here is something I found on a hs-50 points head. note on the head where the holes are. the casting for most of the holes have a wide area. this was something not found on the early hs-40's
I do recall talking to a retired engineer from Tecumseh last year and asking about the hs-50 motor and telling me they new right away that there was going to be a 5hp built shortly after the 4hp. but first they had to do some retooling. I think this head would make sense why they would do something like these. nothing to do with heat.
if you look at the head you can tell it has two parts to it. upper and lower. making it more cost efficient to drill out bolt patterns for small bore engine by using one upper casting. for example a h30 motor . lower casting may have been replace when casting for a small bore ,so the cc's would still come out correct.
so many little changes Tecumseh did in the early days. I do personally like the early hs-40 with the small bolt pattern. that can be a plus when hot rodding and you bore it .010 , .020 or better yet using a wiseco .080 piston. the first design head and gasket set is small keeping the cc's up when boring the motor out. newer hs-40's with the larger bolt pattern you need to watch for the correct head gasket. you could lower the compression with a hs-50 gasket.
I do recall talking to a retired engineer from Tecumseh last year and asking about the hs-50 motor and telling me they new right away that there was going to be a 5hp built shortly after the 4hp. but first they had to do some retooling. I think this head would make sense why they would do something like these. nothing to do with heat.
if you look at the head you can tell it has two parts to it. upper and lower. making it more cost efficient to drill out bolt patterns for small bore engine by using one upper casting. for example a h30 motor . lower casting may have been replace when casting for a small bore ,so the cc's would still come out correct.
so many little changes Tecumseh did in the early days. I do personally like the early hs-40 with the small bolt pattern. that can be a plus when hot rodding and you bore it .010 , .020 or better yet using a wiseco .080 piston. the first design head and gasket set is small keeping the cc's up when boring the motor out. newer hs-40's with the larger bolt pattern you need to watch for the correct head gasket. you could lower the compression with a hs-50 gasket.
just wanted to clarify something a stated yesterday. meant to say keeping the compression up so there is no confusion.....
and something else to watch for when purchasing a gasket set for a hs-40
some kits will have both gaskets in them. this set has both the small gasket and large bolt pattern gasket.
also note the distance from the inner gasket to some of the head bolts on the large bolt pattern.
here is a hs-50 large bolt pattern. note the distance from the inner gasket to the bolts . it's much shorter then a hs-40.
if this was installed on a large hs-40 bolt pattern your compression would drop good amount. not good!
and something else to watch for when purchasing a gasket set for a hs-40
some kits will have both gaskets in them. this set has both the small gasket and large bolt pattern gasket.
also note the distance from the inner gasket to some of the head bolts on the large bolt pattern.
here is a hs-50 large bolt pattern. note the distance from the inner gasket to the bolts . it's much shorter then a hs-40.
if this was installed on a large hs-40 bolt pattern your compression would drop good amount. not good!
I encourage you to actually compare a small pattern HS head (just an H35 head) to an HS wide pattern head side by side, along with the proper HS40 gaskets (yes HS40 had its own dedicated gasket even in the small bolt pattern compared to the H35) rather that just speculate 
You wont find any notable changes in the combustion chamber so there is nothing to gain there. But you will find that the small pattern puts you at about .090" (and I am being generous) from cylinder wall to the threads of the head studs compared to .310" on the large bolt pattern with stock bore of an HS40.
Not to mention the large pattern head has a whole lot more external surface area which, dare I say, helps with the heat down. I don't know what the cylinder wall thickness is running down the side of those early blocks are, I don't have anymore of them here that are disassembled, but I would take that into consideration as well.
Oh and and the only thing consistent as far as deck height of the Tecumseh heads is that they got milled till they were "flat" and blemish free at the gasket area, more so than taking it to a precise measurement. So some you will see with a ridge around the squish band, some are totally flat, some are half and half, all with the same part numbers.
You wont find any notable changes in the combustion chamber so there is nothing to gain there. But you will find that the small pattern puts you at about .090" (and I am being generous) from cylinder wall to the threads of the head studs compared to .310" on the large bolt pattern with stock bore of an HS40.
Not to mention the large pattern head has a whole lot more external surface area which, dare I say, helps with the heat down. I don't know what the cylinder wall thickness is running down the side of those early blocks are, I don't have anymore of them here that are disassembled, but I would take that into consideration as well.
