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Chainsaw Porting Theory

jmssaws

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I'm still trying to understand transfer back flow, I've had 1000 saws apart and have never seen carbon built up in the transfers, obviously it can happen but in my mind something has to be wrong for it to happen.
 

XP_Slinger

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I'm still trying to understand transfer back flow, I've had 1000 saws apart and have never seen carbon built up in the transfers, obviously it can happen but in my mind something has to be wrong for it to happen.

I'm curious on this subject as well. I'm going to check my transfers for carbon tomorrow. Currently my 372 X-torq has 21° of blowdown and if I don't see evidence of back feeding I will be raising the transfers back to stock then a little more to compensate for the deleted base gasket. Also plan on widening, not raising the exhaust to maintain the compression gained from deleting the gasket. Baby steps in finding the balance that we are talking about. I'll be updating the 372 de-stratification thread this weekend.

Great thread guys...keep it going!
 

Moparmyway

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I'm still trying to understand transfer back flow, I've had 1000 saws apart and have never seen carbon built up in the transfers, obviously it can happen but in my mind something has to be wrong for it to happen.

Right thread to begin with, added here .......... and here is the same dumb azz, hack, opinionated answer
Heat

I believe that heat from the crown area is dissipated to the underside, and some of the fuel/oil mix gets burned by it. If someone were to look at all things .......... I believe they would see a pattern of the buildup being in the hottest spots, not necessarily transferr inversion

It could be transferr inversion, but at speeds over 10,000 rpm while cutting, I believe the inertia of the incoming charge would win the battle, .......................... my opinion and $0.50 wont get you a cup of coffee

I will add that I have seen carbon built up in one cylinder at the lower transferr ............ it had lots of chips and dust built up around the cylinder fins, which I believe held in enough heat to cook some mix ............ making it appear that the transferrs were getting transfer inversion

Just a hypothesis though
 

Mastermind

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I've been inside a bunch of saws.

Never seen much staining in the transfers. If it was inversion to that degree, most saws would have it rather than a few. I'm sure some inversion occurs, but fresh fuel will wash away the evidence.......unless something else is amiss.
 

jmssaws

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Without a doubt I've had 1000 apart and never have seen it, it happens obviously but not regularly like randy said.

Was it a quad port you seen it in kev?
 

Moparmyway

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Without a doubt I've had 1000 apart and never have seen it, it happens obviously but not regularly like randy said.

Was it a quad port you seen it in kev?
Nope .............. it was an old 046
 

Stihlbro

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Joey, do you remember if either saw had lots of crap in the fins clogging the cooling air ?

440 was clean, typical sawdust. 044 normal, but larger muffler opening. 359 clean. 066 was dirty but not bad.
Stihls were used by loggers.
 

junkman

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The 036 runs great with the intake at 85 or so. I do think it's shape helps with that.....but, I've never taken the time to shorten it either. I wonder....

Here's one for y'all.

044/046 I did several years ago.

It came back to be fixed a few days ago. In the first build, I had trimmed the piston skirt to add intake duration, and it also was running a pop-up piston. There were two broken jug bolts in the base, and it was in need of a lot of parts....

We used one of the aftermarket cases that Dave sells, and while Jon was getting it ready, I was making a new piston for it. The owner loved the way this saw ran, so I was just copying the old piston, and getting it back in service. Jon already had the piston mounted before I realized that the skirt was trimmed......rather than take it back off, I just left it stock.

Tracy killed trees with it for a few days, and it started flooding. He brought it back for us to check out. He said in smaller stuff, or in soft wood, the old saw was faster...but he was in some pretty big chestnut oak.....and in big hard wood the new version was much stronger. He also reported a longer run time per tank. The only complaint he had ever had about the saw was that it was a thirsty bastard.

So, here we can see that it goes right back to giving a user what they want. Faster in small stuff, more intake duration seems to work, but in bigger wood, the shorter duration allows more torque....

I have found the fastest saws are not always the strongest saws ,Sometimes you have to slow down to go fast .
 

XP_Slinger

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@Mastermind Decreasing blow down without increasing exhaust width to get the gases out faster?

Transfer opening too close to intake closing causing lower pressure in the cranks case?
 

Stihlbro

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So.....looks like lots of mixing in the bottom end then?

Why don't I ever see stuff like that?


These cylinders go several years back. Rode hard and put up wet. I'll guarantee they was run on stihl orange bottle oil. My thoughts are a factory restrictive muffler and hours of use contribute.


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