Topic: Sometimes runs all 4, sometimes just 2 PROBLEM FOUND

[Bailgang]

My 75 550 has been acting strange lately, when it's running on all 4 cyls it runs fantastic but recently from out of the blue it will stop firing on 2 cyls for a bit then as if at the flick of a switch it's on all 4 again, run fine for a bit then back to 2 cyls again at a flick of a switch, no sputtering as if low on fuel from a kinked line or so on just simply immediately quit on 2 cyls. I recently had the float bowls off for a jet change and a bowls were clear of any sediment and I checked some but not all electrical connections and all seemed well so far, keep in mind this all started happening before the jet change but it seems to be happening more often. Now I know I need to do a more thorough check of the wiring but before I go on a wild goose chase could the 4 year old Dyna S ignition be a possible culprit? With Dyna's track record as it is it's easy to lay blame on it but from my experience with electronic ignitions, once a module bad then it's dead, there is no runs for a bit then quits then runs again. For those of you who've had DynaS ignitions and it failed on you, how did it fail? Did it just plain quit on you or did it behave like I've described?

[BobbyR]

I am afraid it is probably your Dyna. If you do a Google search you will see it reported all over the place. It started on mine as like a momentary thing when the motor was hot. Then it started crapping out for longer periods after running awhile. The old Dynas were bulletproof and some have had them for 15 years. There was a period when they changed something and they started crapping out early, like 4 years.
I went PAMCO two years ago, so far so good.

[Bailgang]

I was afraid of that. I think I have a spare points plate around here somewhere, I'll just have to dig it up and hope its condensers aren't bad and see what happens. I'll report later on what I find out.

[Xnavylfr]

Try swapping the yellow and blue wires from the points/DYNA and also swap plug wires #1/4 put on cylinder 2/3 and put wires from #2/3 on #1/4 cylinders and see if the problem moves  to the other cylinders .  You can always do the old SPIT and SIZZLE check on the pipes to see which cylinders are firing!!  Before you throw more trash at DYNA do more T/S, you could have a coil going out when it gets hot.  They will act this way for a while till they just finally crap out!!


Xnavylfr(CHUCK)

[Bailgang]

The problem is that so far it's been intermittent while I'm actually riding and when it does happen I try to make a bee line home which by the time I get there it's firing on all 4 again. I was just going to swap in the points plate to see if would still do it but the prob with that is that the advancer that's in it has been modified for the dyna so it's points cam is gone. I found the points plate but have to scrounge for another advancer, I posted an ad in the "parts wanted" forum but no bites yet so I'll have to go to ebay to nab one.

[BobbyR]

That intermittant loss is very typical of a Dyna that is failing. In my case and others you will find on the web is it starts fine, at some point you can get momentary losses of power and then it can drop two cylinders. I was going up a steep mountain road when she dropped. Made it up to the tops BSed with some bikers and on the way back it was great. 1 block from the house she dropped two.

There is one other thing to check. Follow the wires from the Dyna up to the coils and carefully examine the insulation. I had a set of points give me the same problem, the insulation was scuffed from vibration and would short intermittently. It is worth a shot. I suspect your Dyna is going. Sorry, but it is very common on recently built models.

 

[K3Owner]

Since the heat of the engine is a suspect in the killing of the dyna, I wonder if anyone with this problem can grab a can of keyboard cleaner and ride with it. When the coil stops firing, turn the can upside down on the dyna and freeze it. She is likely to come back. Should quickly find whether the Dyna is at fault and, if so, which of the switches.

Just wonderin'. Freeze spray was a typical benchtop tool in the old HP tech days...

[xsmooth69x]

what 2 cylinders?

1&2? 3&4? fuel getting starved.... maybe fuel kink, maybe the float height is messed up and your starving the carbs

1&4? 2&3? points dyna electrical problem....

check the plugs? anything wierd

[Bailgang]

what 2 cylinders?

