Rebuilding/resetting points ignition systems

[thompson1600]

Hoping to get some information. I have never set up one of the old saws. Would like some help on how to diagnose, test and setup points systems. Hopefully we can start a tutorial on how to. Shortcuts you've found, homemade tools that are handy and other techniques. Thanks

Tom

 

[Lakeside53]

I'll kick it off. Caveat - most of my points based experience is Stihl - and a couple of Mcculloch...

Some of the really old (30 year) Stihl workshop manuals are excellent... Step by step setup and diagnosis. I'll dig around and see what I can copy... small selected portion are o.k under copyright law!

Points based system are very simple and very reliable, and generally produce a "fatter" spark then electronic triggered systems. Adjustment can be a pain if you don't have the factory tools, or, as we use, old flywheels that have been ground away to make adjustment easy. Condensers are a source of most problems, and bad points (burning, pitting etc) are usually because of the bad condenser. We have an old automotive condenser tester that checks the condenser at high voltage. Works great, but the best way is often just to put in a "known-to-be good" condenser. Checking the condenser with multimeter might find a short condition, but high voltage test is the only reliable way.

A couple of tricks with stator plates - on Stihls, look for a factory "strike" mark that was set when the saw was originally made - line it up, and often the timing is spot on. Not about points, but the electronic coil modules like the SEM in TS350 or 056 all have a strike mark from the stator plate to the crankcase. Sure helps...

Want to know when the points exactly open - use a light bulb or a multimeter.

Some systems require an exact TDC offset in degrees, others use a dial indicator in the spark plug hole to find offset in MM from TDC. You need to know which is required before adjustment.

 

[retoocs555]

Here is a rudimentary method for OLD saws.

Many times old saws that have been sitting get corosion on the points (why the saw won't make spark). It's a quick and free fix. First find TDC by rotating the crank until the gap between the points is at it's widest. Then remove the points. File them flat and nice and shiny with a good, fine flat file. Re-install and set the gap with a business card. This process never seems to fail on big old saws.

Stihls are the hardest to do because of the need for the special tool or a ground down flywheel. One thing you can try if you want to put a fresh surface on the points without having to remove them and reset the gap is a piece of emmory cloth folded over. It is possible to get the cloth in there and work it back and forth between the points, but it's hard and often doesn't work.

While everything is open you can check all your wires for continuity with a multimeter to make sure you don't have a wiring problem.

Why so many people hate points ignitions, I don't know... They're more reliable, serviceable, and produce better 'fatter' spark. But my favorite aspect of points ignitions is the cost of replacing one versus buying a new electronic ignition coil.

 

[jimc]

High class points service

Oil on the points - even a trace from the feeler gauge can cause some problems.
We used to pull a dollar bill thru the closed points before installing the flywheel or points cover. If you want a high class job- we'd use a $20..

 

[RaisedByWolves]

Here is a rudimentary method for OLD saws.

Many times old saws that have been sitting get corosion on the points (why the saw won't make spark). It's a quick and free fix. First find TDC by rotating the crank until the gap between the points is at it's widest. Then remove the points. File them flat and nice and shiny with a good, fine flat file. Re-install and set the gap with a business card. This process never seems to fail on big old saws.

Stihls are the hardest to do because of the need for the special tool or a ground down flywheel. One thing you can try if you want to put a fresh surface on the points without having to remove them and reset the gap is a piece of emmory cloth folded over. It is possible to get the cloth in there and work it back and forth between the points, but it's hard and often doesn't work.

While everything is open you can check all your wires for continuity with a multimeter to make sure you don't have a wiring problem.

Why so many people hate points ignitions, I don't know... They're more reliable, serviceable, and produce better 'fatter' spark. But my favorite aspect of points ignitions is the cost of replacing one versus buying a new electronic ignition coil.

Just about gospel right there.


My method for tracing trouble.

#1 check for spark.

Remove the plug from the engine, stick a screwdriver in the boot, ground the screwdriver to the case with only your hand, (ie hold the shaft firmly and touch your finger to the head) and rotate the engine slowly.

If you get bit while slowly rotating the engine, check your plug for spark.

