Advancing ignition timing??

[wigglesworth]

Was talking to a ex-3 wheeler racer and he menitoned something about removing the flywheel key, advancing the timing by turning the flywheel slightly and using toothpaste or lapping compound to hold the flywheel on.He said that you didnt need the key. Is he full of it? Could this be done on a saw? Would it help?

 

[windthrown]

Toothpaste, eh? :monkey:

And I thought that supergluing a 210 flywheel fin was bad enough (but it works!). No need for me to remove the keys, as I have some stripped key 1123 flywheels. Seems that it would be easier to remout the coil up a tad to advance the timing a few degrees though.

 

[Justsaws]

I do not think that you would need any tooth paste or lapping compound for the actual installation. It might be a good idea for setup to insure a tight fit between the shaft and flywheel. Clean up and mate the taper. The key is for alignment only as any slightly loose flywheel will prove.

 

[Tree Sling'r]

If you do, go small, like an 1/8 of the width of the key hole slot to start with. You don't need the woodruff key to keep it in place.

 

[wigglesworth]

What kind of gains can be expected? I would assume it would be harder starting and would probably rip your arm off.

 

[ironman_gq]

too much advance and it might run backwards :censored: I wouldnt expect too much unless the porting can handle it

 

[Lakeside53]

Too much advance and you'll toast the exhaust edge of the piston. You'll also increase the risk of detonation with crappy or aging fuel...

 

[Jacob J.]

Modern pro saws already have a pretty good ignition timing...

 

[Lakeside53]

..and... they won't run backwards.

 

[wigglesworth]

Anybody here ever done it?

 

[Lakeside53]

Some of the race saw builders do it...

 

[wigglesworth]

Based on response, I am assuming "bad idea for a work saw" huh?

 

[tdi-rick]

Some of the race saw builders do it...

Yep, and it's only optimising everything else after it's all been seen to.

What Andy has said in his first post is spot on too. 20 years ago my kart engine builder was always taking the head off, and taught me to do it too, always looking for the tell tale signs of 'the little man with his hammer'.

It's just not worth going that close to the edge on a work saw. Where the factory has it is pretty optimal for the standard squish, chamber shape and porting with average/normal fuel.

Change any one of those parameters though, example, tighten the squish to optimal and it may help to advance the ignition slightly as we have then helped (reduced) the detonation situation, but it isn't a magic pill as and of itself and gains will be minimal.

 

[heimannm]

Most of my saws are older "vintage" kit with mechanical ignition (point & condenser). It is very easy to advance the ignition timing by simply setting the point gap a bit wider. The results are sometime startling, especially when starting.

On the Jonsered 621's the whole ignition system is adjustable to permit setting the ignition timing anywhere you want it.

Indeed the flywheel key is only there for alignment purposes, as long as the parts are clean and free of burrs, etc. properly torquing the flywheel nut is all that's needed.

Mark

 

[blsnelling]

I played with it a little once and decided it wasn't worth it. Go a couple degrees to far and the saw looses all kinds of RPMs. I know the key isn't supposed to be required to hold the flywheel, but I had problems with it slipping on this particular saw. I decided it wasn't worth the hassle and haven't messed with it since.

 

[troutfisher]

If you do, go small, like an 1/8 of the width of the key hole slot to start with. You don't need the woodruff key to keep it in place.

That is VERY good advice. I've smoked a couple motors by going too far with ignition timing.