Husky 550xp 545 w/ complete 562xp Intake & Carb

[Flip]

edit: this is just me being curious.
So please don't anyone tear something apart over it!

What's the venturi size of the AT55a?
I can't seem to find it on Zama site.
Zama does list the el48 as 12.5mm.
No surprise that the bores of the airheads (strato valve) aren't listed, just the part number

If no one gives an answer, I'll measure next time I do a tear down. Both my 562 carbs are AT55a.

 

[legdelimber]

Flip, Thanks. I'm curious about the strato stuff and how it'll change modding criteria.
I get the basic touted principles of piston side channels and a intact tract layouts and why the long runners are needed.
Pretty slick idea, I think.

But when folks start to change any of the air flow restrictions (carb or airhead)
I have to wonder when it might tip any important resonances and alter the balance of airhead to carb venturi flows.
Can a slightly too large of a carb venturi start to delay the fuel pickup and cause a weird leanness at certain rpm?
Seems like the carbs are set a fair bit richer than old single tract saws.
I presume that's to balance the Total airflow into the engine and not have the strato cause a lean running condition.
I would expect one could throw a funny tuning issue into things if the carb bore gets very far from the (factory) ratio of flow between the airhead and carb.
The Poulan pp5020 has an almost almost blubbery state (at bit off idle) before the linkage begins to hit the air valve and balance the flows.

sorry for a long ramble just to partially say that I'm curious when the intake tract tuning starts to fall flat, have "dead" spots and give boggy/laggy response or gets really twitchy to tune the carb needles.
I've got ideas of resonance (think something similar to expansion chamber exhaust) affecting fuel atomization and/or puddling if the flow gets to far outtta wack.

The muses run, but I need to see IF I can somehow collect them into something intelligible and post-able.
One drawback to gut feelings is often the lack of a formalized language to express it to others.

 

[Flip]

@legdelimber

I know exactly where your coming from. I've spent hours writing something up only to delete it because I couldn't make a coherent post about the thoughts running thru my head. I wish I could write a post as clearly as you!

I had some of the same questions about the function of the carb with this new setup. I tried to wrap my head around it for a while until I realized that I was thinking about a carb that was adjusted by a nut with an external tool. This carb adjusted itself with the aid of a computer via some sort of piezo tubes type deal. I tried to forget everything I know about carburetors. My thesis was that a new or master reset Autotune computer didn't care one bit if the carb had(making numbers up here) 11% larger bore that was pushing 20% more mix thru it. Those two factors didn't matter or bumping up the carb one size still allowed the computer to operate within its parameters. The fact that this saw fired right up and never stumbled or hiccupped was the one result I never thought would happen.

It always had snappy throttle response also.

 

[Farmchuck]

@legdelimber

I know exactly where your coming from. I've spent hours writing something up only to delete it because I couldn't make a coherent post about the thoughts running thru my head. I wish I could write a post as clearly as you!

I had some of the same questions about the function of the carb with this new setup. I tried to wrap my head around it for a while until I realized that I was thinking about a carb that was adjusted by a nut with an external tool. This carb adjusted itself with the aid of a computer via some sort of piezo tubes type deal. I tried to forget everything I know about carburetors. My thesis was that a new or master reset Autotune computer didn't care one bit if the carb had(making numbers up here) 11% larger bore that was pushing 20% more mix thru it. Those two factors didn't matter or bumping up the carb one size still allowed the computer to operate within its parameters. The fact that this saw fired right up and never stumbled or hiccupped was the one result I never thought would happen.

It always had snappy throttle response also.

This is quite an interesting project to me. I’m no saw mechanic by a long shot but like to run this size saw. Are you basically trying to get 562 performance out of a 545? Is it actually comparable to a stock 562 now? Sounds pretty cool to me!

 

[Flip]

This is quite an interesting project to me. I’m no saw mechanic by a long shot but like to run this size saw. Are you basically trying to get 562 performance out of a 545? Is it actually comparable to a stock 562 now? Sounds pretty cool to me!

I've done the big saw thing and now am looking to run the smallest saw I can get away with. I'm looking to recreate the stump pulling power of the 2 series huskies with the smooth running, fuel sippin' 5 series saws. The 545 is not as powerful as the 562 but it's a lot closer than it was.

