. IF I decide to take the (harder and more expensive) 238 route, I will remove as much of the aluminum with muriatic acid first and then elbow grease and abrasives second finished with a "brake" hone for master cylinders. The easiest route would be to graft the 42 top end and intake onto the 238 cases...with a few additional parts would be a runner.

Some parts..(The box & most of the parts look like crap so I picked the 42 cover and bottom end...and the two cylinders)

The two cylinders a little closer:

The 42 is the open port cylinder on the left, and the 238 cylinder is the slightly smaller closed port on the right. Couple things to see if you look close enough, the intake port on the 238 is actually larger than the 42's..same with exhaust. And conversely the apparent size of the open transfers is larger than the closed transfers on the 238..and there is a also the 2mm bore difference.

The Model 42 is 42mm x 30mm Bore & Stroke for close to 42cc (hence its model number) and they were a 14,000rmp 2.8hp saw stock.

The Model 238 is a 40mm X 30mm Bore & Stroke for 38cc...I honestly don't know if I would have more saw modding the 42 or the 238! Any thoughts? They seem to have roughly the same intake components ..the 42 seems to be newer. Just don't have a lot of knowledge on these...a learning experience for me and a low risk saw puzzle. to try and hack..and turn this into my small saw for limbs and brush...

saw_nut · January 13, 2011, 01:11:41 PM

The 238 will give you more than the 42 stock or equally modified. Both are good saws. I find the 246 to be the strongest of the 238/42/242/246 family (133 family to make Sawtroll happy). If you want torque these are the wrong saws. They are all about speed. The last 246 I ported is equal in cutting times to a stock 346 OE, but in a class by itself when it comes to limb work.

I have 2 parts 238's here. Cyls are good.

SawTroll · January 13, 2011, 02:28:07 PM

Quote from: saw_nut on January 13, 2011, 01:11:41 PM
The 238 will give you more than the 42 stock or equally modified. Both are good saws. I find the 246 to be the strongest of the 238/42/242/246 family. If you want torque these are the wrong saws. They are all about speed. The last 246 I ported is equal in cutting times to a stock 346 OE, but in a class by itself when it comes to limb work.

.....

Not that it matters much, but it would be more correct to call it the 133 family, as that was the first model (1980). ;)

Saw Dr. · January 14, 2011, 01:04:16 PM

There is an old adage "A piston in the hand is worth three in the mail"....... Or something like that. If you have a good 42 slug there already, what are you waiting for? I doubt you are going to notice .2 horsepower difference on a saw you plan on limbing with anyway. if you are worried about the closed vs open port thing, I'd poke some holes in the side of the 42 piston adjacent to the transfers, and go for it.

You asked for advice.... I got some pics for you. Email shortly.

weimedog · January 14, 2011, 01:47:35 PM

Yes I did! Sounds like a workable plan...might try to build two side by side for comparison sake...Like your "one in hand is worth two in the bush" analogy I guess I can assemble a 42 and then gather junk until I can scrape up a 238..then build both.

weimedog · January 17, 2011, 11:21:39 PM

So it has progressed...starting with a 238 build. Cleaned up the Cylinder & piston as best I could, opened up the exhaust, widened the intake, opened the bottoms of the transfers. The intake was "asymmetric" so I widened the intake to where is is symetric between the wear lines of the skirt. Since the cylinder is dropped .025 inch, I raised the intake around .015 to compensate & add a little duration. Also had to remove .015 from the edges of the piston to make clearance with new deck height. Also assembled with a new ring...then to the muffler mod:

Intake...

Muffler & Exhaust Port. Took the internal baffles completely out. Matched the gasket & muffler inlet to the new exhaust port outlet.

Tripped the chainbrake and then checked for clearance with the modded muffler's outlet...a MUST do when modding mufflers.

weimedog · January 18, 2011, 10:07:17 AM

Exhaust port dilemma ....by dropping the cylinder, that also obviously drops all the ports....the top edge an both the transfers and the exhaust are now lower relative to the piston stroke by the thickness on the gasket removed. Over time I will eventually degree and then go back and correct some of that..just want to get it running as a package first as both the intake area and exhaust area are going to be modified and I will have to adjust things like the carburetor bolt length & all the internals of the muffler.....BUT a glaring dilemma is whats best to correct the exhaust as now the lower edge if below the top edge of the piston at BDC....so..file a bit off the piston? Raise the top edge & do nothing to the piston? Or both...which then means raising the transfers to keep that relationship right.....yea. Stuff to do.

weimedog · January 18, 2011, 11:05:14 AM

Muffler mod..

