Chainsaw Repair

Quote from: 05_sprcrw on April 07, 2011, 04:20:28 pm

Quote from: wannab12 on April 07, 2011, 08:55:22 am

Is it a stock rebuild ? ported ? muff mod. only ? I think these will come into play as well. JMHO.

Steve

It is a stock rebuild. How do those come into play? Isn't the max rpms a saw can handle listed by the manufacturer so even if I modded it wouldn't I want to only tune it to factory specs. For this saw it is 12,500 rpms, if not then what can I safely go to with the saw, I plan on squishing the jug by taking out the gasket and using a gasket maker, and at most a muffler mod as well.

Just say a stock 372xp is set at 13.5K max wot rpm. I have seen woods ported ones hitting 15K-17K out of the wood and the plugs look perfect. 
Now I would prefer to be on the rich side and clear up in the cut for cutting wood all day.

Ok got you, at that point is it a combo of playing it by ear and seeing what you can get away with or is it something that experienced guys just know?

After a rebuild I use heat cycles for stress relief. 

First time running a new piston, rings, bearings and cylinder in I double the oil in the fuel.  Start the saw, adjust the idle speed and set the engine to run for 10-15 min.  Once cool the unit then goes back up on the bench and I recheck all the fastners. 

For cycle two I keep the carburetion rich and begin to dial in the top speed and transition settings.  I set the top rich for a good four stroking.  Again allow to cool and then back to standard mixed fuel and final load based dial in from there.       

Just wanted to pass this along in case you have not heard of this method.  I really cringe when I see a newly rebuilt or brand new engine reved up when cold and put to the wood under full load.  Somewhere its published that a three minute warm up doubles the service life of the engine.       
   

Yes it does take experience to hear that sweet spot at WOT. But once you hear it with your one particular saw you will never forget it.Get a stop watch, a clean even sized log or timber [cant] with no knots.

With your L, idle and H screws set by the owners manuals specs.Have a clean air filter. Warm your saw up with a couple of warm up cuts, then make 2 cuts each cut timed by a helper. Write them down. Then lean  [turn in] the H screw a micro click and time 2 more cuts. Keep doing this until the time starts to get slower. There you have found your sweet spot at the last H setting, while still warm rev the saw at WOT a few seconds at a time and get used to hearing that sound.

Willard.

I've never heard the term WOT used.  What does it stand for?  I'm guessing wide open trottle.

You got it.

Strictly my opinion but a tach is not the ultimate tool in tuning .Nice to have but not as good as an ear .

Once you  do some modifications to an engine those factory RPM specs don't apply any more .That plus the fact that no two saw engines run exactly the same .