On the farm, we've always cut wood to heat all our houses, cleared our land, and are lucky to have an independent sawmill near us so we've always self-logged our farm to keep the lights on during the winter. These clean burning saws are nice not to be sucking down heavy exhaust all day.

 

[Spike60]

Is the CST a paperweight for a civilian like me? I would love to see the data for these saws and at the very least be able to do a master reset. I have run mostly my 550 & 562 the last couple of years as I really like the platform and will be the first to admit that I can't tune an engine better than a computer.

I think you'd be able to do a master or fuel settings reset. But for updates and such the CST has to be linked with the mother ship down in Charlotte.

My own little project is on hold as the bottom end of the donar turned out to be junk this afternoon. Have to scout around and come up with something. Might end up going back into my other thin gasket build, but I really wanted to compare the two of them. Patience usually pays off. Won't be long before something comes in. One of the Lewis guys should have a carcass to mess with. He can have it when it's done. But then they'll all want one just like it. LOL

 

[Spike60]

@legdelimber

I know exactly where your coming from. I've spent hours writing something up only to delete it because I couldn't make a coherent post about the thoughts running thru my head. I wish I could write a post as clearly as you!

I had some of the same questions about the function of the carb with this new setup. I tried to wrap my head around it for a while until I realized that I was thinking about a carb that was adjusted by a nut with an external tool. This carb adjusted itself with the aid of a computer via some sort of piezo tubes type deal. I tried to forget everything I know about carburetors. My thesis was that a new or master reset Autotune computer didn't care one bit if the carb had(making numbers up here) 11% larger bore that was pushing 20% more mix thru it. Those two factors didn't matter or bumping up the carb one size still allowed the computer to operate within its parameters. The fact that this saw fired right up and never stumbled or hiccupped was the one result I never thought would happen.

It always had snappy throttle response also.

The 545 AT module doesn't "know" it's been switched to the 562 carb. Connected with it's original ignition it's still going to do what it was designed to do. In conjunction with the throttle position sensor, (which is the same for both 50cc and 60cc chassis), it is going to meter fuel to maintain RPM's. Under heavy load the larger carb may simply be better suited to keeping the RPM's/power up, where the smaller carb is near the edge of what it can do. And at the same time, the AT will meter less fuel under moderate loads to prevent the larger carb from running too rich and wasting fuel. The coil and module won't allow for any additional RPM's beyond spec, so this is all about grunt in the cut.

 

[AKJonsereds]

I think you'd be able to do a master or fuel settings reset. But for updates and such the CST has to be linked with the mother ship down in Charlotte.

My own little project is on hold as the bottom end of the donar turned out to be junk this afternoon. Have to scout around and come up with something. Might end up going back into my other thin gasket build, but I really wanted to compare the two of them. Patience usually pays off. Won't be long before something comes in. One of the Lewis guys should have a carcass to mess with. He can have it when it's done. But then they'll all want one just like it. LOL

Can’t wait to have a comparison on the 550 saws. Also curious to see a fuel setting comparison? Are these first or second generation saws you will be trying?

Also need someone to try this on a fully ported 550.... for science and stuff.....

 

[Spike60]

Can’t wait to have a comparison on the 550 saws. Also curious to see a fuel setting comparison? Are these first or second generation saws you will be trying?

Also need someone to try this on a fully ported 550.... for science and stuff.....

Yeah, this could get real interesting. So far, we are only talking about first generation saws. In theory, this might also work on the new M2 545 and 550. But someone will have to run through it to see if everything fits as luckily as it turned out with Flip's saw. I haven't even seen the intake ports on the new M2's yet cause we've yet to take one apart. Just haven't seen one fail yet. The M2 filter set up is WAY better than the early 550 or 562, so it would be nice to keep that if possible.

Guess we need a volunteer don't we?

 

[Flip]

I think you'd be able to do a master or fuel settings reset. But for updates and such the CST has to be linked with the mother ship down in Charlotte.

