HS50 VS. HS40

[FloridaMiniBikes]

Where does the extra 1 H.P. come from between the HS50 & HS40 non point engines?
Does the OldMiniBikes 5.5 Arc Billet Rod fit in the HS40?
Taking my first dive into building or blowing up an engine at the age of 65.
Need some guidance, and a Dynocams 245 or 255 cam or two.
Request your guidance before the kidz put me in the old folx home!

 

[mustangfrank]

Where does the extra 1 H.P. come from between the HS50 & HS40 non point engines?
Does the OldMiniBikes 5.5 Arc Billet Rod fit in the HS40?
Taking my first dive into building or blowing up an engine at the age of 65.
Need some guidance, and a Dynocams 245 or 255 cam or two.
Request your guidance before the kidz put me in the old folx home!

Bore size and yes the rod works in HS

 

[delray]

yep bore size and the ARC rod works all day. there is some other factorys that may come into play for horse power differences. some engines come with fix carb's. governor maybe set higher or lower...etc.. you said non points engine. so i am assuming this is your build engine. hot coil, stock steel cam with good springs and retainers is a plus or 245 cam still need 22mm carb header...etc... 255 you really need some crazy mods to get that cam to work real good and rpm's. remember the newer stuff they come with small valves. so i would lean toward a stock steel cam with the correct mods. not that the 245 won't still work and all. just remember too the bike needs the correct mods too if you really want to feel the power change. gearing,correct stall in your clutch or torque converter...etc..

 

[mustangfrank]

I just scored a pair of HSSK55 snow engines with steel 37040 cams, I'm going to play with one of those in an older HS50 and build out the other because I like the cast iron bore and thin rings...nice little factory cam if you can find 'em, mechanical compression release, less lift than a 245 cam if you're not going all out.

 

[delray]

I just scored a pair of HSSK55 snow engines with steel 37040 cams, I'm going to play with one of those in an older HS50 and build out the other because I like the cast iron bore and thin rings...nice little factory cam if you can find 'em, mechanical compression release, less lift than a 245 cam if you're not going all out.

just remember if you try using a newer steel cam with the compression release in a older hs-block the thrust area on the pto cover/cam area is more open and that needs to be filled in or your compression release parts are going to fail. cam also mic's out different(base circle) so you need the lifters too get everything in the ball park. old hs-lifters will work,but they will need to be ground down and will need special tooling or good old home made tooling. metal is very hard and it's so much material that you don't want to grind the valve tips down. for me one big key part is using a tecumseh hot coil on a newer block with electronic ignition. it is a must when hot rodding one of these small blocks. day and night difference when built right.
washer

for example ohh-tecumseh cover that using the release cam. note how small the top area is. just enough opening for the oil to drop into.

 

[mustangfrank]

just remember if you try using a newer steel cam with the compression release in a older hs-block the thrust area on the pto cover/cam area is more open and that needs to be filled in or your compression release parts are going to fail. cam also mic's out different(base circle) so you need the lifters too get everything in the ball park. old hs-lifters will work,but they will need to be ground down and will need special tooling or good old home made tooling. metal is very hard and it's so much material that you don't want to grind the valve tips down. for me one big key part is using a tecumseh hot coil on a newer block with electronic ignition. it is a must when hot rodding one of these small blocks. day and night difference when built right.
View attachment 271554 View attachment 271555 View attachment 271557 washer
View attachment 271556
for example ohh-tecumseh cover that using the release cam. note how small the top area is. just enough opening for the oil to drop into.

I appreciate the information, heard there might be obstacles, I think I'll part out the one engine for the side cover. Planned on gathering my parts and getting advice here before I dove in, you're one of the Tecumseh builders I wanted advice from anyway, so thank you.

Sorry Florida wasn't trying to hijack your thread with my build, just wanted to mention that factory (1/2 horse?) cam.

 

[FloridaMiniBikes]

I appreciate the information, heard there might be obstacles, I think I'll part out the one engine for the side cover. Planned on gathering my parts and getting advice here before I dove in, you're one of the Tecumseh builders I wanted advice from anyway, so thank you.