Oh and and the only thing consistent as far as deck height of the Tecumseh heads is that they got milled till they were "flat" and blemish free at the gasket area, more so than taking it to a precise measurement. So some you will see with a ridge around the squish band, some are totally flat, some are half and half, all with the same part numbers.
here is something I found on a hs-50 points head. note on the head where the holes are. the casting for most of the holes have a wide area. this was something not found on the early hs-40's
I do recall talking to a retired engineer from Tecumseh last year and asking about the hs-50 motor and telling me they new right away that there was going to be a 5hp built shortly after the 4hp. but first they had to do some retooling. I think this head would make sense why they would do something like these. nothing to do with heat.
if you look at the head you can tell it has two parts to it. upper and lower. making it more cost efficient to drill out bolt patterns for small bore engine by using one upper casting. for example a h30 motor . lower casting may have been replace when casting for a small bore ,so the cc's would still come out correct.
so many little changes Tecumseh did in the early days. I do personally like the early hs-40 with the small bolt pattern. that can be a plus when hot rodding and you bore it .010 , .020 or better yet using a wiseco .080 piston. the first design head and gasket set is small keeping the cc's up when boring the motor out. newer hs-40's with the larger bolt pattern you need to watch for the correct head gasket. you could lower the compression with a hs-50 gasket.
I do recall talking to a retired engineer from Tecumseh last year and asking about the hs-50 motor and telling me they new right away that there was going to be a 5hp built shortly after the 4hp. but first they had to do some retooling. I think this head would make sense why they would do something like these. nothing to do with heat.
if you look at the head you can tell it has two parts to it. upper and lower. making it more cost efficient to drill out bolt patterns for small bore engine by using one upper casting. for example a h30 motor . lower casting may have been replace when casting for a small bore ,so the cc's would still come out correct.
so many little changes Tecumseh did in the early days. I do personally like the early hs-40 with the small bolt pattern. that can be a plus when hot rodding and you bore it .010 , .020 or better yet using a wiseco .080 piston. the first design head and gasket set is small keeping the cc's up when boring the motor out. newer hs-40's with the larger bolt pattern you need to watch for the correct head gasket. you could lower the compression with a hs-50 gasket.
well here go, I got a hs-50 next to a hs-40.
and with a good eye you can clearly see a difference in combustion chamber. better yet if a guy has a calipers? you could just measure across and get a more accurate reading.
so there is a big difference. about .120 wider on the 5hp. that's almost 1/8" wider and that would completely change the size of the combustion area(cc's) so yes there is a noticeable change in the combustion chambers.
I don't think I would want to bolt that 5hp head on a large bolt pattern 4hp block.
another reason why Tecumseh using the wider gasket on the large 4hp bolt pattern to help keep the combustion chamber small so the compression would comes out correct with the small bore. maybe on the newer heads the combustion chambers were the same and the head gasket dictated the cc's ? that's a big IF. person would have to look at the newer stuff to figure that one out. back what I was saying early, if you use a 5hp gasket on a large 4hp bolt pattern your compression would drop good amount. not to mention the extra cc's being trap between the head and top of the block/ deck.
also if there was a problem with gasket and heat?(your opinion only markus) why do we not see the same problem with 5hp
head gasket. that too is very similar too where the distance is shorter from the head bolt to inner gasket then the newer 4hp gasket is and to top that off the 5hp has a bigger bore and produces more horse power. your just not making any sense out of this?
my opinion, big part in changing the bolt pattern was a cost saving for them. now all the tooling was the same for the most part and made it much easier cast and machine only one bolt pattern head.
and yes the early blocks have plenty material to bore them out...…..
and with a good eye you can clearly see a difference in combustion chamber. better yet if a guy has a calipers? you could just measure across and get a more accurate reading.
so there is a big difference. about .120 wider on the 5hp. that's almost 1/8" wider and that would completely change the size of the combustion area(cc's) so yes there is a noticeable change in the combustion chambers.
I don't think I would want to bolt that 5hp head on a large bolt pattern 4hp block.
another reason why Tecumseh using the wider gasket on the large 4hp bolt pattern to help keep the combustion chamber small so the compression would comes out correct with the small bore. maybe on the newer heads the combustion chambers were the same and the head gasket dictated the cc's ? that's a big IF. person would have to look at the newer stuff to figure that one out. back what I was saying early, if you use a 5hp gasket on a large 4hp bolt pattern your compression would drop good amount. not to mention the extra cc's being trap between the head and top of the block/ deck.
also if there was a problem with gasket and heat?(your opinion only markus) why do we not see the same problem with 5hp
head gasket. that too is very similar too where the distance is shorter from the head bolt to inner gasket then the newer 4hp gasket is and to top that off the 5hp has a bigger bore and produces more horse power. your just not making any sense out of this?
my opinion, big part in changing the bolt pattern was a cost saving for them. now all the tooling was the same for the most part and made it much easier cast and machine only one bolt pattern head.
and yes the early blocks have plenty material to bore them out...…..
