Author Topic: 1973 CB500 restore build (Read 3908 times)

Gfreak · « **on:** November 23, 2015, 10:34:50 AM »

Hey y'all. New to this forum obviously, but just picked up a project bike for myself this mornin.

Guess i'll be documenting as much as I can on here.

starting pictures:

Bike's sitting on my garage for now until i get some free time to start taking it apart and checking things.

So far, it has fuel delivery. Horn, tail light and electric starter work. No blinkers or headlights turn on, nor does it have spark.

The coil is getting power but nothing going to the spark plugs. Gonna take the tank off and look at that more closely this weekend.

Brake lines are corroded pretty bad, prolly will need to replace that. throttle cable is loose as well ("snaps back" very slowly)

But yea, i'm excited to get started on it!

calj737 · « **Reply #1 on:** November 23, 2015, 11:47:00 AM »

Welcome. Your bike is a "K" not an "F" for the record. The "F" in some descriptions only referenced a 4 cylinder, but accurately yours is a 500/4, not a 500T for a "Twin".

Check your points and condensers for the lack of spark.

Gfreak · « **Reply #2 on:** November 23, 2015, 12:33:11 PM »

Thanks for the model type, tip.

The F I've seen used stood for "four" afterwards.

I know it's technically a "k2" (I believe?) for this year.

Will definitely be checking that first when I get the time.

Thanks!

2strokeTrush · « **Reply #3 on:** November 24, 2015, 01:37:43 PM »

Looks like a late model 550. Motor is not a 500 for sure.

Gfreak · « **Reply #4 on:** November 24, 2015, 07:36:43 PM »

I'm curious, what're you using to make that distinction based on thepicture? (the specific differences) Cause every picture I"ve looked up of a cb500k2 looks exactly like what I have (the engine that is)

calj737 · « **Reply #5 on:** November 25, 2015, 04:28:28 AM »

Looking at the right side clutch basket, the left side clutch cover, and the presence/lack of a clutch cable on the left side (500 is on left, 550 is on right).

If you want absolute verification, look below the carbs on the lower engine case and read the stamped engine number. Yours will likely start with 550-xxx. Also, on the front of the cylinders, behind the headers, the engine displacement for the cylinders is listed (544cc for a 550).

The frame may be a 500 (there should be a VIN tag on the right side of the steering neck, and an engraved matching VIN number on the left side of the neck).

2strokeTrush · « **Reply #6 on:** November 25, 2015, 08:46:38 AM »

Quote from: Gfreak on November 24, 2015, 07:36:43 PM

I'm curious, what're you using to make that distinction based on thepicture? (the specific differences) Cause every picture I"ve looked up of a cb500k2 looks exactly like what I have (the engine that is)

Clutch, front end, gauges, seat lock, cylinder head pattern.......

Gfreak · « **Reply #7 on:** November 25, 2015, 12:32:28 PM »

Y'all are saying that, but the stamp on the Engine block says "CB500E-1006394"

Not 550.

calj737 · « **Reply #8 on:** November 25, 2015, 12:58:29 PM »

Clear picture of the left side of motor, and one of right?

2strokeTrush · « **Reply #9 on:** November 25, 2015, 03:10:00 PM »

If that's a 500 that's the first I have ever seen with a clutch like that. I think it's a misprint honestly or something because I have no idea how a 500 motor could have the internals of a 550 because it's a completely different system.

Bootsey · « **Reply #10 on:** November 25, 2015, 03:11:34 PM »

Looks like there's a screw above the right side cover (shift drum guide screw?) which might suggest they are 500 cases at least?

2strokeTrush · « **Reply #11 on:** November 25, 2015, 03:12:02 PM »

Can also see the 550 clutch holder/engine mount.

jonda500 · « **Reply #12 on:** November 25, 2015, 04:09:17 PM »

Quote from: 2strokeTrush on November 25, 2015, 03:10:00 PM

If that's a 500 that's the first I have ever seen with a clutch like that. I think it's a misprint honestly or something because I have no idea how a 500 motor could have the internals of a 550 because it's a completely different system.

