Author Topic: the mystery 4 to 2 drop out (Read 3105 times)

motocyconomad · « **on:** November 14, 2013, 12:58:22 PM »

When I ride with the gas all open for and extended period (10min)...after, when I slow down or maybe the next day on a mellow ride the bike will drop out two cylinders. the oil pressure drops by half. other members have seen this first hand. The bike if left to sit (after limping home) for a few days will fire up and run on all 4 like nothing was ever wrong.
sometimes after it drops 2 cylinders it feels like they come back for a little blip but then they go out and stay out. it likes to do this in the most awkward times and never in front of mechanics i know, know my bike well.
I got no way of reliably making it fail no way to predict it except that it tends to happen after going over 100mph.

goldarrow · « **Reply #1 on:** November 14, 2013, 01:06:13 PM »

Which cylinders are out?

754 · « **Reply #2 on:** November 14, 2013, 01:06:38 PM »

Do you wash it ? Dont laugh.. I never do that..lol..
If you have moisture in the point cover it can cause that. But should not drop the oil pressure..

kghost · « **Reply #3 on:** November 14, 2013, 01:07:56 PM »

Air, Fuel and Spark.

Since the other 2 don't drop out its probably spark related.

If you can figure out which two drop perhaps that will indicate a coil overheat or fault.

At least if you figure out which 2 you have a starting point.

Powderman · « **Reply #4 on:** November 14, 2013, 03:15:57 PM »

When it drops out next time spray water or spit on the pipes. The dead cylinders won't be as hot as the live ones. Sounds coil related to me but still not enough info to diagnose.

seanbarney41 · « **Reply #5 on:** November 14, 2013, 04:00:57 PM »

oil leak under the points cover at the end of the crankshaft?

TwoTired · « **Reply #6 on:** November 14, 2013, 04:03:50 PM »

When was last 3K tuneup check list completed?
Has anyone looked at the spark plug deposits?

Stev-o · « **Reply #7 on:** November 14, 2013, 06:33:29 PM »

Tom - you had that coil issue on the Rally, you changed coils and was good to go. Did you put those 5(?) ohm coils back on?

kghost · « **Reply #8 on:** November 14, 2013, 06:44:01 PM »

If you have some colored chalk you can mark the pipes.

As the pipe warms up it burns the color off the chalk.

Cold ones will still show the color.

Everything wipes off when done.

Or just use one of those non contact thermometers from Harbor Freight lol

BobbyR · « **Reply #9 on:** November 14, 2013, 07:02:31 PM »

It is important to figure out which ones are dropping. 1-4 or 2-3 your problem is from the those plugs, and up the wires to the coils. If you are riding and can stop grab either one or four and pull it from the plug and it gets worse or stalls it is the other two cylinders.

I had a Dyna that crapped out when it got hot or I ran the bike hard. With wires and coils they will drop 1-4 or 2-3. That info really goes a long way in solving your problem.

mrbreeze · « **Reply #10 on:** November 14, 2013, 07:14:38 PM »

Bro....mine was doing the same thing and driving me crazy. It was intermittent and I was leaning more to a fuel issue till it really set in. Turned out to be the positive connector to the coils. I was blaming it on a bad coil but turned out to be a bad connection to just one coil. The stock Honda harness has a double female that supplies power to the coils. You plug your male wire for each coil positive into this female and if she's crusty.............no or intermittent connect. You can either have her douch and try again or send her packing and make a better connection at that part. Hey..............worked for me!!!

motocyconomad · « **Reply #11 on:** November 15, 2013, 05:28:43 AM »

the coil does get hot. those are stock coils the same ones that cbgia switched out at camp with the Godzilla. i think its 1-4 that drop. the dyna cover could be not totally sealed. it is a weird intermittent fail. it think its the left coil when sitting on the bike. it doesn't matter what coils are on it eventually drops. I dont see any oil inside the points cover. ... for a while I thought I had it fixed ...we thought that its was caused by a miss fire when running the top end in a lean condition, put little bigger jets and it seem to work for a bit. it goes without saying that it fixes itself without any input. now it leans more towards something in the wires or coils but it all looks pretty well connected. and it always runs great over at my shop for tuning and diagnostics.

Duke McDukiedook · « **Reply #12 on:** November 15, 2013, 06:47:14 AM »

Yeah, sounds electrical, start at your ignition and work your way down to the plugs and check and clean all connections.

