Husqvarna 359 Porting

[Rich1911]

Husqvarna 359 porting.  Number 1 of 6

I’ve had to cut this post into smaller sections due to upload file size with the photos. 7 posts in all documenting the process of the rebuild and porting

A few years ago I picked up a cheap 359 that had been trashed when ran on straight petrol. I cleaned up and ported the cylinder, modified the exhaust and carb and was very surprised at its transformation, so much so it’s been my go to saw ever since. I’ve been meaning to rebuild another 359 to the same specification. I started the rebuild a couple of weeks ago.

With the exception of new bearings and an OEM cylinder kit purchased from the US all the other bits are from my parts stock of husky 357’s.

Chassis/Crankshaft

I’ve replaced the crankshaft bearings with new SFK 6202 C3. Crankshaft in the freezer overnight then the bearings heated up on my soldering iron, I rotate the bearings with my fingers every 30 to 40 seconds to evenly distribute the heat until I start getting blisters from the heat (only joking) I know they are ready when the bearing get too hot to touch. Then quickly slide the bearing on the frozen crankshaft (wearing gloves). I use the soldering iron as heating bearings in the oven is more hassle, the soldering iron is easier and quicker. I’ve left the stuffers on the crankshaft. The stock 359 saw doesn’t have stuffers, but I’ve adding them as I feel the reduced volume in the crankcase enables the fuel oil mix to be forced into the cylinder at a higher velocity and subsequently the exhaust gases leaving the saw at a higher velocity, theoretically keeping the cylinder cooler and ultimately prolonging it’s life.

The Crankshaft and bearings go back into the freezer for a couple of hours

Then when the boss is out of the house I put the cleaned crank cases in the oven (oven is not preheated) I let the oven heat up to 180 -190 centigrade and let the cases soak up the heat and expand for 10-15 minutes. I then take one crankcase side out and drop in the frozen crankshaft after making sure I put the correct crankshaft side in the, whilst the other crankcase side is still in the oven I’ll fit the gasket and case guides around the crankshaft and case I’ve just put together. I then place a piece of aluminium flat bar on the gasket, take the other case side out of the oven and drop it onto the bearing on the other crankcase side. The flat bar stops the crankcase dropping too far over the bearing as you’ll never line up the case guides first time.

Then it’s a matter of removing the flat bar, dropping in the 6 crankcase screws and alternately tightening these one turn at a time up until the two halves meet. I don’t use any thread lock on the crankcase bolts.

Then destress the crankcase bearings, I add a clutch nut to the clutch side and flywheel nut to the flywheel side then give them a tap with a copper mallet either side to free the bearings in the bearing cases.

Next installing the oil seals. Both sides are done the same way, isolate the piston top arm ( a piece of wood slid either side of the piston arm) oil the seal I use 2 stroke oil and drop some oil into the exposed bearing, slide the oil seals over the crankshaft until they rest on the crankcase then I add a series of oversized washes/spacers until the crankshaft is covered just beyond the screw threads. Then the easy bit, I start to slowly screw down with either the clutch nut or a flywheel nut to press in the oil seal to the crankcase, the oversized washer limits the depth the seal is pressed in. Then unscrew and remove the washes, perfectly seated oil seals every time.

[Rich1911]

Husqvarna 359 porting.  Number 2 of 6

 

 

Exhaust

I drill a series of 2mm holes around a large section of the internal baffle via the cylinder side of the exhaust, I’d drill the holes progressively larger until all the holes meet. Then remove the section of baffle and clean up the rough edges inside the exhaust with a chain file, it’s a pain of a job to do but I think the benefits outweigh the hassle.  I then just I drilled out the existing exhaust pipe, enlarge the hole and braze in a larger pipe, clean up the outside of the exhaust of brazing flux. See the photo comparing the two exhausts showing the difference in exhaust pipe size I’ve done the math and there is an increase in exit hole area of over 60%.

[Rich1911]

Husqvarna 359 porting.  Number 3 of 6

 

Porting the cylinder

The idea is to increase the velocity of the fuel oil mix around the cylinder and exhaust gases by reducing as much as possible any obstructions to this flow. The tools I use for this is a Dremel and some tungsten carbide grinding bits.

The trick here when removing material is to not force the grind but let the tool do the work, remove small amounts at a time and constantly check your work. Grind up to your markings and never be tempted to grind that little bit further.

