1979 cb650 resto-mod

[Worst cb650 ever]

More progress today - I installed the replacement EBC clutch springs.

I took a chance and put the bike on its side stand and removed the clutch cover without draining the oil.  As I suspected, the side stand caused enough of a lean that only a little oil escaped when I removed the clutch cover.  The gasket was toast - it was hard as a rock and took air tools to remove from the cover and the block. 

I disassembled the clutch and measured the springs and clutch plates for wear.  The clutch plates all had plenty of life left in them, and the springs were the proper length.  However, I could compress the old springs by hand, whereas the new EBC springs I could not.  I suspect the stock springs are shot after being compressed for ~33 years.  In the first picture below, you can see me deflecting the spring with my fingers. 

I had to make a new gasket, as the old one was pieces and dust, so I used a technique I learned a long time ago.  I took the clutch cover and set a piece of gasket paper on top of it.  While holding the paper in place on the cover's gasket face, I tapped it down over the edges of the cover with a small hammer.  The relatively sharp edges of the cover cut into the paper, either cutting it almost all the way through or leaving enough of an impression that a razor blade can make short work of cutting out the gasket. 

I repeated this process on the inside of the cover and soon had a new gasket.  I flipped the cover over and used it to press the gasket against the workbench, and then used a drill to drill the gasket holes through the cover holes.  Tada, new gasket.  Better than spending $15 and waiting who knows how long. 

Sadly, the rain prevented a test ride to determine if the clutch will stop slipping with the new springs installed, but the bike did fire up and rev and run fine on the center stand, so that's something. 

[Worst cb650 ever]

Breakthrough time.  When I rebuilt the carbs, I didn't set the floats right.  I reset them to 12.5mm / 0.5" and the bike runs much better.  I also replaced the broke plastic choke lever with a metal unit from a '78 CB750 carb rack, which ensures that the choke closes all the way now.  I noticed the accelerator pump arm was pushing the pump rod down about half way even with the throttle shut, so I bent that to the proper clearance. 

I also tested all the spark plug boots again, and discovered that one of them had infinite resistance, instead of the ~5k ohm resistance I was expecting.  Fortunately, I had three spare boots that I received with the replacement coils and spark units, so I replaced the dead boot. 

For the first time since I started working on the bike I was able to start it without using any starting fluid.  Couple twists of the throttle to prime the carbs, and after some cranking she fired up.  It is still hard to start from cold, but at least it does start.

With all that work, the bike will run hard up to 7,000 RPM, but then fight itself and misfire, barely getting to 8,000 RPM.  It seems to be running out of fuel.  I picked up a set of 110 main jets to replace the stock 90 jets, so we'll have to see if that fixes the top end problems.  I might give the floats a bit more of a tweak to adjust the fuel level to make sure the idle and main jets aren't getting uncovered. 

Any thoughts on the float height tweaking?  I don't want to flood the bike, but I don't want it running out of fuel either...

[Worst cb650 ever]

I dropped in the 110 jets, and the thing runs like I shot it out of a cannon!  It lifted the front wheel in 2nd and 3rd, which was very exciting on sketchy 33 year old rubber. 

However, it is running quite rich, as I still have the needles shimmed up two washers each.  I think I'm going to remove both washers and see how it runs then.  I wish it wasn't such a PITA to remove the washers, but it is what it is.  Trying to keep the idle at a steady RPM is hard with the shims in as well, so hopefully I won't have to mess with the idle adjustment quite so much.

Next steps, now that it is reliably running, is to address the rest of the age related safety concerns.  The brake master will be rebuilt, the levers will be replaced, a replacement speedometer cable and good used tach will be fitted, the petcock will be rebuilt, the fork seals and dust seals will be replaced, and I will attempt to fit a CB650SC Nighthawk oil cooler.  Also, new rubber (Shinko) is on the way.  Turn signals would be a good idea at some point as well.

Next steps after that are new paint, and possibly re-fitting the GM HEI ignition system I built.  It appears that fuel was the problem, so I'm interested in how the HEI ignition affects starting and performance.  Or, I could just be causing myself more trouble...

[Worst cb650 ever]

More work done...fork seals, new tires, new levers, new mirrors.

Pulled and dismembered the forks:



Old crusty hard as rock seals come out:



New seals go in!



Hey, I've always wanted a hover bike!



New Shinko tires to replace cracked and hard 33 year old rubber - street/wet compound 712s:



Re-sealed forks and wheel reinstalled, speedometer gearbox regreased, new speedometer cable installed, fender chrome polished, and (not shown) underside of fender cleaned, de-rusted, and painted:



Rear wheel reinstalled, and new bar end Napoleon style mirrors mounted to replace the one bent Yamaha mirror that came with the bike:



Better shot of mirror and new clutch lever:



I pulled the brake master to rebuild it, as the brakes have been spongy despite bleeding and cleaning of the caliper.  However, I received the wrong rebuild kit.  The kit I received seems to have been for a dual caliper cb650/cb750, and therefore the piston's diameter is too large.  No problem, I think, I'll reuse the old piston. Except it is cracked in half in the middle.  As they say, "Thar's yar prablem!"  Time to order a replacement kit and send the old one back.

