Tecomec pistons (PORTING HELP)

[Mkinslow]

Gotcha. I remember the widening of the ports from a treemonkey video. Just gotta keep researching a d watching videos. Thanks my friend

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[brandonstclair20]

I would suggest a new thread of change the title to attract more husqvarna 365, 372 gurus


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[Mkinslow]

Good idea bud thanks

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[huskihl]

If it were a Stihl 440 I would want the Ex closer to 100 and the intake in the high 70s, and widen the exhaust 1-2 mm within the piston skirts.

But I think there are tricks with your transfers I'm not familiar with, and those #s may not be the best for your saw.

Someone should chime in who knows this model.

The numbers are similar, but he has a full skirt piston

I'd raise the ex to 103 and leave the upper trsnsfers

 

[Mkinslow]

Pencil marks are port width as of now.

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[RIDE-RED 350r]

Wish I could give you some advice, but my 372 I own that I ported is a 75cc XPW and a completely different topend than your 365. You're on the right track though!

 

[Mkinslow]

No worries my friend. Itll get sorted out.

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[huskihl]

Widen the exhaust and intake to 65% of the bore width but make sure you're at least 1mm from the edge of the skirts. Flatten out the bottom of the intake at 78 and square up the bottom corners a little. If you square them up too much, the bottom corners of the piston will crack open before the floor due to the angled skirts on the bottom of the piston. Match the gasket to the case and transfer that to the lowers.
Try 103 123 78

File away about 1/3 of the flywheel key or until you get about 1/2" of free travel at the outer perimeter of the fw.

 

[Mkinslow]

Thank you for that my friend.

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[smokey7]

Widen the exhaust and intake to 65% of the bore width but make sure you're at least 1mm from the edge of the skirts. Flatten out the bottom of the intake at 78 and square up the bottom corners a little. If you square them up too much, the bottom corners of the piston will crack open before the floor due to the angled skirts on the bottom of the piston. Match the gasket to the case and transfer that to the lowers.
Try 103 123 78

File away about 1/3 of the flywheel key or until you get about 1/2" of free travel at the outer perimeter of the fw.

Very good info here. That xs 365 with the tecomic topend was a real good runner once ported. If those are the numbers used they are good ones.

 

[Mkinslow]

Alright I've figured out how to setup and read the degree wheel. And I've also figured out (by watching masterminds video) how to use the piston ring to get exhaust height and know where to grind too. But how do I get where to cut on intake side?

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[huskihl]

Alright I've figured out how to setup and read the degree wheel. And I've also figured out (by watching masterminds video) how to use the piston ring to get exhaust height and know where to grind too. But how do I get where to cut on intake side?

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Trial and error. I slide the ring in, push it up to hold the piston right at the opening, and mark the cylinder with a sharpie. Grind to the line and degree it again. A degree is about .010-.015"

 

[huskihl]

Alright I've figured out how to setup and read the degree wheel. And I've also figured out (by watching masterminds video) how to use the piston ring to get exhaust height and know where to grind too. But how do I get where to cut on intake side?

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Use the piston ring to double check your transfer timing too

 

[MustangMike]

What I did was to mark the piston at the degree you wanted, and then look at the distance between the bottom of the skirt and your mark. That is not exact, but it will get you close, so go a little conservative. Remember, you can always cut a little more, adding back is tough!

 

[Mkinslow]

I just traced intake port shape onto piston while its sitting at reading, then I moved wheel to where the suggested number might be. Then I measured with caliper and got 2.67mm or .105/inch that the intake needs to be ground down to. ?????? And do I keep the same port shape when I regrind oe should it be flat?

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[huskihl]

I just traced intake port shape onto piston while its sitting at reading, then I moved wheel to where the suggested number might be. Then I measured with caliper and got 2.67mm or .105/inch that the intake needs to be ground down to. ?????? And do I keep the same port shape when I regrind oe should it be flat?

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Widen the exhaust and intake to 65% of the bore width but make sure you're at least 1mm from the edge of the skirts. Flatten out the bottom of the intake at 78 and square up the bottom corners a little. If you square them up too much, the bottom corners of the piston will crack open before the floor due to the angled skirts on the bottom of the piston. Match the gasket to the case and transfer that to the lowers.
Try 103 123 78

File away about 1/3 of the flywheel key or until you get about 1/2" of free travel at the outer perimeter of the fw.

 

[Mkinslow]

Lol. Yep you already said that. Sorry. Thinking too much. Wow

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[MustangMike]

Lol. Yep you already said that. Sorry. Thinking too much. Wow

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Caution, different folks, different technique. I believe TM (and I emulate it) do a broad smile instead of flat, the idea being that the saw will be more responsive and may have a slight hesitation if the intake if flat. Likely also depends on the # you use, but just saying. Also, for the same reason, I often don't widen the intake. I think it depends on the saw how much it needs.

Same with the top of the exhaust, a broad arch, reduces the chance that a ring hangs up. But I don't make the port oval, I make it a little like a trapezoid, a bit wider on the top. I want the exhaust gases to escape ASAP. Usually, the wider the exhaust the better, but the intake may be a balance.

Remember, the exhaust is about 10X the volume of the intake.

 

[Mkinslow]

Caution, different folks, different technique. I believe TM (and I emulate it) do a broad smile instead of flat, the idea being that the saw will be more responsive and may have a slight hesitation if the intake if flat. Likely also depends on the # you use, but just saying. Also, for the same reason, I often don't widen the intake. I think it depends on the saw how much it needs.

Same with the top of the exhaust, a broad arch, reduces the chance that a ring hangs up. But I don't make the port oval, I make it a little like a trapezoid, a bit wider on the top. I want the exhaust gases to escape ASAP. Usually, the wider the exhaust the better, but the intake may be a balance.

Remember, the exhaust is about 10X the volume of the intake.

I gotcha.

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[mdavlee]

Intake shape round for fuel economy and good manners. Square for all out power. I mark on the skirt from bottom and rotate the piston down and then mark it. Measure and grind a little less than the measurement. Everyone judges opening differently too. My 78 might be 80 to someone or 76