Author Topic: 1980 CB650C - Tank and seat time! (Read 13518 times)

DV2000NJ · « **on:** December 22, 2012, 09:11:12 AM »

What's up guys. Back in October I came across this CB650 for $700, and decided it would be a fun first bike to mess around with.

1980 Honda CB650C by Dan Valanzola, on Flickr

Bike has 19,xxx miles on it, came with that hideous crash bar, an even uglier sissy bar, but otherwise was completely stock (I do have side covers, they were just off for some reason). Good blank canvas, since I like modifying things, but HATE un-doing other peoples' "crative" fixes.

When I bought the bike, it ran on all 4 cylinders, and revved freely when choked, but as soon as you opened the throttle a bit with the choke off it would try to die. The guy I bought it from said he thought a float was sticking, so I figured I'd pull off the carbs and take a looksee.

Now, I've got plenty of experience working on modern cars (I've worked as a mechanic while off from school for the last two years), but this is my first time really working on a bike, or anything with carbs for that matter, so I'm sure I'll make some ignorant decisions haha.

Anyway, when I got the carbs (PD50 B) off, I noticed that the bowls were all switched around, and the accelerator pump was on carb 3. The diaphragm was also torn, so I bought a new one, and re-assembled everything. (Everything in there was shockingly clean, as was the tank and inline fuel filter).

So, I figured having a working accelerator pump should fix the issue, right?

Well now, it only runs on two cylinders (1 is dead cold, and 2 only gets lukewarm). What the hell? If I rev it a bit with it choked I'll get some backfires from 1 & 2, but that's it.

Check for spark, got it.

Pull the plugs out of 1 and 2, soaked. So I've got fuel, and I've got spark, I've got air (air filter in the stock airbox looks new), but I don't have fire.

Exams and finals came up, and I haven't been able to touch the bike since mid-November, but I'm on break now, and it's time to get this f*cker running.

I'm at a loss, so I'm turning to you guys. Anyone got any ideas? I'm going to pull the carbs off and set the float heights, but what else should I do while they're off? Anything in particular to check?

Any and all help is appreciated, and I'll try to keep this thread updated with pictures as this thing becomes less ugly.

EDIT: Forgot to add, I did do a compression test and everything was good there, and I also replaced the plugs.

scunny · « **Reply #1 on:** December 22, 2012, 12:17:40 PM »

bet you have swapped the plug leads. left hand coil as you sit on the bike feeds 1 & 4, right hand coil 2 & 3

DV2000NJ · « **Reply #2 on:** December 22, 2012, 12:36:36 PM »

Plug wires are as they should be, that was one of the first things I checked.

Thanks though!

EDIT: I was second guessing myself, and just double checked. Left coil is definitely going to 1 & 4, right to 2 & 3.

trueblue · « **Reply #3 on:** December 22, 2012, 02:38:23 PM »

The idle circuits on these carbs can be a b!tch to clean. It is possible you still have some cr@p clogging them. You need to check and double check everything when doing the carbs. If there are any passages that aren't clear, they will give you trouble.

DV2000NJ · « **Reply #4 on:** December 23, 2012, 07:02:13 PM »

So, found out something interesting a few minutes ago. Pulled the carbs off to clean whatever I could, set float height, etc. For no real reason I decided to check the model number on the carbs, and they say PD50D, NOT the expected PD50B.

I did some google searching, and not a whole lot of info came up on the PD50D. It looks like both the 50D and 50B came on the '80 650C, but I couldn't find anything definitive.

Does anyone know ANYTHING about the 50D and the differences between it and the 50B? Are these even the right carbs for the bike?

HELLLP! Hahaha.

EDIT:
Well, I may have figured at least one thing out. My understanding is that the idle screws (at least for the PD50B) are supposed to be 2 1/8 turns out from fully seated. Well the screws on carb 1 and 2 were both only 1 1/8 out from seated, so I would imagine that could have something to do with the fact that those cylinders won't fire.

