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Old 09-08-2013, 11:34 AM   #1
swanker OP
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Question much higher rpms needed, troubleshooting help

Recently halfway home on the return leg of a short 20 mile ride each way my 78 r100 started having trouble at high speed. It was running great probably sustained speed of ~80mph around 4000 rpm when it felt like it would miss and bog a bit with increased throttle.
Several short, 5 mile, rides later and the problem is more pronounced but the latest more troublesome imo problem is that I now need much higher rpm at lower gears and to get off the line. Where I'd rarely be approaching 4000 when cruising in 3rd or 4th ~40mph, now I'm regularly around 4500 during acceleration.
Power seems a bit lower but not extremely so.

I'm thinking a timing problem at full advance but am confused by the need for higher rpm at lower gears - 2000 or so to get off the line instead of normally being about 1200 or so and that I'm not feeling the misses as much at lower speeds at the 4000 rpm mark.

Planning on checking timing and compression.
Anything else for a quick easy troubleshoot checklist that might explain this behavior?

Thanks!
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Old 09-08-2013, 12:08 PM   #2
B_C_Ries
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Check the Diaphragms of your Carburetors.
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Old 09-08-2013, 12:26 PM   #3
hardwaregrrl
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When was the last time you went through the carbs? +1 on diaphram, check your jets for blockage and oring condition, float levels as well.
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Old 09-08-2013, 12:35 PM   #4
swanker OP
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I'll check the diaphragms but I rebuilt them about 500 miles ago with new o rings and new diaphragms.
I wouldn't expect the diaphragms to be an issue at low speed though, thought that would be more suspect with the high-speed issues.
Wouldn't float levels be more if an issue at high speeds? I also wouldn't think a float level issue would present itself in the middle of a ride.

swanker screwed with this post 09-08-2013 at 12:42 PM
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Old 09-08-2013, 01:21 PM   #5
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Quote:
Originally Posted by swanker View Post
I'll check the diaphragms but I rebuilt them about 500 miles ago with new o rings and new diaphragms.
I wouldn't expect the diaphragms to be an issue at low speed though, thought that would be more suspect with the high-speed issues.
Wouldn't float levels be more if an issue at high speeds? I also wouldn't think a float level issue would present itself in the middle of a ride.
Just trying to pinpoint where you are as far as experience and maintenence is concerned. You asked for a check list. if you're certain about the above, then move on to timing.
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Old 09-08-2013, 06:23 PM   #6
disston
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Timing is certainly worth checking and it is also easy if you have the timing light handy.

But this does have the smell of diaphragm to it. Where did you buy these diaphragms?
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Old 09-09-2013, 11:28 AM   #7
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Quote:
Originally Posted by disston View Post
Timing is certainly worth checking and it is also easy if you have the timing light handy.

But this does have the smell of diaphragm to it. Where did you buy these diaphragms?
"mommies rocket ship smells funny " What does a diaphragm smell like?
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Old 09-09-2013, 11:59 AM   #8
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Depending what ignition you have, the phenolic block on the points may be at fault. Power loss and missing at speed and that speed reducing is a usual sign of the point gap closing up.
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Old 09-09-2013, 02:19 PM   #9
Stan_R80/7
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And, when the point gap closes the ignition timing changes. So, checking the ignition would be 1st on my list if I experienced such symptoms. Good luck!
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Old 09-09-2013, 03:53 PM   #10
Plaka
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Quote:
Originally Posted by swanker View Post
Recently halfway home on the return leg of a short 20 mile ride each way my 78 r100 started having trouble at high speed. It was running great probably sustained speed of ~80mph around 4000 rpm when it felt like it would miss and bog a bit with increased throttle.
Several short, 5 mile, rides later and the problem is more pronounced but the latest more troublesome imo problem is that I now need much higher rpm at lower gears and to get off the line. Where I'd rarely be approaching 4000 when cruising in 3rd or 4th ~40mph, now I'm regularly around 4500 during acceleration.
Power seems a bit lower but not extremely so.

I'm thinking a timing problem at full advance but am confused by the need for higher rpm at lower gears - 2000 or so to get off the line instead of normally being about 1200 or so and that I'm not feeling the misses as much at lower speeds at the 4000 rpm mark.