If you dont get bit while slowly rotating the engine, gradually spin it faster till you do, or concequently you discover there is no spark at the boot, go to step #2.


#2 Check flywheel gap

Usually comes into play when somone has been monkeying around who dosent know what their doing.

Simply place a 3x5 card in the gap between the magnets and the coil and loosen the coil hold down screws. The coil will be attracted to the magnet pinching the card. Tighten the screws and recheck for spark. Still no spark go to #3.

#3 check and clean the points.

Remove the flywheel and the points cover. Take a piece of emory or suitible abrasive (Sap can use his aircleaner) fold it over so there is abrasive facing out on either side and place it between the points. If you have chosen your abrasive wisely it will fit between the points with ease and move freely when the points are open.

Now you can rotate the crank slowly untill the points begin to close up on the paper and by doing this you will be able to saw the paper back and forth and easily clean the points. Rinse the junk out with some contact cleaner and your now ready to set the points to the recommended spec using feeler gages.

Reassemble the saw and again check for spark. Still no spark? Go to #4.


#4 Buy and install a new condensor.


Points are just dead reliable and will become your favorite ignition systen once you become farmilar with them.


.

 

[thompson1600]

If you have to take a saw apart to repair it, or replace seals, what should you do before disassembling the ignition system? Make any marks? What needs to get realigned? Thanks

 

[Lakeside53]

If you have to take a saw apart to repair it, or replace seals, what should you do before disassembling the ignition system? Make any marks? What needs to get realigned? Thanks

You can make marks, but if you're in that deep why take the chance the prior guy messed it up? It only takes a few minutes to check the timing and adjust from scratch.

 

[coveredinsap]

The information contained in the post by 'raisedbywolves' is the kind of stuff that makes this site worthwhile. (the 'sap' comment notwithstanding)

 

[thompson1600]

I see people say to use a multi meter or light bulb to check timing. How exactly do you set this up? What exactly are you looking for? Thanks

Tom

 

[Lakeside53]

you're looking for the the exact point he points open: the light will go out... Hard to see by "eye" unless you have an indicator, like a bulb or multimeter.

 

[thompson1600]

Which wires do I hook the light bulb too. I assume one is to a ground and the other is to? Thanks

Tom

 

[Lakeside53]

Just across the points - ground and the points wire to the coil/switch. Battery in series with the bulb. The points make or break the circuit. Just modify a small flashlight for the purpose. I use a multimeter on low ohm range with and audible indicator - stops beeping when the points open. You may need to disconnect the coil wire as it shunts the points to ground and makes it hard to see what's happening.

 

[Ax-man]

Are parts still available for Sthil saws, specifically condensers ??? Is there a way to test the condenser to be able if it is good or bad??? The only tool I have for testing ignition systems is a multi meter.

Saws having points and condenser were a little before my time but I am getting better at fixing them, but they drive me nuts. I never realized how touchy a saw can be when it comes to the points compared to a four stroke. Seems to make or break a saw in how it runs.

Larry

 

[DOLMARatOs]

I've installed quite a few of the mega-fire style small electronic boxes available from Rotary, Oregon, Stens, etc.

They've worked well on a ton of old saws that we couldn't source new points for. Sometimes worth a try.

 

[Lakeside53]

Are parts still available for Sthil saws, specifically condensers ??? Is there a way to test the condenser to be able if it is good or bad??? The only tool I have for testing ignition systems is a multi meter.

Saws having points and condenser were a little before my time but I am getting better at fixing them, but they drive me nuts. I never realized how touchy a saw can be when it comes to the points compared to a four stroke. Seems to make or break a saw in how it runs.

Larry

Yes, the condensers are available. The old units only lasted 25-40 years, so get a big supply!


Testing a points condensor requires placing a high voltage across them and measuring leakage current. The capacitance is only one variable - they breakdown under load. A multimeter of the "old needle" type can indicate capacity by a flick of the needle, but most modern multimeters are useless. Any that show a "short" or even a high resistance are definitely junk though.

I use an old automotive type capacitor tester. It plugs into the 115V.

 

[Ax-man]

Thanks Lake

Larry