DV2000NJ · « **Reply #5 on:** December 23, 2012, 10:26:36 PM »

Alright, so everything I was able to find on the PD50D listed it as the carb for an '80 650C, so I'm assuming these carbs are correct (and with how stock the rest of the bike is, I see no reason why they wouldn't be original).

So tonight, I set all of the idle screws to where they should be, set all float heights to 12.5mm (they were at about 8mm to begin with), and double checked that the accelerator pump passages are clear. HOPEFULLY when I throw the carbs back in tomorrow the bike is rideable, or at least idles on all 4 (I'm guessing getting the idle screws set properly took care of that).

We shall see, but until then, I know everyone likes pictures.

Float bowls were surprisingly clean.

Set to 12.5mm

I really hope I can ride the bike tomorrow, and get some real damn pictures of it. This is the longest by FAR I've owned a vehicle without properly photographing it.

DV2000NJ · « **Reply #6 on:** December 24, 2012, 09:12:10 AM »

Well, it still won't fire on 1 and 2. I'm just about at my wits end.

CBJoe · « **Reply #7 on:** December 25, 2012, 07:50:13 AM »

Have you pulled the plugs to check them? Are they wet with fuel or bone dry?

Did you mess with the slides or the needles on the carbs? If so, make sure you've put everything back correctly... trying to remember if it's possible to put the slides in backwards on this model carb??

Joe

DV2000NJ · « **Reply #8 on:** December 25, 2012, 08:13:00 AM »

Plugs for 1&2 are wet with fuel after running.

I have only messed with the things mentioned in this thread (float height, idle screws, and the accel. pump). Haven't touched anything else, though somebody who didn't really know what they were doing must have been through these carbs at some point, every time I pull them apart I find something dumb.

I think it's time to just sit down with the carbs and go through the manual step by step before I spend any money on anything.

CBJoe · « **Reply #9 on:** December 25, 2012, 08:24:33 AM »

You might be focusing too much on the carbs at the moment. First you need to ensure that you are getting spark.

How old are the plugs? Swap the plugs between Cylinders 4 and 1 and see if the issue follows the plugs. Depending on the lengths of the plug wires, you can also try and swap 1 and 4 to ensure it's not the boot or wire that's damaged.

Joe

DV2000NJ · « **Reply #10 on:** December 25, 2012, 08:56:26 AM »

The plugs are brand new.

I swapped the wires for 2 and 3, no change, 3 still fired and 2 didn't.

I verified spark at number one, with two different plug leads, and from both outputs of the coil (the coil that fires 1&4).

So:
Since 3&4 fire, I know both coils are getting power.

Swapping wires for 2&3 and having no change shows that both wires are good, and that both outputs from that coil are working.

I manually verified spark at cyl. 1, and 4 obviously has spark since it is firing.

I have compression on all 4 cylinders.

The air filter is new, and all of the boots are sealing properly.

So out of the 4 things I need for "kaboom", I have spark and compression. This leads me to believe I have too much or too little air or fuel, which brings me to the carbs.

Does my thought process seem sound?

And thanks for taking the time to reply, I appreciate any input!

DV2000NJ · « **Reply #11 on:** December 26, 2012, 04:57:52 PM »

I was fooling around in the garage earlier, and just for peace of mind I threw a timing light on each plug lead, and I do in fact have spark on all four.

Going to pull the carbs off in a bit and go through them as thoroughly as I feel comfortable doing at this point.

If anyone has any other advice, throw it my way!

DV2000NJ · « **Reply #12 on:** December 27, 2012, 02:08:24 PM »

Feels like I'm talking to myself in here, but that's nothing new.

Last night I pulled the carbs again, and sprayed just about every passage I could with carb cleaner/compressed air. I also, just to be sure, checked the resistance of all plug leads, and they were all the same.