Don R · « **Reply #13 on:** November 15, 2013, 08:25:45 AM »

If you have two fuel lines and they go through aftermarket filters, a filter can be plugging. Some have seen this recently. I could blow through the filter and air would enter the tank but fuel wouldn't flow back out. I suspect a fuel related gel on the filter media.

heffay · « **Reply #14 on:** November 15, 2013, 08:30:26 AM »

If it is a Dyna S... enuf said... there is a slew of us that have had your same issue, one side of the Dyna starts to fail over time and it usually takes until the bike is warmed up to rear its ugly intermittent head.

I will never put another Dyna on my bikes.

motocyconomad · « **Reply #15 on:** November 15, 2013, 09:41:59 AM »

ya the last one... got sent back, they sent me this new one. I guess I'll go back to my points to see if it happens ( i dont think it will drop 2 with those ) .... I think this is being made at a differant place then older dyna-s got made or by a differant company. I have been suspect of it , as has the electrical guru guy. the pickup on the one side failing could very well be it. strange that it would fail in such a way. you would think that it failing it would be dead forever done deal case solved... but maybe its just that weird. or those pesky viet-cong commies are sabatoging them this way to get me even crazier.

TwoTired · « **Reply #16 on:** November 15, 2013, 09:49:51 AM »

It is quite common that poorly designed/made silicon electrical devices fail with temperature and then resume when cooled down.

Electronic stores sell "cold spray" to test for just that. Shoot a failing device with cold spray and see if it returns to operation. The results are sometimes dramatic, depending on how well insulated the failing component is from the outer case.

motocyconomad · « **Reply #17 on:** November 15, 2013, 11:39:06 AM »

thats too much for me to be fiddling around with...the fact that it can occur like that, is enough for me to bail it and go back onto points. I got that hondaman gizmo that goes along with the points ...I may install one on this bike if I like how it runs on the stocker bike I got , and after having run it through my regular abusings.

TwoTired · « **Reply #18 on:** November 15, 2013, 01:51:04 PM »

Quote from: motocyconomad on November 15, 2013, 11:39:06 AM

thats too much for me to be fiddling around with...

Really? It doesn't seem like much effort to confirm a diagnosis and have real knowledge about what went wrong, rather than just guess and substitute parts until symptoms don't return. Could even help others on this forum. $:-\$

However, losing the dyna-s is no great loss, imo. It was never a good design since it was first introduced.

Whatever you're comfortable with., though.

motocyconomad · « **Reply #19 on:** November 18, 2013, 05:00:45 AM »

Quote from: TwoTired on November 15, 2013, 01:51:04 PM

Quote from: motocyconomad on November 15, 2013, 11:39:06 AM
thats too much for me to be fiddling around with...

Really? It doesn't seem like much effort to confirm a diagnosis and have real knowledge about what went wrong, rather than just guess and substitute parts until symptoms don't return. Could even help others on this forum. $:-\$

However, losing the dyna-s is no great loss, imo. It was never a good design since it was first introduced.

Whatever you're comfortable with., though.

ya thats it for me thanks. after 2 or 3 I'm done thats all the contirmation I need. other folks can read this and make what ever call they want, i'm not testing with my bike for everyone. done with that.

motocyconomad · « **Reply #20 on:** March 14, 2014, 10:42:41 AM »

this happens with points too. I'm baffled as is everyone else.

TwoTired · « **Reply #21 on:** March 14, 2014, 11:34:39 AM »

Have you looked for a dodgy electrical connection?

Probably should confirm that you are losing cylinders on coil boundaries; 2-3, 1-4.
Head pipe heat is one way to confirm.

However, it can also happen with sediment in carbs. Been there. Sediment blocks the pilot jets, but then falls away when the engine stops, only to occur again at a later random time. A good carburetor flush fixed that, after examining the particles in the bowl drainage.

I remember getting ready to try the entrails of a goat on the handlebars at moonrise to exercise demons.

motocyconomad · « **Reply #22 on:** March 14, 2014, 12:27:03 PM »

I think I'm gonna have to do the goat entrails and blood sacrific thing....

it only happens after its been riding for at least an hour or so. the connections have been gone through several times by a few differant sets of eyes.
the carbs having crap in them maybe I have a filter from the tank it looks clean. who knows its a tough case I'll report the demon when I zero in on it.

motocyconomad · « **Reply #23 on:** April 24, 2014, 06:14:55 AM »

So it looks like it was a failing head gasket. took the motor out and put it in a stock system as it was trying to be started I saw oil bubbling out the side of the gasket the compression test says its at about maybe 60psi... still wont know if the wiring system is all good till I run a motor in it that's 100% solid

Stev-o · « **Reply #24 on:** April 24, 2014, 06:27:23 AM »

Let me know if you need parts, Tom

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Author Topic: the mystery 4 to 2 drop out (Read 3105 times)