New Release: MaxFlow under lid "MINI" Filter Kit for Stihl 500i & 661

[Max-Flow Filters]

For nearly a year, we have been telling MS500i operators about our upcoming "MINI" under cover air filter. Just wanted to share our new product now available worldwide — the MaxFlow MINI Semi‑Pro High‑Flow Filter Kit for the MS500i and MS661.
This is a compact under‑cover foam system designed by the original creators of a foam element over a fully sealed support cage. It fits under the stock cover (lid) and delivers a big airflow bump for longer cleaning intervals.
Highlights:

• 115 CFM (oiled) airflow (stock HD2 is 65 CFM)
• Up to 3× longer cleaning intervals
• Full‑thickness foam element holds more oil for extra dust holding without reducing CFM
• Drop‑in fit using the stock sealing system, no gaskets or O-Rings needed
• Low cost, no glued seam replacement filter elements are Made in Oregon, USA
• Semi-Pro refers to any user running less than 10 tanks of gas a week, not skill level. Our 500i MAX Kit (135 CFM) is still available for Pro users

Great option for anyone cutting in dusty conditions or wanting more consistent performance throughout the day, but would like to keep the stock look.
Product link: https://maxflowfilters.com/shop-all...ow-filter-kit-for-stihl-ms500i--ms661-fu59bpa
Anyone planning to try one?

 

[kalispell365]

Two of your competitors (Egan Performance first and then West Coast Saw) have had a setup very similar setup for some time already. Are all the pieces in your kit made in the USA?

 

[Max-Flow Filters]

Kalispell365, thanks for the question. Yes—every component in our MaxFlow kits is designed and manufactured in the USA. All filter elements are produced here in Oregon, and we design and fabricate every part of our system in‑house rather than relying on imported or repurposed pieces.

Regarding the comparison: MaxFlow filters are engineered using the stock HD2 filter and our Pro‑Series MAX cage kits as the performance benchmark. It would be simple to shrink a filter to go under a stock lid and we could have done that years ago, but that’s never been how we operate. Fitting a MaxFlow under a stock cover, with no performance drop, took some time to achieve. But we now offer the perfect balance of oil retention, high airflow (CFM), and surface area. The MaxFlow "MINI" for Stihl 500i and 661 chainsaws has met our expectations across the board.

A few key points from our FAQ that highlight what sets MaxFlow apart:

• Over 40 years of trust and tens of thousands of kits sold.
• Two U.S. patents establishing MaxFlow as the original inventor of the cage‑supported foam chainsaw filter with sealed endwalls.
• Purpose‑built filtration—not a repurposed pre‑filter or sleeve.
• Proven superiority in oil capacity, particle retention, and engine protection, backed by years of testing.
• The only filter supplier that designs and builds all components of its kits, with filter elements manufactured in Oregon for durability and quality control.
• Decades of flow‑bench testing behind every design—no other chainsaw filter matches MaxFlow airflow or testing standards.
• High‑volume covers for Pro and Legacy Series kits, ensuring full protection in harsh conditions. Our black Pro Series covers are widely used by professionals in the field.

 

[sawmikaze]

Do you still have to hack on the 500 kit to get it to fit properly?

 

[Woodslasher]

Do you still have to hack on the 500 kit to get it to fit properly?

I don't know what hacking you're talking about, but a year or so ago I bought a Maxflow kit for my 500i and it fit excellent. No mods required. I've gotta make sure the little ears line up right, that's it.

 

[sawmikaze]

I don't know what hacking you're talking about, but a year or so ago I bought a Maxflow kit for my 500i and it fit excellent. No mods required. I've gotta make sure the little ears line up right, that's it.

That's great.

But the one I bought in October of 2022 I had to dremel out the shroud to make it fit.

 

[singinwoodwackr]

That's great.

But the one I bought in October of 2022 I had to dremel out the shroud to make it fit.

Mine even had instructions

 

[Duane(Pa)]

This is New, so whatever you got in 22 is probably obsolete old news by now...

 

[sawmikaze]

This is New, so whatever you got in 22 is probably obsolete old news by now...

The maxflows I had for 440/60's never changed. They weren't ever obsolete or "old news". They haven't changed since their inception. If they have I hope someone fills me in.

This new under the stock cover is obviously different...but if the current 500 kit with the cover included is now plug and play it's clearly different than it was when it came out.

Or maybe I got a factory lemon...

 

[Woodslasher]

That's great.

But the one I bought in October of 2022 I had to dremel out the shroud to make it fit.

Might be that I had to trim a few spots, it's been going on 3 years and saw mods are very low on the list of things I remember. I seem to vaguely remember trimming a top cover a bit with a pocket knife or drywall knife, it might've been on the 500i.

 

[Stump Shot]

I have an unrelated question for @Max-Flow Filters have/would you consider offering covers in both colors? On numerous occasions the opposite color was wanted for the filter cover. I'm reminded of this having yet another such a request currently happening, that makes the idea fresh on the sure would-be nice list.

 

[huskihl]

The maxflows I had for 440/60's never changed. They weren't ever obsolete or "old news". They haven't changed since their inception. If they have I hope someone fills me in.

This new under the stock cover is obviously different...but if the current 500 kit with the cover included is now plug and play it's clearly different than it was when it came out.

Or maybe I got a factory lemon...

The original 500 cover was a modified 661 cover I believe, but it leaked in the rain. And then a couple years ago they redesigned it so that it fit better. The latest one would be the third iteration if it fits under the stock cover

 

[sawmikaze]

The original 500 cover was a modified 661 cover I believe, but it leaked in the rain. And then a couple years ago they redesigned it so that it fit better. The latest one would be the third iteration if it fits under the stock cover

As I understand it this new "under the stock cover kit" is a semi-pro usage where as the kit they offer with the cover is for more intensive use.

But, I'm slow.

 

[sawmikaze]

Might be that I had to trim a few spots, it's been going on 3 years and saw mods are very low on the list of things I remember. I seem to vaguely remember trimming a top cover a bit with a pocket knife or drywall knife, it might've been on the 500i.

It could also be that I'm slow.

 

[singinwoodwackr]

What was the question?

 

[Woodslasher]

As I understand it this new "under the stock cover kit" is a semi-pro usage where as the kit they offer with the cover is for more intensive use.

But, I'm slow.

That's my take on it too.

 

[sawmikaze]

That's my take on it too.

So...

There are now 2 options from max-flow for a 500i.

1 - this new kit for less frequent use, fits under the stock cover.

2 - the other kit that includes the cover (which apparently has been updated at some point if it no longer requires any modification to fit) for more frequent use.

Not bad for special education, eh ?

 

[huskihl]

So...

There are now 2 options from max-flow for a 500i.

1 - this new kit for less frequent use, fits under the stock cover.

2 - the other kit that includes the cover (which apparently has been updated at some point if it no longer requires any modification to fit) for more frequent use.

Not bad for special education, eh ?

Not bad, Ed.
Not bad

 

[sawmikaze]

Not bad, Ed.
Not bad

Thanks, Tom.

It's helpful interacting with a linguistic intellectual like you.