Part Two: The Intake Port

[Powerstroke Cowboy]

What are the port timing numbers now?

That's a good question. Hopefully I can get them tomorrow sometime. Waiting for the 1/2 drill chuck to finish building my timing wheel setup. All my past saws just had the ports cleaned. Going all in on this one.

 

[Powerstroke Cowboy]

What are the port timing numbers now?

Got the chuck today. Here are the port timing numbers.

69/127/101

 

[farminkarman]

Got the chuck today. Here are the port timing numbers.

69/127/101

Wow, 58 degrees of case compression. I have never worked on or ran a 3120 or an 880, so I am curious to hear what the pros say for this class of saw. I would have to think the upper transfers could be raised a bit and the intake lowered....I won't throw numbers out because it would be a guess that could easily be wrong.

 

[Canadian farm boy]

The last 880 I did I went with 78/122/101 with a 084 intake boot and a 361 coil. The saw had small saw throttle response, tuned nicely and pulled like a mule. Squish was set at .025 and I filed .020 off the flywheel key. Obviously the muffler was also modded.
Kinda conservative by some guys but it was going to be a milling/stump saw

 

[huskihl]

The last 880 I did I went with 78/122/101 with a 084 intake boot and a 361 coil. The saw had small saw throttle response, tuned nicely and pulled like a mule. Squish was set at .025 and I filed .020 off the flywheel key. Obviously the muffler was also modded.
Kinda conservative by some guys but it was going to be a milling/stump saw

That’s exactly where I would build it also for that purpose

 

[Mastermind]

The last 880 I did I went with 78/122/101 with a 084 intake boot and a 361 coil. The saw had small saw throttle response, tuned nicely and pulled like a mule. Squish was set at .025 and I filed .020 off the flywheel key. Obviously the muffler was also modded.
Kinda conservative by some guys but it was going to be a milling/stump saw

This is perfect.

 

[Mastermind]

It's amazing just how little grinding it takes to get these things to come alive. I'm doing a mess of a 088 now. Using a new style MS880 case.....and finding the the flywheels seem to have different timing. Just test ran it today....and it wouldn't rev.

 

[Powerstroke Cowboy]

The last 880 I did I went with 78/122/101 with a 084 intake boot and a 361 coil. The saw had small saw throttle response, tuned nicely and pulled like a mule. Squish was set at .025 and I filed .020 off the flywheel key. Obviously the muffler was also modded.
Kinda conservative by some guys but it was going to be a milling/stump saw

I did see your build on the ms880. That is if the one on here is the one you speak about.

Thank you for posting up what you for port timing. The saw looked and sounded like it ran good.

I do have a 084 intake boot for the saw, an unlimited coil is on order, squish is already set for .025. Now just to get the ports where they need to be. I believe my exhaust will end up around 100 due to just cleaning up the roof of the port.

I do not have a 90 attachment so transfer ports will either stay the same or I will relive the piston where the port is to get the same port timing. Right now even with the piston at BDC the transfer Portis not fully opened. So if it's okay to notch/relieve the piston to get the same transfer timing you did, that would also help get the port open at BDC.

On the intake port. If it's not a problem I might not take it as far as you to keep crank pressure up to help with pushing the air through the transfer ports since I will not be able to open them as much as you did. What are your thoughts on that?

How did you determine the amount to take off the key for ignition timing?

Last question for now. Whats a stump saw? Is that another term for a saw used for felling?

Thanks for you expert opinion! I appreciate it a lot!!

That’s exactly where I would build it also for that purpose

Thank you for the added confirmation!

This is perfect.

Thanks for the confirmation. Three of yall agreeing, can't be all wrong! LOL

It's amazing just how little grinding it takes to get these things to come alive. I'm doing a mess of a 088 now. Using a new style MS880 case.....and finding the the flywheels seem to have different timing. Just test ran it today....and it wouldn't rev.

Is there another thread in this series that talks about ignition timing?

 

[farminkarman]

I did see your build on the ms880. That is if the one on here is the one you speak about.

Thank you for posting up what you for port timing. The saw looked and sounded like it ran good.

I do have a 084 intake boot for the saw, an unlimited coil is on order, squish is already set for .025. Now just to get the ports where they need to be. I believe my exhaust will end up around 100 due to just cleaning up the roof of the port.

I do not have a 90 attachment so transfer ports will either stay the same or I will relive the piston where the port is to get the same port timing. Right now even with the piston at BDC the transfer Portis not fully opened. So if it's okay to notch/relieve the piston to get the same transfer timing you did, that would also help get the port open at BDC.

On the intake port. If it's not a problem I might not take it as far as you to keep crank pressure up to help with pushing the air through the transfer ports since I will not be able to open them as much as you did. What are your thoughts on that?

How did you determine the amount to take off the key for ignition timing?

Last question for now. Whats a stump saw? Is that another term for a saw used for felling?

Thanks for you expert opinion! I appreciate it a lot!!

Thank you for the added confirmation!

Thanks for the confirmation. Three of yall agreeing, can't be all wrong! LOL

Is there another thread in this series that talks about ignition timing?