Sorry Florida wasn't trying to hijack your thread with my build, just wanted to mention that factory (1/2 horse?) cam.

So appreciative of all the great what to do and heads up responses, especially about the cam switch. This old fart beginner is closer to figuring what to do, a little hesitant without an experienced builder looking over my shoulder, but this is a great, "Get up off your ass" and do something push! Thanks to all!

 

[DaddyJohn]

No one mentioned this specifically, but:

HS40 = 172cc
HS50 = 200cc

I'm sure the 28cc bump doesn't account for all of the 1hp difference, but that's the specific displacement contribution.

 

[delray]

just remember if you try using a newer steel cam with the compression release in a older hs-block the thrust area on the pto cover/cam area is more open and that needs to be filled in or your compression release parts are going to fail. cam also mic's out different(base circle) so you need the lifters too get everything in the ball park. old hs-lifters will work,but they will need to be ground down and will need special tooling or good old home made tooling. metal is very hard and it's so much material that you don't want to grind the valve tips down. for me one big key part is using a tecumseh hot coil on a newer block with electronic ignition. it is a must when hot rodding one of these small blocks. day and night difference when built right.
View attachment 271554 View attachment 271555 View attachment 271557 washer
View attachment 271556
for example ohh-tecumseh cover that using the release cam. note how small the top area is. just enough opening for the oil to drop into.

Need to go back double check and mic a newer compression relief cam Base circle. Little different and will affect where the lifters sit i believe.

No one mentioned this specifically, but:

HS40 = 172cc
HS50 = 200cc

I'm sure the 28cc bump doesn't account for all of the 1hp difference, but that's the specific displacement contribution.

not to throw you off ,newer 5hp's are only 195cc. bores size is only 2.795 and you might be little off on the older hs-50's for cc

 

[DaddyJohn]

Need to go back double check and mic a newer compression relief cam Base circle. Little different and will affect where the lifters sit i believe.

not to throw you off ,newer 5hp's are only 195cc. bores size is only 2.795 and you might be little on the older hs-50's for cc

Might be the older HS50's are more like 198cc? Ah, anyway...

 

[FloridaMiniBikes]

Getting a good Edu-Macation here for sure. Reviewed a lot of past posts and the pin thing by CFH also. Found a HS50 with the BB sidecover in the shed, but might mess with a non BB first in case I mess up, (3 or 4 of em in the shed). Got a keep my eye out for a LH195 cam for that lil extra jump as the 245 dyno is getting to rare and costly. Once again, thanks to all, Will get a start on it soon as this gobble gobble joke is over.

 

[cfh]

198cc was before the change in bore size (thick rings), versus the thin ring change. and then it went to 195cc.

HS50 (pre 1998) = 2.812" x 1.938" (or 2 13/16" x 1 15/16") 198cc. These are HS50 models "G" and earlier and HSSK50 models "M" and earlier.
HS50/HSSK50/LH195 (1998 and later)* = 2.795" x 1.938" (or 2 51/64" x 1 15/16") 195cc. These are HS50 modeles "H" and later and HSSK50 models "N" and later.

i'm pretty sure those dates are correct....

 

[markus]

Getting a good Edu-Macation here for sure. Reviewed a lot of past posts and the pin thing by CFH also. Found a HS50 with the BB sidecover in the shed, but might mess with a non BB first in case I mess up, (3 or 4 of em in the shed). Got a keep my eye out for a LH195 cam for that lil extra jump as the 245 dyno is getting to rare and costly. Once again, thanks to all, Will get a start on it soon as this gobble gobble joke is over.

D, I have spare late model mechanicals if you want to go that route, I suggest thicker thrust washer use over what they used since stock is only .006” thickness. Even though Tec was fine with it on the L head side covers (they never changed the oil cutout) I still like a thicker retainer for the release mech. Just have remember to check the side play and compensate if needed depending on thickness used. 38 shipped if you want one.

