Newbie Questions HS40

[hotshoe63]

I am fairly new to the forum. As owner of a few old Rupps, I am seeking some information on a couple of items.
1. In my old Tecumseh manual the specs say the valve seat angle on the hs40 is 45 degrees. However, a diagram on different page shows a 46 degree seat angle. Which is the correct angle?

2. On one of the motors, the camshaft has a fair amount of end to end play. I think this is the internal noise I was hearing when the engine was running. Being a Black Widow motor, the governor was disabled but the internals were intact. However the governor sprocket was missing some teeth, I assume due to the amount of camshaft endplay. Would it be advisable to try and shim one end of the camshaft or maybe build up one of camshaft sockets in either the block or side case to eliminate the movement? Would JB weld be an appropriate filler? I tried another camshaft but still have the end play. Any suggestions appreciated.

 

[Havasu Dave]

Which is the correct angle?

46 degrees. Use a Neway cutter. You can get the valves to seal using lapping tools and compound. (I wont go into multiple angle cutting)

Would it be advisable to try and shim one end of the camshaft or maybe build up one of camshaft sockets in either the block or side case to eliminate the movement? Would JB weld be an appropriate filler? I tried another camshaft but still have the end play. Any suggestions appreciated.

Depending on the amount of play, I'd be tempted to shim it, but I would need to look at it. Some play is fine. I would not use JB Weld. It does a terrible job of dealing with friction and pressure. I'd remove the broken governor assembly and install a good replacement, then rig the carb accordingly if I were going to use the engine on a period correct governed carb. However, if you are not going to use the governor, remove it in it's entirety from the sump cover.

 

[markus]

46 for the recut, really need at least a 30 degree as well so you can get the seat back down to .035 and .045 specs for the face….. they are usually fatter than that pre servicing. Note. New standard ex valves will actually measure thinner on the stem than your original, so if you have the means and it’s in good shape reface the valve rather than replace or go oversize valve.

@ole4 Gave me some info on the shimming at one point but there are no exact parameters that I have ever been able to find. Tec does sell shims, they used them as retainers for the mechanical compression release on the late model hs/ohh cams. They are pretty thin .006 IIRC. I ordered some in larger thicknesses from some supply house to do some shimming when using that style cam. Tec seems to approve of that thin shim but on an HS side cover but it’s got hold back that release across a large oil feed gap. And you can easily flex that shim so I beef them up with a thicker shim. Don’t want to go too tight, I think it helps with lubrication on the journals and probably tappet rotation…..it’s a lot of fun getting that measurement, not so bad if your using a Bearing sidecover with the bearing out.

 

[hotshoe63]

Thanks guys for the replies. I will look for those shims. I saw a Neway cutter for sale but needed to be sure of the correct angle. Marcus, you mentioned resurfacing the existing valves.The intakes will clean up fine I think but the exhaust valve guides are pretty worn resulting in a good bit of play. Not sure how much play much is acceptable but I do have new oversized exhaust valves should they be needed.

 

[markus]

Thanks guys for the replies. I will look for those shims. I saw a Neway cutter for sale but needed to be sure of the correct angle. Marcus, you mentioned resurfacing the existing valves.The intakes will clean up fine I think but the exhaust valve guides are pretty worn resulting in a good bit of play. Not sure how play much is acceptable but I do have new oversized exhaust valves should they be needed.

When you get a cutter set you will know on the guides. Since you can’t lock the pilot for the cutter into a worn guide, I use them as a pass/fail tool. They have a .250 +.001 pilot as well. If that will lock with no rocking about halfway in, I will let that slide at least on the intake side but they run a pretty big clearance on the exhaust side so I that side to be as thought as I can get it with Tecumseh parts. Just did an oversize ex on an H35 (used the same valve) recut along with truing the warped deck and boring the cylinder oversize as well this week, someone just sent a black widow engine yesterday for some work, I hope it’s not too whipped. Have not opened the box yet. Good luck with yours!

 

[hotshoe63]

Thanks Marcus that’s good info. When you bore the cylinders do you bore .010 over where there is good material left? I found a NOS Tec .010 over piston and rings and was going have it bored for that piston. The original block is aluminum and has formed a ridge at the top of the bore, but I did find a pretty good block with the iron sleeve.

 

[markus]

Thanks Marcus that’s good info. When you bore the cylinders do you bore .010 over where there is good material left? I found a NOS Tec .010 over piston and rings and was going have it bored for that piston. The original block is aluminum and has formed a ridge at the top of the bore, but I did find a pretty good block with the iron sleeve.

yes, tecumseh only offered .010 and .020 pistons for the common sizes we use in the MB world. Quite a rarity to find a sleeved HS40, they only ever offered a steel sleeve block on like one engine configuration for a brief time here in North America. If its used you still need to check for out of round down in the bore. They will eat just as bad as the aluminum bores, but they wont look it like the AL's will.

 

[hotshoe63]

I picked it up a few months ago and didn’t realize it was an iron bore, until looking at it closely. If the seller knew it, he didn’t advertise it as such. Notice the button magnet attached to the bore. Thanks for all the good info.