1 open up the intake port on the cylinder. Both intake and exhaust ports are widened to around 70% of the cylinder diameter. The 359 cylinder diameter is 47mm so I widen the ports to around 32mm. I’ll not alter the top or bottom of the ports just widen the sides.

2 as much as possible blend in the lower cylinder skirt to match the crankcase, on the Husky 346, 357, 365, 372 non torq saws removal of the cylinder material is straight forward and can be matched perfectly. The 359 is more of a challenge as the side transfer plates can be removed and you’re limited to keep enough material to not compromise the screws holes that hold the plates on and to maintain an air tight seal when assembled.

The plus side of the 359 is that removing the side transfer plates gives better access to clean up the transfer ports and model the transfer dividers to influence the direction of the fuel oil mix. By removing a corner of the divider the flow of fuel can be channelled to the back of the cylinder pushing the exhaust gases out faster. I prefer to change the shape of the dividers on both the cylinder and transfer plate to help with the flow rather than remove them all together. I’ve also removed material from the lower part of the transfer ports but left the upper transfers as is, my logic being I’m creating a funnel type effect, the same volume of fuel air mix being sucked up a narrowing area again increasing the velocity of the mix.

[Rich1911]

Husqvarna 359 porting  Number 4 of 6

 

3 Widen the exhaust port and also enlarge the exit channel. I then offer up exhaust gasket and heat shield to the exit channel hole and enlarge the hole until they match the cylinder. Then transfer the gasket to the exhaust, mark the hole against the exhaust and enlarge the exhaust intake hole accordingly. I can then give the exhaust a final clean and then spray with stove paint and bake this on with a heat gun.

The cylinder intake and exhaust ports are smoothed inside with 400-600 grit wet and dry. It’s given a thorough clean to remove any aluminium debris from porting and the side transfer plates put back on. I used the existing gasket and also Loctite 518 to ensure an air tight seal.

[Rich1911]

Husqvarna 359 porting  Number 5 of 6

 

 

Setting the squish.

I don’t have access to a lathe, as such I don’t remove any material from the bottom of the cylinder or top of the piston and I don’t get into the realms of timing, degree wheels and resetting the woodruff key on the flywheel etc. I’ll leave that to those with more skills and experience.

I simply put on the piston, four dabs of grease and four pieces of soldering wire 1mm dia (at this stage the piston ring is not installed). I then offer up the cylinder with no base gasket and tighten the four screws. I then rotate the crankshaft until the solder has been crushed against the top of the cylinder. Then remove the cylinder and measure the thickness of the crushed solder. I use the thinnest measurement and cut out a gasket from gasket paper either 0.15mm or 0.25mm thick or a combination of both so the overall gap (squish) between the top of the piston and the cylinder is near 0.6mm but no less than 0.5mm. The squish measurement on this 359 with 0.15mm gasket paper is 0.57mm after I’ve added 518 sealant the final squish will be very close to 0.6mm.  When porting 357’s I usually end up using 0.15mm gasket paper.

 

Installing the cylinder

First the intake boot, plastic partition and clamp need to be put on the cylinder. I have my own way of doing this as I’ve come across dozens of intake boots in the past that have been installed incorrectly where the male intake tube has been crushed or misshaped.

I first offer the intake rubber boot to the cylinder without putting on the plastic partition surround and metal clamp, this way I can tell visually with 100% certainty that the male tube is inside the cylinder impulse hole. I’ll then push on the plastic partition over the intake boot and finally the metal clamp. No special tool for the metal clamp just long nose pliers a screw driver and a raised block of metal to rest the cylinder on whilst fixing the metal clamp. These can be a pig to attach my trick is to hold the clamp in place with a wire ring whilst I bringing the ends together with the pliers and pushing the bottom of the clamp into place with the screwdriver. I’ll then put together the rest of the intake items, impulse hose etc.

Once the piston ring is put on the piston I’ll add a smear of Loctite 518 to the cylinder base then add the gasket paper then another smear of Loctite 518, oil the inside of the cylinder and piston ring and slip the cylinder over the piston and I add medium strength thread lock to the bolts before I install these. I don’t put on the top or brake handle at this point as it makes putting the cylinder on a lot easier without them.

