shindengen FH020 charging query

[fixit58]

OK, this bike is doing my nut in, done the FH020 mod and associated wiring all nice and tidy. NEW battery 2 weeks ago having just bought the bike in the last month as non runner, genny checked and all in order, 15v idle  rising to 45-50v AC revving. 0.3 ohm checks ok on all phases.  Started bike to find just above battery volts and SLOWLY rising to 13.7V. even when revved. tried the FH020 on my old vfr750 and 14.5v straight away so thats all good. even refitted the OLD OE rectifier which I know was Ok as i checked it before modifying to shindengen,.That showed the same slow rise to 13.7v. Although the pos.and neg. are direct to the battery, the rest of the bike should not be affecting charging rate.  I did solder the new yellows near the Stator. rechecked and OK. ( AC voltage checks done at the new shindengen plug anyway and Full battery volts at black shindengen plug too).  This has me scratching my head. someone put me out of my misery.

[MBrane]

Be sure to test the stator hot. They will often show good when cold, but fail when the windings warm up. Also if you can get another meter to compare they have been known to lie.

[airwalk]

Try fuse holder between rr & batt+, have had problems there a couple times. Most recent showed low & fluctuations on voltmeter while fuse remained intact,  previous showed steady & correct meter readings until it finally melted w/,blown fuse, nearly caught fire. Almost as entertaining as chasing intermittent elec. gremlins🥵

[fixit58]

16 hours ago, airwalk said:

Try fuse holder between rr & batt+, have had problems there a couple times. Most recent showed low & fluctuations on voltmeter while fuse remained intact,  previous showed steady & correct meter readings until it finally melted w/,blown fuse, nearly caught fire. Almost as entertaining as chasing intermittent elec. gremlins🥵

Thanks for that airwalk, I have temporarily rigged up a spare shindengen plug straight to the batery posts with NO fuse in and its the same SLOW (snore) rise to 13.6/13.7v. I am now today going to swop my battery from my VFR FT and try that to see if there is a difference. I fitted the fh020 from the 800 onto the 750 and its banging 14.6 in as soon as the bike started. I put the 750 FH020 onto the 800 and guess what, The same slow rise. It has to be sommat up with the new battery as everything else has been cancelled out. fffffrrrruuuussssttttrrraaaatttteeedd isn't the word.  I/ve been biking ,and restoring cars and bike since 1964 and in all my life, I have never had such weird problems.

[airwalk]

I’ll be very interested in your solution. I’ve got an older(‘86) vfr that charges @13.7 & has done for so long I don’t recall it ever being higher, although years ago I changed rr, wiring , etc. chasing a 14+ chg.rate without success. Been cursed/blessed with so many elec. issues I’ve come to think it’s the norm😒…

[Terry]

A while back I found a really good explanation of RRs from a Superhawk forum member called Tweety. I made this into a document for future reference as his explanation is outstanding (and even better when you know English is not his native tongue...)

 

MOSFET Regulator.docx

[fixit58]

11 hours ago, Terry said:

A while back I found a really good explanation of RRs from a Superhawk forum member called Tweety. I made this into a document for future reference as his explanation is outstanding (and even better when you know English is not his native tongue...)

 

MOSFET Regulator.docx 152.72 kB · 8 downloads

Thanks for thatTerry. I have swopped the FH020's over on both bikes so BOTH R/R's are working perfect. The vfr800 on the other hand has had all connections that I altered double checked and all good. 15vAC out of all 3 phases of the Stator rising to 45/50 revving, all POS and NEG are right on to the battery,  Full battery volts present at R/R cables. There is no logic to this bike so far. It just will not charge more than 13.3 or13.4 volts. yet my old vfr chucks in 14.4 all day long. checked with 2 different multimeters just to eliminate discreppancies. (it is wired in exactly the same manner as the 800 on the charging circuit). Now a thing strikes me as I think back. I built a Suzuki GS850 trike over 10 years ago and had similar problems. After buying a known good stator, new battery and new R/R at the time, it would'n't charge either. It turned out to be the rotor magnets. I bought  a used one of the fleabay and it all charged perfect. Is it possible the same scenario here>?? Weak magnets in the rotor? I have done everything that is possible to do with the charging circuit which leads me to wonder about the last part in the system. Bearing in mind, this bike has lain outside in the British elements for 5 years. This bike may turn out to be an expensive paper weight.

[airwalk]

I would suspect stator fault(s) before loss of magnetic properties unless the magnets are electro type, which these aren’t. But this puzzle has come to the grasping straws stage, worth a try if another rotor handy. Years ago I had a similar low output stator & it turned out to have one coil with windings  that would pass continuity/grounding tests but not actually create power. Unwinding showed a spot of corrosion about 10 turns(layers?) deep into the coil, imagine a multi stranded 12V wire with all but one strand broken, will pass continuity & voltage test but can’t really allow full power transmission.

[fixit58]

12 hours ago, airwalk said:

I would suspect stator fault(s) before loss of magnetic properties unless the magnets are electro type, which these aren’t. But this puzzle has come to the grasping straws stage, worth a try if another rotor handy. Years ago I had a similar low output stator & it turned out to have one coil with windings  that would pass continuity/grounding tests but not actually create power. Unwinding showed a spot of corrosion about 10 turns(layers?) deep into the coil, imagine a multi stranded 12V wire with all but one strand broken, will pass continuity & voltage test but can’t really allow full power transmission.

