Let's Talk Transfers

[Lightning Performance]

You just replied to a 5 year old post Kenny.

Yup.. sure did

 

[Brewz]

You just replied to a 5 year old post Kenny.

And Ive learnt a couple neat tricks since then

 

[Short Beardy]

While we are resurrecting old threads I'm a Newbie catching up on reading...
Re Dolmar/Makita 6400 - 7900... can the greater BD of the larger cylinder be ascribed to needing to take larger gulps; the lower transfers might help to suck in more charge to better fill the appetites of the larger top end...?

 

[kårekloak]

Anyone have opinions on this transfer shape? Husqvarna 246 open port jug.

 

[Mastermind]

Anyone have opinions on this transfer shape? Husqvarna 246 open port jug.

They work well.

 

[qurotro]

What's the ill effect when raising the trans too much?
I accidentally raise my 372 trans to 119.
Now the jug has 100, 119, 78
The one I did before has 100, 124, 80 and im satisfied.

 

[Mastermind]

What's the ill effect when raising the trans too much?
I accidentally raise my 372 trans to 119.
Now the jug has 100, 119, 78
The one I did before has 100, 124, 80 and im satisfied.
View attachment 365065

Try it. I've used up to 118.

 

[huskihl]

Mine run 19 and 22° BD

 

[Stump Shot]

What's the ill effect when raising the trans too much?
I accidentally raise my 372 trans to 119.
Now the jug has 100, 119, 78
The one I did before has 100, 124, 80 and im satisfied.
View attachment 365065

The short answer is performance backs off and begins to suffer.
As to why that is, it's because not enough exhaust pressure has been bled off and it begins to overwhelm the transfers for a moment until the primary crankcase pressure rises above it. Meanwhile the crankshaft is still moving the piston and our motor looses a little fill time as our "window" of opportunity begins to close.

 

[Maintenance Chief]

Anyone have opinions on this transfer shape? Husqvarna 246 open port jug.

They look alot like the ProMac 700 transfers.

 

[kårekloak]

Indeed. I'm about to open up the intake and exhaust ports on the 246. I always thought the extra power in 242 versus 246 was the transfer shape, but maybe I'm wrong.

 

[Mastermind]

Indeed. I'm about to open up the intake and exhaust ports on the 246. I always thought the extra power in 242 versus 246 was the transfer shape, but maybe I'm wrong.

I think you are right.

 

[kårekloak]

I think you are right.

Is this also why the 246 have more blowdown Randy?

 

[Mastermind]

Is this also why the 246 have more blowdown Randy?

As a general rule, you will usually find that the tighter, or smaller the transfer ports are, the more blowdown the engine has. But not always. Sometimes you can get a lot of gain by going with less blowdown. Just have to test.

 

[Ketchup]

Sometimes no matter what you do the transfers just aren’t as good.

 

[kårekloak]

Hope I'm not that much off topic, but the nubers on the two saws are:
242:
IN 69, EX 111, TR 126
246:
IN 75, EX 104 TR 127

What you say randy will be logic. In my head the 246 should be much more agressive than 242, but that's not reality.