Braapp-Shack/SCARR Engineering 394 build, DONE :)

[jmssaws]

The more you grind on the transfers or the bigger you make them the less exhaust duration you need.
Your taking tourqe away by hogging out the transfers so you have to get it back with the low exhaust and they run good.
Took me a while to figure that out.

Rpm will come from the transfers and not necessarily the exhaust height.
If I'm going to be over square on anything it will be on the exhaust, I want less intake to build case compression and feed the transfers.
I don't think about transfer height all that much,instead I think of blow down and set them off the exhaust height.
I done this 394 yesterday, it's 98.5 117 82

 

[mdavlee]

The more you grind on the transfers or the bigger you make them the less exhaust duration you need.
Your taking tourqe away by hogging out the transfers so you have to get it back with the low exhaust and they run good.
Took me a while to figure that out.

Rpm will come from the transfers and not necessarily the exhaust height.
If I'm going to be over square on anything it will be on the exhaust, I want less intake to build case compression and feed the transfers.
I don't think about transfer height all that much,instead I think of blow down and set them off the exhaust height.
I done this 394 yesterday, it's 98.5 117 82

You and Shaun do transfers way different than I do. If I add volume I use a finger port instead of opening the whole tunnel.

 

[jmssaws]

You and Shaun do transfers way different than I do. If I add volume I use a finger port instead of opening the whole tunnel.

I make the transfer mouth the smallest point and almost never wide it and make the tunnel a straight shot to the corners.
I will dig that corner out to increase the angle to the intake.

Instead of a finger to help push the charge to the intake side I just aim the transfer more that way.

 

[srcarr52]

I'll add volume to the whole transfer port by widening towards the exhaust side and the outside of the transfer tunnel. When I do this I run more blowdown then normal, and keep the intake duration in check. Like Jason I make sure the narrow part of the transfer is the inlet to the cylinder and pay extreme attention to the aim of the ports. Also I make sure they open in together, a maximum 0.005" transfer port height difference side to side is all I allow.

@RIDE-RED 350r
You are correct about 4-strokes. The exhaust valves are smaller, and usually the cam has less duration on the exhaust unless it's specifically made for boost or nitrous. But it's different in a 2-stroke, we don't have the piston to push the exhaust out. Instead it's relying on the further expansion of the combustion gasses to start the exhaust process, then gets some help from the fresh charge entering from the transfer ports. But that is not directly the piston pushing the exhaust gasses out, there is the volume of the case that has to be compressed and it has to push it all through the transfer ports. Also the transfer port timing is always less than the intake. Then there is the negative effect on crankcase compression from running larger intake duration because there is less time for the piston to compress the volume of the crankcase. IMO run the shortest intake duration possible.

 

[RIDE-RED 350r]

Good stuff to chew on guys, cheers!

 

[XP_Slinger]

Talk about an All-Star team talking about porting in here. Great stuff guys

 

[RIDE-RED 350r]

Well my new WJ-71 carb arrived yesterday, all I had to do was swap the plastic throttle cable catch from my old carb to the new one. New carb even came with no jet limiters of any kind!

Swapped the new carb in this morning and did a quick no-load tune on it. Saw runs flawlessly, a resounding success! Hoping to try it in some wood before the weekend is over but we have a birthday gathering for my mom later today and my in-laws are coming for a visit tomorrow.

Just wanted to post up that the new carb straightened out the problem. I believe the seller on eBay that I bought the carb from has several more. I paid $55 shipped for mine. If anyone is interested let me know and I'll post a link. If I recall that listing didn't come up when I searched "Husqvarna 394 carburetor". Seems like I started searching by the carb make and model to find it for the cheaper price. I recall seeing others listed as for the saw pricing about $25 more

 

[Chainsaw Jim]

Here's another sweet option for a good low end gain. Keep your eyes out for an inexpensive used one and give it a try. If I remember right it's pretty much plug and play with the 395 boot. With the 394 block you finish the little passage on the carb body and swap plates with the WJ carb. It was an out of the box gain compared to the very good WJ that was on it. I also never used the divider in the carb.

 

[RIDE-RED 350r]

Here's another sweet option for a good low end gain. Keep your eyes out for an inexpensive used one and give it a try. If I remember right it's pretty much plug and play with the 395 boot. With the 394 block you finish the little passage on the carb body and swap plates with the WJ carb. It was an out of the box gain compared to the very good WJ that was on it. I also never used the divider in the carb.View attachment 63962

Yeah there isn't much point in keeping the divider in for application on the 394/5. I'm sure you know this, but it's purpose is to keep clean (non-fuel) air supplied to the strato ports on the XT saws. Very good to know there are other options out there.

 

[RIDE-RED 350r]

Well, I put a few new parts on the '94 today. New OEM starter housing, the recoil spring swap over was fun... Called GKS and ordered would SHOULD be the correct chainbrake spring and spring cover. His database does not show the spring cover or spring as NLA so I'm cautiously optimistic. If/when I get those parts I'll be able to get the new clutch cover installed.

The clutch shoes and drum are well worn on the old girl so I'm going to get a new/good used clutch set in a couple of weeks, but for now it works. I decided to try an 8-pin sprocket on it, I think it will pull it.

