Possible electrical issue

[alnmike]

Hey guys, after soaking my carbs for 8 hours, replacing most orings, doing a shim-job, spark plugs, and clutch cable replacement, my bike is still doing the same random thing it was before; loosing all power and dying under 3k rpm.
After todays ride (I had a passenger for like 2 hours yesterday, working like a champ), I stumbled home (with what felt like a cylinder not firing 90% of the time) and squirted some water on my exhaust. Number 2-4 were too hot for water to even make contact (squeeling noise) but number 1 wasnt nearly as hot.

Side note: when I started this morning I had a little white smoke coming out of the number 1-2 exhaust until I took choke off. And this issue occurred when I was 70mph on the highway after about 5 min running, couldnt hold speed when throttle wide open it was going 15mph in 2nd.

Im thinking (hoping) this is just a bad spark plug wire, due to its seemingly random nature. How do I test this, what ohms should I read between the inside of the plug fitting to the chassis (or some other point that I havent been made aware)?

Thanks.



Edit: I started it just now to determine if it was a hot-only issue and it held idle like normal (since the valve shims were done). When I did the work on it, all 4 plugs had too much gap, and all 8 valves were under spec clearance. It held idle muuuuuch better and sounded better after I did the shims/plugs/carb dip.
Another side note: How important is getting correct synching? I made the apparatus to test, but where I should have air screws, theres just a flat metal surface. It ran great yesterday so I dont think they are drastically whacked.

[Steve]

I see red flags flying everywhere.

If you took your carb apart for soaking, you should not see those flat areas where you think your air screws are.

Your bike does not have "air screws", it has "idle mixture adjustment screws".

Those screws are NOT used to sync the carbs.

Sync is VERY important.

Good luck with the home-made tool. The few that I have seen that worked were very cumbersome and time consuming.

Squirting water on the pipes to judge temperature? That's a new one here.

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[almarconi]

Squirting water on the pipes to judge temperature? That's a new one here.

Actually, its a pretty good indicator if your running on all 4 cylinders. If the water rolls off the pipe your not, if it sizzles when the water hits it your good.

[alnmike]

Re-reading my clymers, it says "throttle valve adjust screws" it mentioned air screws on the manometer itself. My fault for going from memory on the lingo.
I looked closer and the flat areas where I was talking about is right next to the choke rail. I see the throttle screws, near the bottom of the carbs haha.
Anyway, my problem isnt a constant one which leaves me to believe my carbs not being synced recently (Has 9k miles total) isnt the original issue.

A picture is worth 1000 words:

http://i8.photobucket.com/albums/a40/alnmike/thumper/IMG_0770.jpg

And not a bad phone picture if I do say so myself.



Edit: Homemade manometer. I made one myself because, as an engineering student, it was fun, but also I dont see how it can fail. I hook all 4 cylinders together with refrigerator hose, with some motor oil in the bottom as the colored liquid thats viscious enough to not get sucked up, and can visually see which cylinder is pulling more vacuum by the heights. I adjust everything to match #3, and am set. I dont see how this can fail, but would love to learn something as always.

Also, I knew from these forums that a good way to tell which cylinder wasn't firing was to feel the exhaust. I didnt want to get burned (again) so I used water. 2-4 howled and 1 barely sizzled, 1 isn't doing its fair share.

[almarconi]

The fact that you have the caps over the mixture screws means that you did not remove the screws to clean them. You can't adjust them either with those caps in place.

Have you used your homemade manometer yet? If you are an engineer do you remember any chemistry? Look at the specific gravity of mercury compared to that of motor oil. Your homemade unit would have to be about 12 feet tall to work.

[alnmike]

I just need a viscous liquid that wont get sucked into the engine. Any small constant (vacuum restricters help with the bouncing) difference in height is enough to see a change, or so my never-done-this-before theory suggests.
A bought manometer is say 6 inches tall (fake measurements, never seen one). Mine is roughly 4 feet. The less dense a fluid is, the more accurate measurements can be taken. It takes less pressure to raise a mL of water than it does a mL of mercury the same height. Assuming one of my carbs isnt at a pressure of 4psi, and another at atmospheric, I shouldnt get any into the engine. And if I do, it wont be more than a spoonful, which I believe is the amount that my manual says to pour into the spark plug hole before storing it for the winter.
I dont know what absolute pressure is inside the vacuum lines, but if you know it, then I could calculate the length of tubing needed to not risk any being sucked into my engine, all the while getting a better sync than someone using heavier mercury.