Planning on checking timing and compression.
Anything else for a quick easy troubleshoot checklist that might explain this behavior?

Thanks!
Check clutch free play.

And why do you you need higher RPMs? Not making power so you rev it higher to find some, or not getting power to the rear wheel so you rev it higher to make up for the dreaded clutch slippage?

Less likely is something robbing power, a dragging brake or severely damaged bearing perhaps. look for big heat after a short ride where there shouldn't be any---a brake drum maybe. Anything over a second degree burn when poking w/ finger is a big problem. Maybe a tire rubbing but if it just started something very big is wrong. A dragging rear brake can actually be a loose footpeg bolt. The relation ship of peg and lever changes and you are stepping on the brake with the size 14s. Usually you notice the peg is floppy.

Not making power is the easy one and usually cheap to fix. Check timing and carburation. Most likely suspects. Make sure you get some valve noise when first starting cold. Check the valves if you want with a go/no-go feeler, stone cold.

Check the advance at full advance, but also shine the timing lights on the advance weights themselves and observe for smooth operation. Dunno if this one works w/ a points in can if you have that. You can observe your flywheel teeth with timing light as well and look for weirdness.

Check dwell with a dwell meter. This is your points gap you are looking at---the actual gap when running, not the static gap. A bad points spring will show up here with the dwell changing at higher RPM (Points bounce).
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Old 09-09-2013, 06:01 PM   #11
disston
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Quote:
Originally Posted by darklight79 View Post
"mommies rocket ship smells funny " What does a diaphragm smell like?
Poetic license.

I do have a title. I am the Bard of Mr. Eagan's. That's now a closed bar in the Dupont Circle neighborhood.

Charlie
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Old 09-18-2013, 12:14 PM   #12
swanker OP
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Timing was waaay off.
I didn't see the S at all in the timing port.
Got it all adjusted and it's running like a champ, backfires and hiccups/burps mostly gone as well.

A few things tho:
1) Whywould my timing go to shit all of the sudden?
2) I saw a double S which I've read is a bent cam but didn't see a double F at high revs, does that jive?
3) I had to wrap the timing light's inductive pickup on the right side plug wire to get a good reading. Placing it around the left side yielded what felt like half the frequency as the right. Is this something that should be of concern? Maybe a bad coil or wire?

thanks

oh, and Plaka, I was revving high rpm b/c I wasn't getting power from the engine which with shit ass timing makes sense, it was missing so much I had to increase the rpms to get enough firing to make enough explosions to make the engine go round
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Old 09-18-2013, 12:49 PM   #13
Plaka
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Quote:
Originally Posted by swanker View Post
Timing was waaay off.
I didn't see the S at all in the timing port.
Got it all adjusted and it's running like a champ, backfires and hiccups/burps mostly gone as well.

A few things tho:
1) Whywould my timing go to shit all of the sudden?
2) I saw a double S which I've read is a bent cam but didn't see a double F at high revs, does that jive?
3) I had to wrap the timing light's inductive pickup on the right side plug wire to get a good reading. Placing it around the left side yielded what felt like half the frequency as the right. Is this something that should be of concern? Maybe a bad coil or wire?

thanks




oh, and Plaka, I was revving high rpm b/c I wasn't getting power from the engine which with shit ass timing makes sense, it was missing so much I had to increase the rpms to get enough firing to make enough explosions to make the engine go round

Gotch. Hopefully you don't have explosions in there. Will destroy engine quick. You want controlled burn.


I believe your 78 has naked points, no? Double image at idle would be bent cam nose. Could also be worn advance unit --especially at the D hole.

Goes away at high RPM might be points bounce or an issue w/ your timing light or ???

Check if the pickup of you light has a directional arrow. my Fluke Tach. has one. It only works if connected backwards (go figure). Sounds like you got a kinda flaky light. Maybe borrow one from the auto parts store (they often offer them free w/ a deposit) and double check.

Check the wires by swapping L to R. The whole wire. But I'd sort the issue with the light first. You have to be able to trust your instruments. Try it on the car or someones elses bike.

Put in fresh plugs. Save the old ones if fairly new. Don't run fancy plugs. If you are running non-resistor, fancy are pretty unavailable anyway. This gets a bad plug out of the equation the cheap and easy way.

