Max RPM for Husky 252RX spacing saw

[scooby074]

Not a chainsaw but im hoping somebody can help. There's next to nothing on the 252 anywheres on the net.

Does anybody know RPM for a 252RX?

Im trying to set max speed. Cant get consistently above 11500 RPM even fully lean...Max on the tach was 12,xxx but it didnt hold that speed so im guessing it was an anomaly. Im getting burbles at around 10800-11000. This is a newly cleaned and rebuilt carb. Im using a EDT7 as a tach. Tri-grass blade and guard is mounted on the shaft.

Manual calls for 13500 as rev limiter speed then -200 RPM for final set. So ~13300 for max speed.

The manual says that the rev limiter can cut in 2-300 RPM under 13500..But im wondering if there was a typo in the manual and they meant 2000-3000 RPM under that would jive with what im seeing?

No matter what adjustment i do on the H needle i cant get above 11,500. It holds 11500 through most of the adjustment. That leads me to believe that 11500 is the rev limited speed.

Can anyone confirm the error in the manual, and 11500 is max speed?

View attachment 196711

 

[scooby074]

Anybody?

 

[trappermike]

It IS possible that something is holding your saw's max. rpms down from the factory reccomended specs. But if you insist on trying to LEAN the mixture out to accomplish it,you will most likely cook(Lean-siezure) your saw.I don't know what the factory specs are,but I would be looking for 12,000 to 12,500 max. Any higher gains no more power but will increase engine heat and decrease oil mixture at the same time. Shooting for those high rpm specs is futile and reckless in my opinion as I can assure your motor's torque peak is actually around 9000.
Forget the high rpm propoganda claims,and set your high speed jet so the engine makes good power and stays cool and lubricated if you want it to last.
The reluctance to rev could be from many causes,the most usual cause is a restricted exaust- a carboned-up muffler screen,carboned up exhaust port,or maybe the stock muffler is too restrictive.
If your cutting attachment is too heavy(Even by a tiny bit)that will drag down rpms too.
Most engines actually run in the 8000 to 10000 range under load,trying to make the engine sing to a billion rpm without load is silly,pointless, and counter-productive.

 

[HiOctane]

By experience,i can tell you this.Dont run a 252 at max rpm or you gonna have a seized piston and cyl in your hand pretty soon.They are easy to seize.As TrapperMike said,forget 13K rpm,jus set it to have no burbles or few burbles WHILE cutting with,no matter the max rpm you get.In my opinion,using a tach to set to X rpm is not the right way to adjust saw or clearing saw,"good exhaust note" is the way to go.

 

[trappermike]

EXACTLY right Hi-Octane.
Regardless of what rpm the tach or factory says,the high speed must be set so that the engine is still "4 stroking"- a slight burbling or stuttering sound at max. rpm,which indicates the fuel mixture is still slightly rich,for best power and cooling.
If the engine will 4-stroke at 13,000 rpm and that's correct for the saw and it's use fine. But some motors just won't do that,then you have to settle for whatever rpm the engine will max. at while still being safely rich,if it's less than rated,too bad,thats as far as you can safely go.
Turning high rpms out of the cut doesn't mean anything(Other than you may cook the motor while impressing your friends with "How high your engine revs!)
Remember that in ALL engines(Even deisels) more fuel equalls more power. Also,as you are turning in the high speed screw to lean the mixture and make it rev more,you are cutting back the fuel,and the OIL in the fuel too! As the high speed mixture is leaned out,the exaust temp. soars,which is actually what fries the piston,combined with the less oil available to the engine.

One day me and another saw mechanic at work watched a guy blow up a brand new Dolmar(He was the Dolmar Sales Rep. visiting our shop),he was somehow convinced his new demo saw should turn 14,000+ rpms and bragging about it,so we told him our new Stihls were turning 16,000 rpm stock....
He took his saw outside,held the throttle wide open and was leaning the hi-speed screw trying to attain the magical rpms,we could hear the saw screaming higher and higher mecilessly:taped::msp_scared: ,finally,mercifully there was a loud bang and it quit,the puzzled salesman loaded it into his van and left. So much for the folly of super high rpms...

 

[trappermike]

To me,all the tach does is confirm to me what rpm the engine is turning,while still being rich enough. A good saw will hit the factory recommended limit while still being safely rich.
Only your ear can tell you if your high speed mixture is set correctly,not the tach. Some saws will barely turn 12,000 but you can still hear it's running too lean,so you must richen it accordingly even if it slows down a bit.