 

[delray]

D, I have spare late model mechanicals if you want to go that route, I suggest thicker thrust washer use over what they used since stock is only .006” thickness. Even though Tec was fine with it on the L head side covers (they never changed the oil cutout) I still like a thicker retainer for the release mech. Just have remember to check the side play and compensate if needed depending on thickness used. 38 shipped if you want one. View attachment 271812

interesting you say they never change the side covers on the flatheads for the cam bushing. how did they fix the problem so the release unit didn't push into this area? you said they use a thicker washer? if so they must of machine the thrust surface down little more to compensate for the thicker washer so the cam would not bind up and have the correct end play. i found the easy way to fix this problem and safe way. was to just completely fill in this area and drill a small hole from the top to feed the oil into the bushing area.

 

[markus]

interesting you say they never change the side covers on the flatheads for the cam bushing. how did they fix the problem so the release unit didn't push into this area? you said they use a thicker washer? if so they must of machine the thrust surface down little more to compensate for the thicker washer so the cam would not bind up and have the correct end play. i found the easy way to fix this problem and safe way. was to just completely fill in this area and drill a small hole from the top to feed the oil into the bushing area.

different strokes for different folks

 

[delray]

caution...also cams with release units don't like to rotate backwards. you can damage it.

 

[delray]

different strokes for different folks

don't take it the wrong way,might be numbers guy markus when it comes to tecumseh's and we all appreciate it. but you just can't slap things together when modifying different parts into other engines without some kind of problems.

 

[markus]

interesting you say they never change the side covers on the flatheads for the cam bushing. how did they fix the problem so the release unit didn't push into this area? you said they use a thicker washer? if so they must of machine the thrust surface down little more to compensate for the thicker washer so the cam would not bind up and have the correct end play. i found the easy way to fix this problem and safe way. was to just completely fill in this area and drill a small hole from the top to feed the oil into the bushing area.

answers in order, They didn't, apparently someone at Tecumseh deemed the thin thrust washer as the CR retainer fine in this application, just use the LH's and the HSSK's that used them as an example..... In fact look up any HS40, HS50, LH195 or HSSK variation that originally used the now NLA (bcr) 33158 camshaft from Tecumseh and you will see they superseded it to the Plastic version of the late model MCR and thats what you will get. other than being composite camshaft the CR is the same parts and setup the same. Its a shitty option, but thats what they did and currently still do.

I didn't say they used a thicker washer, on the L head, I wont post again my solution to what I feel is too thin of a thrust washer becuase it IS serving as the retainer in both applications again since all you did above was reword what I already said in that post.

Your "easy way" may be easy for you, my easy way is easy for me............as stated before different strokes for different folks

don't take it the wrong way,might be numbers guy markus when it comes to tecumseh's and we all appreciate it. but you just can't slap things together when modifying different parts into other engines without some kind of problems.
View attachment 271822

OK, Maybe you should tell that to the designers at Tecumseh that did it as it wasn't my idea to use that camshaft in the late versions and subsequently use it also as the replacement for every HS made since 1971 when the BCR steel cams ran out.

 

[delray]

answers in order, They didn't, apparently someone at Tecumseh deemed the thin thrust washer as the CR retainer fine in this application, just use the LH's and the HSSK's that used them as an example..... In fact look up any HS40, HS50, LH195 or HSSK variation that originally used the now NLA (bcr) 33158 camshaft from Tecumseh and you will see they superseded it to the Plastic version of the late model MCR and thats what you will get. other than being composite camshaft the CR is the same parts and setup the same. Its a shitty option, but thats what they did and currently still do.

I didn't say they used a thicker washer, on the L head, I wont post again my solution to what I feel is too thin of a thrust washer becuase it IS serving as the retainer in both applications again since all you did above was reword what I already said in that post.

Your "easy way" may be easy for you, my easy way is easy for me............as stated before different strokes for different folks



OK, Maybe you should tell that to the designers at Tecumseh that did it as it wasn't my idea to use that camshaft in the late versions and subsequently use it also as the replacement for every HS made since 1971 when the BCR steel cams ran out.

WOW, now your just rambling on....