Had an oiler issue to work out. It was barfing oil from the clutch area and after a couple of test cuts with the 3 foot bar I discovered that not enough oil was getting to the chain no matter how far I turned the pump up. Pulled the oil pump and figured out I was missing the little o-ring that goes between the pump output and the case. I put an o-ring in that seemed to fit right and problem solved..no more oil mess and the chain is getting plenty of oil now. I don't know if it was missing from the get-go or I discarded the original during tear-down due to condition and forgot to get another...But all said and done, problem solved.

So I did a little test-n-tune cutting on some 20" hard maple. Blocking was a cake-walk for this saw as one might expect. It noodled it with authority too but with the 24" bar. I swapped the 24 back on after getting the o-ring back in the pump outlet and wanted to make sure the problem was solved with the beat up 24" rather than abuse that near new 36" if it didn't work out. I was going to have XP_Slinger take a vid, but the snafu with the oiler put the brakes on making a vid for today. We are planning a cutting day tomorrow and I'll see about getting a vid and posting it up then.

As far as the tune, I have it set to it will 4-stroke without delay if I lift in the cut a little bit. It runs very strong and I believe I can tune it a bit higher than it is and still be safe, but I want to get a little break-in time before leaning it down any more. Not that the RPM is the end-all be-all of tuning, but it spooled 12.9k right after making a cut in the hard maple. I think that's pretty descent for a big cube saw, I'm not sure how high a stock 394 can safely spool. But what I do know is that this saw has alot more attitude than the stock 395 and BG deleted 394 at my workplace. All in all, I think this build is success!

Port timing is 98/116/80 with 210psi compression, running 8-pin I'm leaving the ignition timing at stock for now, but it's likely I'll shave the key some to advance the timing down the road a piece.

 

[decableguy2000]

If you dealer doesn't have the spring I may have one. The dust cover my be in someones old stock. I tried to modify one from the new style but never finished. I ended up finding a new OEM cover for mine for cheap on Ebay.

 

[RIDE-RED 350r]

If you dealer doesn't have the spring I may have one. The dust cover my be in someones old stock. I tried to modify one from the new style but never finished. I ended up finding a new OEM cover for mine for cheap on Ebay.

Well the spring is on it's way, the cover is NLA as has been stated.

Looking at the newer style cover and my old style clutch cover, I think I can modify the new style spring cover to work.

So, what do you 394 gurus have to say on the subject of RPM after porting and compression mods? I'm certainly not going to get out of control with the screwdriver chasing a high number. Just curious as to what other modded 394's are safely (generally speaking) capable of? Also, what would be the limit where the internals are being asked a bit too much of? It's my estimation that larger displacement generally means lower safe peak RPM. My ported 372 is capable of 14.4k while still retaining a bit of 4-stroking. I don't think I would ask this of the 394. Thoughts?

 

[Lightning Performance]

I'm no Husqy guy but my work saws over 90 are all set around 13k I'd guess. Never put a tac on them. Tune and cut. The medium saws get a lil H touch if it's small slash. Never the big ones. When the 36 comes out tune to suit the day and the cut at hand like you do.
K.I.S.S.

 

[Big1066ih]

Believe @mdavlee said 13.3k for mine

 

[mdavlee]

13.3-13.5k is what I tune them for working. 14-14.5k for playing

 

[RIDE-RED 350r]

13.3-13.5k is what I tune them for working. 14-14.5k for playing

So it's right where it should be after the mods taching 12.9k, 4-stroking readily with the tell-tale signs that there is room to crank it up a bit more. Good to know, thanks Mike.

I know how my 372 sounds at 14.4k, hard to imagine that big ol' 90-fo hitting that! (Enter Jason stage right with another kick-ass 394 vid)

 

[RIDE-RED 350r]

I'm no Husqy guy but my work saws over 90 are all set around 13k I'd guess. Never put a tac on them. Tune and cut. The medium saws get a lil H touch if it's small slash. Never the big ones. When the 36 comes out tune to suit the day and the cut at hand like you do.
K.I.S.S.

Absolutely, I'm not looking to chase after sky-high numbers here. It's my first experience with a modded 90+cc saw and was just looking for some guidelines so to speak.

The cutting @XP_Slinger and I worked on Sunday didn't call for use of the 394 except to make quick work of flushing off a descent size stump low to to the ground. I couldn't see making a vid of 394 cookies with 14" wood... LOL! It runs very strong and as soon as I get into some good sized stuff to really test it I'll get a vid. Sunday just wasn't the day for that with what we were cutting. We had fun with the 357's though. A ported 357 really puts a smile on my face.

 

[mdavlee]

395 at 13.7k. I've had 372 over 16k and 460 to right at 17k.

 

[RIDE-RED 350r]

395 at 13.7k. I've had 372 over 16k and 460 to right at 17k.

Man that's impressive, the vid and the statement that accompanies it!

Oh, and I'm more than happy to have you post a kick-ass 394/5 vid too

That 395 sounds plenty safe at 13.7k. I see why you can tune it to 14k+ for play, you definitely have some wiggle room there. I'll experiment with mine a little bit once it gets a tank or two through it

 

[mdavlee]

Man that's impressive, the vid and the statement that accompanies it!

Oh, and I'm more than happy to have you post a kick-ass 394/5 vid too

That 395 sounds plenty safe at 13.7k. I see why you can tune it to 14k+ for play, you definitely have some wiggle room there.

That's a Zoo City saw there.