Threw the carbs back on this afternoon, started the bike up, and it seemed to be firing on 2, 3, and 4, but not on 1. Small improvement, but not great. I decided to let the bike idle for a bit, and suddenly, it starts idling better. pulled the #1 plug wire off, and the idle dropped. Put it back on, back to the way it was. Same thing with #2.

Decided to give it a quick blip of the throttle, which in the past made the bike die. But this time, the revs actually rose with throttle position.

Took the bike on a quick lap of the neighborhood, and it's definitely not running well, but it IS running. On 4 cylinders.

Man, am I relieved.

Now I can start with the fun stuff! Cutting, welding, and a seat pan should be started over the next day or two.

trueblue · « **Reply #13 on:** December 27, 2012, 02:29:30 PM »

Keep in mind, the 650's are notoriously cold blooded. Mine loves the choke and also needs a few squirts of the accelerator pump to get it going, especially on a cold day. Until they warm up don't expect them to run on all 4, mine normally starts on 2 then picks up the other 2 as it warms up. Once it is running on all 4 it will still take a good mile or 2 of riding before it will run properly and respond the way it should, but once it is warmed up, it only takes a quick flick of the starter to get it going.

DV2000NJ · « **Reply #14 on:** December 27, 2012, 10:39:29 PM »

Good to know, thanks!

Changed the oil this evening, and everything went according to plan. It's always nice to not see metal shavings when doing the first oil change on an engine.

Now, on to more fun stuff. This is how the bike sits currently:

And I'm planning on doing something like this for a seat (excuse the mediocre photoshops):

And a removable cowl thing something like this (probably bent up out of aluminum, and riveted together).

It should be interesting. I love bobbers, cafes, and a lot of the "Brat" inspired bikes people have been building, so I'll probably be taking inspiration from just about everywhere. The bike won't be anything radical, but I also won't be follwing any formula, just doing whatever the f*ck I feel like. This is the fun part.

EDIT: Looking at those photoshops some more, it looks like I hacked too much off of the frame. My intention is for the seat to still be able to fit two people comfortably, and have that rear cowl thing just to change up the look when I get bored.

steved650 · « **Reply #15 on:** December 28, 2012, 06:53:57 AM »

Hey DV. Looks like you got a nice bike for a great price. I bought the exact same one a couple years ago. I pulled my carbs a bunch of times and went through the exact same stuff you did checking everything to figure it out. Guarenteed it is the small passageways for your slow jets that are plugged, your main jets don't kick in until around 3000rpm. Believe me you can't really get them clean without soaking your carbs. I pulled mine and manually cleaned them a few times and still had rough running.
This is what I did.
Took bowls off, floats off and main jets out. Remove pilot screws as they have a rubber seal that can't soak. I pulled my slow jets even though the manual says they can't be....they came out no problem and went back in no problem. Get a shallow rectangular container with about an 1" of carb cleaner in it and set the whole bank in jet side down so that none of your rubber in the upper parts of the carbs are in. Soak all your jets at the same time. let that sit for about 6-8 hours and you will see all the crap that comes out. First run after I did mine was an amazing difference....ran near perfect with lots of power.

I also chopped my seat and messed around with the rear look of the bike...check my post in project shop. Good luck!

steved650 · « **Reply #16 on:** December 28, 2012, 07:16:50 AM »

Hey DV just realized you had a dropped a note on my thread earlier. If you have to mess with the carbs again give that a shot. Love to see some pics when you get chopping.

DV2000NJ · « **Reply #17 on:** December 28, 2012, 11:31:32 AM »

Thanks Steve, I'll definitely give that a shot. I rode the bike to the gas station earlier, and it's definitely bogging pretty hard under 3000-3500, so it sounds like that might be the issue. My Dad just hijacked it from me to ride it a few miles. He hasn't been on a bike in about 25 years so I'm a bit nervous, but if I can help him catch the bug again, I'll take the risk haha. Plus, he knows that he pays for whatever he breaks.

