Topic: Point gap

[mmtsquid]

What effect does the point gap have on how the bike runs?

[Accolay]

There is a misprint in my old Clymers listing the point gap at .04 instead of 0.4mm. Your bike wont run very well this way.

[MCRider]

What effect does the point gap have on how the bike runs?

If you just want to get it running you can be sloppy with the gap and it will run. For example an old rule of thumb for shadetree tuneups was to use a matchbook, the cover was the point gap and the match was the plug gap. Using a continuity light with alligator clips you can static time it and with those gaps it will start and run fine. after all there is some tolerance to the recommended gap.

But if you want it to be crisp, you need to be more accurate. Using a timing light with the engine running, you can see that if you open the gap the timing will advance and vice versa. So it makes a difference. Also has to do with the quality of the spark, triggering the coils, dwell,  and such.

[TwoTired]

The point gap determines the charge and discharge time of the coils.

If the gap is too large the points never close to charge the coils.
If they are closed for too little time, the coils may not store enough energy to make the plugs spark.

If they are closed all the time, the coils never fire the spark plugs.

If they are closed too long a time the coils draw excessive power and may not allow a spark of proper duration.

The gap has a fairly wide range where the engine will still run.  For optimum spark, it should be in a narrow range.

The spark plug gets harder to fire as it ages.  Keeping the coils at the proper charge level keeps the plugs firing properly throughout their life span.

Cheers,

[vance]

adjusting point gap changes dwell. dwell is usually measured in degrees of rotation for the duration when the points are closed. (as in 98 degrees, meaning the points are closed for 98 degrees of the full rotation of the crankshaft) the importance of setting the correct point gap is to have the points closed for the proper amount of time to charge up the ignition coils and get the optimum spark at the plug. point gap is often set using feeler gauges because most folks don't have a dwell tach to check the actual dwell time. point gap should be adjusted first and then set the timing. you shouldn't adjust your point gap to change your timing. the timing should be bang on the "F" mark for best performance, point gap can be a little off and isn't as critical.

[mmtsquid]

It was kind of strange - I had to replace the head on my 77 CB550K (long story as to why).  When I got everything buttoned back up, the bike didn't want to idle - It wanted to stay at 3K.  I verified that there were no air leaks, pulled the carbs and blew air through every passage, nothing helped.

So I started a tune up from scratch - come to find out, the point gap was WAY narrow - like about .005" instead of the recommended .014.
Fixed the gap, fired it up, and it runs/idles perfectly.

Go figure.

[333]

There is a misprint in my old Clymers listing the point gap at .04 instead of 0.4mm. Your bike wont run very well this way.

And this is why I recommend the Honda manual.  Especially when it's available as a free download here in the forum.

[Accolay]

I agree.
But, my "bible" is kept indoors, safe and clean from the dirty garage. The clymers is falling apart and dirty on the garage floor.

[khardrunner14]

Not to hijack the thread... but I have an older penske dwell tach with 4, 6, and 8 cyl settings. It has black and red aligator clips. Where do I clip them on the bike to use it to help set my points?

Settings are high rpm, low rpm, dwell, and point resistance.