Topic: Going through my CB750 K6

[The other Derek]

I'm starting this thread so I can document everything I do to my K6.  I thought it would be nice to have a record of the work that I'm doing on this bike.  I was (maybe) a bit too eager when I bought the bike, but I still feel like I got a pretty good deal.  I couldn't see everything that needed to be fixed when I test rode and bought the bike- way too excited to finally be getting another motorcycle.  Had an XS400 in my early 20s that got totaled by my little brother after I foolishly gave in to his begging to take it for a quick ride.  Thankfully he was OK.

Since picking up the bike I've fixed the following things:
gas cap latch
rear tail light
seized front brake caliper
neutral light
replaced seat with proper fitting seat
swapped spark plugs for something hotter to deal with carbon fouling

One of the things I noticed before my test ride was that the wiring needs some work.  The PO had the bike running when I first got there and after BSing for 45 mins we finally got down to the test ride.  He turned the key and hit the start button and nothing happened.  There was a bad connection that he knew about and spent another 20 mins getting it fixed.  Seeing the balls of electrical tape on everything had me concerned, but I figured it started right up when I got there so I figured getting the wiring straightened out would be on my to do list.

The to do list is growing, but the bike seems to run OK and I've been able to commute to work a couple of times with it now.  I suspect that I'll continue to find things that need to be done, but the to do list as it stands is:

Clean and adjust carburetors (running rich)
Give bike a thorough cleaning
Fix high beam lamp
Install case guards
Re-rebuild (and paint) front caliper when parts arrive
Find a decent chrome exhaust
Go through wiring and most likely replace harness
Put together tool kit to stow on bike
Install a Gordon's frame kit (frame had already been cut prior to PO)


I've got a MSF Returning Rider class in the morning and hopefully will get lots of good coaching on the K6.

[Steve_K]

Always good to have a plan.  I like making sure the engine runs well and brakes work well.  I then like to get the wiring sorted.  Good electrics help the engine run better.  It will be fun and at times frustrating.  Mostly it will be satisfying when each step is done!  Have fun with your project.
Steve

[Stev-o]

Welcome Krinky. I would add a full tuneup to your list so you know what you have.
Plugs, caps, points, condensers, valve adj and carb sync.
Can you post pics?

[The other Derek]

Got through the valves, cam chain and setting the point gap, but my helpful neighbor kept getting caught under my feet in the garage tonight and I ended up getting frustrated and throwing in the towel trying to set the static timing.  Hoping for a short day at work tomorrow so I can get some stuff done around the house and finish the timing. It's been a long week already and I need to start this again after a good nights sleep.

Here's a pic the PO provided prior to the sale:

[Really?]

Nice green on that bike. You will get through the points/plate. It always good for a nut twist the first time.

Give it time, you will get sooo addicted to the bike that you will find that list grow. Lotsa goodies out there to thin the wallet.

[lucky]

I really like that seat. Great design.

[Stev-o]

I really like that seat. Great design.

Looks like a stock K8

[The other Derek]

I believe it is from a K8.  It's not on the bike anymore because it was too large.  It was shoehorned in between the tank and grab rail and caused some damage to the paint on the tank.  The mounting hardware was rigged and although I like the way the seat looked and how comfy it was, I didn't want to allow any more damage to the paint.  The bike now has a K3 seat (I think) with proper hinges and a lock.

I finally finished the timing tonight.  I ended up re-gapping the valves because they were way too noisy.  Obviously I didn't hit the mark the first time around.  I took a closer look at the points and cleaned them up a little better.  After that I checked the dwell with my new-to-me Craftsman Engine Analyzer and adjusted both sides to 24 degrees.  The static timing was not working for me, so I used the gun to adjust the points to fire at F at 1500 (thats the slowest the bike will idle without stalling).  The battery was getting pretty low by the end of all of this so it's trickle charging overnight.  I may take a second look at the timing in the AM.

Things are sounding much better now, and the idle at 1500rpm is pretty smooth.  It still stalls at slower RPMs.