And that is correct, I did not remove the mixture screws to clean them. Im not about to take a dremel (and buy one) to something that obviously doesnt want to be removable. Every o-ring that I replaced in those carbs looked brand new and were completely pliable. The small holes in all the pieces I removed looked the same before and after the soaking, so I have no reason to expect something amiss in the mixture screws. (Are those air mixture screws, so I got the right name but wrong thing for syncing?)


Also, im not going to use my homemade manometer until I get confirmation that my problem isnt an electrical one, or any way of testing said theory. If I have a cylinder not firing, syncing the carbs is useless.

[almarconi]

A bought manometer is say 6 inches tall (fake measurements, never seen one). Mine is roughly 4 feet. The less dense a fluid is, the more accurate measurements can be taken. It takes less pressure to raise a mL of water than it does a mL of mercury the same height. Assuming one of my carbs isnt at a pressure of 4psi, and another at atmospheric, I shouldnt get any into the engine. And if I do, it wont be more than a spoonful, which I believe is the amount that my manual says to pour into the spark plug hole before storing it for the winter.
I dont know what absolute pressure is inside the vacuum lines, but if you know it, then I could calculate the length of tubing needed to not risk any being sucked into my engine, all the while getting a better sync than someone using heavier mercury.

Mercury sticks have been the tried and true sync tool for years. Your trying to measure the vacuum not pressure, why would your carb be at a positive pressure?

I think that what you will find is that the moment you hook your tool up to the engine, the fluid will be sucked right in. Take four pieces of tubing hooked to a reservoir of engine oil, connect them to your bike, start it up and see what happens. The reason a mercury manometer works in a relatively small package is because of the high specific gravity of the mercury.

And that is correct, I did not remove the mixture screws to clean them. Im not about to take a dremel (and buy one) to something that obviously doesnt want to be removable.

You are simply misinformed. These bikes were jetted lean from the factory, to run on gasoline made 30 yrs ago. Everyone who knows how to clean these carbs, drills the caps out so that they can clean the carbs and better adjust the idle mixture screws.

[Steve]

I just need a viscous liquid that wont get sucked into the engine. Any small constant (vacuum restricters help with the bouncing) difference in height is enough to see a change, or so my never-done-this-before theory suggests.

Restrictors only dampen the pulses. The actual vacuum level remains the same.
As mentioned, it will raise the liquid based on the weight, so a dense fluid will work in a shorter instrument.

A bought manometer is say 6 inches tall (fake measurements, never seen one). Mine is roughly 4 feet. The less dense a fluid is, the more accurate measurements can be taken. It takes less pressure to raise a mL of water than it does a mL of mercury the same height. Assuming one of my carbs isnt at a pressure of 4psi, and another at atmospheric, I shouldnt get any into the engine. And if I do, it wont be more than a spoonful, which I believe is the amount that my manual says to pour into the spark plug hole before storing it for the winter.

You claim to have been an engineering student at one time. Surely you would have learned that OBSERVATION is also part of the process. My mercury sticks are over 2 feet tall. Extrapolating that to your "fake" measurements, your tool would have to be over 16 feet. (Remember almarconi's statement "over 12 feet tall"?)

Actually the less dense a fluid is, the more susceptible it is to variation, and it will pulse more during the measurement.

Yes, it takes less "pressure" (we're talking vacuum, or negative pressure here) to raise a denser fluid to the same height, but we are not raising anything to a specific height, we are trying to measure a given amount of vacuum in a manageable space.

I dont know what absolute pressure is inside the vacuum lines, but if you know it, then I could calculate the length of tubing needed to not risk any being sucked into my engine, all the while getting a better sync than someone using heavier mercury.

The "absolute pressure" is a vacuum, relative to atmosphere, and the actual number does not matter. What matters is the balance between the cylinders. The length of tubing necessary is more dependant on the density of the fluid.

And that is correct, I did not remove the mixture screws to clean them. Im not about to take a dremel (and buy one) to something that obviously doesnt want to be removable. Every o-ring that I replaced in those carbs looked brand new and were completely pliable. The small holes in all the pieces I removed looked the same before and after the soaking, so I have no reason to expect something amiss in the mixture screws. (Are those air mixture screws, so I got the right name but wrong thing for syncing?)

