Topic: Ignition Advanced - Cannot Set to F-Mark

[C317414]

Hello,

Over the years I've owned many motorcycles, and worked with points ignitions and magnetos without any issues.  I've never owned or worked on a Honda SOHC-4 before, and I am stumped:

Background - I bought a 1975 CB550F a few months ago.  The bike was supposedly tuned-up, but it it did not run that well.  I took off the carbs and rebuilt them using Keihin/Honda float valves and float needles, Keihin/Honda O-rings, and brass parts from Keyster rebuild kits.  While the carbs were off I adjusted the valves and points, and set the ignition timing.  Two valves were loose, and the rest were OK.  I set the static timing by gapping the points to .012" and used a voltmeter on each one to set the timing.  The bike started right up, and ran OK.  I checked the Dwell with my ancient, analog meter.  Both sets of points were very close, but I adjusted them to 23 Deg on the 8 cyl scale.

The issue started when I tried to dynamically time the ignition.  I used a non adjustable (no advance knob) timing light connected to an external battery.  The idle timing was 3/4 of the way to the full advance mark, the high RPM timing was way past the fully advanced mark.  When I tried to retard the timing, I found that the points plate slots were not long enough.  I could not move the plate enough to retard the ignition to the F mark.  I tried ignoring the dwell and opening up the points to the max spec, but this still was not enough to get to the F mark.

I decided to check static timing again, this time with a test lamp.  Now I could not statically time the bike, so the light would come on at the F mark.  It was advanced, just like the timing light showed.  Opening up the gap did not help.

This morning I took off the advance mechanism, checked it, and lubed it.  The post on the back is straight, the springs are not stretched, and the mechanism works smoothly.  I reinstalled everything and tried to statically time the ignition again, but got the same results: both sets of points fire between the F and the full advance mark, and I cannot adjust the points plate enough to get them to fire at the F mark.

Note that the points plate and advance mechanism appears to be genuine TEC parts.  I belive that the points and condensers are aftermarket replacements.  The point contact surfaces are good and the are parallel to each other.

I read this thread a couple of times, but it has not shed any light on my situation:  http://forums.sohc4.net/index.php/topic,164027.0.html

What should I try next?

[bryanj]

When you set the gap the timing moves and when you roate the plate the gap alters, after years of doing it you get used to awkwardness, first suggestion would be new, quality(expensive) points

[bryanj]

Enlarging your pic you can see that the faces of 2-3 are not square to each other

[BenelliSEI]

Another note: the 2/3 points plate could move a long way counter clockwise, but then theoretically your fixed set of 1/4 points should still be too far advanced. I would try another points plate….. you could be getting frustrated by a poorly made part!

[RAFster122s]

I'm betting your points might be Daichi and they are crap. Buy a new points plate with condensers from South Sound Honda of Olympia Washington...
The Keyster brass is junk and you are unlikely to get it to tune properly as the brass is sized wrong. Jets R Us or your original brass if Keihin, stylized K on the brass parts, will give you properly sized brass. Sorry to be bearer of bad news...

[Tracksnblades1]

Use Hitachi points and watch you problem disappear..

[C317414]

When you set the gap the timing moves and when you roate the plate the gap alters, after years of doing it you get used to awkwardness, first suggestion would be new, quality(expensive) points

Yes, they are interrelated.   This is not unique to Honda.  This is why I changed the gap in an attempt to retard the ignition, but it was not enough.   

[C317414]

Another note: the 2/3 points plate could move a long way counter clockwise, but then theoretically your fixed set of 1/4 points should still be too far advanced. I would try another points plate….. you could be getting frustrated by a poorly made part!

Exactly...  I'm not too worried about 2/3 at this point.  Im trying to get 1/4 first. 

[PeWe]

0.012" is smallest gap. (0.3mm)
Increase to highest 0.016" (0.4mm) which will help to retard ignition.

If still advanced, cut springs. The end loop to be cut off, create a new with a plier or two bending the last wound out.

I had to do that on my CB750 K2 with fresh TEC points and ok springs. Idle will be more stable too.

[bryanj]

Pewe,  opening the gap advances the timing not retard it

[PeWe]

Sorry, too much cam timing vs valve lash thinking for me
I fiddled with dwell meter at idle last time testing 23-24.5* (V8 setting) last point years.

Cut springs or replace points by Dyna-S or similar.

[C317414]

0.012" is smallest gap. (0.3mm)
Increase to highest 0.016" (0.4mm) which will help to retard ignition.

If still advanced, cut springs. The end loop to be cut off, create a new with a plier or two bending the last wound out.

I had to do that on my CB750 K2 with fresh TEC points and ok springs. Idle will be more stable too.

.

The springs will have no effect here, since I am trying to set the static timing.

[bryanj]

There is a seller on ebay with dyna lookalikes for about $50 that could be worth a try for you

[MauiK3]

My vote is faulty plate or points

[PeWe]

0.012" is smallest gap. (0.3mm)
Increase to highest 0.016" (0.4mm) which will help to retard ignition.

If still advanced, cut springs. The end loop to be cut off, create a new with a plier or two bending the last wound out.

I had to do that on my CB750 K2 with fresh TEC points and ok springs. Idle will be more stable too.

