Stumble, hard start, and backfire...

[dwire]

Recent replacements seen to fail more often.

There may be something to that as my experience with small engines, (SSDD) is that they next to never fail (perhaps the new ones suck?) It depended on who was supplying the parts and what kits they would let you purchase; sans the condenser or not - one small 4 stroke engine maker, before the modern era of electronic ignition, the other half of the breaker point was the end of the condenser, so it had to be replaced; all others not made this way it was optional - and we saw very few go bad; item of last resort while probing about. I might have seen a half dozen in my lifetime; I'll bet that is pushing it...

We are all just pleased your bike runs and does so properly; people's experience and such vary - just as the last poster and I believe another lamented. I suppose it is possible I've just gotten lucky all of those years. Stranger things have happened. Enjoy the ride... Summer is waning...

[Jean]

Pushing the RS up the hill influenced my thinking, obviously.
BUT the carbs are REALLY clean...cleaned them x2 before I changed the cap.

[Manfred]

When my R80RT was having what appeared to be fuel related hard starting, poor idling, and rough running in mid-RPMs - I did a lot of work on the fuel system side with very little improvement. In my case, turned out to be a failing coil, as had been mentioned as a possibility on an older bike (but mine is only a 1987!). New coil made the old girl run like a bat.

[Jean]

I will now quote from the "BOOK OF BOSCH", 1972 English translation. Chapter 9, PP.2.5.

"Faulty condensers (sorry about that, it is an ENGLISH translation) have the effect of causing greater contact breaker point wear and a reduction in ignition performance. The latter becomes noticeable through POOR ENGINE STARTING (caps mine!) as well as MISFIRING in the upper RPM range. A faulty condenser can also lead to COMPLETE FAILURE of the ignition system."

This book also tells us that points have a useful life of up to 30,000 miles or 50,000 km. BUT, if the spring is weak or the points are misaligned, things can go bad faster. Likewise, if the contact surfaces are oily. I'd guess that the cheap points have weaker springs...or springs that get weaker when they get hot. Along this line of thought; maybe the cheap points are not made of Tungsten Carbide so they fail sooner.
So we are back to: "You get what you pay for".

[Major Softie]

This book also tells us that points have a useful life of up to 30,000 miles or 50,000 km. BUT, if the spring is weak or the points are misaligned, things can go bad faster. Likewise, if the contact surfaces are oily. I'd guess that the cheap points have weaker springs...or springs that get weaker when they get hot. Along this line of thought; maybe the cheap points are not made of Tungsten Carbide so they fail sooner.
So we are back to: "You get what you pay for".

The biggest problem with a weak spring is high rpm operation. Stronger springs work more precisely but wear the rub block faster. Weak springs may make up for an inferior rub block material. It's like everything works together.

[dwire]

As promised for your viewing pleasure; a "proper" yet elegantly simple spark tester. (BTW, there are plenty of others in existence, but these surely are the cheapest and easiest to use.) This one even allows say for instance on our two cylinder air heads to compare what is coming out of one side (coil) or the other; simply hook up a wire to the short electrode and one to the long one (standard plug wire attachment the long threaded electrode and we paid more attention to it not coming loose and being set wrong, but that was when used only for single cylinder work...) Anyhow, it is a great example of, A) How much spark one really needs in ambient air to guarantee good ignition under high compression and B) Simplicity in its purest form - someone followed the KISS method with these likely 50 to 60 years ago, perhaps more...

Your ignition system should produce a nice BRIGHT BLUE spark every time it fires; colors in the red, yellows and some anemic whites (you'll see it looks like crap and may not even jump the gap each time...) are all signs of a problem. With this, if one cylinder looks great and the other looks awful or is not existent, with what everyone in this thread knows, where would you go immediately? Not the points, condenser or any such thing as it is doing its job on the other side - naturally check the wiring, but the way are boxers work, you'd be looking at a weak or bad coil on the offending side or a bad plug wire - maybe those elusive resistor cap things I have no clue why they are used other than not to mess with people's radios... Long and the short of that scenario would be you should be able to eliminate even taking the front cover off; well until maybe last as a bad coil "can" do yucky things to points & condensers on occasion. See how easy some little couple dollar doo-dads can make your life? (They likely cost far more these days though I am afraid...)

These have been around longer than I have and if a person ever wanted one, I'd recommend looking at the small engine shops as these used to even have a Briggs&Stratton P/N (even though they were made by an after-marketer) and likely many others. I can attest when set properly as this one is, it will give you trust worthy readings for anything into the 200 psi compression range as that is what my race "motors" (engines) would run as a kid.



Simply pull your plugs, clamp the alligator clip to a good solid ground on the head, jug or equivalent and insert your plug wire(s) - turn the engine over and watch as the magic appears (or DOESN'T ) - piece of cake!

[chasbmw]

So how does that gizmo reflect compression pressure?

[dwire]

What is it that you do not understand about (in this case) air/fuel mixture under high compression having a much higher breakdown tolerance or resistance to electron flow than ambient air? In contrast, spark jumps far more freely in ambient air - that is why the tester's gap is spaced so far apart.

That was why I made the statement I did earlier in the thread and provided the picture with an explanation sbove. One could Google up on Tesla, the nature of capacitors and specialized air gap applications for good facts and figures. In the end, that gap with fuel/air mixture under high compression must become a conductor to ignite the material in the combustion chamber. If that still does not ring any bells when combined with my original comment in the thread, let me know; I added the long version to my up and coming book manuscript.

[Jean]

Good sleuthing, dwire. There is a picture of such a thing in an OLD handbook I have. When I say your photo, I recalled it.
Something like this was used in the dark ages when magnetos and early kettering ignition systems got used on autos!!
Easy to build now using a slice of polyethelene thick-wall tube or some such. The original was in hard rubber or Bakelite. I think Prestolite made one.
On the other hand, it eliminated all that FUN I mentioned where YOU hold the wire and draw the spark.

Yes, it takes a lot more moxie to spark in the compressed atmosphere of the combustion chamber, that's why you need to see about a 1/4 inch spark outside!
PS. Did you make this or is it something you bought or inherited? The ring looks like formica.

[Deleted User 62]

I understand the need for the clamp and the pin opposite it, but why is that third pin there and coming in at an angle?