Topic: Sold my 500, looking at a 750 K3 - some initial questions

[Chachi]

I just sold my 72 500 and there is a 750 K3 I am looking at picking up as my next bike. The 500 was my first bike, I had it for a couple of years and learned a great deal about it from everyone here. I don't have any hands-on experience with a 750 yet. The manufacture stamp is 9/72 and the motor serial and tank stripes confirm it is a K3.

It's a complete running, titled bike - odometer says 10k. It runs and I've ridden it, but it hasn't been on the road for at least 10-15 years. It was stored indoors, but there are some oxidation issues (back rim, engine cases). The carbs were purchased from a salvage yard, I am not sure they are correct to the bike and they may need some attention. I'm going to have my mechanic confirm the motor and transmission are solid and there are no mechanical issues. The side covers, tank paint and seat are in good shape. The tank has been lined by a radiator shop (Red Kote). It needs all your standard stuff - cables, hoses, tires, cleaning, tuning, adjustment - but I want to know all I can about a K3 before I get into it. Especially if there are any specific problem areas to look for.

The rear rim has significant rust - do I look for a replacement or powder coat what I've got? The front rim is fine. The engine cases look pretty rough. Once it's running well I definitely want to clean them up if possible, but I will be limited to what I can do with engine in frame.

[Chachi]

750 K3 rear wheel 18"? I need to take another look at the rusted one that's on here... I think it's a 16", but not positive.

[flybox1]

How much is the owner asking?
A titled runner like this one might get $1500-2500 here in the PNW, depending on time of year. 
If he is asking much less than that, i'd jump on it.
replacement rims are readily available.  I got a nice one of ebay for ~$50.
I'd want to see how deep the pitting is.  Might be easiest (time & $) to source a nicer one to PC.

[Johnie]

They do look like the correct carbs there. At least they look like the ones my K3. There is a number stamped on the carb case if you really need to know. Looks like a great bike only needing OEM pipes to take it back to 1973.

[70CB750]

750 K3 rear wheel 18"? I need to take another look at the rusted one that's on here... I think it's a 16", but not positive.

Originally, yes.  18" wheel.

http://www.motorcyclespecs.co.za/model/Honda/honda_cb750k%2073.htm

[PeWe]

Bike look nice. The tires are old and dangerous for driving so new rim(s) + spokes easy to do + new wheel bearings.
Clean the oxide, fresh paint on motor.
- Why not pull out the engine open it and restore it, valve/seat job, rings + hone, clutch and all gasket, o-rings and seals...paint the cases, cyl, head, polish the alu covers... Winter job. You must be able to do all work by yourself.

[Chachi]

I'll check the rear wheel again. If it's a 16 instead of 18 I'll definitely track down a proper 18 for it if that's what it should have. I'm going to verify that the motor, transmission, compression, etc. are all good and then figure out how best to clean it up and get it going.

It also has a chrome (now pitted) side stand and center stand - that standard for K3?

[Chachi]

The chain guard is chrome as well. Trying to sort out what's original and what's not other than exhaust.

[harisuluv]

From looking at it you can see that the caps look right.  The earlier style had an almost non existent bevel.  They changed around 72 and up to look like yours.  You can see that the choke linkage and looks like the adjust nuts are treated with the gold zinc plating and that would also be 73-76.  If you look right about the mixture screw, it's flat, so it's not a super sport either.  Super sport have a little horn right there.  If they just got randomly salvaged, it is a good match.  I would bet that they are 657B carbs which would be accurate for the bike.  105 mains and 40 idles.  Needle clip in fourth position from the top.

[Chachi]

Where exactly is the stamp on the carbs? I was looking (with tank on), but couldn't find it. The lighting wasn't great either.

[harisuluv]

http://i.imgur.com/mRqlFsKl.jpg[/img]]

[Johnie]

Here is your stock K3...black side stand, black center stand, black chain guard. Click pic to enlarge...

[Duke McDukiedook]

What Johnie said and yes 18" on the rear as said before. That is a sweet Candy Bacchus olive paint, aka the quickest color in the Honda arsenal.
And as the pic above shows the original pipes were 4-4 HM341s.

And unless the engine has horrible compression numbers or the clutch is slipping just do a 3K tuneup and save the engine pulling for when the bike truly needs it, usually around the 40-50K mile range.

[Chachi]

Thanks for all the info. I hope to have the motor evaluated in the next week or so. It fires up and idles, but there was one issue from my test ride - when you shift down to first from neutral the bike would jump and cut off. I finally was able to very gently shift down to first and I could get it going. It's also difficult to find neutral. I know it needs all new cables and I'm sure a clutch adjustment, not to mention fresh oil. But hopefully it is a simple fix and not indicative of a larger problem.

[Johnie]

After sitting for a while your clutch plates are probably sticking. Like you said fresh oil, cables, a clutch adjustment and riding will help to free those plates up nicely.

[bjatwood]

Here is your stock K3...black side stand, black center stand, black chain guard. Click pic to enlarge...

Love the K3 "Fat Stripers"! And a K3 in the "other" color for the year...

[cb650PK]

Looks like it has Harley 16" rim on the back. Very popular period modification, reason for which completely escape me. Must be American thing.

[Stev-o]

Yes, that is a 16" rear wheel, some guys installed them to lower the seat height.  18" wheels are easy to come by.
Finding neutral can be hard with these bikes, nothing to be concerned about.  A new clutch cable/adjustment should help with shifting into first.
The bike needs basic maintenance, use this as a negotiating tool. 
Is the bike in the $1200-$1800 price range? If yes, get it, you'll love it.

[Chachi]

I was able to drop it off today at a friend's shop. He's going to check compression and a few other things to make sure the motor is good.

A few things I noticed today that differ from the owner's manual and other stock pics I've seen:
-The ignition switch is up top vs. the left side
-The clutch has the safety line so it will not start w/out clutch lever in
-The front brake is missing the 'splash guard' - or whatever it is properly called

None of those things are a concern at this point, just mentioning them. As long as the motor checks out, I hope to get started on all the things it needs immediately. Hope to be up and running by the end of year or shortly after.

[Stev-o]

Moving the ignition switch was a common mod, easy to move it back.

[Chachi]

I got the compression checked and all four came out at 170. That's the stock number, right? I was not there when it was tested, but I know it was done with a thread-on connector vs. a metal rod with tip. Drained the oil and it looked OK (no metal, etc.). It also shifted through all the gears while running on the center stand. I think it has a strong motor and less than 11k on it.

The carbs are 657b. What is the correct set up? I'm running stock airbox and the exhaust is 4-1.

105 mains
40 idles
Needle clip in fourth position from the top

I also saw specs here:
http://www.motorcycleproject.com/motorcycle/text/specs.html
http://www.hondachopper.com/garage/carb_specs/carb_specs.html

105
40
Float 26
JN 4 - what does this mean?
Screw 1 - what does mean?

[Duke McDukiedook]

The mixture screw turnout is what screw 1 means, one revolution out clockwise is stock setting.
JN has to do with the Jet needle, I can't remember exactly what but I think it may mean the number of the needle taper.

[Johnie]

Screw 1 is the air screw factory setting. I think what Dukie meant was 1 turn counter clockwise from lightly seated. I thought JN 4 means the jet needle clip is in the 4th notch.