1&2? 3&4? fuel getting starved.... maybe fuel kink, maybe the float height is messed up and your starving the carbs

1&4? 2&3? points dyna electrical problem....

check the plugs? anything wierd

What 2 cyls? That's hard to tell when the headers of 2 cyls that aren't firing at that time are still smokin hot to the touch from when they were firing a moment before and by the time I get home it's back to running on all 4 again.  Highly doubt it's fuel related because there is no power loss or surging leading up to it, it literally happens as if being switched on or off which is why I suspect faulty wiring or a failing dyna and it's rapidly occurring more often and lasting longer.

As it stands now today I was able to find another advancer from a 750 in a box of parts, I removed it's points cam and put it back on the advancer of the 550, put points plates back in, set the point gap, set timing, fired it up and took it for a LONG ride and the bike never missed a beat the entire time. On the other hand with the old dyna I was lucky to get 3 miles down the road the last time I rode it before it started loosing 2 cyls. I was trying to do a process of elimination so other than swap the points back in, no other changes were made, I even left the factory '80s Kaw 3ohm coils that it's using in place.

Does that mean it's fixed now? Sure seems that way at the moment but I'll need a few more long rides and it not missing a beat in the process to confirm it but before I do I'll be swapping the factory 5ohm coils back in tomorrow before the 3ohm coils smoke the points.

[ckreb]

Sorry but unless you did a full inspection on ALL of your wiring connections first you probly just swapped ignitions for nothing. Dyna usually would have to cool down before it would fire again not just pick back up hot. You more than likely had a loose or corroded connection somewhere.

[Bailgang]

Sorry but unless you did a full inspection on ALL of your wiring connections first you probly just swapped ignitions for nothing.

I couldn't disagree more because a process of elimination has to start somewhere. I had already checked connections that were key and all were OK and swapping points back in is no big deal to me, the time consuming part was finding a points cam for the advancer. Anyhow I think the true culprit has been found and it is indeed faulty wiring, take a look at the top red wire in the pic, it's pretty much severed in half but I never spotted it while it was on the bike because it doesn't stand out when wire is straightened out. I just spotted it this morning while taking a closer look at it so the plan now is to repair that wire and put the dyna back in. I'm just glad I didn't jump to an immediate conclusion by thinking a module was at fault and toss the dyna because of that assumption without taking a closer look at it.

[BobbyR]

Great work. I think I suggested you check all the wiring. Nonetheless, congratulations on finding the problem. I was not so lucky, the unit crapped out.

[Bailgang]

Great work. I think I suggested you check all the wiring.

Yes Bobby you and some others all suggested the same so you can all stand and take a bow now and yes I do thank you all. I had the dyna setting on my comp desk this morn with the one end of the wires twisted around exposing the break, I had to use a magnifying glass to make sure but sure enough the wire itself was in 2 held together only by what was left of the insulation. With it on the bike and wire straightened out the 2 ends were close enough to make contact, not a good contact but good enough to fire on all 4's when starting cold but fragile enough to where just the wind from the road could break the contact and drop 2 cyls. At first I found it odd that when it happened it would fire on all 4 again after hitting a bump in the road but seeing how the wire was broke it makes sense now.

Well anyhow the wire was repaired and the dyna reinstalled and afterwards my wife and I gave it a 60 mile ride with the engine never missing a beat the entire time. Thanks again to all.

[BobbyR]

Sometimes it is simple and you get lucky. Enjoy your rides.

[ckreb]

Good catch. Glad you didn't just toss it. Which is what I meant by waste of time. I run into a lot of parts replacers. To me just throwing parts at something doesn't pay off if you can't identify the actual problem even if it does get fixed.

[Bailgang]

Good catch. Glad you didn't just toss it. Which is what I meant by waste of time. I run into a lot of parts replacers. To me just throwing parts at something doesn't pay off if you can't identify the actual problem even if it does get fixed.