When I went to work for Toyota there were 2 other technicians Named mark out in the service department. Someone I knew that was working there always called me that at car shows and meets already so they had that put on my uniforms etc, it avoided confusion. Most people just call me asshole, but the owner of the dealership was not down with that going over the loudspeaker all the time
Bummer with the Ariens HS40's with the electric start is they have those strange half breed shrouds on them. top is like the standard round shroud (up to 1974 on the HS40), bottom looks like a later square shroud and uses the later style wider backplates. They have an oddball aluminum flywheel on them as well with teeth for the starter. The Identification tag will be like an SBH or 1972-73 HS50 usually located on the left side bolted to the cylinder air deflector shroud as those shrouds dont have room for the standard rivet on business card tags in the front
Heres the flywheel those used...well part of one....must have been using a 3 jaw puller on it
Bummer with the Ariens HS40's with the electric start is they have those strange half breed shrouds on them. top is like the standard round shroud (up to 1974 on the HS40), bottom looks like a later square shroud and uses the later style wider backplates. They have an oddball aluminum flywheel on them as well with teeth for the starter. The Identification tag will be like an SBH or 1972-73 HS50 usually located on the left side bolted to the cylinder air deflector shroud as those shrouds dont have room for the standard rivet on business card tags in the front
Heres the flywheel those used...well part of one....must have been using a 3 jaw puller on it
When I went to work for Toyota there were 2 other technicians Named mark out in the service department. Someone I knew that was working there always called me that at car shows and meets already so they had that put on my uniforms etc, it avoided confusion. Most people just call me asshole, but the owner of the dealership was not down with that going over the loudspeaker all the time
Bummer with the Ariens HS40's with the electric start is they have those strange half breed shrouds on them. top is like the standard round shroud (up to 1974 on the HS40), bottom looks like a later square shroud and uses the later style wider backplates. They have an oddball aluminum flywheel on them as well with teeth for the starter. The Identification tag will be like an SBH or 1972-73 HS50 usually located on the left side bolted to the cylinder air deflector shroud as those shrouds dont have room for the standard rivet on business card tags in the front
Heres the flywheel those used...well part of one....must have been using a 3 jaw puller on it
Bummer with the Ariens HS40's with the electric start is they have those strange half breed shrouds on them. top is like the standard round shroud (up to 1974 on the HS40), bottom looks like a later square shroud and uses the later style wider backplates. They have an oddball aluminum flywheel on them as well with teeth for the starter. The Identification tag will be like an SBH or 1972-73 HS50 usually located on the left side bolted to the cylinder air deflector shroud as those shrouds dont have room for the standard rivet on business card tags in the front
Heres the flywheel those used...well part of one....must have been using a 3 jaw puller on it
But the good news about those half breed early HS40 snowblower motors is that you can make them work.
I took the fly wheel and set it on the lathe and turned off the electric start gear ring. After you do that, you essentially have a 32517 fly wheel. It’s actually a little lighter weight than a 32517 fly wheel.
Also on that shroud, with some cutting and some gentle welding you can make it look exactly like a standard Minibike shroud.
Bottom line, don’t avoid those engines. They’re pretty awesome
I took the fly wheel and set it on the lathe and turned off the electric start gear ring. After you do that, you essentially have a 32517 fly wheel. It’s actually a little lighter weight than a 32517 fly wheel.
Also on that shroud, with some cutting and some gentle welding you can make it look exactly like a standard Minibike shroud.
Bottom line, don’t avoid those engines. They’re pretty awesome
got couple like that markus and they are only on the ones with the plastic tank. steel tank models I haven't seen one yet? I even have a early(60's) ariens with a minibike throttle on it. seen them also on there early rototillers. it's almost like a one year thing they did on there equipment with minibike throttle.
Reguarding the throttle control seen on your little small Frame sidepopper H, that's technically not a mini bike throttle, those got modified in the later 60's to be spring return/cable friendly, my belief is in 1968 as that was the big year for major companies to really start switching over to Tec's, and were becoming the commonplace on most bikes due to available configurations. Note that it has a screw instead of a drilled through cable adjuster, no torsion return spring or wide washer to retain it, and some of those have a wavy washer in them to keep the bellcrank tight but movable as well. The pre drilled holes on the main bracket are for cable clamp/retainer (like you see on the later style throttles). They typically used a solid wire type cable with Z bend that went up to the handle or dash of the piece of equipment with one of those T shaped fast/slow levers. You can use them by either converting to the mini bike/spring return parts, or what Rupp did in the 60's was they made a swiveling cable retainer that pressed onto the bell crank where the solid wire z bend type cable would go and included a return spring that went to the engine block. They had to do the same type conversion to the medium frame H engine controls too.
yes markus,it appears to have more a fix throttle with this minibike style linkage. which it would make sense because of the application it is going on, made to hold at a certain rpm. believe I have one or two of the ariens early 70's hs-50's with that steel cover electric start(120v) I never look at it to see what style flywheel it has? i'm summing that would be cast steel. I just might have to take a look...
