HS50 questions

#1
A couple:

Are there any steel sleeved blocks? Neither of mine are.
If not, is it worth sleeving one? I can do them so cost is low.

Are the bearing type covers that much better? I have one, not sure I'll use it.
Has any one put needle bearings in a stock block? Either turning crank, opening block, or a bit of both?

Is 1.94 the longest small frame crank? Or, can a medium be cut down to fit?

Will a side-popper take an 1/8" overbore for 40 slug?

Once a billet rod and modded PVL flywheel are on, where is the next weak link?

TIA
 

markus

Well-Known Member
#3
Pre 1970 H35 and smaller were steel sleeved blocks, they ended that in 1970 from what I have seen and even only the offered the standard bore blocks as replacements after that shown in the parts listings.

Non of the HS40 or 50's were offered with steel sleeves. Never noticed anyone saying they have done it, I have seen people mentioning though that punching out and HS40 block too far and you can get into a mount lug hole for the air deflector on the side.

The ball bearing sidecover of course would be a little less friction. I think it retains the crank better as well, somewhat keeping the crank from pounding on the case and letting the bearing take the beating on the side load. The earliest engines that The small frames are based on (Lauson's last designed engine before Tec bought them) did have a needle bearing on the mag side, but they were a full on oil pump system engine and Tecumseh dropped all that in the early 60's. I could not tell you how it would do or if it would starve on the splash system or not. I think they were also only on small journal cranks (might not have enough room on an HS as it has larger journal on the mag side as does some of the later H engines. Looking at old magazine articles with snipets of "performance info" from the early 70's when they were pushing the limits of these I never see any mention of it being done.

no clue on crank mods

I would think you may be able to punch out the H35 and I would be interested to know myself. The first HS40 in the late 60's actually used the H35 head with the smaller bolt pattern Was pretty thin around the head bolts though, This shot shows the bolt pattern difference and gives and idea of spacing (H35/early HS40 head gasket on a 1970 block)



I thought I had a shot of the 1969 HS I have looking down the bore but I don't, Its the engine on the bottom of that pic.
The H engines are smaller/thinner around the cylinder too so punching it out might get it real thin on the outer walls.

If it can be punched out that would be great though, the later engines, in about 1984, started to use the HS cranks and rods in some of the H engines. So the bottom end is HS40 but spinning a smaller piston and a cam 180 degrees out. One problem though is the front wall of the H engines do not have the spacing to clear a typical Billet rod like the HS engines do.

I would think that the next weak link might fall on the crank after rod and flywheel :shrug:
 
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#4
Thanks, Markus! I'd hoped you'd pop in :)
I've been looking for an excuse to get a thickness gauge.
If the casting is too thin, it may separate from the crankcase, I suppose.
Seeing the pump in the V versions, has me thinking. I'll have to look at an old Lauson.

Sorry, Massacre. I knew it sounded familiar. Maybe a Mod can change title to "Some more HS50 questions"? lol
 

markus

Well-Known Member
#6
Thanks, Markus! I'd hoped you'd pop in :)
I've been looking for an excuse to get a thickness gauge.
If the casting is too thin, it may separate from the crankcase, I suppose.
Seeing the pump in the V versions, has me thinking. I'll have to look at an old Lauson.

Sorry, Massacre. I knew it sounded familiar. Maybe a Mod can change title to "Some more HS50 questions"? lol
wish I could be more help with the "performance" or heavy mods, I personally just dont really do much more than light shop work though due to lack of equipment to play with.

This was probably an old 1/4 midget racer engine that was modded out that some members found last year, looks likes its based off an old HB25. There are some good shots of the internals and what are probably some mods they did. After looking at it better I bet that needle bearing was owner/shop modded in. I still cant figure out how the oil made it was to to the mag side unless that cam is drilled through. Interesting setup though! http://www.oldminibikes.com/forum/mini-bike-parts/123488-vintage-racer-h25.html?highlight=tecumseh
 
#7
wish I could be more help with the "performance" or heavy mods, I personally just dont really do much more than light shop work though due to lack of equipment to play with.

This was probably an old 1/4 midget racer engine that was modded out that some members found last year, looks likes its based off an old HB25. There are some good shots of the internals and what are probably some mods they did. After looking at it better I bet that needle bearing was owner/shop modded in. I still cant figure out how the oil made it was to to the mag side unless that cam is drilled through. Interesting setup though! http://www.oldminibikes.com/forum/mini-bike-parts/123488-vintage-racer-h25.html?highlight=tecumseh
Way cool! Thanks! The V's are drilled through the cam, to lube the upper/flywheel main, so that's likely what it was.
 
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