Author Topic: Nemisis MS460 (Read 3571 times)

farmboy · « **on:** February 13, 2012, 08:48:24 am »

I must have made the saw God really mad. MS460 came in for tuneup. Would start run briefly and shut off. Typical carb. rebuild symptons. Rebuilt carb. same prob. Comp check was 120psi. Piston was scored on intake side no transfer just grooves. Saw is used for stump work and firewood loaner real beatup with poor maintenance. Long story shortened: New piston, new intake boot, new crank seals, new fuel line and filter, new carb. Saw is doing the same thing start, run shut off. Impulse line is good. Pressure test holds 18 psi too high I know(MY buddy was helping me pumping the MityVac while I sprayed soapy water). Crank seals are not leaking checked them twice. Saw is broken down to crankcase. Hold's 18 psi won't hold on vac test. Boils down to case gasket. Am I on the right track? Next question is there a visible way to see vac leak or do you just go by guage?
Shep

EHP · « **Reply #1 on:** February 13, 2012, 09:47:44 am »

most saws leak on the chain oil side of the case so when running they pull chain oil into the motor and smoke like hell, if you cannot get it fixed after putting a crankcase gasket in it I would look at the coil

Cut4fun . · « **Reply #2 on:** February 14, 2012, 02:54:57 pm »

I have a 3750 that was stumping me. Even swamped known good carbs in instead of the rebuilt one and tore back down to put a new ring in it etc.
Seals and crank bearings tested fine by my redneck checks.

Then I stumbled upon a crankcase leak once warm, from the oil tank into the crank area. On the shelf she waits.

Cut4fun · « **Reply #3 on:** February 18, 2012, 10:37:15 am »

Quote from: farmboy on February 13, 2012, 08:48:24 am

I must have made the saw God really mad. MS460 came in for tuneup. Would start run briefly and shut off. Typical carb. rebuild symptons. Rebuilt carb. same prob. Comp check was 120psi. Piston was scored on intake side no transfer just grooves. Saw is used for stump work and firewood loaner real beatup with poor maintenance. Long story shortened: New piston, new intake boot, new crank seals, new fuel line and filter, new carb. Saw is doing the same thing start, run shut off. Impulse line is good. Pressure test holds 18 psi too high I know(MY buddy was helping me pumping the MityVac while I sprayed soapy water). Crank seals are not leaking checked them twice. Saw is broken down to crankcase. Hold's 18 psi won't hold on vac test. Boils down to case gasket. Am I on the right track? Next question is there a visible way to see vac leak or do you just go by guage?
Shep

Just clicked this morning. When my 372 racesaw was being built with new oem crank, ceramic bearings etc by the builder. He was having troubles with a air leak. It would pass the pressure test, submerged looking for bubbles etc.
Then figured out air leak was after it had got warm.
Even though the crankbearings pressed in like normal. When it would warm up (get hot) the whole bearing was turning in the crankcase ever so slightly.
Reason my 372 racesaw ended up with my like new complete 365 special lower end under it.

farmboy · « **Reply #4 on:** February 20, 2012, 09:22:19 am »

This thing fails vac cold. Gonna go ahead and split it and put a crankcase gasket in it and go from there.
Thanks to all. Will let you know results.
Shep

Al Smith · « **Reply #5 on:** February 20, 2012, 07:32:30 pm »

A little secret on those bearing pockets .If you get a loose one raise the metal in the pocket with a prick punch and use Loctite press fit compound .They won't spin then .

farmboy · « **Reply #6 on:** May 11, 2012, 09:36:57 am »

1. new piston
2. new fuel line & filter
3. new carb
4. new intake boot
5. case split new gasket and crank seals done by Stihl tech used Dirko on gasket. Should have done it myself Dirko all over crank throws and rod, buggered bars studs.
6. pressure tested impulse line
Saw now runs turned on l/r sides. Problem now is surging when in bucking position. Tank vent is good.
This saw has made me into Stihl hater! Never had one beat me up like this one has.
Shep

Al Smith · « **Reply #7 on:** May 12, 2012, 10:54:13 pm »

Well firstly you don't need anything on a gasket except perhaps a little bit of oil if you feel the need .

Chances are if it's surging the carb is running out of fuel so it has to catch up .Check the setting of the fuel lever . Long shot is for some reason the return spring on the fuel lever is off somehow .Rare unless you have it ported to the max and are over running the carb .Very seldom happens on most saws .

Al Smith · « **Reply #8 on:** May 12, 2012, 11:12:40 pm »

There's another thing .That saw is supposed to have a Walbro Hd 8A carb .Now there's a couple of carb kits .One has the yellow fiber semi hard check valves and one has the soft black buna-n type .The yellow ones are supposed to be the best as far as long lasting .

I've had this problem on both Walbros and Tillotsons that the danged hard checks don't seal right .Why I have no idea .

If the checks don't seal the carb won't work correctly .

farmboy · « **Reply #9 on:** May 14, 2012, 10:40:58 am »

Actually surging is not exactly what it's doing. Wrong choice of words. It goes from idle to high idle 3000 rpm's to 5,000 runs a minute and drops back to normal idle. It doesn't do it in the felling position. The carb is an HD 16A not HD 8A. Not that it should matter the kit is the same. I guess I'll do ANOTHER (5th one)vac/pressure to see if the intake boot is leaking.
Shep

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Author Topic: Nemisis MS460 (Read 3571 times)

farmboy

Nemisis MS460

EHP

Re: Nemisis MS460

Cut4fun .

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Cut4fun

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farmboy

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Al Smith

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farmboy

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Al Smith

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Al Smith

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farmboy

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