Buying or making up new plug wires isn't a bad idea. Try them to take that out of the equation. If no improvement put the old ones back and the new on the shelf. Their day will come and it's nice to have a new set for diagnostics. I build my own non-resistor wires. Rock solid, last forever and I never doubt them. Whatever the problem is, it isn't my wires. But I run plain jane resistor plugs and get fresh resistors with each set. How cool is that? if you stay with the resistor wires and non-resistor plugs, and you have screw on caps like NGK or something, unscrew them and trim 1/4" off the wire, then replace with the screw into virgin metal. Check the coil end too. Nice and shiny please. I use screw connections there and trim every couple years. . Brass bore brush (gun shop, pick your caliber) are good on the coil end. Gentle. For aggressive, a stainless tubing brush. You will have to get one for 1/4" or 1/8" HVAC copper tube from a HVAC supply. Use dielectric grease both ends

A loose screw is good for going to shit all of a sudden. So is a bad set of points. Index your points plate so you know about where it should be for the set of points you have. If it moves by itself...

make sure rubbing block is solid on the points. If not I would expect continuing grief. You wouldn't be able to adjust.

With points, make up a "trouble light" for static timing and always set it static first. Then put a Tach/dwell meter on it and check at full advance with the strobe light. And check the dwell. Remember it's a wasted spark system. Twice as many sparks as a twin ought to have. My trouble light is a bulb wrapped in a bit of foam and stuffed in a plastic 35mm cartrige film can. Two wires stick out the bottom terminated in micro clips. Bullet proof. Used to live under the seat. Handy as an emergency flashlight too. Hook to battery (ie, make wires long). I'm going to convert it to LED someday (man I got a loooong 'someday' list) for 5VDC operation on the electronic.
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Old 09-18-2013, 03:31 PM   #14
disston
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Ignition points. The principles are the same for hundreds if not thousands of makes and models built before we got all the improvements of electronics which so often can't be fixed. Learn the basics about ignition points and you may never have to be stranded again. At least for some ignition problem.

The amount of time the points are closed is the dwell. It is expressed as a % figure. The points need to be closed for a certain amount of time for the system to work because the dwell time is when the coils are being charged or storing up the electricity needed to create a spark. There is an electric meter type instrument used to set Dwell. It is called a Dwell Meter. Normally we set Dwell on our motorcycles with a feeler gauge. This is the point gap you do when installing ignition points. The point gap and the Dwell are basically the same thing expressed in different terms.

There is a problem with setting Dwell with a feeler gauge after the points have been used. The contacts of the ignition points build a high spot on one side and a low spot on the other. This makes for a contour that is difficult to measure with feeler gauges. A Dwell Meter can still be used in this situation but few riders have these. I have one and rarely use it. Dwell Meters can be had pretty cheap on Ebay but being electric instruments they may not work. If they work at all they can usually be used anyway because absolute accuracy is not really needed.

The tool that makes setting gap with the advance unit off? Not really needed but nice to have I guess. I plan to get one of those someday when I'm getting something else but so far I've done with out one for 50 years or so of wrenching. This tool BTW is not unique to Airheads. We had kits to do this in the old days for any ignition system.

One the gap is set the timing can be set. It is good to set the idle or static timing first and then check timing at full advance with a timing light. A stroboscopic timing light is highly recommended. The ignition timing at full advance is much more important than timing at idle and if the two are being checked anyway they will tell the story of How the advance unit is working.

The condenser is important. We do not have an easy way to test condensers. A VOM can tell you if it is shorted to ground but they can have other problems. My personal policy is to change the condenser every other time I put in new points. Some may change them less. I think some never change the condensers. That is not me.

The ignition fires when the points open. The coils have built up their charge and they fire the instant the points open. You are seeing this when you set static timing with the trouble light and the light comes on when the points open.

So far so good? Now is the part that you should understand. The points Dwell or gap can effect timing but timing does not effect Dwell.

In the beginning we set the gap first, then we set timing. Not the other way around.

If the gap is lessened the points will Dwell longer and they open later. This causes retarded timing. If the gap widens or the Dwell is shortened the points will open sooner and advance the timing. This may seem confusing at first but it is the way it works.

You put in a new set of points. properly gapped and timed them and all was well. Several things usually happen. The rubbing block on the new ignition points set sort of has to wear in. It gets a little shorter. The gap lessens and the points open later. Retarded timing.