.

The springs will have no effect here, since I am trying to set the static timing.

Check timing when engine run, timing light.
That's the functional thing.

Static timing not needed if you know how to be close enough to start it.
Points fine tuned with dwell meter when idling.
Lots of adjustments with points to get it right and run evenly.
I gave up, too much time. 2:3 the worst to get right, timing at F plus same dwell as 1:4.

Read this thread. Very inspiring. Made me to use dwell meter back then.

http://forums.sohc4.net/index.php?topic=147444.0

[C317414]

Check timing when engine run, timing light.
That's the functional thing.

Static timing not needed if you know how to be close enough to start it.
Points fine tuned with dwell meter when idling.
Lots of adjustments with points to get it right and run evenly.
I gave up, too much time. 2:3 the worst to get right, timing at F plus same dwell as 1:4.

Read this thread. Very inspiring. Made me to use dwell meter back then.

http://forums.sohc4.net/index.php?topic=147444.0

As I mentioned before, I already checked the timing statically, and dynamically.  Both methods show the same thing:  The ignition is too far advanced, and the points plate slots do not allow any more adjustment.   I also checked Dwell.

I think the problem lies with the points or the points plate, but I don't want to start throwing money at it until I confirm it.  That's why I was hoping that someone else here has had the same issue and solved it.

[bryanj]

Many have and the normal fix is new, Honda, points which will cost you more than the electronic kit you can get ebay item 353948803034

[HondaMan]

This situation is not unusual with the recent TEC points plates (since about 2018). Like others said above: try setting the gaps to 0.014" (nominal) or up to 0.016" (normal maximum). This will let you turn the point plate CCW a little bit (and the 2-3 plate as well), which is what PeWe was referring to, I think?

Also: make SURE your spark advancer is the right one for the bike. There are CB750 advancers that will fit and look the same, but have 2 degrees less advance than the OEM 550 advancers. If the satmped number on your advance is "AD125" or "300" then it is for a 750. The latter one will not advance far enough without altering the 'stop' ears for the weights. Those 'ears' can be ground back a little for some additional advance, if needed.

The CB550K advancers may have numbers like "404", "323", or even "310" stamped on it.

[C317414]

This situation is not unusual with the recent TEC points plates (since about 2018). Like others said above: try setting the gaps to 0.014" (nominal) or up to 0.016" (normal maximum). This will let you turn the point plate CCW a little bit (and the 2-3 plate as well), which is what PeWe was referring to, I think?

Also: make SURE your spark advancer is the right one for the bike. There are CB750 advancers that will fit and look the same, but have 2 degrees less advance than the OEM 550 advancers. If the satmped number on your advance is "AD125" or "300" then it is for a 750. The latter one will not advance far enough without altering the 'stop' ears for the weights. Those 'ears' can be ground back a little for some additional advance, if needed.

The CB550K advancers may have numbers like "404", "323", or even "310" stamped on it.

Thanks for the information.  From what you are saying the issue is with the plate, and not the points, as others have stated.  I'll try to find an older plate, and see if that solves the timing issue.

The advance mechanism on my bike is stamped, 323, so it appears to be the correct one.

[pjlogue]

I would check that the index pin on the back of the advance cam isn't bent as well as the rod that comes out of the crank shaft and goes through the advance cam isn't bent either.  I would also check that the advance cam and counter weights are the proper ones for your model.  Who knows what the previous owner did as far as parts. 

-P.

[HondaMan]

I would check that the index pin on the back of the advance cam isn't bent as well as the rod that comes out of the crank shaft and goes through the advance cam isn't bent either.  I would also check that the advance cam and counter weights are the proper ones for your model.  Who knows what the previous owner did as far as parts. 

-P.

Umm...on the smaller SOHC4 engines, the advancer is held to the crank with a 6mm bolt. Honda learned its lesson in the 750 about having a shaft in the end of the crank.

But then, that crank [was said to have] originally was from an industrial engine: the holes where that shaft fits is open to the oil supply so as to feed lube to a timing chain, which isn't there in the 750 engine. Honda made their own design in the CB500 and later SOHC4s.

[C317414]

I would check that the index pin on the back of the advance cam isn't bent as well as the rod that comes out of the crank shaft and goes through the advance cam isn't bent either.  I would also check that the advance cam and counter weights are the proper ones for your model.  Who knows what the previous owner did as far as parts. 

-P.

I'll recheck the advancer locating pin.  The rest of the advance mechanism appears original and untouched.  This is a low mileage bike.

[Slow2]

I ran into the situation that HondaMan explained. I ended up buy an older advance unit and then I had plenty of adjustment. I had bought a replacement to get the cam lobe and just decided to use the entire unit. It wouldn’t work. Put the lobe on the old unit and everything was fine.

Ed Bruton

[Slow2]

Forgot to mention, I also had a new points plate. It was off also. I found an old one on eBay and put oem points and condensers on it. Works great!!

Ed Bruton

[HondaMan]

Yeah, about 18 months ago the points were "re-started" again after the Covid crap let up in Japan. It almost looks like they started making the baseplates from scratch, and Covid killed the guy who was making them before, or something? The new ones need wider slots on the 2 lower hole mounts.