Topic: 1980 CB650 Cafe Racer

[Kurlon]

Keep going at it, it seems to be making progress.. Little by little you will get her running perfectly.. Any chance the noise is a timing issue?

It only varies with RPM, frequency implies cam speed, one cylinder at most, which matches the audible locality.  It's a distinct tick.  It's slowly come into it as I've been working on the bike, which has me slightly worried, but I'm going to hope for the best and assume valve adjustment first rather than something more sinister just yet.

As far as timing, are you thinking ignition timing vs it having jumped the cam chain?  I suppose if it HAD jumped the cam chain at some point in it's life that might explain some of the tuning issues I'm encountering... time to get that valve cover off and investigate.

Edit: Bad Honda Engineers, no cookies for you!  You have to take the rocker box off to see the cam timing marks?!  Sheesh.

[Kurlon]

Got the valve inspection covers off, I don't have to worry about loose valves... all feel tight.  So that explains some of what I'm fighting.  I'm going to have to get a tappet adjuster tool before I fix anything though, no way my wrenches are getting in there.

Started checking the timing, looks like my trigger cam is slightly advanced?  When it's lined up with the 1-4 pickup, it shows that I'm not quite at the T mark.  The advancer is working nicely, no stiction in the action.  So I timed it by finding TDC manually and adjusting the pickup plate to match the trigger rotor as noted by the CB650 manual if timing without a light.

[Frankenkit]

you'll want to look at hondaman's FAQs for setting 500/550 exhaust valves just a hair looser than the manual suggests, to avoid burning them. They'll sound just a bit louder, but you'll have the extra reassurance of knowing they'll stay a little cooler.

[Kurlon]

So, cam is slightly retarded, but without a slotted sprocket I'm not going to improve upon that, it's within the range the notch in the cam allows for I suppose.  Valves adjusted, all were tight.  There are two rocker box bolts that are on the verge of stripping, those will need helicoils the next time I'm in there.

The bike will now hold a 1000 RPM idle when warm with the pilot screws at 3.5 turns, and the revs drop when blipping decently, so it's not stupid lean there.  Still doesn't like WOT below 5k, although now it doesn't shutdown, it just looses some umph and stumbles a bit.  Next step is a carb sync, and 95 mains instead of the OEM 90s I think.  Needles will likely get shimmed at the same time.

Put 30 miles on today on my second outing.  (First was cut short by one coil coming unplugged... d-oh!)  Bike is usable now save for no horn, sucky front brake, blown fork seal, blown shocks, missing tank cap and crappy mirrors. : )

[Zaipai]

Ah but its ridable thats half the battle!!

I am sure you will have her all tuned up in no time.

.: Scott :.

[Kurlon]

So, I've put another 150 or so miles on, and made some small improvements.  The front brake is a BIT better, but still not perfect.  I went to flush it and found it almost out of brake fluid.  AH-HA! I thought, there's my culprit, but a flush and bleed later it's still not all that impressive, gotta be the pads and rotor or a crap master.  The carbs are working better-ish.  Once warm (Which takes awhile) it'll settle into a 1200 RPM idle, and occasionally will let you launch using normal revs.  Most of the time it'll load up and start to stumble, requiring some quick throttle and clutch work to build the revs back up over 3500 RPM so you can keep it screaming while you feather the clutch out.  Once rolling you can drop down to about 2500 RPM and still pull cleanly as long as you don't go WOT.  The intermittent idle has me confused, one moment it's ok, the next it will not pull at low RPM and the only thing that can save you is the accelerator pump?

Edit: Oh, I've been offered a 400F gas tank if I want.  It's got better lines than the cruiser inspired 650 tank, but more rust inside.  I'd also have to do some welding to adapt it to the 650 tank mounts but I think that's doable.  If the local radiator shop is game I'm going to have them clean my current tank and while it's off I'll do some mock up work.  If the 650 tank comes out good and the 400F tank is an easy adaptation, it'll get sent out next.

I've also got to do something about my tach.  The odd intermittent whirring I was hearing is coming from it.  It's started getting jumpy too lately so I suspect one or both have run out of lube.  I know I can grease up the cable and put it back in it's sheath, is there any way to re-lube the tach itself?  The eventual plan is a modern electronic dash but for now I'd like to keep the stock bits working if I can.

[manjisann]

I believe the tachs are mostly sealed. I had to pull mine apart and most of the gearing was sealed and didn't seem to be lubable. Plus getting the chrome ring off and then back on is a pain.

Brandon

[Kurlon]

Confirmed my problem is the tack itself, with the cable off the tach it doesn't make any noise.  Hook it up, and the whole tach vibrates badly.

My front brake master also let go today as well.  The plastic reservoir was already sun baked and crazed, the warm temps seemed to be the last straw and it just started leaking from everywhere.  I've temporarily put on a pitbike brake master, but the piston is WAY too small for this system, no mirror mount, and no brake light switch.  It at least does SOMETHING to make wheeling the bike around easier though, as well as not leaking all over the place.

Interestingly, the motor is responding slightly better just off idle today, which implies I may be RICH on the needles/pilots?

[manjisann]

I believe that would be pilots, I don't think needles start kicking in until about 1/4 throttle and stop doing anything after 3/4, that's assuming I'm remembering the diagram correctly.

Brandon

[Kurlon]

I've always used 1/8th turn as the crossover point from pilot to needle control, but I'm certainly right in that tricky area.  Still RPM dependent also, above 3k it'll just yank, below I can get past it with more throttle, below 1500k it's dicey.

[Kurlon]

Two steps forward, hopscotch backwards.

I've been tinkering with another project while gathering parts for the CB.  Got a nice new tank cap, bunch of gaskets, etc.  I loaded the tank up with a 30% strength mix of CLR and water to start de-rusting the inside and had given it a few days to work.  Based on what I could see through the tank opening it was doing a good job.  Today I drained it, flushed the loosened rust out, and went to test it with gas...

Leaking badly along one seam.  Turns out the rust had been masking a leak.  Sucks that the tank is a total loss after de-rusting the exterior, doing a quick spraybomb that didn't look half bad, silver soldering the petcock bung, and buying a new gas cap... but I'd rather find out now than on the road it's a leaker.  So, now, the bike is on hold while I work on tracking a tank down.  Bah.

Edit: Will a 79 tank work on my 1980 bike?

[Frankenkit]

The shape is all different, I'm inclined to think "no" because the 79 frame is different from the 80-82 frame, but maybe? 

[Zaipai]

The shape is all different, I'm inclined to think "no" because the 79 frame is different from the 80-82 frame, but maybe? 

Definitely Maybe.. !! 

.: Scott :.

[Kurlon]

The mounts look similar... I'm inclined to give it a shot at this point as it seems 79 tanks are MUCH easier to find on eBay.

I also was given a Nissin 14mm piston brake master for the front, just need to get a remote reservoir kit and I can resume tackling the stopping side of the equation.

My final potential find, a set of Honda F2 wheels... : )

[cb650]

The 79 tank is longer to the rear mount needs work.  Then the seat will be in the way.

[Kurlon]

Well bugger.

[Kurlon]

I assume 82's are out as well due to shape changes?

[cb650]

A 82 standard is the same but the nithawk is a diff shape.  It will bolt on though.  Remember the 81/2 use a diff size petcock and fuel line.