Saw builds

[drf256]

Back pressure from restrictive mufflers will play a role on where one sets the transfers.

I bet that's why some saws from the factory had very low blowdown.

My own theory I guess.

 

[jmssaws]

I build mostly one particular saw but I've built strong saws from 15 to 25 degrees of blow down so I don't put much stock in it.

 

[drf256]

Transfer height is more important than calculated blowdown in my head.

Then you need to think about cylinder design, Exhaust area/duration and case compression degrees before arriving at any number that makes sense.

It's the entire picture that matters, even though each brushstroke counts.

 

[Brewz]

The Husky 2100 KS cylinder I measured the other day has 15.5* BD and really high intake.
It also has a very small exhaust port opening with the port tunnel to the muffler being very long with little flare

It measured:

With gasket and .055 squish:
Ex: 105.5
Tr: 121
In: 70

Without gasket and .028 squish:
Ex: 107.5
Tr: 123
In: 71

I am chasing as much advice on what to do with it to make it run its best with bars 42" and over.
At this stage I dont want to touch the transfers. They look really good and should provide great direction and velocity.

I am thinking of sanding a tad off the base and using some thin gasket material to keep squish down in the .020's without needing to use sealant. I want to me able to get the top on and off easily to keep an eye on it. These cylinders dont grow on trees.

What do people recon, and most importantly....... Why?

 

[Tor R]

Back pressure from restrictive mufflers will play a role on where one sets the transfers.

I bet that's why some saws from the factory had very low blowdown.

My own theory I guess.

262 had two very different jugs when it goes to BD, but muffler seems to be the same on them, so that bring me over to why Husky changed the TR timing so dramatic.

 

[Deets066]

The Husky 2100 KS cylinder I measured the other day has 15.5* BD and really high intake.
It also has a very small exhaust port opening with the port tunnel to the muffler being very long with little flare

It measured:

With gasket and .055 squish:
Ex: 105.5
Tr: 121
In: 70

Without gasket and .028 squish:
Ex: 107.5
Tr: 123
In: 71

I am chasing as much advice on what to do with it to make it run its best with bars 42" and over.
At this stage I dont want to touch the transfers. They look really good and should provide great direction and velocity.

I am thinking of sanding a tad off the base and using some thin gasket material to keep squish down in the .020's without needing to use sealant. I want to me able to get the top on and off easily to keep an eye on it. These cylinders dont grow on trees.

What do people recon, and most importantly....... Why?

107 is way to low for 100cc

100cc should be in the 96 to 100 range.
My opinion

 

[Redfin]

Back pressure from restrictive mufflers will play a role on where one sets the transfers.

I bet that's why some saws from the factory had very low blowdown.

My own theory I guess.

Your theory is solid Al. I see it the same way with tiny little muffler openings needing more time to evacuate the gases.

 

[Brewz]

107 is way to low for 100cc

100cc should be in the 96 to 100 range.
My opinion

I agree with the too low bit mate, and appreciate your input. I dont want it too high, it will be a long bar and milling saw so I am not after revs so much. More torque.
I have also been told 102* on the exhaust and to lower the intake a few deg.

Anyone else have any thoughts?

 

[Deets066]

You'd be fine at 102, I'd leave the trans alone and lower intake

 

[jmssaws]

I bet it would have more power with the exhaust in the 90's

 

[Deets066]

I bet it would have more power with the exhaust in the 90's

I think so too

 

[Redfin]

I agree with the too low bit mate, and appreciate your input. I dont want it too high, it will be a long bar and milling saw so I am not after revs so much. More torque.
I have also been told 102* on the exhaust and to lower the intake a few deg.

Anyone else have any thoughts?

Are you planning on any machine work? I can tell you mine at 101 with cut base/squish my starter isnt happy.

 

[srcarr52]

I've learned that quad ports like more blow down than dual ports. I've ran 272's and 288's as low as 16. Most quad ports are happy around 20. Also with short blow down it's important to leave the intake duration a little lower so it has more crankcase compression to decrease the exhaust reversing into the transfers when first opened. So you can't talk blow down without intake and exhaust numbers, muffler size and lots of other things. You have to capture the big picture.

 

[srcarr52]

This saw is 159/119/157 duration or 100.5/120.5/78.5 opening and pulls a long bar like a freight train.

 

[jmssaws]

This one is 98 120 83 was 98 123 83 and I hurt it quite a bit by raising the transfers.

 

[jmssaws]

This one is 101 116 78

 

[Redfin]

This saw is 159/119/157 duration or 100.5/120.5/78.5 opening and pulls a long bar like a freight train.

Pretty dang close to what I put in mine with a 395 piston. Fun saw.

 

[srcarr52]

Pretty dang close to what I put in mine with a 395 piston. Fun saw.

This saw has a 395 piston in it as well.

 

[Brewz]

Are you planning on any machine work? I can tell you mine at 101 with cut base/squish my starter isnt happy.

No not planning on machine work at all.
Just a thinner gasket to reduce squish and adjust the ports to make it run.

Thanks for the input folks. Much to chew on now!

 

[Brewz]

Is there an advantage to the 395 piston or is it just because they are available?