No need for a Dremel, a drywall screw will do just fine.

It only looks like it doesn't want to be removable. That's the way the EPA mandated it - 30 YEARS AGO.

"The small holes all looked ..." Well, I don't know how to tell you this, but most of the worst offenders are not visible. It's not the holes that get clogged, it's the long, narrow passages WITH TURNS that are beyond those holes. Dipping or ultrasonic cleaning are the only answers.

Your picture is correct, the sync screws are correctly identified, and the mixture screws are the ones that are coverd by the flat disks. But, they are still not AIR screws. They control the amount of a MIXTURE that is allowed into the cylinder. The amount of air and fuel are preset by fixed jets, these screws only control how much of that MIXTURE gets through.



Oh, and like also mentioned, these bikes were set to run very lean to satisfy the EPA regulations at the time. Anybody that ever worked on them found that they worked much better and got better mileage if those mixture screws were adjusted a bit from stock settings. Most bikes had those screws out about 1 1/4 to 1 1/2 turns. Most of us have found much better results if they are between 2 and 3 turns out.

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[tom203]

If your bike is not running well under 3000 rpm, it's very likely that the idle/ air jet passages are clogged- just because the other o-rings in carbs looked good means nothing. To go to the trouble of making a homemade manometer without first ensuring that the low speed system is flowing is silly. As it has been stated, EPA required lean idle mistures- the plugs were there to prevent tampering, but after 28 years they need removal for thorough cleaning and adjustment. It doesn't matter if the bike has 9k miles or 99k miles. Start here before you worry about balancing carbs.

[alnmike]

My problem is not that it idles poorly. When I got on the highway for a time, I think a cylinder started mis-firing. This is the problem I need fixed.

As far as absolute pressure, you cant have negative pressure, even space has a little bit. What vacuum means is less than atmospheric, 14.7psi. Or some mix of those numbers. I dont know what pressure is being pulled by the vacuum, maybe 10psi or so, not talking gauge pressures. 10psi is really a 4.7 psi vacuum.


If you have 1 cylinder at 10psi, the rest at 12psi, it will not suck anything into the engine. My manometer isnt open to the atmpsphere, it has 4 tubes connected to each cylinder. So they all pull against eachother and I see the RELATIVE pressure, and adjust accordingly. The mercury manometers are all vented to atmospheric pressures and have to be calibrated before use.


As far as the mixture screws go, ill end up taking them out now that i know a screw works fine. Also, I know that the passages are the ones that get clogged, hence the 8 hour carb-dip soaking.

I dont claim to have been an engineering student at one time, I am one now, and so far ive been keeping from getting absolutely technical, because
a) Id rather spend time working on my bike, or doing homework than to do research to defend an internet forum post
b) The spirit of my questions are all that matter, im looking for help for my problem, and while willing to learn a bit about the next step I need to take (which I have, mixture screws), I'd rather focus on whats causing cylinder 1 to not fire. I dont believe its fuel, no reason it should completely shut off, intermittently, when hot. That leaves air (again, unless I miss something, it shouldn't get turned off), and spark. With new spark plugs, its either the cable (I could switch 1 with another one, I think 3), or whatever supplies the spark. I haven't tracked this down yet as school has started back up, but its probably a coil (which ive never seen before) or a distributor.
I dont know if it sparks each cylinder a bunch of times per engine rotation or just once.

[tom203]

You can approach solving your poor running issues any way you like. The folks in this forum are giving you their advice, based on their experience and it's FREE! No need to get defensive- they are trying to help. Don't leap to conclusions about why it's not running right. This is a four cylinder motor- if one cylinder was not working at all, don't you think the other three could manage? Your original post refered to poor low speed, "stumbled home", etc. Your recent post reveals that you haven't studied the ignition system that well- there is no distributor and plugs 1 and 4 fire together. Spend sometime in these forums and you'll pick up lots of helpful info that might simplify your life.

[Steve]

As far as absolute pressure, you cant have negative pressure, even space has a little bit. What vacuum means is less than atmospheric, 14.7psi. Or some mix of those numbers. I dont know what pressure is being pulled by the vacuum, maybe 10psi or so, not talking gauge pressures. 10psi is really a 4.7 psi vacuum. ...

True enough, but I dare say that NONE of us speaks in "absolute pressure" when we are working on our bikes. We talk about "pressure" when speaking of oil movement and air in the tires and we speak of "vacuum" when talking about intake restrictions.