For reference when ordering from Parts N More, the correct kit P/N is 08-0231 NOT 08-0210. 

Picture of the wrong stuff:



So there she sits, until I get the replacement rebuild kit.  I also received a replacement tachometer (cb750's use the same tach), and an oil cooler assembly off a mid 80's CB650SC Nighthawk.  I'm not sure the cooler will be a bolt on affair, but we'll see.  The '79 CB650 is reportedly the hottest running SOHC 4 Honda ever made, partially because of the cam and partially because of emissions, but hopefully the extra fuel from the larger jets and the cooler will help prolong the life of the oil and the power train in general, and prevent the idle and drivability issues that start happening when a bike gets hot.

[interceptor]

Looking good.  I really like the 650's.  I don't they get enough respect.  I like how your fixing everything as you go, too. 
As far as forks go, I've found some on craigslist for $150-$200.  Sometimes that includes everything like wheel and tire, brakes, master cyl, ect.  Keep your eye out, and I'm sure you'll find one.  Also try craigslook  (claz.org).  Not many people know about that one.  You can set your distance to travel, too.  Good luck.

[Worst cb650 ever]

Thanks for the luck and the link - I'll be sure to use that. 

Of course, now that I've rebuilt the forks, mounted a new tire, and am overhauling the stock brakes, I don't want to spend money on a replacement front end    Too many options!

[interceptor]

Ha.  I know what you mean.  I'm trying to keep my bike stock but I'm always thinking of how I can modify it.  Then I hit myself in the nuts and tell
myself to cut it out and just get the damn thing on the road.   

[Worst cb650 ever]

I feel that if a part fails and a better/newer replacement is available, then I should consider "upgrading."  Car's clutch wears out?  Time for a lightened flywheel and a stronger clutch!  Bike's clutch springs are worn?  Time to put in 10% stiffer springs!

However, I try (try being the operative word here) to get any vehicle, car or bike, running well stock before I start messing with things.  I'm not sure where I'm at with this bike, however   It seems like every time I get it moving under its own power, I end up tearing into something else and it becomes immobile again.  Someone's going to end up with a very thoroughly sorted bike when I'm done with it, however.

[Worst cb650 ever]

After getting the incorrect set in the mail, I finally received the proper K and L brake master cylinder rebuild kit, and used it to overhaul the gummy master cylinder. 

For reference, here's a picture of the order that the pieces go - you will probably be able to figure it out like I did, but I'm such a nice guy that I'll save you the effort:



The piston was snapped in half.  Oops.



Also, as you clean out the master cylinder casting, make sure that you open BOTH of the holes that lead from the reservoir to the cylinder bore.  In this picture, you can see the larger fluid hole on the left, and the smaller bleed hole on the right.  You may have to use a very small drill bit (I used a PCB board dill bit) or a piece of sharpened guitar string to open up the smaller hole, as mine was stuck tight with old brake fluid. 



Voila, a working reassembled master cylinder.  I replaced the o ring that seals the reservoir to the casting, but chose not to spend the $60 for a new reservoir as even though mine is ugly, it is solid.

[Worst cb650 ever]

Welp, I pulled the carb needle shims, thinking I had fixed the idle issues that had been plaguing me. 

I guess I should have not been surprised it idled like crap and had to have the throttle tickled to stay running until I turned the idle knob in big time. 

After much head scratching and thinking, I came to the conclusion that the slow jets must be the issue - the bike has plenty mid range and up top when it is running almost exclusively on the main jets, but idles for crap, takes forever to warm up, and tends to stall when the clutch is let out.  Rather than drop $22 + $13 in shipping  for a set of new #35 slow jets (the press in jets are a real PITA to find), I opted to order up a $13 pin vise and drill bit set.  A #80 drill bit is 0.3429 mm, which is pretty darn close to the 0.35 mm hole diameter of a #35 Keihin slow jet. 

I carefully started to "drill" through the slow jet, and was surprised to dislodge crusty crap.  It appears all the slow jets were reduced to almost half their diameter by crap.  I had soaked these jets in old school carb cleaner, and then in the Pine Sol dip of doom, cleaned them out with copper wire, and there was still crap hanging on in them.  Gah! 

Next step is to reassemble the carbs and try again.  Hopefully I'll get a decent cold and hot idle out of the bike now. 

Also, the master cylinder reservoir is leaking.  The plastic of the reservoir is shrunken with age, and will not seal right.  Rather than spend $60+ on a new reservoir kit, I opted for this ebay find:

http://www.ebay.com/itm/150814486315

$27 shipped for a brand new master with an integral reservoir.  I will be sure to let you folks know how good it is when it gets here.  The old master, leaking and all, felt great with the rebuild kit in it and the braided stainless steel line.  Anyone want to buy a rebuild brake master with a leaky reservoir to further fund this madness?