I got a load of paperwork including service history with this bike and there is an excell sheet with all things replaced on the bike . This bike had a generator less than 10K miles ago according to the guys list, ( albeit with the OE R/R). He even listed degreasing chain, coolant changes and everything with dates and mileages.  pretty impressive.  Would a test on the 3 phases with a 55W car bulb show any problem do you think? God I love these VFR's and have had most models from way back to FG 1988 but this one is just getting past a joke. My 1996 FT is an absolute peach and has been faultless. I notice , looking at the options for flywheels, that 2002/2003 ones are different to 2003 onward models.Flywheel/Rotor sizes seem bigger on later ones. I would need to remove stator casing to confirm the size of this one. BUT?? Are the stators the same external size?? does anyone know?? I can't find out if this bike has had the Genny recall.

[airwalk]

Testing the ac w/bulb could show a phase that’s weaker in output but you should use a 60-100 watt ac(household) bulb. I believe the rotor size&stator changed 2003 on as you say, dimensions would be available from a source more knowledgeable than I am🤔 check out roadster cycle for testing procedures, he used to have lotsa tips on there, testing w/bulb being one of them…

[fixit58]

OK, For all that have been following my posts on this Frankenbike., I finally nailed it down. Today I removed the stator cover just to convince myself of the rotor size and to have a "feel" at the magnets. The 2 rotor sizes are 107mm OD and 115 OD, Mine has the smaller.  The larger ones are fitted from 2003. My bike must have been the earlier one. Anyway, the stator looked nice and clean with no visible scorch marks. So looking at the wiring from the stator to where I soldered the new 12g wires just outside the end casing it all looked ok but did notice prior to refitting the cover that there was evidence of a blackish burn mark on the cable securing clip inside the cover. This I removed to have a look and found one of the wires had been trapped and cut into and was JUST touching the clip. Service history showed a new HONDA stator less than 10k miles before me getting this bike. Unknown to me where or who fitted this but it seems they were a little heavy handed on fitting the stator. I Re-arranged the wires and insulated the 3 of them separately just to be double sure and MAGIC, I have charging voltage of 14.5V.,  and 14.2V with main beam and heated grips on full. That will do me , as they say. What a nightmare this journey has been. Thanks go to all who commented and answered. Now to get on with checking the brakes out and painting the fork legs. UK MOT next.

[airwalk]

I recall how good it felt to finally solve an electrical issue on my ‘86(took weeks), congratulation & kudos 😅

[Gaz66]

On 5/24/2025 at 1:32 PM, fixit58 said:

 

Hi Matey.

 

Electrical gremlins are a real pain sometimes.

What's Batt voltage fully charged/ not connected? should be 12.8V, any less & battery's either a duff unit or charger's shagged, test an hr after charging, batt needs to be cool.

What's Batt voltage connected? 

What's Batt voltage tested at with meter Negative on right side chassis ground point & meter Positive on Batt Positive?

What Batt voltage, tested with meter Positive on starter side of starter relay & meter Negative on Batt Negative?

What's Batt voltage tested at starter with ignition "ON", meter Positive on starter & meter Negative on Batt Negative?

What's Batt voltage tested at starter with ignition "ON", meter Positive on starter Positive & meter Negative on starter body?

What's Batt voltage tested at starter with ignition "ON", meter Positive on starter Positive & meter Negative on engine near starter ground?

 All quick/easy but vital tests that will highlight any gremlins in an ageing loom.

 

How are you testing the Stators output voltage?

How have you wired Stator & R&R up?

It's highly likely you have some corrosion in chassis ground somewhere, have you checked the orange multi-ground block taped into the loom just forward of the R&R?

 

Warm bike up first, Test charge voltage at battery @ idle & @5,000rpm, ensure lights are on main beam, system needs a load for correct testing, what voltages are you seeing?

Do same charge output test with meter ground lead on right side chassis ground & Batt positive, follow main earth lead from battery, it should go direct to starter motor body, remove starter & clean to bare metal where starter & motor touch, clean ground cable (both ends) while ground cable is off starter & battery, Ohms test cable,  any high resistance,  cable is done & needs replacing, buy a length to 8AWG multi-stand copper earth lead, don't waste money on that chinese tinned wire crap on sale thru eBay, buy proper copper cabling, use new crimp on connectors if you can source the angled type that's fitted or re-use old ones if they've not gone brittle,  but they need to be cleaned up like new.

Add some of this anti corrosion paste to your toolbox, it'll 100% stop new copper cable corroding inside the crimps, you can use it inside any crimps on copper multi-strand, just paint it into copper wire with an old toothbrush & crush fit crimps, if you plan to solder em as well as crimp, don't use anything other than acid flux or it won't solder, you'll need a blow torch, keep all cable below torch & heat the crimp connector only, solder will wick the crimp, no solder iron will be hot enough.

https://www.heamar.co.uk/ideal-30-024-1-2oz-tube-of-noaloxr-anti-oxidant-compound.html?

 

Let us know how you get on?