Improving electrical robustness? - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 15 (permalink) Old 10-30-2017, 01:55 PM Thread Starter
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Improving electrical robustness?

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Following my CDI controller issues (see other thread), I've come across all sorts of info. both on this forum, and from talking to various specialists, dealers, etc. It seems to be (well) known that if the Alternator fails it is likely have a dramatic effect on the rectifier, CDI, ECU. If it "fails to negative) the impact is a lot less; "failing positive" (which must have done) causes instant and delayed impact. Two things occurred to me:

1. Does this forum have an "anecdotal troubleshooting" library, e.g. "If X fails or is troublesome, you may want to check out Y". It may be useful in helping diagnose stored-up problems?

2. Surely the purpose of all the fuses in the electrical system is to prevent catastrophic and knock-on failures. I am surprised there is nothing between the alternator and spark plug to prevent voltage surges, etc. taking out other critical (and expensive) components. Talking with one Honda dealer he was familiar with these type of failures on older Hondas, but said that since introduction of the Can Bus, this was not such a problem. I'm thinking of putting some fuse/protection in place to help protect the major components that are expensive and increasingly-difficult to get hold of. Has anyone done some of this already, and is willing to share? Or have any ideas of a simple solution? Just interested to discuss "prevention" instead of "cure" for a change :-)

Cheers
Simon

(UK-spec. SP2, 2002 owned from new, 45k miles)
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post #2 of 15 (permalink) Old 10-30-2017, 02:38 PM
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Well for a simple and cheap solution I've used dielectric grease on all my rides since my 93 CBR900. When I worked in the MC dealerships one thing used to be one of the first indicators of a problem was oxidation at the AC generator/ rectifier connector. I think they are still 3 blade plastic connectors and so open to oxidation. The resistance goes up and usually a field winding in the stator fries. Also the heat makes the wires at the rectifier and plug brittle. Grabbed the plug to the rectifier one time and it crumbled in my hand. When I got the RC I greased the plug first thing and made sure battery connections are checked periodically. About a year later I installed the PC3r and greased every connector I could put my hands on during the install. I'm told the new mosfet reg/rectifiers run with less heat and are more efficient. Most recommend the Shindengen FH020AA unit. There's a website called Roadster cycle which makes kits and supplies the genuine Shindengen rectifier to most 2 and 3 wire generator systems. A google search shows a lot of other sources but be careful as there are counterfeit units out there. A genuine unit is around $115 or so. Hope this is of some help.
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post #3 of 15 (permalink) Old 10-31-2017, 04:16 AM Thread Starter
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Good tip about looking after the connectors. Yes I always keep my connectors "serviced" (cleaned and lubricated using a de-oxidising spray), and I replaced my broken original rectifier with a Mosfet item, made by MTP Racing in Germany, which they state as a Shindengen equivalent. Ideally I'd like to add some in-line protection between Alternator and rectifier, Alternator and ECU, rectifier and battery, etc. basically providing isolated protection against voltage surges (in the event of component failure), where there is none at present.

(UK-spec. SP2, 2002 owned from new, 45k miles)
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post #4 of 15 (permalink) Old 10-31-2017, 10:33 AM
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Fuses don't necessarily protect against voltage surges though

Do you want to load the bike up with MOVs maybe?
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post #5 of 15 (permalink) Old 10-31-2017, 12:18 PM
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+1 on inspecting the connectors

Installing a voltmeter (or a voltage LED) will tell you when the altenator/RR combo is under/overcharging.

I have a Signal Dynamics LED on my Rc and an old skool VDO on my VF..

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post #6 of 15 (permalink) Old 10-31-2017, 12:26 PM
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i'd like a better explanation of "failing negative" and "failing positive"



are you talking about an RR failure? ie diode failing open vs failing shorted?


MOVs would protect against that, but would cause other damage in the process.
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post #7 of 15 (permalink) Old 11-05-2017, 11:53 AM Thread Starter
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Sorry Wibbly I'm not clued-up on the acronyms, so don't understand RR and MOV. In terms of the failure modes, the guy meant that if a coil/winding in the alternator failed, it could cause a shot to ground (the nicest failure), or a short such that you get a huge positive voltage spike that takes out other components (which is what I had). With all the signals from the alternator (including ignition pulse generator), there is a max. positive voltage thatch system is designed for, but it seems nothing is in place to trap (fail safe) out-of-spec voltages. I was simply curious as to how easy it would be to put some fail-safes in place to protect these critical components. This is the only problem I've ever had on the SP2 in nearly 15 years of ownership, and it's knocked my confidence a bit in wanting to take a long tour again on the SP2. Are there other issues lurking that will leave me stranded, etc.? May be it was bad luck that my alternator failed (it was a real mess inside with two banks of windings damaged), and these knock-on failures are just "an accident" and having replaced everything it will be fine for another 15 years! I am surprised the battery (only 3 years old) is still going strong, but I may put on a replacement as a matter of caution.

(UK-spec. SP2, 2002 owned from new, 45k miles)
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post #8 of 15 (permalink) Old 11-05-2017, 11:59 AM
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What sort of short would have the alternator producing higher voltage? I'd like to know. A short between coils wouldn't push the voltage up. Neither would a short to ground.


The alternator output is normally well over the bikes operating voltage anyway, It's also ac.

A failed rectifier could possibly push system voltage up if the thyristors failed shut. Or if the regulating circuit failed.



An MOV is an electronic component whose resistance decreases with voltage. If the system voltage went high the mov would short it an open the main fuse. You would have to install the MOV between positive and negative on the load side of the main fuse for it to work.

Last edited by Wibbly; 11-05-2017 at 12:09 PM.
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post #9 of 15 (permalink) Old 11-06-2017, 03:58 AM
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At the end of each season, I inspect the wiring/connectors and measure the AC output of my bikes before putiing them in winter sleep.
That (together with the DC voltmeter in the dashboard) gives me piece of mind.
Can things still go pearshaped? Yes, but mechanical/electrical failure comes with the territory...






If it come to a failure I cannot fix by the roadside, there is always roadside assistance...









(one advantage of living in a "socialist" country, the tow truck was there in <30 minutes.. sorry, could not resist... :-) )

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post #10 of 15 (permalink) Old 11-07-2017, 02:30 PM
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Originally Posted by Wibbly View Post
What sort of short would have the alternator producing higher voltage? I'd like to know. A short between coils wouldn't push the voltage up. Neither would a short to ground.


The alternator output is normally well over the bikes operating voltage anyway, It's also ac.

A failed rectifier could possibly push system voltage up if the thyristors failed shut. Or if the regulating circuit failed.



An MOV is an electronic component whose resistance decreases with voltage. If the system voltage went high the mov would short it an open the main fuse. You would have to install the MOV between positive and negative on the load side of the main fuse for it to work.
MOV (Metal-Oxide Varistor). A semiconductor with a set upper threshold voltage level that, when the upper voltage level is exceeded, will shunt the current to ground.

Normally found in the low-cost surge suppressors for home use. If you remove the cover on a power strip, the disk shaped object is the MOV.
Definitely not protective in extreme cases. A lightning strike will obliterate an MOV and zap your electronics as a result.

As a side note, the best UPS I've seen was a Sola ferro-resonant UPS.
Had a customer we installed a 5 KVA unit for their computer systems, that took a direct lightning strike. Melted the ferro-resonant coils, but saved the computers.
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