Need help with a Tecumseh HS40 engine

FunWithStuff

Well-Known Member
#1
Hello! I have been working on restoring a Tecumseh HS40 engine for a mini bike and I would like some help identifying a problem I am having with it.
I have recently bought a new knockoff carburetor off of eBay for the engine and installed it on the motor. This motor hasn't ran in a long time so when I started it with the choke open it wanted to run rough and smoke a lot.
Eventually the smoke cleared up so I figured I would take it off choke and see how it runs. When I close the choke valve it always wants to die and it will not stay running. I've tried adjusting the idle screw (the screw at the top of the carb by the throttle) but have had no luck. Are there any other adjustments that I need to make on the carb or does my engine possibly have a different problem that does not involve the carb? I'm new to HS40 carbs and do not know entirely how they work.
I appreciate any help I can receive.
 
#4
Start with both the high speed(bottom of the bowl) and low speed (side of carb) at 1 1/2 turns out from lightly seated. You can then adjust from there once the engine is at operating temperature.
 

FunWithStuff

Well-Known Member
#6
So I tried adjusting the high and low screws and that seemed to help but now I am having another problem. When I removed the spark plug I noticed it had black sludge all over it. I was able to wipe it off so I suspect that it is oil. It is also all in the cylinder head. I replaced the oil with new oil (before starting) but I suspect this black oil was left over from storage. Should I be concerned about this or is this normal for an engine that hasn't run in a while? This wasn't affecting the engine running before but I'm afraid it may in the long run.
 

FunWithStuff

Well-Known Member
#7
It may also be carbon buildup too which shouldn't be bad I just want to make sure. I just didn't think the engine would build up so much after running for such a short time.
 

rugblaster

Active Member
#8
I've worked on three Tecumseh's in the last few weeks, two H35's and a H40. The only ones I have ever worked on.....The way I look at it, these motors are about 50 years old and I'm not going to waste my time messing around with worn out junk. On all three, I bought gasket sets, piston rings, crank seals, valve parts and what ever else I needed to completely overhaul the motors......Those China carbs you are speaking of have worked for me, but I take them apart and check passages and float level etc. So far so good. The idle circuit and main jet are, more or less, infinitely adjustable. There is no sense chasing performance problems with a motor of questionable integrity.
 
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