Partially Restored 74 CB550

[Seabeowner]

I proved to an apprentice that i could be as accurate with a feeler gauge as he was with a dwell box, it is down to experience and practice.
All the 500/550 are not the same, there are at least 2 different advancers with different advance curves, when i was in the trade i NEVER had a bad set of daichi contacts OR condenser, now its different due to change of factory and QC.

Seems any old numbers may have been superseded but whatever, I have three different parts lists and manuals for four variations of 500 and 550 and they are now all called up as the same so Delta has a point.
The most important thing is that the spark comes at the right time in the cycle and I believe that they are all 5 deg BTDC at idle and 25 deg fully advanced. Also there needs to be enough time to (for a better word) energise the coils. Presumably dwell plays a part here but of course the time will in change inversely according to RPM.
And anyway I'm grumpy as I just sheared a bolt off in the sump of my 500 and it was not in anyway tight. So I'll be laying underneath it tomorrow.

[davidcumbria]

Thanks for the heads up. I’ll post some photos when I get stuck. Christmas duties going to be getting in the way of my fun  in the garage a fair bit 😉😅

[McCabe-Thiele (Ted)]

On my 500 I bought some pattern 550 bar switches from Germany as they were what seemed a good price.

As you will see from my 500 project my wiring took me a while to sort it out as I had the wrong bar switches- I did a spreadsheet to help me figure out the wires in the bowl. I will PM you a copy of my wiring spreadsheet Dave - obviously there might be a few differences between the 500 & 550 but you might find it's helpful in terms of what colours are used for what.

I found the horn & the starter solenoid appear to work in one of two ways either the button was an earth or it supplied power looking at the internal switch wiring. My findings for my switch gear are at the bottom of the spreadsheet.

[davidcumbria]

A bit of a jump out of sequence but I recently came across this thread on the us forum which has so much of interest about the set up and design characteristics of these bikes. It explains about the ignition and cam timing and flat spot issues.  I reckon it should be a sticky in the tips and tricks section. Apologies to those who already are very familiar with it.

http://forums.sohc4.net/index.php/topic,7401.msg67251.html#msg67251

[deltarider]

That socalled 'flat spot' is a consequence of the design (think dimensions and in particular bore x stroke) of a 4 cylinder 500/550cc engine. I have read an explanation in a german motor magazine by an engineer over 40 years ago. Also I remember an article on the same subject by a Dutch engineer, which has later been published in a book. In principle this phenomenon can't be helped. The good news is, that it is only noticable when you accelerate from midrange RPM without shifting down. When you accelerate hard from a stop and do not upshift unless near 8000 RPM, you will not notice a flat spot. Anyone can try this out for himself. The Honda CB500/550 offers two bikes in one: a very conversational - if that's the correct word - one, that even a child or an 80 year old can ride and a sporty one, when revved. Many Honda products, including cars, have this characteristic.
Much in that thread you've referred to, is questionable and many claims have remained unproven. From time to time it has therefore been met with criticism from some, including yours truly.

[Johnny4428]

I hadn’t read that post before David. Some very interesting and helpful information there.

[deltarider]

I have kept count. So far no CB500/550 owner has reported an improvement by cutting coils of the advancer springs to cure that flat spot and one owner even reported the opposite when his full advance was reached at a higher rpm than what Honda had designed as standard.
Although I have asked for proof and/or substantiation from the OP, I never got it.
Personally I fail to understand how it can ever be benifical for the advance and driveability. Whenever I open my throttle from idle, full advance is reached within a tenth of a second.
A positive effect has been reported by a Swede, but that concerns a CB750. This is all we know so far.
Real tests are welcome ofcourse.

[K2-K6]

I'm skeptical too about the detail within that list of modification. 

Some directly contradict each other, the settings of timing do offer evidence to show why it's not the panacea that's projected.

The discussion is though much more linked to the one on here about camshaft modification for these engine and likely more productive to discuss it there rather than derail this bike build thread.

[davidcumbria]

Update on work since last post.
With good help from Ted I managed to get all connections made and all electrics working after a bit of playing around with indicators not flashing etc.

Went for the first start and to my dismay petrol started pouring out of the plenum drain even though I had tested float height and valve seating on all carbs during the rebuild. After tapping the float bowls it settled down. I reckon the floats somehow got stuck and due to having a high mounted aux tank  head and  flow of fuel overwhelmed their efforts to seal and the overflow pipes capacity to vent.

After a lot of spinning the engine did start, puffed out a lot of smoke but finally was running on all 4, idling smoothly and picking up ok. No fuel dripping. Best of all the engine much  quieterso seems like the  new primary chain, cam tensioner and valve cover have done their job. Will provide a link to a video when I can figure out how to do that.

My restart attempts came to a sudden halt when all electric  power lost and the  main fuse blew. No problems at all with fusing during the electrical reassembly. I traced the problem to problems inside the aftermarket right switch gear.

That has turned into a two day saga of stripping and trying to rebuild the switchgear. Basic problem is that the soldered terminal for the power supply to the start switch when assembled has a tiny clearance of about 0.5mm from the handle bar. The switch gear doesn’t have a handlebar location peg so when moving slightly under throttle turning it could make a dead short with the handle bar. Bang goes the main fuse for which the po had fitted 50A - bit of a smoking gun I think with the emphasis on smoking ! I also discovered the kill switch was working intermittently. Don’t know if it had been dismantled previously but there may be questions of the internal  quality of these vs oem.

Rebuilding the switchgear while not wanting to pull the cable through has turned into a nightmare of inaccessible c clips, lost or missing detent ball bearings, new failures in soldered joints due to all the disturbance, and the final straw a spring pinging out to god knows where. 10 hours wasted effort so I’ve given up and bad temperedly ordered a new one. Best advice would be to not even try to do this without pulling it all through - hindsight a wonderful thing. Need a couple of days off now to recuperate. But the good news is it runs and with new switchgear in place I won’t be forever worrying about what reliability issues I may have left in there.

[Oddjob]

The new switchgear a copy or an original Honda one?

[davidcumbria]

Cmsl made in Japan aftermarket. Be interesting to compare with previous

[Oddjob]

Lets hope it doesn't have the same fault, saying that it should have the locating pin fitted.

[davidcumbria]

There doesn’t seem to be a hole for a  pin in the bars as well ?

[Oddjob]

The bars have the hole for the wires but not the hole for the pin?

[davidcumbria]

Yes that’s how it looks. I was surprised how the switch gear and throttle went from completely unsecured to tight enough to withstand the considerable torque from throttle movement as the two screws finally tightened up to grip the handlebar. There was also some insulating tape on the bar which I now think was an effort to prevent the shorting.