1982 Honda CB900F “Holly”

SquidHunter

Active Member
Yeah, the regulator is just under the left side cover, easy enough to get to. Are you talking about the exposed system w/ the oil pressure gauge? Looks cool but I'd like to retain the cover, and don't necessarily want to switch back to a lead-acid battery (believe it has an agm currently). What battery are you running?
I’m running an agm battery. The one I got isn’t exposed. I’m sure if you call them they’ll fix you up with the older style.


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Snout

Active Member
Not sure how similar the F is to the C version other than the obvious chain/shaft, but mine will scrape the header too, and is cold blooded as well. I had some issues with the small contacts in the starter button, but other than that it has been a great bike for the money. Once you get it sorted it will treat you well.
 

CALfeRacer

Fat man on a little bike
Finally got around to testing the charging system. Resistance on the rotor checked out (4.4 ohm) and resistance on the windings was a little high (0.8-1 ohm). I got no charging at any revs though, and couldn’t get a voltage between the white and black wires coming off the stator.
Two suspect areas are the plug being beat up and the second black wire of the reg/rec not going anywhere. I need to look at the PO’s wiring diagram and try to figure out what’s going on with the M-Unit wiring.
 

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CALfeRacer

Fat man on a little bike
On a different note, I put on the “new” tail section and am really happy with how it looks. Just need to decide if I want to remake the tail light/plate bracket to move it further out or not. It was already tucked in the cut tail section, and I kind of like how it looks from the sides as-is.
 

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CALfeRacer

Fat man on a little bike
Took a little time to look at the PO's wiring diagram and pretty quickly realized the problem probably lies with the second black wire off the R/R not being connected to switched 12V. Going to set up a jumper tomorrow and see if that solves my charging problems. I did also notice his diagram appears to be for an older twin and not this bike... Drawing only has two plugs (one per coil) and Y/W/P wires coming off the stator. Also no sign of the Dyna ignition module.
 

Maritime

Well-Known Member
I'd start from scratch and check all the PO's work. Some folks don't understand wiring and you can chase your tail for weeks trying to figure it out. Get the factory diagram, unplug everything and wire one system at a time until you have it all correct. with the M unit it should be faster than looking for what the PO might have done wrong.
 

CALfeRacer

Fat man on a little bike
I got a factory diagram from Oregon Motorcycle Parts. I'll check his wiring sometime this week, but I do want to start with that regulator wire since right now everything else seems to be working fine. All the other wires from the R/R are hooked up correctly per the factory diagram. One positive to the current state of the world is now I'm working from home so I've got a little more time to spend down in the garage.
 

CALfeRacer

Fat man on a little bike
Finally some progress! Looks like my problem was the volt sensing wire off the R/R not being hooked up. I wired it to the switched +12V on the m-unit shared with the ignition coils. It’s charging now, with bolts rising to 14.7 then stopping as revs increase (checked at 3k and 5k). Tomorrow is supposed to be sunny so I’ll go for a ride and see how she does!
While I was at it I also replaced some old connectors with new ones courtesy of Matt at Sparck Moto.
 

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pidjones

Well-Known Member
Glad to hear it is getting there! The new connectors help cofidence, even if they aren't needed!
 

CALfeRacer

Fat man on a little bike
Test ride was delayed by a lack of sun and then a set of fouled plugs. Put in new plugs and went for a ride last night, good news is she's running good! Didn't hook up the battery tender and measured no voltage loss at the battery after 24 hrs so I think the electrical issues are behind me. Now on to the mechanical bits I want to address.
 

CALfeRacer

Fat man on a little bike
Went for a ride today, ~1 hour total. Once warmed up she ran great in the canyons, had a blast going around for ~45 minutes. Last 10 minutes was spent on the highway heading home, and noticed some surging when trying to cruise at ~75, then after 5 minutes or so started to run a bit worse. Almost seemed like a slight miss? Not sure what’s going on, any ideas?
 

CALfeRacer

Fat man on a little bike
Went for another test ride, pretty sure it’s not getting enough fuel while cruising at speed. Got on the highway and it easily ripped up to 80+, but then same thing again where it wouldn’t accelerate past ~70-75 after a few minutes and was almost surging/stuttering. Got off the highway, then after a couple minutes everything was back to normal.
I’m going to start by running some seafoam through to see if there might be just a tiny clog somewhere, if that doesn’t work then I’ll pull the carbs and clean out the float bowls, and clean the petcock. If none of that works I’ll get a pingel petcock and see if that fixes it.
 

pidjones

Well-Known Member
I'd check two things; one is to hook up a voltmeter that you can see at speed - either bungee on a DVM or preferably pick up a small LED voltmeter on ebay for wedge in place. I liked the one I bought to test the CB750F so much that it is now permanently mounted in my '79 GL1000 shelter dash and another is going in my GL1000 custom. Ignition requires more power at higher RPM, so make sure it is there. Second, if your floats are adjustable (some are fixed plastic and you can't change them), make sure your fuel level is high enough. If the float needles have been replaced, measure their length to make sure they are correct. So, number 2 requires carb removal. I'd check #1 first.
 

cxman

Active Member
DTT SUPPORTER
"I think the electrical issues are behind me "

on a dohc never never ever say that

check and see if the potting compound on the back of your igniters has been melting

it sounds like you have a bad/overheating igniter or over voltage heating them up

also check your voltage at the coils or ask matt for a coil relay mod setup and just do that

so that issue is behind you
 

CALfeRacer

Fat man on a little bike
Thanks for the advice guys!
I’ll get a voltmeter and install, that’s easy enough.
The carbs are Keihin CRs, and from my understanding the PO did play around with them to get the tuning pretty close so not sure what he did. Might be worth just pulling and checking the float heights.
The PO installed an aftermarket ignition module (Dyna 2000) and coils, so would I still have igniters or are they built in to the box?
I’ll check voltage at the coils. I assume I should do this at idle, 3k and 5k?
 

CALfeRacer

Fat man on a little bike
Installed the volt meter and went for a test ride. It’s hooked up to the power and ground on the right coil.
IGN on: 12.4-12.8V
Hot idle (~1300rpm): 13.2-13.4V
2000rpm+: 14.3-14.5V
Doesn’t seem like it’s getting excess voltage, but 14.4V at 2k rpm seems like a lot to me? Not sure, just spitballing.
Also, seafoam in the tank didn’t help. I’ll pull the carbs and check/set float heights at some point as my next step.
IMG_3043.jpg
 

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