The mercury manometers are all vented to atmospheric pressures and have to be calibrated before use.

One of the selling points of my mercury manometer was that it does NOT have to be calibrated. Yes, it's vented to the atmosphere, but there is no way to calibrate it because mercury is the standard against which everything else is calibrated.

b) The spirit of my questions are all that matter, im looking for help for my problem, and while willing to learn a bit about the next step I need to take (which I have, mixture screws), I'd rather focus on whats causing cylinder 1 to not fire. I dont believe its fuel, no reason it should completely shut off, intermittently, when hot. That leaves air (again, unless I miss something, it shouldn't get turned off), and spark. With new spark plugs, its either the cable (I could switch 1 with another one, I think 3), or whatever supplies the spark. I haven't tracked this down yet as school has started back up, but its probably a coil (which ive never seen before) or a distributor.
I dont know if it sparks each cylinder a bunch of times per engine rotation or just once.

Just because the plugs are new does not mean that they are good.

Your plugs are paired 1/4 and 2/3, so you would want to swap the wires for 1 and 4 to see if the problem followed the wire. If that shows no change, swap the plugs.

There is no distributor on the bike. The coil on the left side (it's up under the tank) will fire cylinders 1&4, the coil on the right will fire 2&3. Each cylinder gets fired every time the piston comes to the top, so one spark will be at the top of the compression stroke, the other will be at the top of the exhaust stroke.

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[almarconi]

People like the OP give me a headache. They have a problem, you offer advice and then they reply with some theoretical bull sh*t. You can read all the theory you want but there is no better teacher than the experience you get from actually doing the repair yourself. What more can you add when the OP knows everything..well in theory anyway.

[alnmike]

First off, I apologize if I sound a bit defensive. There were what seemed to me to be personal attacks on my intelligence and career path, I did get a bit defensive. I am now going to try to not continue the path this thread is taking.

What I meant by calibrating is you hook all 4 tubes up to the same cylinder, one at a time and get them to read the same measurement, then you can hook the 4 tubes to each cylinder to sync the carbs. Thats the procedure in my clymer's manual.
I assumed that because my spark plug cables are labeled 1,3 on both the 1st and 3rd cable, and 2,4 on the other two that they went together. Im very glad that I didn't decide to test that out today before waiting on replys. I saw that the inside two are shorter than the outside, which was also a factor to not do my own test.

I have a new data point today. I started the bike and went up a long hill, was going fine until I crested, then got the same loss of power symptoms that I did before, did a U-turn and coasted in gear down the hill, and the bike was back to normal after it cooled off. (I now confirm this is a heat related issue now).

If the consensus is that un-sync'ed carbs is the cause of my problems, ill just sync them. I haven't read in this thread yet that thats my problem, I added it to my original post as an attempt to give all the information I had, even if unnecessary to help you guys find my problem. This thread has now become solely based on manometers and syncing. Again, if my issue is indeed not electrical then let me know and ill adjust the mixture screws then sync the carbs, I just dont want to do this to find out it was something else, fix that, then have to sync again.

Thank you for the previous help and future. I have learned a few things already in this thread and hope to continue.

[almarconi]

I don't know the maintenance history of your bike but there are certain maintenance items that must be done to an old bike if you ever hope to get it running reliably.

Here are the some of the steps

1. check and adjust your valves
2. properly disassemble, dip, replace o-rings, reassemble carbs, bench sync
3. install new carb boots and intake holder o-rings if your bike has them
4. install clean air filter, make sure air box is installed and sealed properly
5. install carbs, adjust throttle cable and choke linkage
6. set idle mixture screws using highest rpm method or use a colortune
7. vacuum sync the carbs

You also need to make sure your fuel tank is clean and the petcock if working
properly.

If you did not remove those caps and mixture screws, then you did not properly clean your carburetors. Period..end of story. One of your cylinders is not firing because the carbs are probably dirty. Take care of the basic maintenance first and then see how the bike runs. You may have to pull the carbs a couple of times before you get things working properly.

In terms of electrical, you may want to consider new plugs, plug caps, wires and coils. The service manual gives a test procedure to determine if these components are good.

Sometimes fuel problems can appear to be electrical and sometimes electrical problems appear to be fuel related. Until you know for sure the carbs are clean, valves are adjusted, carb boots are fresh, no air leaks..etc can you start ruling things out.