If the felt of the points plate is out of grease an no new grease is added the wear of the rubbing block can be quite severe and the new points worn completely out before their time.

It is common for the screw holding the points gap setting to not be tightened enough. The points move and it changes timing.

Over a longer period of time as the tips of the ignition points wear away metal is transferred from one contact to the other. This has an effect to close the gap some. This is a much slower effect than the others mentioned.

So this is how they work and what usually goes wrong. It sounds like the points on your bike wore in some way or the holding screw was loose. Some how the Dwell increased which changed timing. It is possible that resetting the timing will work. It is a fact that our bikes have a lot of leeway inherent in the system because we are using an ignition system that is suitable to fire 8 cylinders for a system to fire 2.

I will do an entire treatise on the proper installation on another day, maybe.

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Old 09-18-2013, 04:46 PM   #15
Plaka
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Quote:
Originally Posted by disston View Post
Ignition points. The principles are the same for hundreds if not thousands of makes and models built before we got all the improvements of electronics which so often can't be fixed. Learn the basics about ignition points and you may never have to be stranded again. At least for some ignition problem.

The amount of time the points are closed is the dwell. It is expressed as a % figure. The points need to be closed for a certain amount of time for the system to work because the dwell time is when the coils are being charged or storing up the electricity needed to create a spark. There is an electric meter type instrument used to set Dwell. It is called a Dwell Meter. Normally we set Dwell on our motorcycles with a feeler gauge. This is the point gap you do when installing ignition points. The point gap and the Dwell are basically the same thing expressed in different terms.

There is a problem with setting Dwell with a feeler gauge after the points have been used. The contacts of the ignition points build a high spot on one side and a low spot on the other. This makes for a contour that is difficult to measure with feeler gauges. A Dwell Meter can still be used in this situation but few riders have these. I have one and rarely use it. Dwell Meters can be had pretty cheap on Ebay but being electric instruments they may not work. If they work at all they can usually be used anyway because absolute accuracy is not really needed.

The tool that makes setting gap with the advance unit off? Not really needed but nice to have I guess. I plan to get one of those someday when I'm getting something else but so far I've done with out one for 50 years or so of wrenching. This tool BTW is not unique to Airheads. We had kits to do this in the old days for any ignition system.

One the gap is set the timing can be set. It is good to set the idle or static timing first and then check timing at full advance with a timing light. A stroboscopic timing light is highly recommended. The ignition timing at full advance is much more important than timing at idle and if the two are being checked anyway they will tell the story of How the advance unit is working.

The condenser is important. We do not have an easy way to test condensers. A VOM can tell you if it is shorted to ground but they can have other problems. My personal policy is to change the condenser every other time I put in new points. Some may change them less. I think some never change the condensers. That is not me.

The ignition fires when the points open. The coils have built up their charge and they fire the instant the points open. You are seeing this when you set static timing with the trouble light and the light comes on when the points open.

So far so good? Now is the part that you should understand. The points Dwell or gap can effect timing but timing does not effect Dwell.

In the beginning we set the gap first, then we set timing. Not the other way around.

If the gap is lessened the points will Dwell longer and they open later. This causes retarded timing. If the gap widens or the Dwell is shortened the points will open sooner and advance the timing. This may seem confusing at first but it is the way it works.

You put in a new set of points. properly gapped and timed them and all was well. Several things usually happen. The rubbing block on the new ignition points set sort of has to wear in. It gets a little shorter. The gap lessens and the points open later. Retarded timing.

If the felt of the points plate is out of grease an no new grease is added the wear of the rubbing block can be quite severe and the new points worn completely out before their time.

It is common for the screw holding the points gap setting to not be tightened enough. The points move and it changes timing.

Over a longer period of time as the tips of the ignition points wear away metal is transferred from one contact to the other. This has an effect to close the gap some. This is a much slower effect than the others mentioned.

So this is how they work and what usually goes wrong. It sounds like the points on your bike wore in some way or the holding screw was loose. Some how the Dwell increased which changed timing. It is possible that resetting the timing will work. It is a fact that our bikes have a lot of leeway inherent in the system because we are using an ignition system that is suitable to fire 8 cylinders for a system to fire 2.

