Author Topic: Do sheared teeth on the advancer mechanism affect timing? 1975 CB550K1  (Read 1475 times)

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Offline tkarahalios

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So I was checking my timing with a strobe light. The static timing seemed pretty good. The advanced timing was off quite a bit. I figured that I may have weak springs and decided to disassemble to take a look and see if I could find replacements or use the method described on this blog site of cutting off half a loop of each spring to tighten them up.

When I took the advancer apart I noticed that the two teeth that are supposed to be on the top surface and interface with the larger nut have been sheared off (see photo). I'm not sure when this happened. There were no bits of metal in the points case so it may have been a while. I suspect they were sheared off by me or the PO(s) when advancing the motor to adjust the points and valves by torquing that larger bolt. (I don't typically remove the spark plugs, I will in the future).

Now my question. After looking at the mechanism and the mounting carefully it seems to me that the sheared teeth should have no effect on the timing. Is that correct? It seems like they only help with allowing someone to use the larger bolt to advance the motor. Am I missing something here? Any thoughts appreciated.




« Last Edit: May 20, 2016, 08:52:42 AM by tkarahalios »

Offline nicks2319

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Those teeth are just to keep that top bolt in place so you can spin the engine manually. They don't effect the timing. But I'd still hunt a better condition unit down.

Offline flybox1

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+1, wont effect timing. 
Loss of the little alignment pin at the back of the advancer..the one which fits in the end of the crank....that one you cant lose  ;D
...but dont throw it away.
The plate is still good.  So are the weights and springs and circlips  ;)
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Offline Bodi

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This is what happens when one tries to turn the engine over using that big nut. It looks like it should handle a lot of torque... nope.

Offline tkarahalios

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So using this as a moment to learn how to turn the motor over in the future in order to adjust the points or valves...should 1:

1) use the big nut but make sure the spark plugs have been pulled first to remove the compression
2) remove the spark plugs and use the kick start
3) some other way?


Offline strynboen

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1 vorks fine.
..i even use my battery driller for rotating..to get oil pressure...just be care not to build um too big moment..um..and absolut no plugs inn

« Last Edit: May 20, 2016, 01:03:00 PM by strynboen »
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Offline Deltarider

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The static timing seemed pretty good. The advanced timing was off quite a bit.
Adjusting the breakerpointsgap (dwell) can cure this.
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1) use the big nut but make sure the spark plugs have been pulled first to remove the compression
In 36 years I've never removed the plugs and never had a problem. Just be gentle when engine is hot.
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Offline mystic_1

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Agreed, I've turned motors over using that nut, without removing the spark plugs.  Just go slow and don't Hulk Hands it.



There's a locator pin on the back of the timing unit that indexes it to the crankshaft, so those ears being sheared off won't affect your timing.

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Offline tkarahalios

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So two more questions.
1) what is the torque for the advancer mounting bolt?
2) I assume torquing that bolt is accomplished by holding the larger bolt-washer with a spanner while torquing the center bolt. Since I have sheared ears on the advancer mechanism is there any way to lock up the motor so I can torque down the advancer bolt? Do I leave it in first gear?

Offline mystic_1

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Woah Woah, see above about Hulk Hands.

The advancer is retained on a 6mm bolt on 550's, standard torque value should be something like 5 foot pounds. 

"slightly more than snug" using a 1/4" drive socket is what I'd suggest.  Blue locktite for insurance.

You shouldn't really need to lock down the motor do to that.

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Offline Deltarider

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what is the torque for the advancer mounting bolt?
1,1 - 2,5 kg/m. Personally I do not use my torque wrench for lighter bolts and nuts because I don't want to loose my skills. Therefore my tip: tighten it up to just before it snaps  ;D And for this particular bolt, a T-handle is best.
« Last Edit: May 21, 2016, 08:46:26 AM by Deltarider »
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Offline alacrity

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what is the torque for the advancer mounting bolt?
1,1 - 2,5 kg/m. Personally I do not use my torque wrench for lighter bolts and nuts because I don't want to loose my skills. Therefore my tip: tighten it up to just before it snaps  ;D And for this particular bolt, a T-handle is best.
I love this advice: "tighten till just before it snaps."   Of course it's correct, but it's like the question I was asked a million times when teaching track riding/race skills, "how fast can I/should I be going through xyz corner?" The answer of course is always, "as fastest possible speed given conditions, skill, equipment, tires, and all the other variables that doesn't result in a crash."  So how do you find that speed without crashing?   Same answer to how you find that maximum bolt torque without thread stripping or bolt head snapping...   You don't.   So you gotta stop somewhere south of that "whoops, too far" past the limit result, and where THAT is comes from feel, experience, judgement, awareness, caution, preparation, and a little luck too maybe.  :-).  I always recommend this o friends they before working on these old bikes, that they have a set of left hand drill bits, spare correct-size bolts and an m6 time sert kit standing by for the inevitable...
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Offline mystic_1

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One thing I like to recommend to people starting out with mechanical work is to take a bit of scrap bar stock or plate stock, in both steel and aluminum, drill some holes in them, thread them, and then run bolts into them and intentionally try to break the heads off by tightening.

