Topic: '71 CB500 Four Scrambler

[Stev-o]

Yes, you can bench test the carbs for float function and float bowl leaks. Most guys don't do it though. 
I have tested bowls as I did have one leak once on a K5. 

[DurangoCB]

Thanks, Stev-o.  Looks like this thread is just you and me.  LOL

I was just searching for jetting@altitude tips and finally went through most of the Thoughts from Hondaman thread.  Holy crap- what a wealth of info. 

I noticed yesterday when I cleaned my carbs that someone has swapped the jets (stock main is 100, idle is 40... this bike has a 95/40) at some point.  It has always lived in Colorado at around 5,500' so Hondaman's beta was spot-on (come down on the main jet by 1 for every 1,000' elevation where you live). 

Drilling out the emulsion tubes now interests me but I'm a little intimidated by such tiny numbers, i.e. .040 

Parking this here for my own future reference:  http://forums.sohc4.net/index.php?topic=92347.0

Anyway, got the carbs cleaned up and mounted back on the rack.  Tedious but not difficult.  I'm hoping to see if the bike will start up mid-week, if I can find time between work and kids. 

[Scramps]

I got lucky with my carbs, they were more or less clean and ready to go when I got them. They’re externally a little shabby looking, but everything was internally open and clean. I still replaced the carb bowl gaskets and o-rings, though, just as a precaution.


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[DurangoCB]

I got lucky with my carbs, they were more or less clean and ready to go when I got them. They’re externally a little shabby looking, but everything was internally open and clean. I still replaced the carb bowl gaskets and o-rings, though, just as a precaution.


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That's a nice bonus^.  My CB500 was clean when I bought it, in all the ways that matter most (fingers crossed in regard to engine still).  Two of the carbs being in pretty horrid condition was a surprise.  I keep reminding myself that it really is about the learning and the journey.  If it weren't, I would have just shelled out 10x as much money and I'd be rolling around happily on shiny new BMW R nineT and my wrenches would be tucked away in the toolbox. 

[DurangoCB]

I managed to get a battery on this bike for the first time today and just had to get a video of the moment. 

https://www.instagram.com/p/BftxzjGBPoy/

Clearly the fuel delivery is way off the mark, but we'll get that worked out.  Anybody have a link to a good sequence/checklist I could follow for dialing in the carbs when they're this out of whack?  I set all the air mix screws back to factory rec.  Some had been way in the last time it was ridden, some were way out. 

Anyway, all four barrels are firing, the carburetors are holding fuel and there's no oil pouring out onto the bench, so I'm celebrating. 

[Moto nut]

That’s great!, that bike was pretty much idle for the last 25+ years, you’re doing all the right things, when I get to the point you’re at right now I’ll usually run rotella oil with an ounce of sea foam per quart of oil for a good internal cleaning for short periods of run time ( bringing up to operating temp ) while you fine tune the carbs, set timing, when happy with the way the bike runs and your ready for a test drive, drain oil and replace with a good quality motorcycle oil.....

[DurangoCB]

Sounds like a plan- thanks for the tip.  I have a couple bottles of Seafoam on hand, so I'll drain a few ounces of oil and replace it with Seafoam. 

Over dinner tonight I was expounding to my kids about the wonders of a combustion engine, how amazing they are and then how much more amazing when one that is 46 years old and sat for more than half of its life is willing to come back from hibernation and start growling again. 

[Moto nut]

YEAH, like I said before you ride, replace the cleansing oil that has the sea foam....

[seanbarney41]

from your video, what makes you think it was running on all 4?...sure didn't sound like it

[DurangoCB]

All four headers were hot.

[seanbarney41]

Ok, could be wrong

[DurangoCB]

Ok, could be wrong

You're right if what you were saying is it sounds like crap in the first 5 minutes after sitting for 23 years.  LOL  I wasn't expecting too much from her. 

[seanbarney41]

Well, if everything was right, except for say, a bad plug wire, or a plugged idle jet, it's gonna sound like crap whether it's 40 years old or brand new...I have fired up "just a few" of these.

[DurangoCB]

Wait- are you under the impression that I have this thing tuned and I think the way it sounds is peachy? 

Haven't touched the valves, ignition timing, or cam chain.  I just wanted to see if the bike would start and it did.

If there's a way that all four headers would be hot without all four cylinders firing, I'm all ears. 

[seanbarney41]

I did assume you had done that stuff...I have been fooled by pipes that get kinda hot, but its not really running.  Pipes should be hot enough to vaporize a good squirt of water within a couple minutes.  Cylinder may be firing intermittently or only when the throttle is opened enough for fuel to be drawn from the needle jet.

[DurangoCB]

I did assume you had done that stuff...I have been fooled by pipes that get kinda hot, but its not really running.  Pipes should be hot enough to vaporize a good squirt of water within a couple minutes.  Cylinder may be firing intermittently or only when the throttle is opened enough for fuel to be drawn from the needle jet.

