Stihl MS500i chainsaw complete tear down

all right we're gonna do uh almost a complete tear down on a steel ms500i i've never tore one of these down um i've only owned it for this will be my second day i put i think 11 tanks through it maybe 10. uh runs really good it's very light saw uh what was it uh 79 cc's almost 14 pounds um about a half pound three-quarter pound lighter than a 572 full pound lighter than uh 73 10. uh this is a fuel injected saw has a primer bulb right here that primes the fuel system you have to when it's cold hit it seven times to build up pressure to start it has no choke means it's fuel injected decomp comes off the top right magnesium clutch cover has a captured bar not stainless steel muffler good balance good power um i don't know if it's rev limited because i can't find my tack my boys borrowed it and uh never returned it um but it sounds like it's limited by fuel that's a gas but it sounds like it's limited by fuel meaning one that over rips i i believe it's pouring more fuel into the cylinder to slow itself back down not 100 sure but it certainly sounds like that i won't know until i get my my attack comes tomorrow a new of palm attack coming tomorrow and then i can see if the rev bounces around on it pulls at 28 really nice it's a little bit faster stock than a 572 and a 565 elephants in the room it's very expensive 28 light bar in the united states is around 1400 bucks which is that's really getting up there um it does not have any kind of air injection system i don't know why steel decided not to implement that on this saw just as your standard max flow type filter on it and then your vents on the on the outside it has no air ducting from the actual flywheel to pre-clean air i have not opened this up since i started cutting with it like i said 10 11 tanks it is not fuel efficient big surprise being fuel injected i guess i had it in my head that it would be very efficient with its charge in its burn but she eats fuel i would say more than a 461 definitely way more than a 572 with strata i haven't really compared it to my ported 7310 yet but that does kind of drink some fuel as well um anyway i think uh we'll tear this in tear into a little bit and see what the guts look like basically when i'm done with this i'm just going to pull the rings off and then i'll prepare to to figure out what i can do to get a little bit more power out of it i'm going to pull the rings and then time it and whatnot time the ignition on it as well to uh to uh see how many degrees before top dead center it fires um well yeah let's get into a little bit here pop the cap for the first time that we got dust i cut a lot of hard ash today and that and i ripped most of it actually i didn't uh cut it lengthwise very much today we did a lot of ripping for firewood you can see the filter there it does have fines in there a couple of chunks of ribbons of wood in there a little bit on the top cover and we got dust in there too no big deal blow this off quick well let's do this first get that chunk out of there so we don't end up with that motor knock anything in there and it's really clean in there you can see that the cleats have quite a bit in them for not having air injection that uh yeah doesn't help out very well but the intake itself it does get underneath the filter but there's nothing on the butterfly there's nothing on the inside of the throat or anything it means it's fuel injected it has one butterfly and kind of looking it over earlier i do not see a throttle position sensor so i don't know how the ecu understands where the throttle is i'm guessing it's going off of rpm maybe when we tear it down a little bit we'll see maybe a hidden sensor maybe there's a barometric sensor built into the injector itself i don't know it might be in the intake too so i'm going to blow this out a little bit here so we don't end up becoming the motor top off one quick release on that pretty standard stuff from steel looks like we got a large partition wall to keep heat out we got some wires coming up here from the flywheel some hoses that is quite a bit of dripping wood in there like i said captive bar nuts would be standard for the industry anymore pretty small clutch cover like most nails clutch 3 8 rim 7 pin um mag case let's see what we have to mess with though so let's pop the top handle off two plastic ones and then we got a limiter on top looks like it's got a rubber sock for the limiter we've got an av spring up top with a cable limiter in it and then two bolts on the bottom handle we have an av down here kind of goes up and i don't know at a 45 and interesting design there how it captures the bar there we go slides out and forward it actually separates the handle that's a surprise so the the foot plate is separate from the av and bolts through into the handle that's interesting separate there here is our limiter stop and it is it's a hard plastic thinking that might be where my vibration is coming from um when i'm pulling on it kind of hard that's translating into the handle maybe upgrading that to a rubber rubber cap might be something i'll look into here all aluminum handle like i said top av has a limiter spring or a limiter cable inside see here muffler looks like pretty standard steel stuff is just stainless steel four bolts hold the front plate on bottom two go into the mag case there is a washer on there there's only a washer on the clutch side interesting hollow front they got a crush washer like they always do on the interior for ceiling muffler is all but hollow better get my light out for that you guys aren't gonna be able to see in there go straight into the piston looks like a dual ring very very small exhaust port like 50cc size exhaust port that's that's interesting maybe you don't have one of these things yet milwaukee i'm sure dewalt does too but they make a six-inch t27 that's rated for uh impact these are amazing you have to have these great for cylinders so muffler very simple screens right on the inside here like i said extremely small exhaust port very interesting