Second one I've seen - I believe these are european only models.. John

2strokeTrush · « **Reply #13 on:** November 25, 2015, 04:21:23 PM »

That's the weirdest thing I have seen today. Never knew they existed

Gfreak · « **Reply #14 on:** November 25, 2015, 06:57:10 PM »

I'll try and get a picture up in a little bit, gotta find a cord for my phone haha.

So assuming the print on the block is to be believed, you're saying this is a European model? That's wierd, wasn't expecting that lol.

But you say it's impossible to have the 500 in a 550 casing? Are they that different, and not just a bored out version of itself?

Gfreak · « **Reply #15 on:** November 25, 2015, 07:23:28 PM »

Also for the build: Haven't had a ton of time to work on it with work and all.

But I've taken the carbs out and almost through cleaning them.

Both coils will need to be replaced, as well as most of the wiring. Whoever had it before me spliced a TON of wires and did a pretty #$%*ty job of it.

Cylinders are also fairly low on compression. #4 got me about 55 psi, while 1-3 got me about 35 until I squirted some oil in there and they bumped up to the same as #4.

Gonna clean out the tank and finish cleaning the carbs on friday.

2strokeTrush · « **Reply #16 on:** November 25, 2015, 09:48:24 PM »

Clutch System is different completely and yes it is bored out more.

calj737 · « **Reply #17 on:** November 26, 2015, 05:23:08 AM »

Stock displacement on a 500 is 498cc and 550 is 544cc. It would be a good deal of work to use a 550 transmission and clutch within a 500 set of cases. Doable, but lots of work for no real benefit.

From the sound of it, your motor needs a very good going through. Low compression is not unusual for a motor thats sat for a long while. Compression leaks can come from: valves that need to be adjusted, rings that are gummed up from sitting, carbon build up in the head preventing a good valve seal, etc. Don't fret yet about it. Get it running, cycle the motor through a few heat cycles, and re-test with a motorcycle type compression tester. You just may get very different results.

Gfreak · « **Reply #18 on:** November 26, 2015, 08:48:55 PM »

Yep that's the plan! The I can see the back of the valves from where it is now, and there's a TON of carbon buildup on em.

Happy thanksgiving y'all, My plan's to head back over to the garage tomorrow morning since i've got the day off work. Should be able to finish the carbs, clean the tank. and start working on some of the wiring. And seeing if it's even worth salvaging (new harness is like 100$)

Gfreak · « **Reply #19 on:** November 27, 2015, 03:48:56 PM »

Finished cleaning the carbs and tank today, both looking pretty good. Got the handlebar assembly/wiring harness and all the linkages attached up there off. Wiring harness is in really bad shape, tons of frayed/broken wires. Probably gonna get that harness so I don't have any issues.

Gotta get those coils next as well.

Gfreak · « **Reply #20 on:** December 04, 2015, 07:18:21 PM »

got the coils, got the carbs rebuilt (new gaskets and such, reverted back to stock jets as I have the stock airbox for the bike.)

Now just gotta order the wiring harnes, should be able to get that in a coupla days. and it'll hopefully be running in time for Christmas!

This weekend imma take the intake manifold off and do a valve adjustment and change the oil.

calj737 · « **Reply #21 on:** December 04, 2015, 07:34:48 PM »

When you remove th intakes, replace the o-rings on the backside. They are likely hard by now and want to be supple to seal well.

Trad · « **Reply #22 on:** December 04, 2015, 07:42:10 PM »

The 500 is the picture posted last in the thread has PD carbs. Not sure if anyone mentioned that.

Gfreak · « **Reply #23 on:** December 04, 2015, 10:04:40 PM »

Will take a look at those o rings for sure. Thanks man.

As for the PD carbs...is this an aftermarket brand? I'm a bit unsure what you mean haha.

Edit: After a bit of searching, do you mean the carbs that come with the 550k3?

calj737 · « **Reply #24 on:** December 05, 2015, 02:53:38 AM »

Quote from: Gfreak on December 04, 2015, 10:04:40 PM

Edit: After a bit of searching, do you mean the carbs that come with the 550k3?

Correct.

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Author Topic: 1973 CB500 restore build (Read 3908 times)