ported 365 special

[Frammo]

hi all
have been porting few husky 3 series saws,decked, machined squish,opened exhaust all run around 190 compression....have one big question
for a professional porter....why after porting does the range between lean and rich drop off points (low needle) decrease.saws all run fine but
am interested .thanks

 

[huskihl]

Never noticed a difference. Most saws don’t even need the tune changed once ported. But everyone ports differently. Likely something to do with your intake port or timing

 

[Frammo]

cheers for reply,always tend to have to lean mine out from standard on H..they dont run too bad but just curious.
have played with lot of numbers eg ex 94-100 and inlet tand to stick at 79-80 ...transfers always messing

 

[huskihl]

365 cuts pretty well down around 100-102. No real need to raise it much (unless for a race saw) when you can get the exhaust port 70% as wide as the bore.

 

[drf256]

I’m unclear what you are asking, but if your wondering why a port job on the same saw with the same carb requires the H needle to be leaned, it’s because more airflow through the Venturi pulls more fuel.

It’s counterintuitive. When I put an 044 carb on an 026, the big Venturi and low displacement won’t flow enough air to pull adequate fuel through the carb. I’ve had to drill the standard 68-72 jet orifice up to 82 to get it to run right.

So if you’re pulling more air through the Venturi, you’re pulling more fuel.

Again, I’m a bit unclear on your question.

 

[Frammo]

I’m unclear what you are asking, but if your wondering why a port job on the same saw with the same carb requires the H needle to be leaned, it’s because more airflow through the Venturi pulls more fuel.

It’s counterintuitive. When I put an 044 carb on an 026, the big Venturi and low displacement won’t flow enough air to pull adequate fuel through the carb. I’ve had to drill the standard 68-72 jet orifice up to 82 to get it to run right.

So if you’re pulling more air through the Venturi, you’re pulling more fuel.

Again, I’m a bit unclear on your question.

hi ,original question ...when the saw is standard there is a big range between lean and rich drop off points(tuning L needle) and after porting this range reduces making them a little more finnicky to tune on low end

 

[drf256]

I believe that’s all in the muffler mod. I’ve noted the same thing.

My bet is that it’s part of why the OEM chokes up mufflers. I’ve notice a much wider range of tune with restricted mufflers.

Part of why I like Autotune saws. Harder to burn up.

Is it true tune or different sound? That’s I am not sure of.

 

[Frammo]

I believe that’s all in the muffler mod. I’ve noted the same thing.

My bet is that it’s part of why the OEM chokes up mufflers. I’ve notice a much wider range of tune with restricted mufflers.

Part of why I like Autotune saws. Harder to burn up.

Is it true tune or different sound? That’s I am not sure of.

much appreciated ,will try some variations and see....most are running 80%of exhaust port area..it is a true tune the three i have ,have been running for about 3 years now,just initial set up takes a "trained ear"..thanks agin