[Worst cb650 ever]

Yup, cleaning out the slow jets with a drill bit did it.  Of course, now I have to readjust the choke idle speed, because with the choke out it wants to idle at 6k RPMs.  Oops. 

With the cleaned slow jets and the 110 mains it is running great, but a bit rich.  As an experiment, I pulled the air filter and opened up the air box some.  Still runs and revs well, so I'm thinking velocity stacks.  Everyone loves velocity stacks right?  The stock air box plenum is distorted by heat or time or general bloody mindedness, and it keeps pulling the rubber boots off of the intakes for the carbs, which does me no favors in getting this thing tuned.

Has anyone put something like foam over velocity stacks to keep more than just small birds out of the motor?  Velocity stacks are great and everything, but I would like to avoid doing a Cucamonga rebore on a bike with only 8,000 miles. 

[Worst cb650 ever]

After getting some input from forum members, I decided to try to repair the stock intake system.  I bought a good used air box off of ebay, and seeing it makes me really understand how messed up the one that came with the bike was.  Hopefully that will help with tuning, as I know that intake air leaks on any vehicle can cause issues. 



The new box isn't as "mushy" as the old one either - it actually feels like hard plastic.  More news after the box is installed!

[Worst cb650 ever]

So, what started out being a quick removal of the air filter housing / rear fender in order to install a replacement carb -> filter housing air box turned into removing the swing arm and all the ancillary bits, cleaning off 33 years worth of oily mud and muddy oil, and then priming and painting lots of the bike.

Spoilers; eventually I did install the replacement air box.

In this page from the service manual you can see how the air intake system works.  My biggest issue was that what is labeled the air cleaner chamber was melted and smashed in where it joins with the air filter housing / rear fender.  I was able to find a good replacement on ebay, and it was immediately obvious that the one on the bike was a mess.



However, to do it right, I felt that I needed to remove the air filter housing / rear fender.  To do this, I needed to disconnect the shocks and lift the back end of the bike in the air to give myself enough room to remove the housing.  Of course, there were about 1,000 other pieces that had to come out first, like the battery and the rear chrome fender.

Once I had the air filter housing out, I discovered that the crankcase ventilation hoses were hooked up to the wrong spots on the air filter housing.  Huh, having the valve cover vent going into the wrong spot can't help anything, and no wonder I never got any water out of the condensation trap drain!

At this point, I was feeling saucy, so I decided to partially strip down the bike and get some paint on the frame.  It was a beautiful sunny day, not too hot, perfect for painting.  I removed the rear wheel and then pulled the swing arm.  The next step was cleaning 33 years of grunge off the swing arm and rear wheel, and cleaning 33 years of chain lube out of the drive sprocket housing on the side of the transmission.  The chain, a non O-ring unit from DiD, got a dip along with the sprockets in some 87 octane.  The swing arm and the sprocket cover ended up in there too, as there was a lot of crud caked onto those parts. 





The engine and center stand were cleaned on the bike, and really shined up nicely.  I took the wire wheel to the swing arm to get some loose paint and surface rust off of it, and then wiped it down with acetone.  I hit it with three coats of self etching primer, and then with two coats of satin black.  It ended up looking sharp!



I also cleaned several areas on the bike where there was surface rust, and hit them with the self etching primer and the satin black.  There was no bad rust on the bike, only some surface rust from being outside.  Someone took care of this bike at one point, but it had become neglected in its later life. 




After the paint had dried, everything had to go back together, starting with the swing arm and rear wheel.  I lubed the swing arm bushing while it was off the bike, as the zerk fitting is hard to get at on the underside of the swing arm.  Everything went back together well, except I discovered that the right hand exhaust mount was bent, causing it to foul the swing arm at full droop.  I straightened that out, touched up the paint on the swing arm, and finished that up.





Now I could actually install the new air cleaner chamber, along with the air filter housing / rear fender.  Everything went back together nicely, and for the first time since I've had the bike, the carb boots slid right into place.  I reinstalled the plastics, seat, and tank, and had a bike again!

After some fiddling, the bike fired right up without the choke.  Hmm.  It is running pretty rich, which is about right since the 90 main jets have been replaced with 110s, and the air box is now leak free and almost all stock, with the exception of the air filter cover being missing.  I think I'll try 95s or 100s and see if the bike stops fogging for mosquitos. 

[Worst cb650 ever]

Woo, read over 1000 times! 

The new master cylinder is Bethpage, NY as of today, so hopefully it should be at my door soon.  I'll be comfortable with putting paint on the tank when I no longer have a brake master gently sprinkling the tank with brake fluid.  On the plus side, there is a lot less paint to strip...

[CHOPPERRICK]

Looks like you"ve got a good start it! It's nice to see another CB650, They're very rare in my area. Everyone thinks it a 750. I just sold mine(with many tears ) after 18 years of working on it. Here's a few pics of how it finally turned out.