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tecumseh hm80 engine tuneup ?'s


mkd55's Avatar
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12-17-05, 12:43 PM   #1  
mkd55
tecumseh hm80 engine tuneup ?'s

have an ariens 924 snowblower that i bought new in 86 .it has a tecumseh hm 80 8 hp engine that has been acting up . i just took the carb off and sprayed cleaner all over and made sure it was to spec. 11/64 float setting.initial idle mixture adjustment was 1 turn out and high speed was 1 1/2 turns out. i started the engine and warmed it up and adjusted the slow speed mixture needle to get best idle and rpm,then adjusted the high speed out till peak rpm attained and then slowly turned needle in till engine started to stumble then backed it out 1/2 turn. everything good so far! when i idle it back down for 30 sec. or so after the above adjustments were made and take it to full throttle the engine coughs black smoke and balks some untill it clears itself and then runs fine at full throttle. this told me it was too rich somewhere,low speed? thinking that one needle setting affects the other needle setting i was stumped on how to have the low and high speed adjusted as i did for best performance and had it too rich when going from slow to full throttle. upon scratching my head some this is what i did.i warmed the engine up thourghly and then while at full speed 3400rpm i started to turn the slow speed mixture screw in until the governor arm just started to waiver and then backed it out till it just stopped. then i ran it to slow speed and adjusted the slow speed rpm to 2150 rpm's. next i ran it to wide open again and started to turn the high speed mixture in(the one at the bottom of the bowl)very slowly a little at a time and eventually the governor started to waiver again and then turned it out just till the waivering stopped. this seemed to eliminate the stumble going from slow to full throttle and got rid of the little bit of popping it had at full throttle once in awhile.doing all the above has made the engine run fine when warm but has made it somewhat cold blooded at first startup compared to the way it was prior years and before these last adjustments. next snow i will see if it runs under load without any stumbling or dying out. i have done all of this work with little references to go on other than what i have read on forums like this one . does it sound like i have this engine carburetor adjusted reasonably close and if i have to adjust the high speed mixture a little richer will that change affect the slow speed mixture as well. my only big concern is how it is now so cold blooded compared to how it use to be,but it seems to run fine after it is warmed up. any comments would be appreciated!

 
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12-17-05, 03:55 PM   #2  
sounds like you have it doing alright...though it shouldn't stumble at all, should keep up with you throwing the throttle up real quick, and back down quick. your using the right heat range plug right?

 
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12-17-05, 04:24 PM   #3  
mkd55
heat range for plug

it's the one that's suppose to be in the machine. it's the resistor type but the non resistor # is cj8 champion. i got almost all the stumble out of it by adjusting it by my last post procedure.i guess i thought you do the idle mix low setting than crank it up to high and adjust that for best run and the stumble going from low to high would be taken care of.it wasn't. lucky the carb has never been mishandled and the needles were real sensitive to slight adjustments. you happen to know what the idle rpm and high speed rpm are suppose to be? i set them 2150 and 3400 rpm and i read somewhere were you shouldn't run these small engines more than 3600rpm.

 
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12-17-05, 08:59 PM   #4  
sorry, don't know specifically, puey or cheese, or someone else would know exactly.

 
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