That makes sense.  I've owned bikes since I was a kid, but I've never owned a vintage bike and I'm so damn excited that I'm sure I was more giddy than it deserved just because that bike made noise after almost 30 years.  I've settled back down.   

In fact, last night it all started getting real, or feeling that way.  I have many questions and hope you fellas have answers.

[DurangoCB]

I started designing an under-seat battery tray last night.  (I realize half of you will stop reading at this point.  LOL)  I plan to make it myself, but unfortunately I also started welding just last night.  NOT PRETTY, so far. 

Never underestimate the humble cereal box.

For those of you who have made or purchased battery trays, how deep is yours and what do you have in it? 

[DurangoCB]

Disassembly is about 3/4 done and I felt a little like, "Oh Shinto, what have I done?"  But we'll get there, little by little. 

Ordered several new things. 

Aftermarket MC and inline front brake switch.  New SS braided brake line. New front caliper piston seal.
MAC 4-into-1 exhaust with reverse cone (scored a pro deal through a friend)
Dunlop K-70s (couldn't afford the Avons)
Exhaust gaskets (mine didn't have any?)
Oil Filter bolt (old one came loose easily but the head was chewed up and rusty enough to make me nervous)
New headlight mounting brackets.  Not sure what HL I'll use, but LED would be nice if it didn't look TOO Sci Fi. 
Pods and jets (my ticket into a cage fight between myself and my carburetors?)
Weld-on Kickstand since the original owner cut the mount off the frame to accommodate the 4-into-2 exhaust.


The next steps are to detab the frame, weld a kickstand back on, then either send the frame to powder or buy a gun and paint it myself.  Then I have about 60 hours of polishing ahead of me. 

[DurangoCB]

Speaking of polishing, I get the impression that once the uppers are rusty like this, you either have to cover them up with something, replace them or ride them rusty. 

True?  No chance at all of polishing them back up, even somewhat? 

By the way, those headlight brackets that have a rubber plug that almost seems DESIGNED to trap water in them... dumbest design ever? 

[DurangoCB]

Ah, electrical.  All the mechanical stuff, suspension, bearings, engine (mostly), even paint and relacing my wheels... all of that I feel very confident with.  What is giving me some anxiety is the wiring.  It's all greek to me.  Resistors, blah blah blah.  I have a step learning curve ahead of me because I am yanking ALL of the stock wiring. 

I want to relocate a couple things, but even if I didn't, the stock wiring is brittle and so hard to work with.  I'm going to build a new loom from scratch so I can use a Li battery, relocate the ignition key switch to the L side of the battery box, etc. 

Anyway, long leadup to a simple question.  What is the trick to get these brittle old connectors off???

[DurangoCB]

And finally, just wanted to share one of the 2-3 bikes that is driving my vision.  I know most of you here have already seen it, since Justin used to be an active member of SOHC/4.

Obviously, I'm not going to create a custom muffler like that and I do want turn signals (and a center stand... and my carbs will have drain tubes LOL), but otherwise, that's pretty much how I want my bike's stance to be.  And I'm copying the color scheme, at the request of my wife, who I will hopefully be giving the bike to. 

I also want some manner of front and rear fender.  Something at least partially effective but minimalist.  Probably chop the stock fenders. 

[Stev-o]

Speaking of polishing, I get the impression that once the uppers are rusty like this, you either have to cover them up with something, replace them or ride them rusty. 

True?  No chance at all of polishing them back up, even somewhat? 

 

No chance!

Look at your pic of the white connectors. on the top, there is a little prong. Use a small screwdriver to open it and then unplug the connector.

[Flyin900]

Those will never clean up to new as the rust/pitting is too far gone, although here is a solution I have used on the same conditions on forks that have rusted under the triple tree areas or the fork ear covers. Stay only on the rusted areas don't move down onto the good chrome areas of the forks when doing this repair.
Use some sandpaper to clean those areas up and at least get them down to bare metal. If they are normally covered with fork ears or the triple trees then not a big deal. I would start with 220 grit to knock down the worst of the rust and then move to 400 and then either 600 or 800 grit to get the area smoother again. Use a little WD40 on the sandpaper to lubricate it as you sand away.
Once you get them decent then you are going to need to protect the bare metal from rust again and probably a good rust resistant paint will help slow the rust starting again.

[DurangoCB]

Thanks, fellas!  That's helpful.  Sorry to post my questions in two separate sub-forums but it seems like most of what is posted in the Project Shop isn't seen by very many people. 

[Stev-o]

...most of what is posted in the Project Shop isn't seen by very many people. 

Dont be so sure of that, your thread here has over 700 views. 
For whatever reason, most guys wont answer questions...fear of being wrong?