First Port Job - Husqvarna 365 Build

[Artemis]

Hey guys, it's been a while since I've posted here, but I'm back!

I've acquired a 1997 365xp from my In-laws for $200. It's in rough shape but I thought it's the perfect saw to finally experiment on and do a full port job. I'm hoping some of you more experienced porters can chime in and give analysis and criticisms so that I get this right on the first go.

The saw runs and behaves surprisingly well with only 98 PSI. I dont exactly trust my compression tester though, so the actual PSI may be higher than that, and I suspect that it is simply because I dont expect a saw to actually run with PSI that low. Anyways, the piston is scored moderately but still useable for my purposes, and everything else is in half decent shape.
I've tried my hand at gathering data on the port timing, something I've never done before. I made a degree wheel and fastened it to the flywheel, and my port results are as follows:

• Exhaust: Opens at 103°, down to BDC
• Intake: Opens at 82°, up to 31°
• Transfers: Opens at 122.5°, down to BDC

Squish at edge of cylinder is .045 at the largest, and .041 at the tightest, measured at 4 points around the cylinder head.

In this build I'm prioritizing torque over RPM. I'll be doing a base gasket delete, OR if I can get access to a lathe; machining the cylinder down to achieve .020 squish using the base gasket. I would also like to turn the piston into a pop-up or domed piston head if the lathe option is available.
A muffler mod is obvious and I'll most likely build a dual port muffler, no screen.

So in your professional opinion, regarding port alterations, what's the best way to tackle each different port? I dont have a right angle dremel so I imagine I cant touch the transfers very easily, but I'll do what i can if i can reach. I'd like to spend most of my energy on getting the intake and exhaust done right. Note: this is not the X-torq motor. I'm thinking with both ports I will widen them up as wide as I can go while staying about 1 mm in from the piston skirts. Good idea or bad? why?
The tricky part is modifying the opening time of each port, and this is where I'd really appreciate the insight. What do you suggest I do for changing the port timing? Bearing in mind I'd prefer more torque than more RPM.

I dont want to change out the stock Zama Carb unless you guys think it wont be able to supply enough fuel for the build. My 372 has a Walbro that I've heard good things about, but I'd imagine it's also pricey to buy the same one.

Any other suggestions? I'm all ears.

 

[Ronie]

I'm not a porter but have done a few of my own saws, this is what I'd do if your goal is torque. Since you can't get to the upper transfers, I would would widen the exhaust to 65% of the bore, widen the intake a little, gasket match the lower transfers and do a base gasket delete. I'd also double check the intake number you got, if it really opens at 82 degrees, I'd raise the floor up to around 78 with JB Weld.

 

[Ronie]

You could also remove the flange at the lower transfer and smooth everything out. This is how I did my 365.

 

[Ronie]

Couple of more pics of the intake and exhaust.

 

[Artemis]

I'm not a porter but have done a few of my own saws, this is what I'd do if your goal is torque. Since you can't get to the upper transfers, I would would widen the exhaust to 65% of the bore, widen the intake a little, gasket match the lower transfers and do a base gasket delete. I'd also double check the intake number you got, if it really opens at 82 degrees, I'd raise the floor up to around 78 with JB Weld.

Noted. Looks like you did a good job! I'm curious, has anyone tried lightening the piston head at all?

 

[Artemis]

Update: I did a test cut and pulled the Cylinder. Here's how she looks! Next step is grinding material away. wish me luck.

 

[Ronie]

Update: I did a test cut and pulled the Cylinder. Here's how she looks! Next step is grinding material away. wish me luck.

Keep us updated.

 

[Artemis]

got the intake done today. looks good to me except for the small nick beside the transfer ports. not sure if you can see it in the pics. I'm not too concerned about it, but I'm wondering if you think it will make a noticeable difference? Other than that I gave it a tiny chamfer around the edge within the cylinder so it doesn't scrape the piston skirt, and then hit that lightly with some 120 grit sandpaper to take any burs off. it feels smooth to the touch.

I tried taking it as wide as I could before interfering with the transfers so I hope I didn't take off too much lol.

