Tecumseh Hssk50 wont fire

C

cfh

Well-Known Member
#25
#25
try closing the gap? not sure what you mean. spark plug gap is .030 which is what it should be. air gap on cdi is .012 which is stock.
regarding valve lifters... they are same (exhaust/intake) and the valve lash is .006 which is stock.
i know the flywheel is aligned correctly and has *not* spun the keyway.
 
sparkwizard

sparkwizard

#26
#26
I'm still thinking your mixture is lean, so I would try a shop rag wet with fuel held over the intake port.
That might get it to fire, but it wouldn't tell you why it was lean.
 
ole4

ole4

#29
#29
cfh said:
try closing the gap? not sure what you mean. spark plug gap is .030 which is what it should be. air gap on cdi is .012 which is stock.
regarding valve lifters... they are same (exhaust/intake) and the valve lash is .006 which is stock.
i know the flywheel is aligned correctly and has *not* spun the keyway.
Click to expand...
air is a insulator more compression requires more voltage for the same gap. Closing the gap is just a diagnostic test to try to figure out why your test is failing.
 
sparkwizard

sparkwizard

#30
#30
Skipp said:
Or just assemble the damn thing and try! It could have been together and apart twice by now…..just my opinion….
Click to expand...
If the basic long block won't run, and he installs the carb and intake, and it still won't run, what would you do?

Don't answer. I would spray starter fluid into the carb. I think you would, too.
 
Skipp

Skipp

#31
#31
I’d start all over….check everything…especially the key….. take a few hours….make sure good sesl on head gasket….like ole4 states fire at the correct time fuel and compression….something simple….even the slightest bend in the key. bad condenser things like that….but all this is my opinion and how I chase….not for everyone…
 
C

cfh

Well-Known Member
#33
#33
I broken out the compression tester and found both motors to be under-par at about 65psi. In my experience anything below 100psi does not run. so i guess that's the problem with them not firing. the thing is, i can't really fix this, since rings are not available. what kills me is the ring gap is .015" and .017" on these motors. and the bores are perfect with original cross hatch still present.

ideally it would be great to buy some oversize .010 or .020 rings, and adjust the ring gap to .008 to .010". but since rings aren't available, i guess these motors are unusable. it's sad really...
 
C

cfh

Well-Known Member
#34
#34
for those that question my proof of life bench testing engines, here's a video i did on the process i use. this particular motor had compress of 100psi...
 
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Skipp

Skipp

#35
#35
cfh said:
I broken out the compression tester and found both motors to be under-par at about 65psi. In my experience anything below 100psi does not run. so i guess that's the problem with them not firing. the thing is, i can't really fix this, since rings are not available. what kills me is the ring gap is .015" and .017" on these motors. and the bores are perfect with original cross hatch still present.

ideally it would be great to buy some oversize .010 or .020 rings, and adjust the ring gap to .008 to .010". but since rings aren't available, i guess these motors are unusable. it's sad really...
Click to expand...
Do you know the part number of the rings you need?
 
creia

creia

#36
#36
Did you ever get spark? If you do have spark, even at 65PSI (which IS pretty low) it should still at least fire and (barely) run, but it will not have much power.
As far as low compression goes, air is either getting by the rings, the valves, or both. A diagnostic tool that I added to my inventory a few years ago is a "Cylinder Leak Down Tester", which will tell you where the air is going/escaping. I bought this one from HF and have been happy with it:
https://www.harborfreight.com/cylinder-leak-down-tester-64918.html
Another thing to think about...
Assuming that you did lap the valves properly, are the valve guides excessively worn/oversize? If they are badly worn, the valve can have too much side-to-side slop and not come down and seat squarely (and seal properly) once the engine starts rapidlyspinning and they are going up and down. They might seat just fine during a static (non-running) test, but that might not happen once they are put into motion.
Michael
 
C

cfh

Well-Known Member
#37
#37
i will check out that leak tester.
both engines the valves are nice inside their valve guides. pretty much perfect.

as for rings, these are thin ring HS50 engines. really hard to get these rings, in any of the sizes. of course all tecumseh rings are hard to get, or any type. i'm trying to stick to thick ring variants because those seem slightly easier to find. well at least they did. now no tecumseh rings are easy to get...
HS50 piston rings (thin): #40006 (replaces #36076)
HS50 piston rings (thin): #40007 (.010 over, replaces #36077)
HS50 piston rings (thin): #36078 (.020 over)
 
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