My own little project is on hold as the bottom end of the donar turned out to be junk this afternoon. Have to scout around and come up with something. Might end up going back into my other thin gasket build, but I really wanted to compare the two of them. Patience usually pays off. Won't be long before something comes in. One of the Lewis guys should have a carcass to mess with. He can have it when it's done. But then they'll all want one just like it. LOL

If I were just able to look at the data and do resets, that's all that I need. Seems to me that the AT saws from the last couple of years don't need learn like they use to. Seems like they come out of the box already "in the zone." I sold my 2013 562 for a 2019 562 and it feels like a MK II because the little gremlins in the old saw are gone.

A long term project is to slowly open the strato ports. Did the engineers maximize the fresh air slug or can we go bigger and use less mix to push the exhaust out. I'm hoping the CST will show when it goes lean due to fresh air in the combustion chamber. I'll ruin this cylinder but have the recipe for future builds. Is it possible to have the holy grail: more power with better fuel efficiency?

 

[Flip]

Yeah, this could get real interesting. So far, we are only talking about first generation saws. In theory, this might also work on the new M2 545 and 550. But someone will have to run through it to see if everything fits as luckily as it turned out with Flip's saw. I haven't even seen the intake ports on the new M2's yet cause we've yet to take one apart. Just haven't seen one fail yet. The M2 filter set up is WAY better than the early 550 or 562, so it would be nice to keep that if possible.

Guess we need a volunteer don't we?

Part of the reason I didn't do both saws(besides not knowing if it would work) is that I was waiting to see what the 562 MK II looked like and what I could swap to the 550.

I looked at the Mk2 filter and didn't know if it would fit. If it almost fits, I can carve out some wood in the same shape and use a heat gun to heat shape the top cover to make it fit. Wouldn't look quite factory but would work.

 

[Flip]

But someone will have to run through it to see if everything fits as luckily as it turned out with Flip's saw.

Every morning I look to see if you've done yours yet. Your right though, the total number of successful conversions is one so it's still an unproven modification. It went together so well and ran so good, I feel confident about it, I just don't want to be know as "JMS Flip" around here.

 

[Flip]

If anybody is interested in doing this and wanting the intake gasket and thinner base gasket, it won't take but a second to make a set of these gaskets and I can drop them in an envelope.

Drop me a PM if interested. I'm on the tractor the rest of the day but will check my PM's tonight.

 

[cuinrearview]

Every morning I look to see if you've done yours yet. Your right though, the total number of successful conversions is one so it's still an unproven modification. It went together so well and ran so good, I feel confident about it, I just don't want to be know as "JMS Flip" around here.

Every morning I check to see if you've uploaded a vid to youtube

 

[Spike60]

Part of the reason I didn't do both saws(besides not knowing if it would work) is that I was waiting to see what the 562 MK II looked like and what I could swap to the 550.

I looked at the Mk2 filter and didn't know if it would fit. If it almost fits, I can carve out some wood in the same shape and use a heat gun to shape the top cover to make it fit. Wouldn't look quite factory but would work.

The word I got is that there isn't going to be a 562M2. There MAY be some enhancements for the air filter and a new top cover that along with a different partition wall adds the heat barrier down the road. But not a total redesign as with the 545/550.

 

[cuinrearview]

Bump

 

[Fullkip]

I converted one of my 550s over to the el48 carb. I had everything except the 560 filter.
I can't get it to pass a pressure test..
Gonna make up another gasket with thinner stock. It leaks at the upper outer edge of the stratos. I tried it raw dog but it wouldn't seal, leaked bad.
So back apart it comes.

 

[Fullkip]

Dang I just realized I forgot to trim the carb floor wall.... Not good puts everything in a bind.
The saw was stock except for a muffler gutting. The jug that's on it now has been cut. Squish, base, and flange.
Not ported yet , just cleaned up the casting swarf. The pto transfer cover has been trimmed .
Most often it's the little things that give u grief... lol

 

[Fullkip]

Thanks Flip for this new angle on these 545/550 saws.
Once its running I'll check the fuel settings...
I won't get much done until I get more free time. Tough week of cutting ahead...

 

[Fullkip]

Welp I have some feedback...
I got the el48 carb wall boot to seal up on my 550. Passed vac and pressure test. Put the el48 carb on with the 550 TPS brain.
I got it together and she was running on the 5th pull...
It runs pretty good pulls better than it did. I need a 560 / 555 air filter.
Once I get an air filter and get some run time on it I'll get the carb data on here.