electrical gremlins??

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mark zervoudakis

electrical gremlins??

#1 Post by mark zervoudakis » Sat Sep 03, 2005 5:59 pm

Can anyone assist? One morning my RZ500 was going fine (recent engine rebuild with low kms and generally in very good condition) then in the afternoon it would barely run at all. An inspection of the fuel system ruled out that set of possibilities. A few symptoms :<br>* bike idles barely and produces very little power<br>* it looks like only two cyliders are firing, based on temperature of pipes when last running<br>* the plugs are fine <br>* I can only get a good spark from one side of one coil .. the other coil doesn't want to give a spark at all from either side .. this seems a major problem <br>* I have trimmed and cleaned all the connections between coil and plug without any change<br>* a local Yamaha dealer has suggested it may be a problem with the stator but I can't tell based on a visual inspection alone<p>Has anyone had a similar problem before? The sudden appearance of the problem is a bit off putting. Is it possible that the coils have suddenly died or is it more likely another electrical component is playing up?<br>Without a lead to go on I will have no choice but to leave it to the local Yamaha dealer to tell me what the problem is. Any assistance will be greatly appreciated.<p>thanks mark zervoudakis (Australia)
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akso@iprimus.com.au

Wyn Belorusky

Re: electrical gremlins??

#2 Post by Wyn Belorusky » Sat Sep 03, 2005 7:38 pm

The wires in the harness are 20 years old now and can break. Check continuity in all the wires in the harness that go to the coils.<p>Before you do any other electrical trouble shooting, make sure your battery is in good condition and fully charged.
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RZVWyn@aol.com

James Hunter (CLUB RZ / E

Re: electrical gremlins??

#3 Post by James Hunter (CLUB RZ / E » Sun Sep 04, 2005 6:29 am

Dear Mark, would you be interested in joining the register for CLUB RZ Australia, if so email me with your address and I will send you a copy of "Story of a 2 stroke nutter", and then maybe I can direct you to somebody in your area who can help, cheers mate.
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mark zervoudakis

Re: electrical gremlins??

#4 Post by mark zervoudakis » Fri Sep 09, 2005 8:52 pm

Thanks for the help. I am still tinkering and I have some more information that hopefully will assist. <br>* the battery voltage is fine (over 11.5V)<br>* there are no obvious shorts to the frame, etc that I can see .. I am reluctant at this stage to pull the harness apart.<p>PLEASE NOTE : I have put everything back together and I have noted some very strange behaviour.<br>* There is good power measured going to both coils (measured directly from the orange and black wires that feed the coils ... well over 100v from a gentle kick) BUT only if neither coil is plugged in to the orange and black wires. If I plug in the upper coil than I lose power to the lower coil. If I plug in the lower coil then I lose power to the upper coil. When I unplug the wires going to both then suddenly they both have power going to them. This is very weird. The voltage for both lower and upper is the same. <br>* I then tried to start the motor .. it started and as before it only ran on two cylinders .. I can confirm that only the front right and rear left (as if you were sitting on the bike) cylinders are firing .. I checked this a couple of times and nothing changed. <p>Feel free to post any suggestions that come to mind.<p>Thanks markz
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akso@iprimus.com.au

Rob

Re: electrical gremlins??

#5 Post by Rob » Sun Sep 11, 2005 3:43 am

Wow - that is some weird stuff going on. Are they factory coils? Are you certain the orange wire is plugged into the terminal marked + on both coils - it is hard to see, but one side has a + cast into it. They also need a good ground to the mount - the lower has a ground wire going to the bolt that mounts it, the upper grounds through the frame, so make sure that both coil mounts are grounding well to the frame and are not rusty or corroded. The mounts also like to crack and break, which can cause grounding issues. Some people just run grouns to all the mount bolts on the coils to remedy problems. It is very strange that only 1 cylinder in each bank is firing. The coils fire both plugs at the same time, one cylinder is at the top of it's stoke and one at the bottom, so if one of the 2 is firing, then the coil is presumably ok and the issue would be with wire, plug cap, plug (or lack of compression). Since on cylinder on both banks is firing, then it sounds like both coils are working! The only other thing that is notable, is that the 2 cylinders that are firing are the two that would fire at the exact same time (both are at TDC at the same time) and the two that are not firing are the other pair, almost like the cdi is not telling the coils to fire when they are at TDC - do you get spark with one of those plugs out when kicking it over? It is possible the pickup behind the stator is only reading the one firing point per revolution, other than the 2 pickup points and thus it is only telling it to fire 1 time per revolution instead of 2!<p>Sorry hard to diagnose this way, I would start by making sure every component passes the test procedure in the manual, the coils are to spec the output on the CDI is correct and the signal wire coming from the stator (it is the pair of wires that are in the stator harness, but not in the big plug, they are separate on their own little plugs - make sure they are not corroded or something - those wires are down near the lower coil) I doubt it is the CDI unit itself, as they are more of an all or nothing issue, either one coil doesn't fire and the front or rear bank don't fire, or nothing works at all!<p>So in summary, I would check everything to manual specs and then check to make sure the signal from the pickup is working correctly.<p>Rob
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roadkillrobert@yahoo.co

Rob

Re: electrical gremlins??

#6 Post by Rob » Sun Sep 11, 2005 3:46 am

One more thought - this usually will kill it totally and nothing fires, put the kickstand switches fail occasionally and should just make it not run, but I guess it could have a loose connection and be intermitant (I doubt this) but just in case, unplug the sidestand switch and take a piece of wire and bridge the 2 terminals in the plug on the bike harness to complete the circuit.<p>Rob
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roadkillrobert@yahoo.com

mark zervoudakis

Re: electrical gremlins??

#7 Post by mark zervoudakis » Sat Sep 17, 2005 8:02 pm

Thanks for your helpful comments Rob. From all that you have said I am starting to wonder if it may be the CDI unit itself that is playing up. I've had a look at the pickup and can't imagine why it would only be triggering from only one of the triggers on the flywheel. And as you said if the coils are firing for one set of cylinders they are probably OK. I have checked the wires going to the coils and have even swapped them over but this produces no change at all .. ie. the same two cylinders fire by themselves. Is it possible that the CDI is only sending a signal to the coils when the front RHS and rear LHS pistons are at TDC? As I can't actually open the CDI I am not able to check for any dicky connections. At present I am not equipped to do any more testing. This is all I have for the moment. Please post follow-ups if anyone has a brain wave. <p>thanks mark
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akso@iprimus.com.au

Rob

Re: electrical gremlins??

#8 Post by Rob » Sun Sep 18, 2005 4:00 am

If it is the CDI, it is always hard to tell and even harder to test, unless you have a spare and they are expensive and hard to find. If you have a good friend with an RZ, that is the easiest place to start and just swap them to test it out beyond what the service manual tells you that you can test.<p>Good Luck!<p>Rob
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