Small Engine question

[Anonymous-0]

I have a 1978 Briggs 8HP horizontal shaft engine.
Poor to no spark.
Fiddled with the ignition coil and what I noticed is no matter how its positioned it can't be mounted so that it has the recommended .030 gap above the magnet. Due to lack of travel in the mounting the largest gap is .015.

Magnet strength seems fine.

The question. Any issue with chucking the flywheel in the lathe and turning .060 off the diameter of the flywheel and magnet assembly?

 

[Bill Krosnicki]

I usually just use a business card to set the air gap. Make sure you clean the rust off the magnet and coil. Did you file and readjust the points? The flywheel needs to come off for that, or you need to put an electronic ignition on it. Considering the cost, I'd keep the points.

 

[John T]

I dont like the sound of machining the flywheel, you would be milling away a part of the magnet Ima thinking......Ive not had trouble if the coil is a bit too close as long as theres no physical contact, the farther away Id think the spark energy would decrease.

Cant you drill/machine/ream the coil mount holes to change its distance??? Ive set them as low a 0.010 away on some engines

Best luck Ive had is to clean n polish and remove any light surface rust off the flywheel and magnet as that build up can weaken the spark energy.

If the distance is correct (or a bit too close) and the wires and plug are good and the magnet is clean n rust free but still a weak spark the coil may be going bad???? At slow RPM the sparks weaker then at fast RPM remember

Im guessing this does NOT use breaker points??? i.e. just the coil against the flywheel system. If it does like some older engines Id sure check and replace if necessary those first

John T NOT a small engine man

 

[Butch(OH)]

My experiance is the closer they are to the passing magents the more spark you will have until the point of touching. I doubt if your .015 gap is the problem as long as it is not actualy touching. Do not turn the flywheel O. D. in any case.

 

[Fritz Maurer]

THE GAP IS SUPPOSED TO BE .006!

 

[Anonymous-0]

No points.
Extending the slots I've seen the small coils delaminate while being milled in the past. Figured I'd not go that route (yet).
I hit the fly wheel lightly with steel wool before setting the gap. I'll put a little more elbow grease into it.

Thanks
Ray

 

[RayP(MI)]

Like Bill says, I set gap with a business card, or a matchbook cover. As close as possible without touching flywheel.

 

[Pete T]

I would get a new magnatron coil, set it with a business card, like other post have said & be done with it. If it has points this will do away with them.Coils will go bad on B&S, although not very often.I don't think I would try turning the flywheel down.

 

[supergrumpy]

I have one of those "no points" B/S engines, guess it fires when it feels like it

check the coil connections to ground, see if resistances are proper on the 2 sets of coil wires

on some I have slid the windings off and swapped in another set

try another spark plug

 

[old]

Many things can cause that. Check and then double check your points and the gap on them and make sure they are clean and shiny. Also make sure the gap between the mag and the flywheel is correct. A simple piece of electrical tape works well for setting the mag to flywheel gap. Also check for end play at the crank shaft shaft coming out of the block. I have had more the one older B/S engine that the shaft bushing got so bad that the shaft it's self would move so much that it would cause a loss of spark

 

[Dannie1]

WORKED ON SMALL ENGINES FOR YEARS IF MAGNETS ON FLYWHEEL WILL HOLD A SCREWDRIVER IT IS GOOD.IF NO POINTS REPLACE COIL.

 

[Greenday]

30 is way to much gap! This would also give you poor spark

 

[LJD]

All the Briggs engines with two-leg armature coils get gapped at .006" - .014".

All the aluminum 7 and 8 horse engines have an air-gap of .010"- .016"

All the Briggs engines with three leg armatures get gapped at .012"-.016" except for Models 19, 23, 193400, 200400 and 233400 that get gapped at .022-.026" if three-leg and .010"-.014" if two-leg.

I'm assuming you've got a 190000 series aluminum block engine? If so, air gap is set .010"-.016"

 

[buickanddeere]

Butch is correct

 

[El Toro]

Use a post card set over the magnets and set the coil on top of the postcard and use one hand to snug the coil against the post card then tighten the mounting screws. The see if you have fire to your plug. Don't machine the flywheel. Hal

 

[Bryan in iowa]

Don't do it ! IT worked before . Tighter gap is better . Business card ,let magent pull coil tight , tighten mounting screws ,bingo ! Ifno spark you have other issues .

 

[jackinok]

points and condenser good?like the others say dont turn the flywheel.coils is probably bad or getting weak.if it has any cracks in the insulation its definitly bad.

 

[guido]

Hello ray_woods,
Cleanig the flywheel will not have any effect on the spark.The gap is not the same on all engines.Give the model# and i'll look it up for you.2 and 3 leg armatures have different gap settings. 2 leg armature are usually .014 or less. 3 leg armature are from .012 to .026. If I had to take a guess, I would say.006 to.010 for a 2 leg armature, and .012 to .016 for a 3 leg one. It all depends on the engine model for the settings. As other suggested leave the O.D. of the flywheel alone.
Clean the contacts, doesn't take much to keep them from sparking.
A good ignition will jump a gap of .187.
Also check the size of the breaker points plunger, minimum size is .870 good luck!
Guido.

 

[guido]

Hello ray_woods,
I've just sread one of your raplies, with an electronic igniton, set the gap at .010 to .012.
.015 is too much gap. Also set the plug at least .030
Guido

 

[Texasmark1]

Magnets don't have to be squeaky clean, like an electric circuit. The magnetic lines of flux can flow into the iron of the core very easily....actually that's the reason for using a core in the first place, and surface condition isn't that big of a deal.

In non tech terms, the gap takes away from the core function which is to increase the magnetism of the total component. Milling will reduce that gap. How much and all the effects, depends on what you are working with, and does it matter or not depends what it's used for. Probably in an ignition circuit it would depend upon what kind of condition the plugs are in. New plugs probably wouldn't notice a pretty good increase in the gap. Crudded up/hard to fire plugs surely would.

Mark

 

[Texasmark1]

ERROR. When I said "milling will reduce the gap" I meant to say it would reduce the effect of magnetic flux in the core. It will increase the gap obviously.

Sorry.

Mark

 

[Texasmark1]

Course, as mentioned, the magneto can be moved closer to the flywheel. On gap, I used to use a brown paper bag which I could stick between the two, loosen the mag and allow magnetic attraction to suck it up against the bag, tighten her down and twist the flywheel till I could get the paper out.

Mark

 

[donjr]

Try popping the flwheel off and replace the aluminum key in the shaft. Just a little shear will cause the spark to be off. It also makes it easy to take some sandpaper and buff the rust off the magnets while it is off. Depending on the engine, there may also be a round cover behind the flywheel covering the points.

 

[BrianJasper co. Ia]

Air gap is .010 to .014 on 4hp and larger aluminum and cast iron 2 leg coils. It's on page 25 of the out of production briggs repair manual.

 

[Anonymous-0]

The magnet metal will eat your cutting tool.