Porting Farmertec 372xp BB

[morbius18]

I'm working on porting a few husqvarna cylinders to test on my saw. It's a 365sp and I got it dirt cheap with a bad crank. Cylinder had some transfer and it needed a new piston.

On the OEM 48mm cylinder, I widened the ports, opened up the lower transfers, slightly widened uppers, opened up intake and exhaust, port matched and modded muffler

The numbers for the 48mm are:
Intake: 75*
Exhaust 105*
Transfer 120*

It ran really well.

I pulled it to lower the intake to around 80*

I got a good deal on an OEM 50mm 372xp p&c, so I figured that I'd pick up a farmertec 52mm to test.


I've finished with the intake ports on these and moved to the exhaust.

This is where I'm confused.
The 52mm farmertec with the intake done is:
Intake: 82*
Exhaust: 104*
Transfers: 128*

I'm shooting for the exhaust to be around 100*, so should I slightly raise the exhaust port? Or the exhaust and transfers together to keep the blowdown close? The squish is bad with the china special at .037 without gasket, so I'm trying to keep all the compression that I have on this.

 

[morbius18]

This is the exhaust opening on the 48mm cylinder, I'll do the same size for the others, but want to try a step on the 52mm.

 

[huskihl]

Your port work looks decent. Every now and then HLSupply will have Tecomec 365 cylinders on sale for about $30. Give one a try sometime.

I'd keep your intake up to around 78

 

[morbius18]

I guess I should say the numbers that I was shooting for.

Intake: 80-82
Exhaust: 100-99
Transfer: 122

With a blow down around 22-23

 

[huskihl]

You'll have plenty of rpm by widening the exhaust. I'd leave the ex down. 102-4 22° bd 78 intake

 

[morbius18]

You'll have plenty of rpm by widening the exhaust. I'd leave the ex down. 102-4 22° bd 78 intake

Thanks. I'll give it a try that way. Just have to widen them now.

The farmertec cylinder had a horrible oval shaped intake port, byt the exhaust isn't too bad. I hate most of their cylinders, and probably shouldn't have gotten it, but for 12 plus shipping from china I do not have much in it.

 

[huskihl]

Thanks. I'll give it a try that way. Just have to widen them now.

The farmertec cylinder had a horrible oval shaped intake port, byt the exhaust isn't too bad. I hate most of their cylinders, and probably shouldn't have gotten it, but for 12 plus shipping from china I do not have much in it.

Same saw, same chain, next day. Using the numbers above

 

[Gypo Logger]

Nothing to lose in trying the BB Farmertec, I have at least 9 out there, but don't use their wrist pin clips.
I've had three that worked their way out or broke and destroyed the piston.
The best one I have is on a 362xpg small mount casing. It makes the trees piss their roots.

 

[Mike Gott]

You'll have plenty of rpm by widening the exhaust. I'd leave the ex down. 102-4 22° bd 78 intake

That’s with a RWJ on I’m sure? Or don’t that make much difference? It sure did when I put it the one Allen did for me. His #’s are pretty close to yours other than the intake is at 83*, my brothers is at 78* and don’t run like mine. But yours runs real nice

 

[huskihl]

That’s with a RWJ on I’m sure? Or don’t that make much difference? It sure did when I put it the one Allen did for me. His #’s are pretty close to yours other than the intake is at 83*, my brothers is at 78* and don’t run like mine. But yours runs real nice

Yes. Rwj. Same carb in both vids

 

[morbius18]

Nothing to lose in trying the BB Farmertec, I have at least 9 out there, but don't use their wrist pin clips.
I've had three that worked their way out or broke and destroyed the piston.
The best one I have is on a 362xpg small mount casing. It makes the trees piss their roots.

The clips go into the garbage as soon as I open the box. Was the compression decent on those you have done?

 

[morbius18]

Same saw, same chain, next day. Using the numbers above

That is much faster. Is there a reason you use the 365sp 48mm over the 372xp 50mm?

 

[morbius18]

Yes. Rwj. Same carb in both vids

I probably have the least desirable carb also, the zama. Is the xtorq RWJ a better option than the HD ones?

 

[Gypo Logger]

The clips go into the garbage as soon as I open the box. Was the compression decent on those you have done?

Yes, the comp was good, although I don't have a tester to prove how much. On most of them I did a gasket delete.I looked through all my old stuff and found at least 8 372/365 jugs and pistons in various condition with casings that I will be playing with this winter.

 

[morbius18]

You'll have plenty of rpm by widening the exhaust. I'd leave the ex down. 102-4 22° bd 78 intake

So it appears I'm going to have to raise the exhaust port slightly to correct it, and give a arch to it. Top is FLAT. It looks like an upside down port. It isn't even either, higher on one side than the other. I can widen it 2mm on each side and still be at 63% bore opening. It would leave about 1.5mm space on each side of the piston.

Farmertec exhaust port shape:


Bore with square markings, It looks like a blind chinese slow kid did this port. Bevels are really bad too:



Exhaust opening size:

 

[huskihl]

That is much faster. Is there a reason you use the 365sp 48mm over the 372xp 50mm?

I was making a gtg saw, and 65cc fits in the 4 cube class

I probably have the least desirable carb also, the zama. Is the xtorq RWJ a better option than the HD ones?

The RWJ is much bigger, but it's much more problematic. It has a divider in it where the top half is just air and the bottom half is for air with fuel. The jetting isn't quite right when not used on a strato saw

 

[Mike Gott]

I was making a gtg saw, and 65cc fits in the 4 cube class


The RWJ is much bigger, but it's much more problematic. It has a divider in it where the top half is just air and the bottom half is for air with fuel. The jetting isn't quite right when not used on a strato saw

What sort of problems do you experience? All I’ve noticed is they are a lot more finicky tuning them

 

[huskihl]

What sort of problems do you experience? All I’ve noticed is they are a lot more finicky tuning them

Its not an issue cutting small diameter wood when the rpm's are up. It's when I stuff it with a long bar and aggressive chain. Possibly due to the richer tune running a longer bar. If it bogs at full throttle and I hold the trigger wfo, it floods and is slow to recover. Like when you get chips packed between the bar and chain.I sometimes have to shut the saw off and hold the trigger open while I restart it. It does it on both the 365 and 372. Not so much on the 7900 and 390 as they can take the extra fuel

 

[blsnelling]

That exhaust port is a snagged ring waiting to happen. Yes, you need to raise it. Yes, the transfers have to come up.

 

[blsnelling]

The RWJ is much bigger, but it's much more problematic. It has a divider in it where the top half is just air and the bottom half is for air with fuel. The jetting isn't quite right when not used on a strato saw

Iv'e had no problem using them on other saws including 372, 390, & 395.