MillerModSaws plays with 440R/046D Hybrid

[Mastermind]

I found something several years ago that seems to work pretty well. The tighter the transfer tunnels, the lower the opening point needs to be.

For instance, on a two port engine, I might use 118, and have went as high as 114. On a quad port engine like the 390XP though, I will probably use 122 as a starting point.

 

[cuttinties]

I see lots of people use 118 for transfer height, what makes this such a good number?

There's a few reasons that's common. First off exhaust height. Common exhaust height on 34-40 mm stroke saws is 100-102. Some guys like 18* blow down and some like 16*. Now another thing that plays a role in this is case compression. This is affected by intake duration and transfer height. The lower case compression is important to free a saw up. But a tame work saw with forgiving power band is going to be in the ball park of 38-45* of case compression. This leaves you with intake durations in the neighborhood of 154-160. So as you're seeing by now there's a lot of numbers that can be used for similar results. The biggest factors when dealing with the transfers is how well the saw scavenges. The better scavenging the more power. This is where you see the difference between saws and power made.

 

[cuttinties]

So when you are building a saw, let's say you have it all back together and run it, how would you determine if you needed to go a few degrees more on tranfer or stay where you are at? Would you be able to notice 3 to 4 degrees?

Changes made in the correct places can be very noticeable in 2* increments.

 

[cuttinties]

Any news on this saw yet?

 

[Deets066]

Any news on this saw yet?

Interested to see how the tweaking turned out as well

 

[MillerModSaws]

I love all the knowledge that has evolved here. Here's what u got.i need some jets or drills lol. I tore it apart cause it would not hold its rpm in the cut. It was four stroking about 11000. Leaned out to 14000 but but just wasn't right. Tore apart and pressure/vac test again. Found a small leak at the comp release. Fixed that and I pulled the main jet out. Used a set of torch tip cleaners to open the jet to the next size. Then I lowered the pop of pressure. I went to much so I need to change that back. It's wanting to flood when warm starting. However it's four stroking hard at 14000 now. So if it wasn't hailing here today I would have got a vid. New tester came in today here's what u got for comp. So I will get a vid and what would you guys like to see. By noodling my firewood it seemed much better. We will see.

 

[cuttinties]

I love all the knowledge that has evolved here. Here's what u got.i need some jets or drills lol. I tore it apart cause it would not hold its rpm in the cut. It was four stroking about 11000. Leaned out to 14000 but but just wasn't right. Tore apart and pressure/vac test again. Found a small leak at the comp release. Fixed that and I pulled the main jet out. Used a set of torch tip cleaners to open the jet to the next size. Then I lowered the pop of pressure. I went to much so I need to change that back. It's wanting to flood when warm starting. However it's four stroking hard at 14000 now. So if it wasn't hailing here today I would have got a vid. New tester came in today here's what u got for comp. So I will get a vid and what would you guys like to see. By noodling my firewood it seemed much better. We will see.

What carb is the saw running?

 

[Deets066]

What do you mean by lowered the pop of pressure?

 

[MillerModSaws]

What carb is the saw running?

The stock 440 carb.

 

[MillerModSaws]

What do you mean by lowered the pop of pressure?

The pop off pressure of the carb.

 

[cuttinties]

The stock 440 carb.

Which one?

 

[cuttinties]

What do you mean by lowered the pop of pressure?

Pop off pressure is the pressure needed to cause the needle to release fuel without any assistance from metering lever. The only thing that I find important is that a carb holds 15 psi wet.

 

[cuttinties]

Which one?

HD 17a, HD 16 or Zama c3m-s5d?

 

[MillerModSaws]

Pop off pressure is the pressure needed to cause the needle to release fuel without any assistance from metering lever. The only thing that I find important is that a carb holds psi wet.

Thank you for answering that. It has an HD17C

 

[cuttinties]

Thank you for answering that. It has an HD17C

I've seen some pretty outrageous saws run with those HDs without drilling. I personally like the Zama (not typically a Zama fan) on the 1128 saws. Drilling jets is the last thing I do to a carb. The first thing is understanding that ports will affect what may seem like carb issues. Intake duration at 156 should not be flowing enough to give you carb issues. I can think of 4 things that I can get more out of a carb without drilling. But I ruined a few carbs learning just the same as you are. You'll never know until you try it. I'm sorry for interrupting your thread. Hopefully we'll see your results soon enough. If you have any questions feel free to shoot me a message.

 

[blsnelling]

I've never had to drill the carb on either a 440, 460, or hybrid. I've had them turn close to 16K, with an intake duration of 170°, without issue.

I did just have to drill a 461 main jet. That was the first time I had a saw demand more fuel than the stock carb could flow. So, rather than purchasing the optional larger jet, I just drilled it.

 

[Mastermind]

I have to drill the main jet on every 461 I do.

 

[KG441c]

I've never had to drill the carb on either a 440, 460, or hybrid. I've had them turn close to 16K, with an intake duration of 170°, without issue.


I did just have to drill a 461 main jet. That was the first time I had a saw demand more fuel than the stock carb could flow. So, rather than purchasing the optional larger jet, I just drilled it.

Brad how could u tell it needed more fuel?

 

[cuttinties]

I have to drill the main jet on every 461 I do.

5100/5105 is another example of saws I have to drill. Just never needed to on the 440 or 460. Doesn't mean it can't happen

 

[blsnelling]

Brad how could u tell it needed more fuel?

I couldn't get it rich enough. The jet simply couldn't flow as much fuel as the saw was demanding. I could barely get the saw below 15K. It would turn 15,800 and still 4-stroke slightly, but I wanted the ability to make it richer for work and for colder temps when more fuel is needed.