Author Topic: Can’t adjust timing correctly  (Read 895 times)

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Offline Bigmant

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Can’t adjust timing correctly
« on: March 09, 2022, 07:58:05 PM »
Hey gang!

Ok, now for the next problem in my rebuild!

So I can’t seem to get the timing right when I static time the bike. For 1-4, my test light comes on, and I have to clock the backing plate almost as far right as it will go to get the light to come on. Switch over to 2-3 and the light won’t come on at all in any position as I rotate the crankshaft.

This is done  after gapping the points to .014. I’ve checked the blue and yellow wire, and I am getting power through both. Swapped coils and I still get the same thing. Am I doing something wrong? Anyone ever see this happen before?
‘74 CB750 K4 Owned by my father and now me

Online bryanj

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Re: Can’t adjust timing correctly
« Reply #1 on: March 09, 2022, 10:41:39 PM »
Yup, when you rotate the plate the gap alters, you have to keep checking both
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Bodi

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Re: Can’t adjust timing correctly
« Reply #2 on: March 11, 2022, 06:01:36 PM »
If the plate is loose even a little in its mount, you will be chasing your tail.
You can find a shim thickness that fits between the tabs and the plate so it just turns then glue little pieces in place. Trying to tap the tabs in usually snaps them off.
Gap is not critical, you may need to adjust it to get timing right. This affects dwell of course but that as well is not critical. Presumably it is specced so the coil has time to charge at redline.

Offline HondaMan

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Re: Can’t adjust timing correctly
« Reply #3 on: March 11, 2022, 06:30:10 PM »
If the plate is not a TEC brand or a Hitachi brand plate, but instead a Daiichi brand, it will be very loose in the mounts. This will let it slide up & down (and all over) when you turn it. To make matters tougher, the Daiichi plate's points are not the correct geometry: you will have to go to 0.016" gap on the 1-4 points to get it close to time. Then the 2-3 points will probably have some othr gap, like 0.012" or so, to time up nearly correct.

If Daiichi: you can get things closer to stated specs if you widen the slots in the baseplate, or just use a TEC or Hitachi baseplate with the Daiichi points installed on it.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline Bigmant

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Re: Can’t adjust timing correctly
« Reply #4 on: March 13, 2022, 09:36:20 PM »
I just wanted to update this!

So as it turns out, after reading a post on this website from a similar thread, I realized  the points gap was making a much bigger difference than rotating the plates. So I widened both as far as the spec would allow and that got the timing extremely close.

However, the bike will still not start, and there is no spark being delivered to any cylinder. I am seeing a lot of sparking from the points, so I am replacing the capacitors and the coils to see if that cleans it up. The ignition system is 50 years old, so it’s probably time. I know most people say the coils don’t typically go bad, but it’s cheap insurance.

More to follow! But at least the static timing is spot on now!
« Last Edit: March 14, 2022, 07:37:13 AM by Bigmant »
‘74 CB750 K4 Owned by my father and now me

Online PeWe

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Re: Can’t adjust timing correctly
« Reply #5 on: March 14, 2022, 05:07:02 AM »
I tapped my cases on my K6.
Sharp metal hammer right on which made them to swell with ignition plate mounted. On the outside but not much from the side.
I had "do not crack in my mind".
Right on top must work too, let it swell both sides.

I hammered each one a little to hopefully get it centered.
A few turns around until plate sat tight.
Plate did not have any play sideways after that.

Plate sat with its 3 screws  loose when I used the hammer.



My K6 case has alternative mark for correct TDC with advance max clockwise. It has a play before tighten it. That mark used when timing the cam.

Otherwise advancer in max counterclockward position before tighten it which match true TDC with stock mark.

I see now that this informative webpage is updated 2022!
https://www.motorcycleproject.com/text/sohcign.html

Cutting the advancer springs 1/2 wound another must  if you want to get proper timing at idle with full advance not to early.
Done that on 2 CB750 (3 advancers). First for my Pamco ignition on my K6 that had its stock advancer with horrible sloppy springs, advanced a lot until springs had any effect.

