Topic: CB750 K2 Barn Find Restoration: Presents!

[Lucien Harpress]

Got me ALL kinds of cool stuff for this project since I last updated.  First up?  Airbox and carbs, courtesy of Johnie.



Even though I'm going to need floats for these carbs, they are probably the cleanest set I've ever seen, on any bike I've ever owned.  Which is awesome, as they're going on the worst condition bike I have ever owned....

The airbox looks awesome as well.  So good I decided to see what it looked like on the bike.



Which is great, because it's going to have to come OFF again to pull the engine.  But it's only two bolts.   

My second set of presents just showed up today.







I spent WAAAAYYYY too much on these, and they aren't perfect (you can see a hole in the end of exhaust #4), but compared to what I have now?  No comparison.

I'm still working on rebuilding my hand controls, but I'm done buying stuff for a while.  Next update:  Engine pull!

[SOHC4 Cafe Racer Fan]

They might not be perfect but those are some great looking pipes!

[Lucien Harpress]

...well, minor setback.

I decided to try to refurb my controls tonight.  While crusty and a bit frozen, everything appeared to be there, and just required a good cleaning.

Cue two hours, a stripped screw, and multiple springs and ball bearings shot across the room into oblivion later, and I've essentially ruined both sets of my controls (right and left).

 

Looks like I'll be saving up for a new set of THOSE...

[pipeguy]

Wow nice pipes, gotta get me a set of those! If you don't mind saying, where did you find them and how much aprox?

[754]

 Sometimes you can find broken switch housings with the parts you need. Sometimes from other models.
 example same Hi Low OFFswitch in silver that has a drum front brake lever
 or left side with mirror mount broke off
 right side top with broken kill switch.... stuff like that.. dont toss anything..

[Johnie]

When working on those switches I find it really helpful to place a white blanket or towel under the work area. That way those small parts don't bounce so far and are easier to find. Been there

[Lucien Harpress]

Wow nice pipes, gotta get me a set of those! If you don't mind saying, where did you find them and how much aprox?

I got "lucky" (for a given definition of the term) on an Ebay auction.  The seller had them listed for $675, with free shipping, and nobody bid but me.

As I said, they aren't perfect- in addition to the dents and holes, there is a LOT of crusty bits on the inside of the header pipes.  But thankfully you can't see much of it when the pipes are on the bike, if you keep it polished you can barely tell anyway, and they are SO much better than the pipes I pulled off.

My initial plan was to buy each pipe separately as I was able, but my luck I would be stuck looking for one pipe and never find it.  Also, with the going rate for individual CB750 pipes, I was going to end up spending about $700 anyway.  Like I said, a bit more than I wanted to pay right now, but probably the best I could do at the time.

As for my switches-  I'll hold on to what I have.  I'm pretty ham-fisted, so I managed to mess up quite a bit.  I'll keep an eye out at swap meets and whatnot for replacements, but I'm not holding my breath.  On the plus side, at least I don't need them for a while...

[Lucien Harpress]

I'm still picking at it.  I'm nearly ready to pull the engine- I think all I have left to disconnect is the clutch cable.  After that, I'll get the block out, get the head, off, and take a peek inside the pistons.  Everything feels okay from the outside, but it won't hurt to take a look anyway.

I've also got a large oil stain on the front of the block, and research tells me the oil passage o-rings could use a change.  Hey, the motor's out- why not?

[Lucien Harpress]

OOOOOH buddy, this topic has been dead for a while, but I've been doing some work.

Hopefully I've updated to the point where this thread left off, but here's what I did in the meantime (apologies for any repeats):

-New frame
-Engine out, cleaned up (enough), all new rubber you can get with the valve cover and cams out.
-The best parts from two bikes into a third frame, back together.
-Original sidecovers cracked and original tank was rusted through, find replacements.
-Get replacements painted and installed.

It's to the point where I can get it up and down the road, and while there's still a few crucial things to take care of (TIRES, fork seals and oil, brake line, correct length throttle cables, some wire repair), I can see the light at the end of the tunnel, and I am liking what I see.

As a side bonus, here's a short video after about a 15 minute flogging.  Idle is a bit high, I'll admit, but for having almost nothing done as far as tuning, I think it's doing okay.)

[andy750]

Wow great job! Love the colour of the tank very very nice - where did you get it painted?

Good luck finishing it off you look very close!
cheers
Andy

[Johnie]

Very nice...what a change. Just beautiful! Are you able to crank down the idle a bit?

[Lucien Harpress]

Thanks.  The paintwork was done by Ronnie Jennings over at cb750kfour.com, and I couldn't be happier.  He took care of the paint, decals, gas cap, and chrome tank trim.  He could've taken care of emblems as well, but I didn't need those.  Even the accesories he did help me with literally only cost as much those same parts off eBay (ie, no extra charges for labor).

All told, with paint, gas cap, trim, and some body work, it only cost me $610, plus the initial $40 shipping to get the parts to him in the first place.  Now, it's not 100% flawless, but for 600 bucks it is beyond acceptable.

Other priorities?  Fork seals and boots, upper brake line, correct length throttle cables, tires and new coils.

Compared to where I started, a list that short is amazing.

As for the idle, it kind of wanders from 1.5k to 2k RPM when the bike is nice and hot.  It settled down to about 1.5k right after this video was over.  However, while I could adjust the fast idle down a bit, I don't want to get too involved before I replace the coils- the original plug wires are about the consistency of cottage cheese, and it's a small miracle they work at all.  Once I get everything to "acceptable", then I figure I'll start dialing it all in.

[andy750]

Wow thats an excellent price! Especially with all the added extras. Thanks for sharing the cost. I am debating whether to have one of my tanks painted or leave as is so this gives me something to think about.

Hanging idle: I had similar symptons recently - see my K4 project page. I started off with a high idle (2000 rpm) and tried the following:
1. Changed carbs - both sets had been rebuilt using only OEM parts - no difference
2. Changed engine/airbox rubber to new OEM - no difference
3. Changed the new DENSO spark plugs to new NGK D8EA - this helped though admit could also have been the HT leads (as checked connection to plug at same time)
4. Adjusted airscrews from 1 to 1/4 turn out - this made it worse which led me to...

For me the answer was air screws. Even though I thought I had set them correctly to 1 turn out - I still got rough idle. Around town test rides were giving me one answer but it was an extended day ride in the country that allowed a range of rpms and riding conditions. I then set the air screws to just under 1 turn out and this solved my rough/high idle.

You clearly have read a lot about this issue and have already done extensive testing but try and eliminate what its not. My bike ran great at 1/4 to WOT so I knew it was somewhere in the idle circuit. Just had to see what made it worse/better.

Good luck in figuring it out.
cheers
Andy

[kap384@telus.net]

Looks great!!

[MauiK3]

Removing the engine is pretty easy by laying the bike on its side and lifting the frame off.