 

[Artemis]

When viewing the photo of the inside of the cylinder, you can see 2 shiny spots, 1 in the middle and 1 on the right hand side. those are nicks

 

[Artemis]

this is a better pic

 

[Ronie]

got the intake done today. looks good to me except for the small nick beside the transfer ports. not sure if you can see it in the pics. I'm not too concerned about it, but I'm wondering if you think it will make a noticeable difference? Other than that I gave it a tiny chamfer around the edge within the cylinder so it doesn't scrape the piston skirt, and then hit that lightly with some 120 grit sandpaper to take any burs off. it feels smooth to the touch.

I tried taking it as wide as I could before interfering with the transfers so I hope I didn't take off too much lol.

I don't know if that nick would affect the saw or not. Maybe someone more experience can help you out. @huskihl @Mastermind Worksaws

 

[huskihl]

I don't know if that nick would affect the saw or not. Maybe someone more experience can help you out. @huskihl @Mastermind Worksaws

Looks to me like that spot would be fine. Just make sure it’s beveled

 

[Artemis]

Got the exhaust opened up. This was significantly more nerve racking in that the material is not as thick on the cylinder compared to the intake side, and the length of travel from the opening of the port to the exit is twice as long as the intake. As a result I spent about an extra hour carving it out, paying very close attention to how thin the cylinder material was getting. My worst fear would be to get too greedy and open a hole in the side of the port. When I put the cylinder on the piston to check my work, I hadn't realized that it was slightly twisted off center which made it seem like I had taken too much material off the right hand side. I figured all the fuel in the crankcase would just slip up the transfers and directly out the exhaust without ever making it to the combustion chamber. You can imagine how my heart dropped when I thought I just messed up the whole job! But then my relief was equally as much when I realized the cylinder wasn't centered, and after centering it properly over the bolt holes everything sealed up nice.

I've decided not to touch the transfers, as they are the open kind that resembles troughs a little bit, not tunnels like what is typically seen. I'm not familiar with the actual term for them. I think they will be able to move enough fuel/air as it is.

Now it's time to polish!

 

[Ronie]

Make sure you put a nice chamfer on your exhaust port so you don't hang a ring, it doesn't look like it has one in the pic.

 

[NSEric]

Your 365 has the open port cylinder(the transfers are open to the piston), I'd get a aftermarket 372 cylinder for it, they run a bunch better and are really cheap.

 

[Huskybill]

My experience in porting saws is limited. On the early swedish dirtbike engines I widen and raise the exhaust port. Lower and widen the intake ports, I open up the transfer ports at the base. I lower and flare the rib in the center of the transfer port to a knife edge, but I halfmoon it to keep the flow more in the middle of the transfer port. Then I cut 1/8” off the bottom of the piston. Some of this info came from a 2100 that was ported that was raced.

 

[Artemis]

I tried polishing the ports and I managed to smooth over any rough edges, but ive given up on the thought of having a mirror finish in there. Besides, I'm kind of hoping the dimpled finish will act somewhat like the surface of a golf ball and help the air to actually flow better. in any case, its as smooth or smoother than stock so it should work just fine. I will make sure I have a nice chamfer on the edges.
Next step is the muffler mod! and then cutting the squish if I can find a metal lathe somewhere...

 

[Huskybill]

With the exhaust on a two stroke I think about adding a mini chamber not too far from the port. I feel the faster the exhaust flows out the quicker the intake is sucked into the transfers/cylinder. We may need more than a muffler mod but it’s a good place to start.

 

[Artemis]

Update:
The award for the most hoky cylinder decking setup goes to me. I dont have access to a lathe so I had to get creative in finding a solution for decking the cylinder. As you can see in the picture, I had a dremel clamped to my table saw in such a manner that I could remove material from the base of the cylinder. I am fully aware of how it looks and the potential for things to go wrong haha, but it worked! The squish is down to .020 dry fit with no gasket, and I will take off more in order to achieve .020 with a gasket included and a very light coating of permatex motoseal to help fill any potential air leaks. I did a base gasket delete on my 372 and it has only motoseal between the cylinder and case. That stuff works great! I'll be tackling the muffler mod tomorrow as well. Wondering if I should advance the timing a hair? maybe 1 degree or so? Otherwise I'm slapping it back together and seeing how it runs.

 

[Artemis]

Muffler mod is done! I opened up the exhaust port as much as I could below the deflector, and I bent the deflector up a little more. I also cut the backside and the exhaust gasket to fit the new port dimensions on the cylinder.