You wouldn't believe how close I was to tossing it because once all was well with the points installed and the bad rap Dynas have been getting lately I almost immediately assumed a module was bad but for what ever reason I decided to set it in the house and wait till another day to take a closer look at it. On the other hand all of you can say "I told ya so " because I should've taken that closer look the moment I unplugged the dyna from the harness.

[alacrity]

Ockham's razor...

It's right something north of 80percent of the time in my experience...

[Bailgang]

RATS!! I spoke too soon. The problem has come back though a bit different than before so a much more thorough look at the entire harness is in store. What a bummer because it was running so sweet and flawlessly after I repaired the wire and all the miles I put on it over the weekend as well as riding it to work yesterday never missing a beat the entire time but I got halfway to work this morn and it started happening again, luckily I had some spare vacation days.

[lucky]

Make sure to check the coil wire going into the Dyna coil.
I was having a problem when my Dyna coils were only a couple months old and found the coil plug wire connection was completely covered with corrosion.

[Bankerdanny]

If the two cylinders that cut out are a paired set (1-4 or 2-3) that points to a coil problem.

[Xnavylfr]

If the two cylinders that cut out are a paired set (1-4 or 2-3) that points to a coil problem.

That statement is NOT always true!!! It can be ANYTHING in the system that pairs the 2 cylinders!! DYNA MODULE/WIRES/CONNECTIONS /COILS/PLUG WIRES /CAPS/PLUGS. Seldom will you have mated cylinder problems with plugs/caps and plug wires but it can happen!

Xnavylfr(CHUCK)

[BobbyR]

Well actually the wires and caps can cause two cylinders to drop. The nature of the waste spark system make that happen. The engine block is actually part of the circuit. Whne you bike is running pull #1 wire and #4 will drop. If anything from the coil on down does not conduct, you will lose both cylinders.

Ther was a case on here where one cylinder dropped. Turned out to be a bad plug the circuit was complete so the other plug fired. That is an oddball.

[Bailgang]

I'll get back with you guys tomorrow on this and try to explain things because there are certain things you need to be aware of before anyone starts debating what's wrong and all could be contributing factors. The broken wire I mended was without a doubt a factor but obviously something more is going on. What made it diffrent today was that I did feel a slight power loss or surge on the way home though it didn't drop 2 cyls like it did going to work. What's driving me crazy is that it runs just fine 99% of the time and I can't seem to properly test it during that 1% because I never know when it's going to happen. I didn't touch the 550 once I got it home today because I instead spent all my time working on the 750 installing a new drive chain and sprockets on it. I wanted to have at least 1 bike that was ready to go if I needed it. I'll go into more detail about the 550 tomorrow.

[Bailgang]

The coils are factory 3ohm TEC coils from an 80 sumtin Kaw, the reason I chose them was because the original 5ohm coils were in bad shape plus the later model coil I could replace the plug wire. I knew from the start that the 3 ohm coils combined with the dyna would be working my charging system pretty hard so LED turn sigs and taillights were installed to give alternator a break and in the 4 or 5 years I've had it this way there has never been an issue with charging.

The coils however are showing their age and are cracked, it's been like this for over a year and had applied silicone sealant on the cracks but I'm open to opinions on whether they're any good now because of the cracks.
At the moment both coils are measuring around 2.8 ohms. Before checking that I cleaned the spade connectors which were pretty dirty, while I had the volt/ohm meter out I checked the resistance on the spark plug resistors and that's where things got interesting. I got no reading at all (infinite resistance) on the resistor for the #1 cyl, I've never had one of those resistors apart but if that cyl was firing which it was then that coil had to be working pretty hard to make that spark happen combined with dirty spade connections could it be possible that 1-4 coil was overheating?

Still more checking needs to be done to insure there aren't any pinched wires as well as cleaning as many connections as I can but that will have to wait till tomorrow.

[74750k4]

Was having similar issues. Back to TEC coils, and points plate. ALL is well. Dyna S sent to Dyna for eval. Have not heard from them yet. I have since found a shorted Dyna 3 ohm coil that was in there. This might be the complete problem. Then again, it's a Dyna S, so all bets are off.