Guys with hot snowmobile engines will install exhaust temp. guages,so they truly do know if their jetting is rich or lean,those motors are exspensive to cook.

 

[dancan]

Not meaning to Hijack the tread .
Since we got a couple of Husky clearing saw guys here , how do I keep the blade nut from working it's way loose on my 265rx ? It has a new nut and washer last year , new blade and on it's 10th or so tank of fuel it started to work it's way loose again .

 

[dancan]

Oh , and welcome aboard scooby074 !

 

[trappermike]

Are you locking the blade in the proper manor and getting the blade nut good and tight?
Also that should be a "Nylock" type nut,if the nylon in the nut gets worn out it won't hold well,cheap to replace. For added security,put 2 or 3 drops of red Locktite on the nut,that should keep it on.

 

[dancan]

All new from Husky and scrench bending tight .
The first time it was happening I replaced all that stuff and thought the problem was solved , then it came back .
I like the loctite idea .
This does not happen on my FS550 (nut and shaft are longer) .

 

[HiOctane]

Not meaning to Hijack the tread .
Since we got a couple of Husky clearing saw guys here , how do I keep the blade nut from working it's way loose on my 265rx ? It has a new nut and washer last year , new blade and on it's 10th or so tank of fuel it started to work it's way loose again .

Others models will come loose too,like my 345 FX.I notice while using it,that it loosen when i was getting almost stuck in "large" bushes few times at close intervals and succeded to pull out,the blade comes very hot.I think heat is the problem when nut loosen.Nylock gets soft and dont do his job anymore.And dont think im an expert using them,i use it flor short period of time each year,ive done only 1.2 ha this year.Using Loctite gonna help for sure.

 

[trappermike]

The wrench matters,if you are using one of those cheapo wrenches from the manufacturer or aftermarket,fits the sparkplug and all sometimes,with the short round flimsy handle and sometimes are like a deep socket and awkward to stay on the nut,they are too awkward(And dangerous when they slip off and your knuckles go into your newly sharpened blade!:msp_scared. Many times I've watched people tightening the blade nut with the cheap "toolkit" wrench and I just wince in fear...
Simply go get a real combination box-end wrench where you can really apply some muscle to the nut,wear your leather glove to protect your hand.For some of our pro customers we would weld a strong handle(Like a 10-12" piece of light rebar) onto a 6-point socket,that's the best!

I actually maimed my hand pretty good using a stupid make believe $1.99 fit-all wrench,requiring getting my knuckles sewed back together at the hospital,as I was tightening the nut after doing a brilliant blade sharpening and the wrench slipped off,forgive me if I won't use those things...

 

[trappermike]

By the way,the blade,linehead or whatever attachment you have on your brushsaw will make a big difference in max. rpm. For instance,with a linehead on,just having an inch or 2 much line out will dramatically drag down the top speed of the motor,so with a line head on I would be setting the max. rpms with the lines a little short,if they're too long it will never get to peak speed no matter how you adjust the carb. But if you set max. rpm with the lines long,then when the lines get short it will probably be over-revving.
So maybe if your brushsaw doesn't seem to want to rev to max. specs there may be nothing wrong with it if the attachment you have on is heavier or harder for the motor to turn.Different attachments will definitely change the top revs.
Put a tach on a machine with a line head,as you extend the lines the revs drop a lot. I encountered a lot of trimmers in for repair that "wouldn't rev",all that was wrong was that the line cutter blade on the guard was clogged with crud or missing,so the lines were simply too long and the motor wouldn't rev at all. Clip the lines shorter to a proper length,fix the line cutter and bingo,they rev fine.

 

[scooby074]

First, thanks for the welcome guys. Been a member for a long time, just never post. This time i was stumped so i needed an answer!

If you check the excerpt in my first post, youll see the manual's procedure. They recommend checking with either the grass or wood blade. They also mention about the 13,xxx rev limiter. Honestly i wonder if this saw even has a limiter. Ive never had it pushing close to 13k, usually around 10k but wanted to turn it up to get a bit more out of it after the carb rebuild. Husky's procedure is basically rich till it burbles then lean to you hit the limiter, then back it off a bit. I guess the question is "Where is the limiter?" 13500k or 11500k

Im going to just do it the old way, better rich than lean anyways. so long as it doesnt stumble off the start i should be happy. even if its not screaming. I was more curious if husky was wrong or can you actually get 13k+ out of one of these.


I usually have good luck with the nut. Tighten with the factory wrench and a dab of loctite. Check the nyloc nut. It has to be good. It has a limited number of uses. If its a brand new one, thats interesting. Not sure what to recommend there other than loctite.