we got a gasket comes apart in one assembly exhaust port put those in there very tiny and almost no room to expand it very thin walls top and bottom you're not going to horn this thing out interesting pop the recoil off everything is locked tight we do have some air ducting in here that goes up to the top of the cylinder it looks like they're trying to force as much as they could up to that cylinder to keep her cool last to start of course it is kind of a bugger to pull over i don't know what the compression is going to be yet but you can also see how small the diameter is here for turning it over so i think that might have something to do with it flywheel is extremely thin the only one issue i have had with the saw is once it is hot i mean when you're putting pulling noodles for quite some time i found that i couldn't use the decomp um it would not pop it it would not start it while it would pop and try to start but it wouldn't blow the decomp out so then it would just die so i'd end up pulling the decomp out with my fingers and then as long as you just don't use it once it's hot it was perfect that might be something that runs in as compression comes up i don't know but it is something to note that is something that i did have kind of an issue with got our leads for ignition comes off the ecu which sits on the clutch side in here behind it goes all the way down here and then there's a retainer screw underneath that holds it in place get the filter holder out of here lift it up and out of position just another partition for a filter holder pretty standard now for the butterfly looks like we got a mess in here butterfly that's all it is it's just a metal plate with one single butterfly linkage is very simple to deal with i'm going to blow this out though so again i don't get anything in the engine wow you can see after about 100 hours this thing is going to be packed full crazy okay i'm going to do this off camera a little bit more in there than i anticipated okay so the throttle plate throttle body whatever you want to call it just pops right out that's all it is just a spring in the plate and a throttle plate very simple there's no sensor on it there is a port right here that was drilled and then tapped and then another airport right there so i don't know i honestly don't have a clue what that does because it is well it's not open to atmosphere it's open to the actual to the vacuum of the intake system set that there got a ring in here keep the intake from collapsing standard stuff all right so we got some wire management on the right side i'm going to pop that one out got some wires that run up and underneath here don't see where the throttle linkage comes out this wire set goes over to the primer system just like so we're going to pull that out and over to this side and then we've got a blue plug right here for the center that goes to the that goes to the fuel injector we've got four wires and we've got another four pin set that goes up and over this partition wall right here and there wire management is pretty good and then that goes down this other partition wall it goes down to the flywheel pop that off that other one loose and that one goes the other direction there we go that's out and out of the way looks like we've got one screw that holds this partition here we might have to pop see if that yep that's separate from this plastic piece so that should come out with a cylinder right there don't see anything else you've got the hose that goes to the injector right here that comes off the primer assembly we've got fuel crank case so in the center it looks as though we have uh the crankcase impulse for the pump this one goes to the injector it looks like and then this one goes to the tank see if we can pull that assembly out of there oh no did they use one t25 i don't know if i have one of those out let's see here yep t25 there there's a little retainer plate right there keep that screw that there we can see our hoses a little bit better so this one goes to the injector no i'm sorry this one goes to the impulse this one goes to fuel feed this one goes out to the injector and this one right here is a return from the injector back into the tank so it continuously circulates um av mounts we got one right here we had the one in the front the one on the side and then [Music] yeah that's it so okay that's separate now pull that pump assembly out they are all barbed it looks like they are on there they're running any kind of pressure they would have to and be that is yeah that's our fuel feed right there it popped out of the tank itself there's a rubber grommet so this is separate from the hose that goes down into the tank and here's our pump right there oh cap comes off so here's a pump assembly wire harness that goes to the stop to the kill and once the the system is primed the vacuum or the the impulse from the crankcase continues to pump set that off to the side now we're down to intake boot press that through there's that hose there is the fuel injector return and the impulse right there okay now we got our separate dump that out so here's your handle assembly fuel tank trigger assembly here's your breather it's built right into the tank there's no hose that goes to it you can see the ecu right there and the coil assembly controls the fuel intake manifold quite large here's your fuel injector with the harness that goes to it and your impulse feed this goes to underneath the coil i'm assuming there's a stator right there is a release and right there's a release so to separate that we'll have to take this excuse me this little torque out which i don't have set out either see what size that guy is and it is a 10. lift that wire out put that screw back [Music] in now we have our harnesses separated from the injector itself i see no other harnesses going in i'm also not seeing a still not a throttle position sensor i don't see one at all there's three bolts right there that one is released i'm assuming at this point we can just pull the cylinder out before we get too far pop the