And I'll definitely be posting plenty of pictures, I'm a photographer, that's what I do.

Shameless self plug, but it's my build thread. If anyone wants to look at some photos, lots of which contain cool cars, and some cool bikes,
click on this -> www.flickr.com/photos/danvalanzola There's even some F1 stuff in there if you get far enough.

DV2000NJ · « **Reply #18 on:** December 28, 2012, 01:14:08 PM »

Got a phone call from my Dad about 20 minutes after he left, I was thinking the worst. Said the bike died and wouldn't restart. I drove over, hopped on the bike, was able to push start it, and yelled back to him as I was riding away to "DRIVE THE TRUCK HOME".

Appears I have some sort of charging issue. Not a big deal though, that means the bike was running long enough to kill the battery.

Progress. It's all about progress.

DV2000NJ · « **Reply #19 on:** December 28, 2012, 10:56:31 PM »

I'm pretty drunk right now, but I guess I'll keep posting in here.

Measured the resistance of the rotor earlier tonight, and it came out to about 20 ohms (well above the 4-6 or 4-10 ohm range, I forget what it should be at the moment). Gonna take a trip to the junkyard in the morning, last time I was there they had an '81 or '82 650 in the yard, gonna try to steal the rotor, and whatever else I can off of it.

In the meantime, here's a picture from my phone of the bike actually outside the garage/driveway.

Got the CB650 running! by Dan Valanzola, on Flickr

trueblue · « **Reply #20 on:** December 29, 2012, 04:24:17 AM »

Just be aware the a second hand rotor is likely 30+ years old and the biggest killer of the rotors on these bikes is age. The varnish on the wires gets brittle, flakes off and shorts out the rotor.

DV2000NJ · « **Reply #21 on:** December 29, 2012, 05:58:33 AM »

Oh yeah I know. I'm just hoping to get this thing on the road for cheap at the moment. Once I'm working again it'll be done right.

Plus, it's an excuse to visit the junkyard haha.

steved650 · « **Reply #22 on:** December 30, 2012, 03:27:24 PM »

I had the same rotor failure problem on my first long ride....with a bunch of harley guys! Once I got it fixed I made sure to blow their doors off on the highway just to reassure them who was boss lol....my little 650 smoked a 1200 sportster on open highway well above 170km haha. I had to by a new knock off from ebay...was about $140.

DV2000NJ · « **Reply #23 on:** December 30, 2012, 07:32:40 PM »

Quote from: steved650 on December 30, 2012, 03:27:24 PM

I had the same rotor failure problem on my first long ride....with a bunch of harley guys! Once I got it fixed I made sure to blow their doors off on the highway just to reassure them who was boss lol....my little 650 smoked a 1200 sportster on open highway well above 170km haha. I had to by a new knock off from ebay...was about $140.

Well, I actually re-tested the rotor tonight and it appears to not be the issue. I still want to test it with a multimeter that isn't older than the bike, but the resistance definitely isn't at 20 ohms like I originally thought.

In other news, my mini turn signals came in from Dime City Cycles yesterday. Made up some brackets to mount them using the lower triple-tree clamp bolts. Still have to wire them up and paint them, but I'll deal with that tomorrow when it's a little more than 30 degrees in the garage. On to the pictures.

Just a bit smaller!

If you're a fan of stouts, this is highly recommended.

Comparison.

And both.

Super interesting stuff, I know. It's been a while since I've worked with metal, so I'm starting small haha.

EDIT: I just walked past the bike in the garage, and the way I mounted the signals looks like sh*t. Gonna redo it tomorrow with a simpler, cleaner bracket.

steved650 · « **Reply #24 on:** December 31, 2012, 05:46:25 AM »

Hey if your new minis are LED you'll have to the change the flasher unit to an electronic one....originals are mechanical and work off current. Its looking good.

News:

Author Topic: 1980 CB650C - Tank and seat time! (Read 13518 times)