Topic: Dad's 1978 Honda CB550k

[newday777]

This could be it then.  I never did that maintenance task! It would be amazing if this solved my idle issue!

Do you have a strobe timing light? You need to test the advancer with a timing light to see if the advancer is working properly. Full advance at 2,800-3,000 rpm. Before that and you know that you will need to clean it up, and possibly cut the springs.

[joegeis]

I had set timing with my test light, not a strobe.

God love CMC. They have a video for everything! I'll follow this video later this week. Is there a way to tell if it is "out of spec" once removed? Or do I need to clean, reinstall and set timing to determine if this is my problem? If it is, do I just replace the springs?

https://www.youtube.com/watch?v=NWmeU3OALfU

[newday777]

I had set timing with my test light, not a strobe.

God love CMC. They have a video for everything! I'll follow this video later this week. Is there a way to tell if it is "out of spec" once removed? Or do I need to clean, reinstall and set timing to determine if this is my problem? If it is, do I just replace the springs?

https://www.youtube.com/watch?v=NWmeU3OALfU

Yes with a strobe timing light

[joegeis]

okay, well I'll have to procure a strobe timing light if that is necessary. I did already disassemble, clean, lube and reassemble the advancer and verify timing with my test light (no adjustment was needed - I marked plate location with a sharpie before taking it off). Everything looked to be in pretty good condition. Very minimal corrosion but the grease was all dried up and sticky.

Quick test shows some improvement. Cold start idle was quite a bit more even, with less idle screw adjustment. After running 1 minute at a steady 1600 rpm, after revving to 3000 rpm, it would come back down to 1600, albeit pretty slowly. This is an improvement over previous where it would hang and 3000 until I messed with the idle screw very often. Granted this was all of 10 minutes of testing. I'll evaluate more the next time I take the bike out.

Would replacing my advancer springs result in the idle coming back down more quickly?

quick google search results: Would this work for strobe timing?

Edit - found a video on setting strobe timing. CMC of course

[newday777]

Yes that timing light will work.
Again check with the timing light to know if the advancer is working properly.

[grcamna2]

How snug do both your advancer springs feel before you twist the advancer ?

[RAFster122s]

Replacement of springs may not be needed. Removing loop and reforming end is usually enough. I think Yamiya has replacement springs if you are ordering things from them you could add them to your order. If you need to reform them you can decide after you have ran them for a while if you need to replace them.
Air leaks can cause idle to stay up and not decay right away too. But you have ruled that out.

Be methodical and don't change a bunch of things at once lest you never know what caused your issue or if you introduced something else...
It is nice that you can run the bike without the points cover for testing purposes...

[joegeis]

I had to pull the spring 1-2mm in order to stretch it over the post, so it's not loose. I ordered the strobe light,  so I can test that later this week.

With all new intake rubber,  I would be shocked if there was an air leak.

[SOHC4 Cafe Racer Fan]

Looking for a "second" for BOTM:  http://forums.sohc4.net/index.php/topic,180400.0.html

[joegeis]

Strobe light arrived and I'm looking at the dynamic timing. Here is a video. I let the bike run for a couple of minutes. It was holding a steady 1200 rpms without the idle wandering. I'm having a hard time telling if the timing is good or not. The F line is bouncing back and forth, and I'm not sure what "right" looks like. Is this just the way it looks, or is something else off causing it to bounce around?

https://photos.app.goo.gl/5YCxfbZhQrvTs3PW7

It's not in the video, but I tried this at 3000 rpm to see if it would smooth out, but it just bounces faster. Is this a symptom of loose springs?

[calj737]

Hold the throttle to 2800-3000 and the timing marks should be steady then at full advance. If not, you might have a spring fatigue issue.

[joegeis]

Had it steady at 3000 rpm and it was bouncing the same amount,  but faster. Should I cut half a turn of each spring and try again?

[BenelliSEI]

Are you saying the F mark is bouncing around the fixed point? If that is so, then the springs are weak and a 1/2 loop might help. Do as little as possible and see if there is an improvement…..,

[joegeis]

Watch the video in the link I posted and you can see exactly what I mean

[seanbarney41]

take the inductve clamp of your light  and clip it the other way.  Also sometimes helps to power the strobe from a battery seperate from the bike

[BenelliSEI]

Sorry….. video is not clear enough….

