Tecomec pistons (PORTING HELP)

[sixonetonoffun]

Card stock works great to protect the cylinder and as a guide. Especially when raising quad transfers.

 

[Mkinslow]

Card stock works great to protect the cylinder and as a guide. Especially when raising quad transfers.

Man I been watching a lot of videos from mastermind ,treemonkey and several others on YouTube. Seems there's several ways to do this. I've got some more pieces to gather up and then I'll be ready to start coming to the point of figuring this porting out and getting started.

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[MustangMike]

Unfortunately all of my knowledge is with the dual port Stihls, so I'm no help with specifics to your saw, but I'm sure someone will help you out.

 

[Mkinslow]

Unfortunately all of my knowledge is with the dual port Stihls, so I'm no help with specifics to your saw, but I'm sure someone will help you out.

No worries bud. I believe several will be able to help me out. I been wanting to figure this out for a while now. Thanks for your help so far and in the future lol.

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[Mkinslow]

Do these numbers seem remotely accurate?

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[Mkinslow]

This is my 365 with right at a years run time. Keep in mind I dont cut a terrible amount. Mostly fire wood for the shop and cutting for others that need it. So around 20-30 tanks on this saw.

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[huskihl]

When you figure your intake timing, it's from the time it opens til it closes. 67° opening should be 134° duration.
I figured with no gasket that they were around 73 or 74

 

[Mkinslow]

Lol I'm an idiot. I read the wheel backwards. Its setting on 73*

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[Mkinslow]

But at 73* I get 214 duration. Is that right. From what I've been reading you take the timing number and times by 2 then subtract that number from 360 and that's the duration number. Maybe I missed something.

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[Mkinslow]

I'm finding my tdc then rotating same way as saw is running till EX just starts to open, then rotating till top of piston starts coming down to just the top of transfer,then still rotating in same direction I rotate till I see skirt coming up to bottom of intake.
I'm I supposed to come all the way up and then back down to get intake.

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[MustangMike]

I believe since the intake opens from the bottom, it is just the # X 2.

 

[Mkinslow]

That's what I thought I read but I'm not sure now lol.

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[Mkinslow]

So the numbers are better like this?

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[MustangMike]

The degree wheel I printed goes from 0 - 180 in both directions, so the direction you spin it does not matter. You should get the same # both ways.

 

[huskihl]

Yep Mike's right. Intake is the easy one
Just double the number

 

[Mkinslow]

Good deal so I've got that part figured out. Now I gotta figure out what to do with the numbers to make improvements if at all possible or when to just leave it alone. All I've done to this cylinder is clean up the casting lines and smooth it out.

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[MustangMike]

Now is when you need someone more familiar with your model saw. Me giving you advice for a Stihl won't help you here.

 

[Mkinslow]

Now is when you need someone more familiar with your model saw. Me giving you advice for a Stihl won't help you here.

Your good bud. Any help figuring this out is good with me.

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[Mkinslow]

I thank both of you for your help so far.

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[MustangMike]

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.