making a 385xp better

[riley1056]

I'm rebuilding the top end on my 385. I got a used oem 385 cylinder on the way. I'm going to port it. I have experience porting 2strokes but this will be my first chainsaw job. I've read as much as I can find on this particular saw but would still appreciate your suggestions on the best way to go with it. I don't have access to a mill to deck the cylinder, so to this point this is what I've come up with. I'm going to widen the exhaust and intake as far as the skirt will allow me I'm going to match the bottom transfers with the case and gasket and grind em to make em flow mo. Then I plan to replace the gasket with l something like aluminium to try to get me 20 thousands squish from what I've read u can't just delete the gasket in this saw. Since I'm going to drop the cylinder I'm going to loose some timing on my exhaust but I'm debating wether to just leave or to raise the exhaust maybe 2mm to get that back. I'm not going to mess with the upper transfers because I don't really have the tools to get at them properly. How's my plan sound any suggestions and criticism is welcome. Thanks in advance.

 

[Onan18]

I wouldn't just assume that you cannot delete the base gasket, bolt the jug down with two screws, no ring(s) on the piston and measure the squish, might surprise you. If you find you need more clearance you can make a custom gasket from material of the appropriate thickness to get you to 20 thousandths.

 

[riley1056]

That's what I was planning to do. Do u think I should leave the exhaust alone or try to bring it back up?

 

[Onan18]

I am not the man to ask on that, but logic would seem to dictate that if there is more time for the expanding gasses to act on the piston before the exhaust opens, then the saw would make more torque. Of course I am sure there is a tipping point where this would become detrimental to performance. I would try it without raising the exhaust first, if it does in work out its not too hard to pull the jug back off. I am sure Scott, Randy, or Brad will be along soon enough to correct me though.

Joe

 

[Gypo Logger]

I found some figures for a KD 385, pretty sure it was a pop up. It's still running today after ten years of heavy use.
Intake: 165
Ex: 168
Tr: 130
John

 

[riley1056]

I've heard the port is a little high from the factory but maybe I'm thinking of the390 jug. Yea lowering the exhaust will make it torquer and lower revving but the compression increase will have that same effect the porting I've done I raised the exhaust and then brought the compression up to regain that low end torque but that was a totally different application and the head setup allowed changes in compression with interchangeable domes.

 

[mdavlee]

385 has a lower exhaust than a 390. The gasket delete should get you in the ballpark of .020" squish. I wouldn't widen everything to the max as you may decide to raise or lower the ports later and end up with more time/area than you really want.

 

[blsnelling]

Don't change any port timing unless you put a degree wheel on it first.

That would mage a strong and fast saw with those KD numbers: 96, 115, 83.

 

[riley1056]

I was gonna really do it without the wheel that's why I was considering leaving the timing where it ended up because I really can't change the upper transfers anyway The last mota I ported was on a banshee it was 9 years ago exhaust was 192 transfers were 143 intake was just cleaned up compression was 190psi and it made 70 hp and had broad power completely different animal.

 

[riley1056]

I've never worked with anything without a tuned exhaust

 

[riley1056]

I guess I can come up with a wheel and put on it and get something to get those transfers with if y'all think that's worth the gain. Will I see enough increase from that or will have decent gains leaving the timing alone and just opening it up and get it smooth. This is not a race saw just a work saw.

 

[redfin]

385 has a lower exhaust than a 390. The gasket delete should get you in the ballpark of .020" squish. I wouldn't widen everything to the max as you may decide to raise or lower the ports later and end up with more time/area than you really want.

Pay close attention to what Mike offers.

 

[mdavlee]

I guess I can come up with a wheel and put on it and get something to get those transfers with if y'all think that's worth the gain. Will I see enough increase from that or will have decent gains leaving the timing alone and just opening it up and get it smooth. This is not a race saw just a work saw.

If you're not going to put a wheel on it muffler mod it and leave it be really. You might get a small change but the tightened squish will give most of that.

 

[riley1056]

Im listening believe me. I really am confident in my grinding and polishing I just don't have all the tools I had in the past. I'm really just working with air die grinders right now or I've probably got a dremal around here somwhere

 

[riley1056]

So u saying just mod the muffler get the squish right smooth it out and let it run? You don't think I should go ahead and widen the exhaust and intake?

 

[Mattyo]

husqvarna 385xp build - bearings and machining:

This is what I did ....not a "how to" but more of a "how i" do it

 

[bcaarms]

Tlandrum has a thread on here somewhere where he did a 385 that I ended up owning. Lots of good info in that thread. The saw was amazing.

 

[riley1056]

That looked good. I'm essentially trying to accomplish the same result without the mill. I'm probably going to just get the squish where I want it maybe I get lucky and can just get rid of the gasket and at least get in the neighborhood. Probably going to leave the timing where it lands clean up any casting flaws match the bottom transfers and open that up the best I can polish up the exhaust and see how it does. The only thing really still up in the air is widening the exhaust and intake should I go ahead and do it while I'm grinding on it anyway? Is there a lot to be gained there?

 

[riley1056]

Tlandrum has a thread on here somewhere where he did a 385 that I ended up owning. Lots of good info in that thread. The saw was amazing.

I'm reading on that one now I may go ahead and just go all the way and do it right hell why not

 

[Flat47]

I pulled the base gasket out of mine and haven't yet done anything to the muffler and I am very happy with the outcome. Muffler mod is coming soon, though.