Mock up installation...after a little run time & deug..all this gets taken apart and cleaned & painted....

weimedog · January 18, 2011, 11:55:06 AM

Now the other end...First thing is the Carb for the 42 has a larger outlet than the 238..so its going on this saw puzzle!

It bolts right on:

Also the throttle & tank from the 42 is going on..the throttle in particular is a much nicer arrangement and also keeps me from having to hack up the 42's carb linkage attachments.

And without the Three Bond....wow..its the glue that makes these blended old saw puzzles work!

weimedog · January 18, 2011, 06:43:42 PM

42's air filter, carb, gas tank/handle, ignition, and throttle linkage installed.

42's cover & handle bar

New guts to the pull start courtesy of "Chainsaw's & More" in Cortland..they have NOS Husqvarna stuff from this era (Where I got the 238 rings from..)....I was dead in the water with this one without their help.

Assembled....ready to test.

Really want to start it! Better wait until 2 morrow.

weimedog · January 18, 2011, 07:57:39 PM

Couldn't help myself...just set the hi and low speed mixture adjustment screws to 1 turn out...went out into the garage put some 32:1 mix it it..five pulls later and you can listen for yourself..just blipped the throttle...not full throttle..it just jumped to RPM's really quickly..what this video doesn't show (its right by the garbage can for the next step in this saws life if it didn't run!) what it doesn't show is how that thing jumps to RPM's and jumps in your hands as it pops to RPM's.

http://www.youtube.com/watch?v=s6ge6PnpeM8

SO..tomorrow I'll put a bar and chain on it and see if it will cut wood.

AND...I'm looking for a good piston for it. If I find one, its coming apart again and all those ports are getting polished and that exhaust will be raised along with the transfers to compensate for that base gasket being removed....for now..IT RUNS!..wasn't certain it would.

saw_nut · January 20, 2011, 08:30:14 PM

I have a couple 238 pistons here somewhere. I will see if I can find them. I put a Husky 262 carb on my 246 build. Just had to swap throttle shafts. It runs great.

HolmenTree · January 20, 2011, 09:53:48 PM

Weim I think you have too much exhaust outlet there, but I might be wrong , the length of the outlet pipe might be enough to keep it at about 80% of the exhaust port.

Willard.

Spike60 · January 20, 2011, 10:50:35 PM

Quote from: saw_nut on January 20, 2011, 08:30:14 PM
I have a couple 238 pistons here somewhere. I will see if I can find them. I put a Husky 262 carb on my 246 build. Just had to swap throttle shafts. It runs great.

Just for info, I checked on 238 pistons for Weimy, and they are NLA from Husky. 242XP stuff is still available.

weimedog · January 21, 2011, 01:43:43 AM

Quote from: HolmenTree on January 20, 2011, 09:53:48 PM
Weim I think you have too much exhaust outlet there, but I might be wrong , the length of the outlet pipe might be enough to keep it at about 80% of the exhaust port.

Willard.

It certainly howls now! I've heard that 85% rule. Usually with a saw with stock port timing. I didn't have the coil/flywheel distance set right and it sort of bogged at around 14K...now it zings past 14..I haven't held it WOT long enough for my tach to catch up. I have cut a few frozen oak (18in) logs and it handily out cuts my 455 & warmed over 46c Poulan/Jred. Very surprised at how this one turned out wanted more torque from an RPM saw..think i got some more. I actually tacked a couple of spacers to see if smaller was better..and there was no difference on this one. So far from what I have seen 100 percent of port x-sectional area works well with the other mods. This one has significant changes to the bottom of the transfers and intake x-section like that J-red and a little more intake duration...seems to work well. Curious to see how it stacks up with a few other 40cc saw in a week or so at out GTG..if it bombs..oh well!

weimedog · January 21, 2011, 01:47:01 AM

Quote from: saw_nut on January 20, 2011, 08:30:14 PM
I have a couple 238 pistons here somewhere. I will see if I can find them. I put a Husky 262 carb on my 246 build. Just had to swap throttle shafts. It runs great.

i would like to see pics of that..and if you have a video that would be really cool. How much different was that 262 Carb?

saw_nut · January 21, 2011, 08:27:48 PM

Will see what I can do for pics. The 242,246,254,257 and 262 all have the same basic carb body. Throttle and choke plates are the same size. Venturi is bigger on the 262 carb.

Have a video if I can get it posted.