I will do an entire treatise on the proper installation on another day, maybe.

HaHa, I beat Plaka!
Sigh...one wonders why those marvelous points went away? There was plenty of money being made selling them again and again and again as they wore out in few miles. Perhaps manufacturers wanted better fuel economy, more powerful ignition (makes up for developing weaknesses in other wear parts), less service (set it and forget it), more stability (no changing settings), longer life (replace every couple hundred thousand)...?

Points: maybe it's this, maybe it's that, perhaps they/re worn, perhaps some associated part is funky (cam noses, advance shafts), set them again and again and again then just replace them and start all over.

Electronic: It works or it don't. No maybes. No fussing. if it don't work replace it in 5 minutes and continue on.If it works it's obvious and nothing required. No setting, no lubing, no constant replacing...no actually knowing how to do it all (and more to do than seems) much less trying to pull it off by the side of the road in the rain. No guessing---digital is like that. mechanical is not.


In all fairness to the older and long obsolete technology, electronic stuff can get intermittent and you do have to be more clever with that than a set of cooked points. But it's uncommon. A set of points will die what? 15 or 20 times for the life on an electronic? Every time the timing degraded.

Still looking for the thread where the Ops timing got so out of whack the bike would barely run---and he/she had an electronic ignition. COuld happen I suppose. But beancans don't tend to move, even if the screws are slack (only torque on them is the counter torque of the advance and the drag of the bearings and the o-ring is stiff). Not like you have mechanical bits constantly rubbing together---wearing out every mile you ride.

But I can be quite the Luddite and am anything but an early adopter. I had neither a computer nor a cell phone until someone gave me one and insisted I use it. Points? I lost those for an electronic the first chance I had. No maintenance, good-to-the-last-drop timing and very powerful ignitions just can't be beat---except by fear


Quote:
It is a fact that our bikes have a lot of leeway inherent in the system because we are using an ignition system that is suitable to fire 8 cylinders for a system to fire 2.
If there is a BS contest going on, you just won. 8's fire one cylinder at a time. Look at the distributor cap sometime. By the time you subtract everything that won't work on an 8, you're holding a coil.


Quote:
Ignition points. The principles are the same for hundreds if not thousands of makes and models built before we got all the improvements of electronics which so often can't be fixed. Learn the basics about ignition points and you may never have to be stranded again. At least for some ignition problem.
Those wonderful cars of yore litter our junkyards. With points, you WILL be stranded again, read on:

Quote:
The amount of time the points are closed is the dwell. It is expressed as a % figure.
Sorry my points expert, but back when I was working with points (not sure you were born yet), dwell was measured in degrees like everything else. Looking at My Dixon Tach/dwell meter, something of a museum piece like the points it serviced, the scale is still in degrees.



Quote:
There is a problem with setting Dwell with a feeler gauge after the points have been used.
Problems, problems, problems. Know how to set the dwell on an electronic ignition? You don't. it's preset to the correct value and never changes.


Quote:
The contacts of the ignition points build a high spot on one side and a low spot on the other. This makes for a contour that is difficult to measure with feeler gauges. A Dwell Meter can still be used in this situation but few riders have these. I have one and rarely use it. Dwell Meters can be had pretty cheap on Ebay but being electric instruments they may not work.
Kinda like light bulbs, ovens, refrigerators and all that other newfangled crap. Never know when it's gonna work or not. My dwell meter is at the bottom of a pile of pullers and greasy bore hones and set of pickle forks. For a loooong time. Still works. No batteries helps. Stuff with batteries, now that's what you don' want to trust. pacemakers and hearing aides...shudder.


Quote:
If they work at all they can usually be used anyway because absolute accuracy is not really needed.
Uh, yeah it is. points ignitions are weak and they steadily degrade with time. You do want to nail all your settings, then they last the longest. Give away some dwell and as they wear...

Quote:
The tool that makes setting gap with the advance unit off? Not really needed but nice to have I guess. I plan to get one of those someday when I'm getting something else but so far I've done with out one for 50 years or so of wrenching. This tool BTW is not unique to Airheads. We had kits to do this in the old days for any ignition system.
Put one on your collar old dog. What they do is get away from needing the rubbing block dead on the top of the cam by simulating that cam 360*. Reduced error. Remember, you need to be accurate to have the setting last as long as possible. A bit off here, a bit there...soon you're back trying to figure out why it runs poorly. A system with preset dwell and no wearing parts? Set it for timing, once, and it stays that way.

