Homelite ST-285 max rpm?

lambs

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Hi guys,
I am working on an ST285BC Homelite trimmer (aka UT20581E), and cannot find a reference for max rpm anywhere.

Hoping someone has a manual for it and can advise...thanks for your help!
 

jp1961

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Hello,

My Intertec Small Air Cooled Engine repair manual (16th edition) doesn't cover your model ST-285, but data for ST-200 and ST-210 show 3350 to 3500 for idle and 6800 to 7400 for max engine speed. Page 213.

Regards

Jeff
 

lambs

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Hello,

My Intertec Small Air Cooled Engine repair manual (16th edition) doesn't cover your model ST-285, but data for ST-200 and ST-210 show 3350 to 3500 for idle and 6800 to 7400 for max engine speed. Page 213.

Regards

Jeff
Thanks! I set it for 7000 and that seems to work pretty well.
 

bertsmobile1

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Hi guys,
I am working on an ST285BC Homelite trimmer (aka UT20581E), and cannot find a reference for max rpm anywhere.

Hoping someone has a manual for it and can advise...thanks for your help!
there is a very good reason why top working speed is very rarely listed for small hand held engines.
This is because production variations can cause variations in excess of 1000 rpm , what is a safe running speed for one can be seize & explode speed for another .
Most equipment makers manuals will list a MAX top speed, or in car parlance the redline speed, not to be exceeded.
The high working speed is always set by finding the rich/lean balance point.
If you go to the carburettor makers manuals , you will find all 3 commonly available carbs , Walbro, Zama & Tillotsen have exactly the same method of top speed tuning,

Unfortunatly people of the electronic calculator generation, or latter can not accept that there is not a single absolutely correct number, because all through their education there was always one & only one correct number for everything.
I come across this problem all the time in the vintage & veteran motorcycle movements with the under 50's who just can not bring their minds to believe that there is not a single , always correct number.
And even worse this number can change depending which brand of fuel is in the tank, what the humidity is etc etc, This is not as big a problem for tools cause very few will be running them for 2 or more continious hours.

To pander to these generations a lot of 3rd party manual publishers put in a number.
Hopefully the number is what was measured when they tuned one of the engines they were writing about.

The process is the same with all hand helds .

In my case I tune them without the air filter so that with the filter in place the engine will be slightly rich.
Then the air filter is fitted and the tool tested to determine if the tuning is correct.
This of course requires you to do three things most find extremely difficult.
Look, listen & think .
Watch the exhaust with the engine under load. Excessive smoke = too rich , no smoke at all COULD BE too lean.
Listen to the engine, the sound of too rich & too lean are very much different .
Decide which way your tool is out and make a VERY SMALL adjustment then retest and by VERY SMALL we are talking 1/16 th of a turn or less.

And tested means just that, trimmers get a full length of line fitted & are tested in long grass so the engine is working hard and chainsaws are set cutting hardwood the full length of the blade.
So 7000 rpm could be the "Right" number +/- 1500 rpm.

And yes on more than one occasion, the throttle cable had to be loosened off because the "Right" top working speed was higher than the makers listed "MAX SAFE WORKING SPEED".
 

jp1961

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I've converted a handful of weed whacker engines to model R/C airplane use and depending on diameter of the prop (and pitch),,,6k to 8k seems the norm.

Regards

Jeff
 
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