Hs-40 build

delray

delray

Well-Known Member
#1
#1
been a very busy summer and now I finally got a change to start posting my hs-40 build. the engine was originally a snow blower motor and for some reason the ID tag on this one was missing. from what info I have found on how Tecumseh made things and change things in the early hs-motors this engine appears to be around a late 68 to 1969.



at first there was no attention to do anything to this engine. I was just pulling it off of my shelf to look at the mag and points setup and to see how I could modifly it for another person engine I was helping to build. after getting into the block and all I notes right away there was no real run time on this engine and the inside was in very good condition.




my first option was to go with a NOS wiseco 2 ring piston for a standard bore.


and then at the last minute I found a newer style .020 over hs-40 piston that use the thinner style rings and I new right away i'm going with that...:thumbsup:



here is another reason why I wanted to stay away from the vintage pistons. see in the picture of the stock hs-40 next to a ohh-piston with the thinner rings. my opinion i'm not a big fan running the thick style rings for a performance application.
yes this engine is going to rev to the moon. well maybe not that high....:rolleyes:

 
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delray

delray

Well-Known Member
#2
#2
the crankshaft needed attention right away. crank was never drilled out. on the snowblower they just use a pulley and set screw.
here it is next to a rupp crank. notes two things about this crank that will come into play. one the crank is only 2 1/4 length. that seems to be standard for the most part back in the day and will work just fine for my setup. second thing is it has a 1 inch crank journal for the bearing area. also note(no picture) this engine came with a thrust washer on the crank and that will be use again.



need to drill out the crank for this 5/16 bolt. off to the lathe...……


drilled and now tap


 
delray

delray

Well-Known Member
#7
#7
next step was to make the 1 inch journal fit into a roller bearing cover. I found a odd size mm bearing that work out just perfect. I had to do little finessing to the ID bearing(.012 or so) and the reason didn't make the the crank journal smaller . I would of lost my ID for the seal to hold back the oil and I wasn't about to try hunting down a odd ball seal that would maybe fit? so the only thing I had to do for a pto seal was to use a Tecumseh ohh-seal. they are set up to seal a 1 inch crank journal and the OD seal has the same size as the older vintage bearing covers did...:thumbsup:

and yes the governor parts did come off..:rolleyes:
 
delray

delray

Well-Known Member
#8
#8
ok guys this is where it gets crazy. and I mean crazy. what I wanted to do was install a needle roller cage and use the harden sleeve too. yes making this a full rolling bearing engine.

needle roller was rated some crazy amount. nothing near what this little guy could do.



first thing was to get the center bushing square up on my mill



then come down with the boring bar and open it up.




both the top and bottom oil ways where open up more to allow the oil to go into the needles and drain back out the bottom.


also note I left enough thrust area on the inner block surface too.
made sure the roller cage went in correct so the the oil feed would work correct.
 
delray

delray

Well-Known Member
#10
#10
next step was to machine little material off the crankshaft and install the sleeve. nice thing about this sleeve I found it had a odd size ID measurement. big enough that it did not interfere where the oil seal area on the crank. another couple thousands or so and I would of lost the crankshaft size where the seal would of been.
work out good.


end up having couple thousands interference with the sleeve and crank so nothing would move. after freezing the crank and heating up the sleeve it drop right on.


bearing fits good.



made a quick aluminum tool to install the roller cage into the block. that too had couple .002's interference so the bearing would stay in it's place.




small video of it spinning with just the crank and valves mocked up and flywheel snogged on loose.

video it with my phone ,so the sound is no good...

https://youtu.be/ejx1Rws-d1I
 
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delray

delray

Well-Known Member
#13
#13
see in these two pictures how much the flow is restricted in the bowl area with the factory machine steps. all that can be easily clean up. I do caution porting the back flat wall on both intake and the exhaust. that area can be thin. think if I built another super bad ass hs-50 flatty i might try welding the back side up (outside casting)and do some more porting,but for this little guy I don't see needing to do that at all.



first thing I like to do is spend little time and tape up the the seats real good so they don't get damage. something I tried on this project and have seen done many times in the past on porting . keep the intake a corse finish and polish finish on the exhaust.

 
delray

delray

Well-Known Member
#14
#14
here is another little crazy part I desided to do with the valves. I purchase set of briggs narrow stem SS valves and cut them down to size.



first thing was to cut down the top to the correct size.



and then the end of the stems.


and then make a new groove for the locks.



and then grind a new face on my old hall valve refacer
https://www.oldminibikes.com/forum/shop-tools/155643-valve-grinder.html


then use my new neway cutting set to give me a 3 angle valve job.





if I wanted I could of made the stock briggs valves work. the intake was a 1.125 and the exhaust 1.00

I never double check to see if the intake would clear the side of the chamber head. it would of been very close if not hitting it? now on a hs-50 I believe would be just little bigger and that just might work on that motor. either way on the Tecumseh valves in my opinion they are plenty big enough.

 
FirePowerMinis

FirePowerMinis

Active Member
#15
#15
NKI25/30 bearing? (Either a WAG, or what I used)
Planning to lighten up and back-cut the port side of the valves?
Maybe move the seat out towards the edge, too?
What's your throat to valve diameter ratio?
Zero criticism, just curiosity.
 
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delray

delray

Well-Known Member
#16
#16
firepowermini, the bearing I use was mark as a BA1612Z IKO G6 . I also stumble across one that has the full rollers in the cage and with the oil in the outer cage too. they both seem to have the same clearance with the sleeve installed.
here is a picture of the other bearing and part number KOYO B-1612


and it does have the hole in the outer cage for oil. picture just does not show it.
yes, I believe it's a 30 degree on the back side on the valves. if it's going to help? it won't hurt either.
I would like to maybe try angle the valves on a future hs-50 build and sink the valves little and channel(block/deck) it out to the piston. but then your talking about machining the piston down ,milling the head so you could try getting some of your compression back. there would be a lot of dinking around just to find out there was no ganes……...:doah: never know until you try...:shrug:


buy the way for some of the guys are wondering why I install a sleeve on the crank ,because the crank is not harden enough for the rollers and it will chew up the crank.
 
H

Havasu Dave

Moderator
#17
#17
delray said:
buy the way for some of the guys are wondering why I install a sleeve on the crank ,because the crank is not harden enough for the rollers and it will chew up the crank.
Click to expand...
Yes, I was one of the guys wondering that, but hesitate to come into someone's build thread and start asking a bunch of questions.

The reason I wondered is because that West Bend crank isn't any harder, and the magneto side needle bearing rides on the crankshaft. No chewing. Thanks for posting this build, as I am finding it interesting.
 
delray

delray

Well-Known Member
#18
#18
not sure with the 2 strokes. there has to be some kind of treatment to the bearing surface for the rollers. on my type of crank it's just a cast steel crank and cast vs harden rollers isn't good.
 
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