 I found Hondamans post old about it. One of the best free upgrades.

My K2 was not that bad but I could not get the ignition correct at idle. 1mm before the case mark (advanced). Fixing the springs made it. Full advance not too early either.

Both engines true TDC verified.

I have written about this in lots of posts now.
Hallelujah, I have seen the light!! (in correct position)

Only my K6 cases needed to taste the hammer.

My last build has really tight fit. Tested TEC and Dyna-S plate.
Late 1975 number.

My K2's 1972 cases also no need to hammer tighter.
« Last Edit: March 14, 2022, 10:40:04 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline HondaMan

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Re: Can’t adjust timing correctly
« Reply #6 on: March 14, 2022, 08:48:00 AM »
I just wanted to update this!

So as it turns out, after reading a post on this website from a similar thread, I realized  the points gap was making a much bigger difference than rotating the plates. So I widened both as far as the spec would allow and that got the timing extremely close.

However, the bike will still not start, and there is no spark being delivered to any cylinder. I am seeing a lot of sparking from the points, so I am replacing the capacitors and the coils to see if that cleans it up. The ignition system is 50 years old, so it’s probably time. I know most people say the coils don’t typically go bad, but it’s cheap insurance.

More to follow! But at least the static timing is spot on now!
Don't be too quick to throw out those "old" condensors! They dpn't go bad. If they have not been run for 10+ years they need about 1-2 engine heat-up cycles to restore them, that's the nature of their internal dielectric, which is a wax-based, self-healing compound if they are Hitachi, Denso (ND) or TEC brand. Even the FEW (Italian) ones are pretty much this way.

If your new condensors (or even the old ones) were/are Daiichi brand, you will find they do not work, or they don't work after about 15-20 minutes of run-time. I get a LOT of e-mail about this issue.
Right now we are struggling to find good condensors for this very reason. Sparking at the points normally indicates the coils are being discharged and the plugs are sparking, unless the plug caps are old and have burned themselves open-circuit. If the plug caps are more than about 12k ohms then the spark will be very weak, often not visible in daylight or under bright shop lights - but it is there.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline Bigmant

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Re: Can’t adjust timing correctly
« Reply #7 on: March 14, 2022, 08:19:47 PM »
I just wanted to update this!

So as it turns out, after reading a post on this website from a similar thread, I realized  the points gap was making a much bigger difference than rotating the plates. So I widened both as far as the spec would allow and that got the timing extremely close.

However, the bike will still not start, and there is no spark being delivered to any cylinder. I am seeing a lot of sparking from the points, so I am replacing the capacitors and the coils to see if that cleans it up. The ignition system is 50 years old, so it’s probably time. I know most people say the coils don’t typically go bad, but it’s cheap insurance.

More to follow! But at least the static timing is spot on now!
Don't be too quick to throw out those "old" condensors! They dpn't go bad. If they have not been run for 10+ years they need about 1-2 engine heat-up cycles to restore them, that's the nature of their internal dielectric, which is a wax-based, self-healing compound if they are Hitachi, Denso (ND) or TEC brand. Even the FEW (Italian) ones are pretty much this way.

If your new condensors (or even the old ones) were/are Daiichi brand, you will find they do not work, or they don't work after about 15-20 minutes of run-time. I get a LOT of e-mail about this issue.
Right now we are struggling to find good condensors for this very reason. Sparking at the points normally indicates the coils are being discharged and the plugs are sparking, unless the plug caps are old and have burned themselves open-circuit. If the plug caps are more than about 12k ohms then the spark will be very weak, often not visible in daylight or under bright shop lights - but it is there.

Good to know! My problem is I can’t even get the bike to start at all haha. So the heat cycles won’t do me any good. I measured the caps, and they come out in the 11 ohm range, so perhaps they are going bad? If they are, I am getting new coils, wires and caps to complete the set. So all of the ignition system will be new here pretty soon and It’ll hopefully fire up.
‘74 CB750 K4 Owned by my father and now me