One thing I did notice tonight is a little clunk in the lower case (I think) as the engine stops.  The cam chain tensioner was adjusted this week, but I'm now wondering if I should take a closer look at the tensioner or if the clunk is related to something else. 

Gotta find tires soon too.  Sounds like I can't go wrong with BT45s.  I'm thinking I'll try to change them myself as I've done dozens of bicycle tires.  Certainly this will be a little more challenging, but I'm not sure that it's worth $80 to pay the local shop to do it (and I'd still have to pull the wheels).  The rims are far from pristine, so I don't think I'd do any damage that I'd regret.

[Stev-o]

Bought BT45's for my K4 earlier this year and love em.

Get new tubes and rim strips too. Free shipping here...

http://www.motorcycle-superstore.com/1/28/396/6012/ITEM/Bridgestone-Battlax-BT-45-Sport-Touring-Front-Tire.aspx

[The other Derek]

Here's a recent pic with the new seat:



Also here's a quick video where the clunk when killing the engine can be heard.  Not sure if this is something I should worry about.
CB750 K6

Still got to get to the carbs.  May be this week if work goes well.  I'm considering picking up the HF ultrasonic cleaner.

I'm also planning another trip to the salvage yard to try to pick some parts next weekend.  My shopping list is growing.  Really hoping to get lucky and find a 4-4 exhaust, but that's not really on the priority list ATM.

[The other Derek]

Thanks for the link Stev-o.  Tires, etc.  should be on their way this week.

My MSF course instructor strongly recommended that I get them replaced soon.  I'm hoping the new tires will take some of the squirrelly-ness out of the ride. 

[Really?]

The tires may help a bit with the squirmy feeling but if you can move the swing arm when up on the center stand, that can be most of what you feel.

I had a rebuilt front end, tapered neck bearings, new tires, new shocks and it felt squirmy at about 70mph plus. Swing arm moved from side to side - swing arm bearings were shot. HM changed out the bearings and it basically removed all of it. There is a little something going on at about 90mph plus up front, haven't figured that out yet. Motor mount bolt are tight too.

[Stev-o]

+1 - check the lateral play in your swing arm. If your going to pull the wheel for new rubber, may be a good time to replace the bronze bushings too.
Check for play in your front end too. Tapered head bearings areca popular upgrade on these bikes.

PS. I would not be concerned about that noise.

[scartail]

In regards to the clunking sound...  I had an odd clunking sound too when I bought my bike. It was a big mystery. I even took off the heads and everything looking for it (wasted $$$, ).

Well, it ended up being the stator. Basically, the PO had removed at one time, and only put 2 of the 3 screws in, when re-install.

Anyway, just an idea.

[The other Derek]

Got some parts coming in the mail (carb rebuild kits, tires, etc) and I am heading to the salvage yard in the morning to try to find a few things.  That may be the extent of the work that I do on the bike this weekend, but I'm slowly making progress.  The caliper parts that I ordered last week finally came in so I may try to tackle that after I get home tomorrow.  That slow drip needs to go. 

Next weekend should be interesting.  I'm excited to see what I can accomplish with the carbs.

I have a friend heading to the salvage yard with me.  Her VT500 needs a few parts too.  Hopefully at least one of us scores tomorrow.

[The other Derek]

The salvage yard trip was less satisfying than I had hoped for.  The CB750s were pretty well picked over.

I did get my caliper done this morning though.  It was nice to ride into work this morning.  I stripped, cleaned and painted everything over the past couple of nights and couldn't wait to see if my leaky caliper would be fixed.

The squeaking was just about gone and so far I haven't found any signs of leaks.  Pretty satisfying.

My satisfaction from this mornings progress was destroyed this afternoon when I got an email from PayPal saying that the charge from the buyer of my old K8 seat had been reversed.  Pretty upsetting.  I just read the Brimmer thread last night too. Too f'n funny (the Brimmer thing that is). 

I'm pretty pissed about the seat, but I'm hoping that there will be a resolution that doesn't require a trip to Cleveland.   

