HS 40 help

#1
I have an HS 40 that I would like to freshen up. It has an aluminum cylinder that is lightly scored. I think the cylinder has worn to where it has little or no compression. I'm thinking that a .010 oversize piston and new rings will clean it up. Can the aluminum cylinder be bored? Everything else inside this engine looks good. I'm looking for advise from some of you Tecumseh experts.
 

oldfatguy

Active Member
#2
I wouldn't bore it unless it is absolutely necessary. You should measure the cylinder to see just how much it is worn. Measure at the top and bottom to check the taper and then check if it's out of round. I have found that most of the time low compression on these engines is usually caused by the valves leaking. Take them out and clean all the carbon off the valves and the seats. If they are in good shape and not burnt then just lap them into the seats a bit. Make sure you check the valve lash to make sure they are closing all the way. Sometime the lifters are slightly different lengths and if they get switched it could cause the valve to not close all the way. Check the end gap on the rings to see if they are worn and need to be replaced. last thing is buy a new head gasket. If the engine wasn't smoking when it ran you probably can get away with a simple rebuild. Usually by the time the cylinder is badly worn , the crankshaft and most everything else will be too.

hope this helps you
 
#3
I wouldn't bore it unless it is absolutely necessary. You should measure the cylinder to see just how much it is worn. Measure at the top and bottom to check the taper and then check if it's out of round. I have found that most of the time low compression on these engines is usually caused by the valves leaking. Take them out and clean all the carbon off the valves and the seats. If they are in good shape and not burnt then just lap them into the seats a bit. Make sure you check the valve lash to make sure they are closing all the way. Sometime the lifters are slightly different lengths and if they get switched it could cause the valve to not close all the way. Check the end gap on the rings to see if they are worn and need to be replaced. last thing is buy a new head gasket. If the engine wasn't smoking when it ran you probably can get away with a simple rebuild. Usually by the time the cylinder is badly worn , the crankshaft and most everything else will be too.

hope this helps you
Good post.
 
#4
Fatguy is correct.

But if you have the money I always wondered what would happen with like a really big oversize bore for one of these engines. The kits are available I seen them on rupp parts
It's always nice to dream :)
 

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