Partially Restored 74 CB550

[davidcumbria]

Sorry Bryan my  late night memory was playing up mains are definitely 100 ( not 105) and I’m pretty sure pilots are  38 but not more than 40. My chart says recommended jetting for k1 is 100/ 40

[deltarider]

For those interested in the recommended settings (Honda) back then, consult the overview attached. It has been out for years and has not been challenged so far. It does NOT deal with aftermarket parts.

[davidcumbria]

Thanks DR  so my jetting looks ok given delkevich  state no changes needed . Needle position is 4 th. Is that from top or bottom ?

[deltarider]

As far as Honda carbs, always from top, not from tip.

[davidcumbria]

I redid the plug cap/lead connections and also opened the idle air screws to 2.25 turns out. Another test ride ( lucky with the weather ) and I'm delighted to report thats done the trick for now. 

Picks up with out significant hesitation from below 2k revs when opening throttle and revs cleanly to 5 k which is as far as i want to take it for now. Love the way it picks up from 30 mph in 5th gear 1500 rpm and no stuttering. cylinder no 1 plug is still sooty and my temperature gun shows it running cooler than the the other three cylinders but more than happy enough for now with how its running. 

Hearing the engine idling so so quiet and smooth for the first time outside the garage is just a joy after being knee deep in knackered shells, jammed gearbox and damaged crankcases at the start of this thread. link to video of the bike below. I have a little play with the idle adjuster to show it running smoothly at the bottom of the rev counter,

Just waiting for my seat trim. have decided not to put a strap over the seat as it would not match the slightly aged cover. the chrome could be better on the rear mudguard/ light but I actually quite like the non mirror dazzling patina and it works well with all the shined up stainless steel bolts i have fitted. Many thanks to all on here who have coached, encouraged and provided parts along the way.

looking forward to riding the bike and meeting up with some of you this year.

https://youtu.be/0GzZUrDeHhU

[Johnny4428]

Looking and sounding good David. Lovely colour too. In my opinion it is nice for some bike fixtures to show their age. As long as they are presentable.😜

[McCabe-Thiele (Ted)]

Well done David, all done in around 10 months - looks /sounds good in the video.

I'm on month 17 now tbh I've done nowt since November of any significance - I plan to come out of hibernation sometime around March/April.

[Nurse Julie]

Well done, enjoy.

[deltarider]

So... the tachometer is from a CB750?

[davidcumbria]

Many thanks DR I  had no idea. It matches the speedo in size. Looking at the red sectors I agree.

Also I have looked into this now which explains a lot. The 750 tach ratio is 4 to1and the 550  is 6.7 to 1. So on my 550 with a 750 tacho the  indicated revs are way too low.

 1000 indicated is actually 1667 and 1150rpm  tickover would indicate as 690 rpm. This is why I always felt it seemed to revving too fast when setting the tickover using this tacho and why it is happy to tickover well below the 1k mark.

 I need to put a mark  on the tacho at 5500 which equates to the 9250 red line on a correct 550 tacho. Damn good job you pointed this out or I would  have been revving the nuts off it and wondering why it wouldn’t Rev up to the red line.

This  really puts my mind at rest because listening the noise my engine makes at indicated 5000 ( only seen revving in neutral - max on the road so far has been very briefly 4000 (6700) )  I was already feeling uncomfortable about how much more it had got to get to the 750  red line at 8000. .This would  be actually be 13400 in reality so was never going to happen and could have got messy!

So funny reading all this they love to be revved stuff and this conflicting with my mechanical sympathy about what I was hearing and the Rev counter  was showing and now a big sense of relief. We live and learn - especially on this forum👍

[McCabe-Thiele (Ted)]

I've obviously missed something as I never saw your rev counter except briefly in a video so amazed that DR spotted it was a 750 unit. Amazing how we can make ourselves believe a Gauge reading even though it feels wrong in our heads at least for a while.

It reminded me of when I first had my old Honda 250 Super Sport after the 250 Dream - the engine speed always sounded much lower than the rev counter reading as the two firing strokes were closer together on a 180 crank than on a parallel twin. All I heard was the one firing bang as the two power strokes were closer together. I suspect the smoother balance of a 180 crank helped make the revs seem less than the needle was reading.

[davidcumbria]

Agreed Ted. I thought I had previously confirmed the tacho was ok using an old a test meter but probably got the scale interpretation wrong due to this engines  confusing wasted spark and crank speed points drive.

I  don’t think there is a fix for this while retaining the 750 tacho but pretty sure I can live with it now I m clued up.

Was kind of musing about doing a super dream as my next resto…

[McCabe-Thiele (Ted)]

Although my a Super Sport was a slightly more modern with a round headlamp not square I much preffered the standard 250 Dream. It was easier to live with on a daily commute not needing the constant gear changes.

As a young man of course the Sport version meant it was faster, it had more students looking at it in the bike shed. Oh the shallow naivety of my youth. 😁😁😁

[deltarider]

Actually it wasn't difficult to spot. I have heard enough CB500 and 550s in my life. On hearing the sound and a quick glance at where the dial was, I concluded: this can't be right. Then I had a look where the red zone begins.
So it was the sound in combination with the rpm the dial indicated.

[davidcumbria]

It also explains why, as mentioned in a previous post, at a supposed idle of 1100 rpm my timing mark when strobed had already moved off the F mark because it was actually revving at 1700 rpm. All is becoming clear!

I have looked at trying to convert the tacho which is in good cosmetic condition to read correctly but there seem to be conflicting opinions. . I reckon Camshaft tacho drive can’t be swapped but is there a gear drive in the instrument itself that could be swapped from a rough 550 eBay tacho ? Not sure how the internals of a tacho work. I’ve read enough to decide that if it requires opening up / re closing the ferrule I won’t be doing it myself.