Quote:
One the gap is set the timing can be set. It is good to set the idle or static timing first and then check timing at full advance with a timing light. A stroboscopic timing light is highly recommended. The ignition timing at full advance is much more important than timing at idle and if the two are being checked anyway they will tell the story of How the advance unit is working.
I never had a strobe light before I got an electronic that could only be set at full advance. The static and advanced timing are bolted together if the advance is working, one is utterly dependent on the other. The only thing the strobe tells you is if you advance is working. If the static is right and the full advance isn't, something is broken.

Quote:
The condenser is important. We do not have an easy way to test condensers. A VOM can tell you if it is shorted to ground but they can have other problems. My personal policy is to change the condenser every other time I put in new points. Some may change them less. I think some never change the condensers. That is not me.
There is an easy way to test them. Charge it up and touch it to your tongue (or a meter), if it didn't charge, it's no good. Don't stick a big one on your tongue.

When in doubt, throw it out. Always be in doubt. man, talk about big hammers. if I did that with an electronic every 50,000 when I check timing, failures would be unknown

Quote:
The ignition fires when the points open. The coils have built up their charge and they fire the instant the points open.
Not really. But close. it's a resonant circuit with the condenser discharging repeatedly through the coils.

Quote:
You are seeing this when you set static timing with the trouble light and the light comes on when the points open.

That's cause the points aren't shorting around the light anymore. You connect it condenser to ground. But the light still makes a path to ground for the current through the coils. They don't fire.



Quote:
So far so good?
You don't ask that with electronic ignitions. it was good from the start and you long since went riding.


Quote:
Now is the part that you should understand. The points Dwell or gap can effect timing but timing does not effect Dwell.
Is this getting complicated yet or what? I need doctorate in points theory to work on the silly thing? Electronic ignition: Don't forget to turn gas on or it won't run.

Quote:
In the beginning we set the gap first, then we set timing. Not the other way around.
Wait, the deal's changed?

[QUOTE]
Quote:
If the gap is lessened the points will Dwell longer and they open later.
This causes retarded timing. If the gap widens or the Dwell is shortened the points will open sooner and advance the timing. This may seem confusing at first but it is the way it works.
How is something that's confusing a better thing? if you set points every 2500miles and you tour a lot so your cumulative speed is 50 mph then you set points every 50 engine hours. If you ride 6 hours a day 5 days a week then you're setting points every week and a half---ok I take back what I was thinking . You could probably remember it all every other week when you set points..

Quote:
You put in a new set of points. properly gapped and timed them and all was well. Several things usually happen. The rubbing block on the new ignition points set sort of has to wear in. It gets a little shorter. The gap lessens and the points open later. Retarded timing.
So you put in new points and the first thing that happens is they go out of adjustment and you have to fix them? This is a superior system? hello?

Quote:
If the felt of the points plate is out of grease an no new grease is added the wear of the rubbing block can be quite severe and the new points worn completely out before their time.



It is common for the screw holding the points gap setting to not be tightened enough. The points move and it changes timing.
Just how long is the list of "gotchas"?? You left out cleaning the points entirely. Know what happens when there is a trace of oil on them from your feeler gauge? This is the never leave ya' stranded? except, except, except...

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Over a longer period of time as the tips of the ignition points wear away metal is transferred from one contact to the other. This has an effect to close the gap some. This is a much slower effect than the others mentioned.
As every inch of the way your timing is changing. And it's not all that powerful a system. The poor points can only take so much. So not the fattest sparks, not the most energy to punch through crap on spark plugs, a poor joint in a wire, etc. Gets ya comin' and goin'

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So this is how they work and what usually goes wrong.
Why isn't this sounding very robust?



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It sounds like the points on your bike wore in some way or the holding screw was loose.

HaHa, I beat Plaka!
Or the points plate was loose and the dwell was fine. Or, or, or. Gets to be a list doesn't it. The electronic has two components. Either can fail. But they last so long that if they ever do you forgot the diagnostic. I carry a note just in case.

Don't bait bears

Plaka screwed with this post 09-18-2013 at 05:44 PM
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