flywheel off 13. and see what i'm doing flywheel knocker tool if you don't have a flyable knocker tool i would suggest it plus the varna will sell you one otherwise you can make your own i just take a nut and a piece of stock weld them together for about any application there's no external coil on this i can see and we have a ring of magnets flywheel is extremely light i should probably get a weight on that thing because man nothing is light no alterations may cause burst hazard there's our stator looks like we've got a pickup down here i'm assuming a crank position sensor interesting i think i'm going to leave all that alone so we've got a it has to be a crank position sensor i'm seeing no obvious indication of where it would trigger off of but for the ignition there has to be a crank position sensor being as there's not a coil mounted on it specifically so somehow electronically it knows where the top dead center is five eight so let's pop that off before i get the cylinder loose we have a cmr 6h for a plug one of the little guys and pop those out there we go so we have a small intake port a small exhaust port and a very small front fed peel that off get a better idea here very small front fed transfer port interesting the way they're going about this we got quads and the quads are large um the quads look like they're about double the size it's that actual feed port there now the tunnel looks huge but the inlet is is pretty small see if you guys can see in there there's your intake cylinder quality of course looks really good there is your exhaust and there is get the right angle there's your transfers there's a slant back cylinder the way this whole the whole fins are angled uh the cylinder in the case itself slant back to save space this is very thin won't be able to widen or make that very big at all and then the case itself it is bottom fed front fed right there and it's small crankcase volume looks very tight we have plastic cage bearings on both sides slab side piston we have one locator pin on the intake side and one locator pin for the rings on the exhaust side another thing to keep out watch out for the wash the wash looks okay it's not cleaning the top of the piston off perfectly but it looks decent and we've got two dollar signs on that piston good quality stuff and it is a steel steel branded cylinder you know the look of that crank case here and where your impulse port comes off of everything is quite tidy crankcase is quite small for a 79 cc saw it's interesting okay now back to the injection system looks like three bolts unless there's a hidden one seeing that that comes unless off retained by the top yeah there is a bolt in behind so that does come off it is actually the clamp for the intake boot so this the pressure fitting slides over that that partition manifold there over the intake and that is a pressure fitting to hold the intake tube on blow this off all right we have a rubber gasket that is molded in it's got a relief for it our intake right here the boot goes around this collar and then we have our fuel injector right in there so that as the air comes in uh it squirts let's see the angle here squirts kind of straight into the intake charge right there there's not much of anything i can take apart i don't think this looks like a one piece i might be able to pop this cap off but i don't want to risk ruining the injector itself necessarily though i'm assuming there is an o-ring in there right here educated guess looks like a fuel pressure regulator it's vented to atmosphere around here and i can see there's a diaphragm with a spring so as the fuel comes into the unit and then goes and circulates it keeps a certain pressure for to keep the the injector feeding the appropriate amount of volume per pulse opening um that the ecu controls kind of neat the only thing that really baffles me at this point though is how it knows when the throttle is open it must be going off of a set map in the ecu that when it sees it rpms increase it must just add the appropriate amount of fuel per rpm instead of having like a throttle position sensor i don't see that there's a barometric sensor anywhere on this because this just gets power and this just grounds so that's just for opening it so yeah i'm curious and how they know how to map the fuel as the throttle's flipped a little bit of wizard wizardry going on there and the programming i'd imagine back to the ecu it's not a t27 t25 [Applause] one screw on the bottom leave the coil see if there's a trick to getting this out oh yep there's a stop so we have to move the side plate without breaking it there's that one went so this filler plate has to come out and then the ecu can clear looks like i have another piece right here the wire management that sits right here also needs to come out to clear the ecu and we have some date codes and uh identification codes on the ecu and the fuel management system right here it is all well it's like it's a tub and then it's resin filled in the top to keep it sealed off it's got nice rubber o-rings inside here for the um for the plugs keep that nice and dry interesting setup you can see this that's already full of sawdust down in here and they have some vent holes down there um i'm assuming to let air rise through there and keep the ecu cool i can see that that is going to be completely full of sawdust in a short amount of time so yeah thoughts kind of a tech geek so this is neat neat to see i'm going to pull the rings and uh put my timing wheel on it and see where we're at for port timing and it looks like all the ports are extremely small so and the cylinder quality looks amazing i'll see what the squish is and i don't know maybe i'll make a video on that who knows maybe i'll just port it test it poured it have fun with it sell it like i usually do if you made it 38 minutes into this thanks for watching

Channel: mweba1

Views: 9,653

Rating: 4.9266057 out of 5

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Id: uzRUU9UO1rw

Length: 38min 3sec (2283 seconds)

Published: Wed Oct 28 2020