[joegeis]

Yes, the F mark is "bouncing" around the fixed mark. The fixed mark is stationary.

When I flip the induction clip, it does not strobe at all. I'll try attaching to a different battery. Assuming that doesn't change anything, I'll cut half a turn off each spring and test again.

[joegeis]

Okay, I shortened the springs a half a turn. I immediately noticed that the engine would come back to idle speed after revving MUCH more quickly. The throttle would not float around 3000 rpms as it would before, even when cold.

At ~1200 rpms, the T F marks continued to look like they "bounced" around quite a bit. However, at 2000 rpms, they definitely smoothed out. I managed to capture pictures rather than a video that give a good indication of what the readings look like. To be honest, I truly do not understand ignition timing, and what all this is actually doing, so I'm not sure if this is good or not. This is with no changes from where I had static timing set.

Fairly steady timing at 2,000 RPM:


Going to take it for a test ride to see how it feels and if the rpms hang anymore.

[BenelliSEI]

Let’s start from scratch. Your timing light is hooked up to a battery and the induction lead (the one sensing the spark pulse and making the light flash) is clamped to the #1 spark plug cable. What you are trying to achieve is full detonation of the charge (air/fuel mixture) with the piston at the top of its stroke (TDC Top Dead Centre). At idle, the spark fires only a few degrees before the piston reaches TDC to achieve this. At over 2500 rpm things are happening so fast that the weights on the advancer are rotating the points cam ahead, setting the spark to fire almost 30 degrees before the piston reaches TDC in order to get the “bang” at the right time. Make any sense?? Read the attached photo from the factory manual.

At idle, you should see the F 1.4 mark appearing to align with the fixed mark on the case. Your first picture above, looks like what you should see at idle, not at 2000 rpm. If that is the case you need to advance the timing by rotating the points plate counter clockwise until you see that F 1.4 mark line up at 1000 rpm.

Staying with the #1 cylinder, now rev it up and see if you hit the total advance marks line up. They are two stamped lines to the right of the F1.4 mark that should come into view as you rev it up. They should straddle the fixed mark. Take pictures at idle and +2500 rpm and show us what you see.

You’re getting close. When you get this right, your bike will run MUCH better.

[joegeis]

Thanks Benelli, that helps!

So, a couple things then,

1. Even though I cut the springs and they are definitely providing more resistance, I still had inconsistent readings at idle speed (I was at 1,600 rpms, not 1,000). Seems that the lower the rpm, the more "bouncy" and illegible the readings are for me, still.
2. Assuming the issue in #1 is resolved, at 1,000 rpm, I should see the line immediately to the left of F 1.4 line up with the fixed mark on the case, and at 2,500+ rpm, the F1.4 will should be to the LEFT of the case mark. (If I am understanding, the advancer spins clockwise, which means that the firing is happening sooner?)
3. For some reason, at higher rpm the reading is very stable and clear, and does not "bounce" anymore since shortening the springs.

Tomorrow I will start over and will gap the points again, set static timing again and then grab more pictures (or videos if its bouncy) at 1,000 and 2,500 rpm.

Thanks!

[BenelliSEI]

2. Careful here. The T mark is TDC. The F1.4 is just to the RIGHT and is advance at idle. The marks for FULL advance at 2500-3000 RPM are even farther to the RIGHT.

[MauiK3]

Not sure if this has been discussed.
The induction timing lights often have an arrow indicating which way they clamp to the plug wire. The arrow points to the plug.

[BenelliSEI]

Not sure if this has been discussed.
The induction timing lights often have an arrow indicating which way they clamp to the plug wire. The arrow points to the plug.

True! Mine also is pretty sporadic at idle and strobes more consistently at higher revs. I used to have a 3” piece of stiff, tightly wound spring that snapped onto the plug and then the plug cap snapped to the top of it. When you clipped the clamp around the spring, the light worked 100X better. I put a short piece of shrink wrap around it and it worked well on SOHC motors……  it bounced off into never-never land a few years ago (never to be seen again)! 

[denward17]

I don't know 550 bikes that well....

Could it be from a bent shaft on the end?  see this thread....

http://forums.sohc4.net/index.php/topic,193574.0.html

[BenelliSEI]

I don't know 550 bikes that well....

Could it be from a bent shaft on the end?  see this thread....

http://forums.sohc4.net/index.php/topic,193574.0.html

Also true, but watching the video it seems OK?