It's a great starting exercise to build out basic machining skills.  You could also then practice using easy outs, left handed bits, etc, all without having to risk precious real parts.

Plus it's fun breaking #$%* sometimes ;)



On the CB750 the arrangement is a bit different, there's a stud that mounts to the crankshaft, the advancer goes onto that, and is retained with a 6mm nut (10mm socket size) with a flat washer under it.  Otherwise it's a similar mounting arrangement, basically.  When tightening the nut, I like to use a 1/4" drive ratchet (5 inch handle), and apply force with only my thumb and first two fingers, with my fingers "choked up" on the ratchet handle about half way or a bit more, and then apply pressure until the nut stops turning.  By not using the whole handle length nor the whole force of my hand, i'm pretty much guaranteed to not be able to generate enough force to strip the threads.  I do use blue locktite, never had any issues.

There is a feel to "just before it snaps" but you can only really learn it by snapping a bunch of things first.  :)

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Offline tkarahalios

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Thanks for the advice everyone. I ordered a replacement advancer mechanism on eBay just because it hurts knowing there is something kinda broken on my bike even if it doesn't affect its performance. In the meantime I got the bike running well on the old one. I adjusted the timing using a timing light. It's pretty close. The static timing seems to bounce a lot so it hard to tell exactly where it falls but I am visually averaging it out to being at the "F" mark. The dynamic settles to a steady measurement easily.

Any ideas as to why the static measurement is jumping around 3-4 mm on either side of the "F" mark? I just ordered replacement stock coils since the old ones seem suspect. Any other ideas?

Offline Deltarider

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Any ideas as to why the static measurement is jumping around 3-4 mm on either side of the "F" mark?
Breakerpoints that are not mounted correctly could cause this. A dwellmeter could tell. Maybe the plate needs to be shimmed.
It's sad that so many can't leave the plates alone where they could have timed the ignition precisely by just adjusting the breakerpoints gap.
Quote
I just ordered replacement stock coils since the old ones seem suspect.
Coils rarely fail. You are not the only one that suspects his coils. I don't know why this is. Maybe it's because coils are mysterious in the way they work with invisible magnetism.
« Last Edit: May 22, 2016, 07:35:57 AM by Deltarider »
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Offline mystic_1

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Static timing is just to get things in the ballpark, the timing light will tell you the truth.  If it's good on the timing light, you're GTG.

How old are your points, what brand are they, and what condition are they in?

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Offline Airborne 82nd

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Get a 1/4" palm ratchet for your bike I like it a lot for the small stuff. That and some JIS bits to go with it.

Offline tkarahalios

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My points are about 2 years old with less than 1,000 miles on them. I was out of town all last summer for work reasons so I didn't have a chance to ride or make improvements last year. Hence I'm eager to enjoy this summer!
I checked them with a dwell meter and they are good from that respect. I also etched the plate so I can easily get it back to where it was. The only significant change I made was moving the 2-3 point sub-plate a few millimeters.

They are the Daiichi points and condensers which are not a good brand I have learned. I just ordered a pair of stock OEM Honda points on eBay. I was planning to replace the points and reset the timing when they arrive. I was going to to reuse the Daiichi condensers. I am assuming their condensers are pretty good quality, but will test them according to the Clymer's manual. Are Daiichi condensers decent quality?

So, at 2500 rpm my dynamic timing is spot on. At 1000 rpm, it jumps plus or minus 4mm around the "F" mark. Is that normal or should it be stable and lined up exactly with the "F" mark? Is that due to an erratic idle? I'm planning to learn how to do a carb sync soon and hoping that might help. I've never done one since I bought the bike form the PO (2+ years ago). From the condition I got it in, I don't the previous PO ever did one either.

Airborne 82nd, I agree, I bought a palm ratchet and T-handle from a company named Vessel on eBay a while back that comes with JIS bits and it quickly has become my go to tool for everything on the bike.

Thanks for all the advice I've been getting. This site has been extremely helpful!

« Last Edit: May 23, 2016, 08:12:42 PM by tkarahalios »

Offline Deltarider

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At 1000 rpm, it jumps plus or minus 4mm around the "F" mark.
You could try with the timing light connected to an external 12V battery. How does the idle sound?
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Offline tkarahalios

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Do sheared teeth on the advancer mechanism affect timing? 1975 CB550K1
« Reply #19 on: May 24, 2016, 03:46:01 PM »
Quote
At 1000 rpm, it jumps plus or minus 4mm around the "F" mark.
You could try with the timing light connected to an external 12V battery. How does the idle sound?
The idle is a little rough. I'm going to learn how to do a vacuum sync and see how it sounds afterwards...

Offline strynboen

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use a extern blower to cool the engine.
.a first try to syncro takes a bit long.
..try to adjust on more karbs and find a mittel vay..and hit a kommon vaccum.
.dont take one at time..its impossibel to do one at time..and bay that schrev kombi Tool..to turn the schrevs..it help#s a lot..it fit both 400 and 500 and 550..so is kind universal..have not tryed a 750..
i kan not speak english/but trying!!
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