Rather than cutting the piston to open the transfers sooner, might I suggest investing in one of these: https://luckydogmfg.com/products/angled-porting-handpiece-kit
They are made by @srcarr52

 

[Canadian farm boy]

The amount of ignition advance is just a trial and error thing for me. “Most” stihls like .025-.030 off the key but on a big azz 880 they can get mean when trying to start and I wanted to keep the saw easy to start especially if it was on a mill.

Stump saw is exactly that. Used for flush cutting big stumps close to the ground.

If you really want to try and raise the transfers and your patient with a steady hand you can use a couple stacked 1” dremell cut off wheels.

 

[Powerstroke Cowboy]

Rather than cutting the piston to open the transfers sooner, might I suggest investing in one of these: https://luckydogmfg.com/products/angled-porting-handpiece-kit
They are made by @srcarr52

Now that's a pretty piece! Thanks for the link. Cutting the piston would give me the port timing I want plus allow the port to open more. Right now the transfer port will not fully open and I can't help but think it will cause the air to deflect/bounce back and up disturbing the air above it and hinder flow. Am I off on that thinking?

 

[Powerstroke Cowboy]

The amount of ignition advance is just a trial and error thing for me. “Most” stihls like .025-.030 off the key but on a big azz 880 they can get mean when trying to start and I wanted to keep the saw easy to start especially if it was on a mill.

Stump saw is exactly that. Used for flush cutting big stumps close to the ground.

If you really want to try and raise the transfers and your patient with a steady hand you can use a couple stacked 1” dremell cut off wheels.

Okay, Gotcha. This clone might not be the same.

Thanks for the explanation.

That sounds like a good idea. Not saying my hand is steady though!! Lol. Thanks for the idea.

 

[farminkarman]

Now that's a pretty piece! Thanks for the link. Cutting the piston would give me the port timing I want plus allow the port to open more. Right now the transfer port will not fully open and I can't help but think it will cause the air to deflect/bounce back and up disturbing the air above it and hinder flow. Am I off on that thinking?

I think you are mistaken….raising the upper transfers means they will be more open at Bdc just like you would have if you notched the piston.

 

[huskihl]

Now that's a pretty piece! Thanks for the link. Cutting the piston would give me the port timing I want plus allow the port to open more. Right now the transfer port will not fully open and I can't help but think it will cause the air to deflect/bounce back and up disturbing the air above it and hinder flow. Am I off on that thinking?

Cutting the piston to fit the transfer timing you want messes up your squish clearance and leaves a whole bunch of the charge wasted within the band. Just a heads up

 

[Ketchup]

Now that's a pretty piece! Thanks for the link. Cutting the piston would give me the port timing I want plus allow the port to open more. Right now the transfer port will not fully open and I can't help but think it will cause the air to deflect/bounce back and up disturbing the air above it and hinder flow. Am I off on that thinking?

Many transfer uppers never open completely. If you have the majority of your port area don’t worry about it. It’s not perfect, but few things in life are. Especially clone jugs.

If you want more area stretch your upper towards the intake. (Watch your ring lands).

 

[Mastermind]

Cutting the piston to fit the transfer timing you want messes up your squish clearance and leaves a whole bunch of the charge wasted within the band. Just a heads up

I'd listen to this fella.

 

[Powerstroke Cowboy]

I think you are mistaken….raising the upper transfers means they will be more open at Bdc just like you would have if you notched the piston.

I must not have articulated my reply well. For that, I apologize. Yes, that's why I was thinking/asking about notching the piston. That way it would be like raising the upper transfer, while at the same time allowing more of the transfer port to be open at BDC since the piston blocks part of the port at BDC. Does that make more sense than the first time I tried?

Cutting the piston to fit the transfer timing you want messes up your squish clearance and leaves a whole bunch of the charge wasted within the band. Just a heads up

I hear you. I was thinking more of just a notch right where the transfer port is, not the whole piston. Kind if the same idea as notching the piston to fit the exhaust port roof to get a "flat" port top.

Thanks for your patience. I did choose this clone so if I mess parts up, it's not a big deal. I only paid 489.00 for the kit! LOL

 

[Powerstroke Cowboy]

Many transfer uppers never open completely. If you have the majority of your port area don’t worry about it. It’s not perfect, but few things in life are. Especially clone jugs.

If you want more area stretch your upper towards the intake. (Watch your ring lands).

Thanks for the suggestion. I hear you load and clear. If things where perfect porting would not be needed.

 

[Powerstroke Cowboy]

I'd listen to this fella.

Sound advice.

 

[Mastermind]

I must not have articulated my reply well. For that, I apologize. Yes, that's why I was thinking/asking about notching the piston. That way it would be like raising the upper transfer, while at the same time allowing more of the transfer port to be open at BDC since the piston blocks part of the port at BDC. Does that make more sense than the first time I tried?


I hear you. I was thinking more of just a notch right where the transfer port is, not the whole piston. Kind if the same idea as notching the piston to fit the exhaust port roof to get a "flat" port top.

Thanks for your patience. I did choose this clone so if I mess parts up, it's not a big deal. I only paid 489.00 for the kit! LOL

What he is saying is that when you take a notch out of the piston, you'll have a huge squish clearance in that area when the piston is at TDC. That will cause fuel mixture to be trapped. Tight squish is a good thing.