Echo 490 to ported 4910…to cs-5484

[Ketchup]

Before piston mod:

After piston mod:

Sorry for the loose test log. Somebody went wild and cut our entire lot into firewood (me). It’s hard apple and flares away from the camera.

 

[Ketchup]

Not the best videos but you can hear the improvement as much as see it. But I still can’t dig it in like I want.

What do people think? Push the uppers a little higher? I want a bit more torque.

 

[farminkarman]

Not the best videos but you can hear the improvement as much as see it. But I still can’t dig it in like I want.

What do people think? Push the uppers a little higher? I want a bit more torque.

Can't remember....did you try advancing ignition timing at all? On the 4910 I did, I wasn't able to do any advance...perhaps a 490 needs it?

 

[Dolkitafreak]

Can't remember....did you try advancing ignition timing at all? On the 4910 I did, I wasn't able to do any advance...perhaps a 490 needs it?

I’ve never had a light on a 490, probably worth a try!

It’s better for sure, I think there’s more to be had yet. Not sure if higher trans will help or not.

 

[drf256]

I like the piston and extension mod. That was an area I had forgotten on mine and had to go back in for. Good work.

I can’t remember what your new numbers are, but you reduced case compression between the extension and piston modification.

Id raise the transfers for that reason, you lost some pressure, even with your 50*+ of case compression.

Pointing the intake towards the lowers won’t do a thing, pressure is pressure in the case once the skirt closes the intake floor.

My guestimometer puts you right near what Greg is saying. 105 ex and 122/125 on the transfers. Maybe even 120/122.

If you have an extra slug, you can try the old notching the crown trick and see if it keeps gaining as you raise them.

 

[Red97]

I may have missed it, what did you do for a muffler mod?

 

[thedude74]

Right now, I think the problem was an oversight on my part. I came to it a few days ago, but only got to fixing it last night. @Dolkitafreak , you mentioned it, but at the time I didn’t know what you meant. I think this is why Echo went to the windowed piston. The 490 was killing transfer flow too early. A simple mod to the skirt seems more called for than full windowed piston, it would be interesting to run both in the same saw.
View attachment 365310

Haven’t run this yet, but I’m confident it will be an improvement. I’ve also been running an 8pin. Not sure if this little saw can handle that. More test cuts, then we’ll see about taking the transfers highe

I did the piston quite similar on my cs490 based on Doc's @drf256 earlier findings.
Currently at 107 exhaust 65%, 125(no stagger) 75 JB welded intake floor ...widened a bit over stock. .040" off the base and .020" squish.
Cut the t restricter out of the intake elbow and blended a bit.....runs pretty strong about 1/4 to 1/2 turn in on the H needle after hitting the limiter @13,600. Muffler is about 70% of exhaust port.....id really like an unlimited coil.

Take my findings with a grain of salt....Im just a firewood hack with a dremel, some files and big dreams. Lol

 

[Ketchup]

I did the piston quite similar on my cs490 based on Doc's @drf256 earlier findings.
Currently at 107 exhaust 65%, 125(no stagger) 75 JB welded intake floor ...widened a bit over stock. .040" off the base and .020" squish.
Cut the t restricter out of the intake elbow and blended a bit.....runs pretty strong about 1/4 to 1/2 turn in on the H needle after hitting the limiter @13,600. Muffler is about 70% of exhaust port.....id really like an unlimited coil.

Take my findings with a grain of salt....Im just a firewood hack with a dremel, some files and big dreams. Lol

Those numbers are very similar to mine now. Raised transfers to 125 last night. We’ll see!

I may have missed it, what did you do for a muffler mod?

So far it’s single port. Not quite double the size of the hole left when I removed the pipe. Darn muffler melted onto the scabbard in our bucket truck. Had to burn the plastic off with a torch.

FWIW, I replaced the original screws that held the deflector with 3mm hex heads. Lots of those on this saw and the original phillips were stripping already.

 

[Woodpecker]

Those numbers are very similar to mine now. Raised transfers to 125 last night. We’ll see!


So far it’s single port. Not quite double the size of the hole left when I removed the pipe. Darn muffler melted onto the scabbard in our bucket truck. Had to burn the plastic off with a torch.
View attachment 366461
FWIW, I replaced the original screws that held the deflector with 3mm hex heads. Lots of those on this saw and the original phillips were stripping already.

Yeah I did that too those Philips screws striped way too easy.

 

[Dolkitafreak]

Yeah I did that too those Philips screws striped way too easy.

If you heat the muffler and tap on them some it seems to help a lot. Flat blade screwdriver seems to fit better.

 

[Woodpecker]

If you heat the muffler and tap on them some it seems to help a lot. Flat blade screwdriver seems to fit better.

I used a little heat and got them out. Then I just did the same as ketchup and haven’t touched them since.

 

[Red97]

Those numbers are very similar to mine now. Raised transfers to 125 last night. We’ll see!


So far it’s single port. Not quite double the size of the hole left when I removed the pipe. Darn muffler melted onto the scabbard in our bucket truck. Had to burn the plastic off with a torch.
View attachment 366461
FWIW, I replaced the original screws that held the deflector with 3mm hex heads. Lots of those on this saw and the original phillips were stripping already.

I would add 1 to the other side as well. Needs to flow.

 

[thompsoncustom]

How does your muffler exit hole compare to your exhaust port size?

Same with the intake side? Hows the intake boot, air filter plastic, and carb compare to your intake port size.