[Rich1911]

Husqvarna 359 porting.  Number 6 of 6

 

I then pressure test and vacuum test the saw to make sure everything is sealed and holds pressure/vacuum and also check the fuel tank vents properly. Then assemble the saw as normal adding new fuel hose  and fuel filter, one further job is undertaken and that is to smear gasket sealant (Hylomar Blue) around the base of the chain oil pick up pipe before it goes in the saw body. I also modify the chain plate by depressing slightly the area which sits on top of the chain oil feed pipe. When the chain bar is fitted and tightened up the depressed area of the chain plate squeezes the chain oil feed pipe against the oil pump. Both these mods I find will stop any chain oil leakage when the saw is stored.

 

Carburettor

A few options here, Walbro HDA (199 or 198 or 197) or Zama C3 EL42

I’ll always opt for the Walbro first as it delivers more fuel than the Zama but the Zama is a more reliable carb and seems to idle better.

I’m happy to use the Zama on ported 357’s but not on the 359 without first modifying the Zama main fuel jet as it just doesn’t deliver enough fuel to pull the chain when the bar is buried full length in wood.

As you’ll see the Zama feed hole (Zama is the silver jet on the right) to the main jet is considerably smaller than the Walbro. I tried a trick I picked up from the US web sites, if you drill through the Zama feed hole all the way through to the other side of the main jet it increases the fuel delivery. I use a 0.5mm drill. Don’t try and use a bigger drill thinking a bigger hole will be better, it won’t work. It simply bogs down the saw with too much fuel when revving hard. Also I found this doesn’t work on the 357 even after porting but it worked a treat on my first 359. I’ve put a Walbro 198A on this 359 but will probably change it to a modified Zama later.

The compression of the saw when built was 175psi. I expect there will be a further increase to this when fully bedded in. I’ve set carb to run rich the rpm at 12900 for the time being and I’ll check and increase this to around 13600 after about 10 tanks of fuel when it should be bedded in.

The saw accelerates hard, there are no flat spots or delayed pickup when squeezing the trigger. I’ve not cut any wood yet but it will get a full day’s work this weekend.

You may be asking why bother with the 359 and just use a 357XP instead? The difference between the two are the 357 has 46mm cylinder and 359 has 47mm, the 357 has stuffers on the crankshaft and the 359 doesn’t and the 357 max revs 14000 whereas the 359 max is 13600.

Well I’m fortunate enough to run both saws, both 357 and 359 are ported, both scream and are fantastic to use but the first 359 seems to accelerate more aggressively and certainly pulls better in the wood which I put down to the modified Zama carb so it’s always the saw I pick up first….

Time will tell if the one I just built works as well.

I hope this may be of help to anyone thinking of porting saws it’s good to share information.

[billpierce]

Interesting read thanks for posting!I'm Not quite there for doing more than exhaust modding just yet but will get there in sure. Seems enough juat keeping everything sharp and well maintained! Ta

[Brian_32]

first off - I know this is older, but...Fantastic post! This is exactly what I was looking for.  I'm new to this sight, was a member at another sight (shall remain anonymous), but stalked more than I participated.  I just picked up a "used" 359, that turned out to be a very tired 359.  That said the I've pulled it apart and the cylinder and piston both look great, just some discoloration around the ring on the exhaust side of the port.  I ordered a Caber ring and gasket material - everything else I need I believe I have, but I'm going to attempt to port my cylinder as you did in the post.  I have access to a machine shop at my work, so I'll take advantage of what I can.  As of last night, I finished cleaning everything thoroughly (probably the most time consuming part of the job) and plan to get the cylinder marked accordingly as you mention above - then I'll bring it in Monday and see what we can accomplish.  I can't wait to get this back together, I've rebuilt plenty of saws, but never "built" any, looking very forward to seeing the results.

Edited March 12, 2021 by Brian_32
grammar

[adw]

359 had an open transfer port cylinder, not the best cylinder to get the best performance from.

[Brian_32]

10 hours ago, adw said:

359 had an open transfer port cylinder, not the best cylinder to get the best performance from.

True, but they were decent saws in stock form, I only use it for firewood, and being the first saw I've tried porting, it's the perfect candidate. I'll have the cost of a ring and gasket material in it when I'm done, and should something go wrong when porting, I'll go straight to a 357xp kit for the closed port cylinder.