Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I recently picked up a Airens ST1032 snowblower. It is in good shape but, when I bought it it was taken apart. The previous owner said it did not have any spark. I replaced the points and condenser and I also removed the cylinder head cover to check the condition of the piston and valves. They look good but i did notice a hair line crack in the cylinder head. (the part the spark plug screws into). It does not appear to go all the way through.

I am in the process of putting the motor back together, but with the cylinder cracked, I am also considering getting a new motor all together. How do i know if the head is trashed? It does seem to have a decent amount of compression, but it hard to tell, because i dont know what "normal" is for that motor?

It is a 10hp tecumseh HM100 motor

Any advice?

dvdkea wrote:
Have you completely dis-assembled the carb down to it's basic components?  I.e. pulled and cleaned the jets, run wire and blown compressed air through the galleries, set float to spec, checked for manifold air leaks?  I've worked on a lot of carburetors for over 35 years and have never come across one yet that I couldn't fix.  Sure, might have taken a while to get it right but that was usually caused by being in too much of a hurry on the first or second go around.  

I did take the carb completly apart. Removed the jet, remover the chocke butterfly, and throttle butterfly, everything was apart, soaked it, and blew out all the passages, etc.

Something i did notice. The choke butterfly is bent. it appears to have been slightly beant so it would open and close. I did try to straighten it, got it flat, and the choke would not operate. Could the beant choke butterfly be causing this issue? 

If the engine is stalling because it's flooded, that could be attributed to the choke engaging after the engine is warmed up.  However, it it's a problem with fuel starvation, the choke will have no effect on that.  Next time you have it running and it stops, pull the spark plug to see if it's got any fuel on it.  If you don't see fuel, try to see if you can detect the smell of gasoline on it.  If you have evidence of gasoline, the engine is probably stalling from being flooded.  If not, you have fuel starvation.

I think it is starvation. I can keep it running with the choke off if i keep pushing on the primer. I have tried several adjustments on the main jet and also the air\fuel mixture with no real difference.

 

    If you can keep it running well for a while on primer then your gas line, float, needle are probably ok and no vacuum leak.  The float is working but the level could be off. 

    Your main jet needle should look like the one on that website i.e. the tip cut off.  7's and below had the pointed tip.  8's and above cut off.  You could try the nut and jet from the good working carb. 

    Some carbs are wicked fussy about the float level.  They are basically the same so I think it’s do to the way the machine sits.  Some ST824s sit level, some droop towards the handlebars and some a bit forward.  You seem starved so you could squeeze the float tab a hair to see if that helps.  If you can run for a short period (no prime) then it stops then let it sit for a while and it starts and runs for a short period again then it’s probably the float level.

    Are your carb linkages opening the throttle plate when you put it on full throttle?   You could open the choke butterfly and look in to be sure.

   1 turn on the idle and 1 ½ on the main jet are enough to get a carb to run so don’t bother with trying any adjustments until fine tuning after you locate whatever the problem is. 

 

   Seems like crud or a float adjustment. 

It is a new plastic float, the one that was originally in there was brass. The main needle jet does have the tip cut off, so it appears to be the correct one and is identical to the one that was in the carb before rebuild.

in this case, when adjusting the float level, i want to allow more fuel into the bowl, correct?

The carb linkages do open the throttle part way when the lever is at "fast" I was under the impression that this was normal, and the govenor would open the throttle more when needed. Is that correct?

I did install a inline fuel filter, could that be causing problems? but, then again, the carb from the st824 works fine with it.....

Trouts is probably on the right track.  I agree that it's probably a float setting issue.  I had a little two horse Evinrude engine that I couldn't get to run right for the longest time.  I was too lazy to pull the engine cowling off to take the carb out and tried to adjust the float with the carb on the engine.  Not a chance.  I had to take the engine apart and pull the carb to get the float setting right.  As he says, they can be very finicky.

The float and float needle work on the  principle of leverage.  When the float goes to the bottom of the bowl, causing demand for fuel, the float needle either opens on it's own with gravity or is pulled open via the float lever and a very small wire clip attached to the float needle and float lever.  The adjustment of the float is very critical and often only hav a millimeter or two float movement allowance.  If you have a fuel starvation issue, that means the float cannot move low enough and is not allowing sufficient movement of the float needle to permit sufficient fuel flow.  

I've had occasion when I couldn't dial in the float in and had to get creative.  So I carefully put the carb in a vice and rigged up a small bottle of water to the fuel hose going into the fuel inlet.  I then allowed water to flow down to the carb and controlled the float by hand to watch how much movement it needed to stop/allow the water flow.  This method is OK to get it close but water is heavier than gasoline and fine tuning might be necessary.  Focus on the float setting.  Sooner or later, you'll get it right.

    Never used a plastic float.  I don’t know if they ride different or are set the same way.  You can ballpark it by setting similar to the brass float then subtracting a hair from the tang to open slightly early.

 

>>The carb linkages do open the throttle part way when the lever is at "fast" I was under

>>the impression that this was normal, and the govenor would open the throttle more

>>when needed. Is that correct?

   Yes, the linkage throttle movement is a gross movement so it’s probably fine.  The governor is generally active at slowing down the motor (pushed internally by flyweights) or passivly being pulled back by throttle springs.

 

>>I did install a inline fuel filter, could that be causing problems? but, then again, the carb from the st824 works fine with it.....

 

   Also, draining fuel out of the nut will double check that  Remember, you just cleaned your carb and having problems which act like the carb is dirty.  You might want to check things again because it looks like some area you cleaned or set right is now dirty or set incorrectly.  It won’t need another dip but poking the passageways and verifying the float will probably cure it.

   Every time you put the gas line back on you are pushing hard on an old line that can easily break off crud immediatly or loosen the wall  which will fall off later.  Chances are the line did not come off easily and you had to use pliers or wedge a screw drive behind the line to get it off.  That puts a lot of stress on an old line. 

   

I think the emulsifier jet/ nozzle is slightly plugged and needs to be cleaned...

-Friiy

I give up. I adjusted the float several times with no difference in the way it runs. I ordered a new carb today.