 

[Dolkitafreak]

How does your muffler exit hole compare to your exhaust port size?

Same with the intake side? Hows the intake boot, air filter plastic, and carb compare to your intake port size.

Muffler hole is smaller than exhaust port by a fair amount, dual ports are certainly a gain on them unless you go much bigger than stock deflector.

Intake side is adequate for 50cc, the WT is a small venturi but they can still make power for sure.

 

[Ketchup]

Muffler hole is smaller than exhaust port by a fair amount, dual ports are certainly a gain on them unless you go much bigger than stock deflector.

Intake side is adequate for 50cc, the WT is a small venturi but they can still make power for sure.

My muffler exit is roughly 100% of exhaust port area, but the sound is pretty muffled, so maybe it’s still not flowing enough.

Everyone acknowledges the carb is a point of constriction on these saws. I believe @drf256 tried to bore one but discovered the fuel passages are very close to the stock bore. Drilling the main jet may help. I’m turned out surprisingly far on my H needle.

Driving the wife’s car right now and there’s a strict “no chainsaws in my nice car” rule. Testing has to wait a few days until I’m back in the truck.

 

[thompsoncustom]

My muffler exit is roughly 100% of exhaust port area, but the sound is pretty muffled, so maybe it’s still not flowing enough.

Everyone acknowledges the carb is a point of constriction on these saws. I believe @drf256 tried to bore one but discovered the fuel passages are very close to the stock bore. Drilling the main jet may help. I’m turned out surprisingly far on my H needle.

Driving the wife’s car right now and there’s a strict “no chainsaws in my nice car” rule. Testing has to wait a few days until I’m back in the truck.

there was a member on one of the chainsaw forums that took a muffler and welded it closed and then slowly kept opening it up all the way to 400% of the exhaust port and recording the differences and gains. 125% to 150% seemed to be the sweet spot tho there was a small increase from 150% to 400% there was also a down side past 175% of the exhaust port it was having idling issues. I believe the saw was a ms260 but I'm not 100% sure.

as far as the intake goes I know when I ported my ms260 it was ok but it became a whole another animal when I put a ms460 carb, 038 intake, and vstack/filter.

 

[Ketchup]

there was a member on one of the chainsaw forums that took a muffler and welded it closed and then slowly kept opening it up all the way to 400% of the exhaust port and recording the differences and gains. 125% to 150% seemed to be the sweet spot tho there was a small increase from 150% to 400% there was also a down side past 175% of the exhaust port it was having idling issues. I believe the saw was a ms260 but I'm not 100% sure.

as far as the intake goes I know when I ported my ms260 it was ok but it became a whole another animal when I put a ms460 carb, 038 intake, and vstack/filter.

Muffler outlet size varies enormously from one model to another and the porting matters too. I’ll zap a second deflector on the FW side. If it hurts I can always add screens.

The cylinder is very different on the 4910 but the intake shares issues with the 026/260. WT carb, overly tight carb box, restricted filter. I would like to keep the filter cover on if possible. We’ll see if I made gains with the transfer bump. If not I may get angry and cram an HDA in there hatchet style.

 

[thompsoncustom]

Muffler outlet size varies enormously from one model to another and the porting matters too. I’ll zap a second deflector on the FW side. If it hurts I can always add screens.

The cylinder is very different on the 4910 but the intake shares issues with the 026/260. WT carb, overly tight carb box, restricted filter. I would like to keep the filter cover on if possible. We’ll see if I made gains with the transfer bump. If not I may get angry and cram an HDA in there hatchet style.

Looking at the carb for the 490 I bet the HDA-12 like what I just used on my wildthing would drop in there nicely.

Ya I really wanted to keep my air filter cover on my ms260 too but I ran it with a modify stock filter vs a V-stack and a 45 degree cone style filter and the gains were just to much to run the stock setup, but like you said there not the same engine/design so maybe you'll get away with it.

 

[Ketchup]

Looking at the carb for the 490 I bet the HDA-12 like what I just used on my wildthing would drop in there nicely.

Ya I really wanted to keep my air filter cover on my ms260 too but I ran it with a modify stock filter vs a V-stack and a 45 degree cone style filter and the gains were just to much to run the stock setup, but like you said there not the same engine/design so maybe you'll get away with it.

The carb box is pretty small. I think you could only run an HD carb if you left the cover off. Getting the rear horn on would be a challenge even then. For most any carb other than stock the boot will have to be changed. The bore is too small to accommodate a larger butterfly. The stock boot is quite short. I haven’t found one that short in a larger bore.

I ran the saw yesterday. Definitely better! I still don’t like the 8 pin. Or my bar and chain. I was on the clock wrenching on chippers so I couldn’t do proper timed cuts. I’ll try to make a video on Monday.

 

[Dolkitafreak]

The carb box is pretty small. I think you could only run an HD carb if you left the cover off. Getting the rear horn on would be a challenge even then. For most any carb other than stock the boot will have to be changed. The bore is too small to accommodate a larger butterfly. The stock boot is quite short. I haven’t found one that short in a larger bore.

I ran the saw yesterday. Definitely better! I still don’t like the 8 pin. Or my bar and chain. I was on the clock wrenching on chippers so I couldn’t do proper timed cuts. I’ll try to make a video on Monday.

It is very short. I bolted a WJ onto stock boot and butterfly operated but you have zero chance of getting a filter horn on it. Length of stock boot makes it tough like you mentioned.