[Stev-o]

What's the deal with the seat?

[The other Derek]

Someone posted that they were looking for a K8 seat.   I shipped it on Monday and today got an email from PayPal saying the payment had been reversed because it was not an authorized transaction.  I've got an email into the buyer for an explanation. The package is still in transit.

I'm tempted to be sitting on his porch waiting for the mail delivery.  Cleveland isn't all that far from Detroit.  Probably not the best idea I've had though.

[The other Derek]

The seat deal got worked out.  I think it was just a mistake on the buyer's end.  Prolly shoulda just taken a deep breath instead of venting.

Was hoping to get to the carbs today, but I had no luck finding a carb syncronizer locally, and I don't want to start on them until I have everything I need to finish the job.  I've got a feeling fear that cracking the carbs open is going to result in a lengthy, frustrating experience.  Always good to keep picking up skills though.   

Due to not being able to find a sync locally for purchase, I opted to go the DIY route.  I should have it assembled in time to delve into the carbs yet this weekend.  It's been a slow process, but I'm hoping that the carb sync will smooth out the idle.  Was even willing to even pay the dealership price, but for the 25% extra, it needs to be on the shelf.  Cost wise, I'll probably end up saving $40-50, but more importantly I really wanted to take advantage of the long weekend to get this done.  Better planning would probably benefit me for the next project.

I also threw together a DIY soda blaster and it works, but only for a few seconds with my little pancake compressor.  There's a larger one (20gal) that I can borrow from work, but it'll probably still be slow going.  I'm wondering if toothpaste and elbow grease will get me the same results.

My plan for the carbs:
Disassemble and clean (w/Simple Green + HF ultrasonic; maybe DIY soda blast the outside first)
Reassemble with new Keyster kits
Sync with the DIY manometer
Celebrate

BTW, I really appreciate having you guys and this site for a resource.  It's a lot easier learning this stuff from all of you than it is reading my Clymer manual.  Thanks guys.

[Stev-o]

Reconsider using the Keyster carb kits, too many bad reviews.
Look here...   [Digger approved]


http://www.vintagecb750.com/products/6/fuel-system

[lucky]

Sometimes PO's are the greatest threat to the motorcycles' life.

[The other Derek]

I can't help but think that I'll be the PO someday.  Hopefully the current owner is not detrimental to the life of this bike. 

We ended up putting ~170 miles on the bikes on Sunday and I had to help another friend move afterwards.  Monday was far less productive than it should have been (I was beat) and I'm already looking forward to the weekend so I can try to wrap a few things up.

I ended up finding a stuck link while riding on Sunday.  At this point I'm just going to replace the sprockets and the chain.  I think I may need to find a good degreaser too.  It's looking a little soupy under the cover.  Too bad I pulled the stick out before I remembered to grab the camera.


Here's a shot with the stuck link and the rear sprocket.  The rear wheel needs a good scrubbing too.  I still haven't peeked at the rear brake either.  It functions, but I'm sure it needs some work.

[Stev-o]

Looks like you may be due for chain and sprockets.  Gunk Foamy Engine cleaner works good.

[The other Derek]

I pulled the chain and sprockets and ordered a new RK x-ring chain and JT sprockets.

Tires, tubes and rim strips are also on the way.  Went with the BT45s.

At this point I've gotten 2 of my 4 carbs cleaned and rebuilt.  My bike has had idle/starting issues and I am using the Keyster (I know, but I already had them) kits to take everything back to stock.  There were a few issues with how the carbs were set up:
   40 slow jet (staying the same)
   110 main jet (changing back to 120)- staying 110 as thats what came with the kits.  Stocks are 120?
   jet needle at 2nd gap from point (moving back to the middle gap)
   throttle stop screw at 1/2 turn out (starting at 1 full turn out)
   sealant on the bowl gasket (rubbery and lots of scraping to remove)

I'm currently running a 4-1 exhaust and am curious to see how she runs with changing everything back to stock.


Here's the carbs at the start of the day:

[Stev-o]

Is there a baffle in your exhaust?