Topic: Static Timing - Ran out of adjusment

[njlantis]

I am currently setting my static timing on a 1978 Honda CB750k. I was able to get the points gap in spec and the timing dead on for the cylinders 1-4 but I had to basically bottom out all the adjustment available in the base plate (see photos). Because of this I am unable to get the timing for cylinders 2-3 correct, I am at the limits for all of my adjustments in the 2-3 plate and the base plate. I can't help but feel like I am missing something, it doesn't seem right that I would need to be hitting the adjustment limits to get the timing correct.

Background on my process to this point:

1.) Set 1-4 points gap to 0.014" at 90 degrees from the "F" mark or the center of the tang after the 1-4 section on the advance mechanism
2.) Checked timing position and it was very early, adjusted the base plate accordingly
3.) Checked 1-4 points gap based on new base plate position, was still good for 0.014"
4.) Checked timing position and it was closer but still early so I repeated the above process and was able to get the timing dead on with the base plate adjusted to its limit.
5.) Repeated the same process for 2-3 points gap and timing checks, but I ran out of adjustment before I could get the timing perfect for 2-3. The picture attached shows how far off timing for 2-3 is at the adjustment limits

So to summarize, static timing is good for 1-4 but I have no more adjustment to get 2-3 correct and I'm not sure where to go from here.

[bryanj]

When you move the points plate the points gap always alters, is a juggling match to get both fight

[njlantis]

When you move the points plate the points gap always alters, is a juggling match to get both fight

I understand that, I've done this process tons of times trying to get it right and every time I move the points plate I always check the points gap as well. Every time I do it, even if I have the points plate start in a different position, the juggling match always leads me to the end of my adjustment limits

[madmtnmotors]

Change your point gap to change the final timing position. Point gap is given as a range from .012 to .016. Try adjusting towards the small end. If that doesn't help then go the other way towards the high end. You should be able to get the timing in range by manipulating the point gap.

EZPZ 

[bryanj]

Next question is what make of points have you got and how worn are the nylon heels?

[M 750K6]

Your process step 1.), is that the point at which your points are at their widest gap?

[HondaMan]

It appears that you have a different brand of 1-4 points from the 2-3 points: the latter appear to be TEC, the 1-4 has no marks - probably Daiichi China?
The points contacts themselves on the 1-4 side are not matched, i.e., the moving-arm points contact is not centered over the stationary one. This is common on Chinese-made points.

When I run into this, I realign the non-moving contact arm of the 1-4 points set first like this (and use a timing light: if you are turning the engine with the big nut by the points, you have probably bent the spark advancer's shaft, and this will artificially advance the timing and also make the timing 'jitter' widely when the engine is running - this will make it impossible to properly set the points timing accurately):
1. Set the timing for your TEC 2-3 points first. Do this by setting their sub-baseplate into mid-slot of the 2 smaller slots, set the points gap to 0.014", and on the 2-3 mark as seen under the strobe light.
2. Now readjust the gap of the 1-4 points to 0.012"-0.016" by bending the non-moving contact of this points set, so as to get its opening close to the 1-4 "F" mark. Then adjust the whole baseplate for the fine-tuned on-the-mark timing of this points set.
3. Now fine-tune the position of the 2-3 baseplate to get it timed just right.

This may, unless you're good at bending angles into the 1-4 points' contact arm, leave the 1-4 points contacts not parallel with each other - heck, you've probably already noticed the moving pad isn't centered over the stationary one when they came out of their box, anyway! This is the big failing of the Chinese points: their geometry is 'off' a little bit. When running directly with the coils this will burn a semicircle-shaped contact area into the points instead of a circular area, but they will work OK. If you use the Transistor Ignition in conjunction with these points, it will work fine, and last for a VERY long time as the points will then stop wearing over time.

[njlantis]

It appears that you have a different brand of 1-4 points from the 2-3 points: the latter appear to be TEC, the 1-4 has no marks - probably Daiichi China?
The points contacts themselves on the 1-4 side are not matched, i.e., the moving-arm points contact is not centered over the stationary one. This is common on Chinese-made points.

When I run into this, I realign the non-moving contact arm of the 1-4 points set first like this (and use a timing light: if you are turning the engine with the big nut by the points, you have probably bent the spark advancer's shaft, and this will artificially advance the timing and also make the timing 'jitter' widely wen the engine is running - this will make it impossible to properly set the points timing accurately):
1. Set the timing for your TEC 2-3 points first. Do this by setting their sub-baseplate into mid-slot of the 2 smaller slots, set the points gap to 0.014", and on the 2-3 mark as seen under the strobe light.
2. Now readjust the gap of the 1-4 points to 0.012"-0.016" by bending the non-moving contact of this points set, so as to get its opening close to the 1-4 "F" mark. Then adjust the whole baseplate for the fine-tuned on-the-mark timing of this points set.
3. Now fine-tune the position of the 2-3 baseplate to get it timed just right.

This may, unless you're good at bending angles into the 1-4 points' contact arm, leave the 1-4 points contacts not parallel with each other - heck, you've probably already noticed the moving pad isn't centered over the stationary one when they came out of their box, anyway! This is the big failing of the Chinese points: their geometry is 'off' a little bit. When running directly with the coils this will burn a semicircle-shaped contact area into the points instead of a circular area, but they will work OK. If you use the Transistor Ignition in conjunction with these points, it will work fine, and last for a VERY long time as the points will then stop wearing over time.

I'm not sure if they are Chinese points or not, I ordered them from 4into1.com. I was under the impression that they were oem replacements but maybe I was mistaken. If they are chinese manufactured then do you have any suggestions where to find oem replacements? The only reason I replaced them was because I was ordering new condensers because I was suspecting they may be the reason for some weak spark that I was experiencing and decided to just replace the ignition components while I was at it. As for the spark advance shaft I wactually just replaced this because the previous owner of the bike had bent it, I have been very careful to not bend the new one, spark plugs pulled when turning the engine over. I will give this process a try though, thank you for the advice.

[njlantis]

Next question is what make of points have you got and how worn are the nylon heels?

The points are brand spankin new from 4into1.com

[njlantis]

Your process step 1.), is that the point at which your points are at their widest gap?

Yup, the gap is set at the widest gap on the cam

[newday777]

Next question is what make of points have you got and how worn are the nylon heels?

The points are brand spankin new from 4into1.com

4into1 sells Chinese junk points and condensers.

Get them from Honda
The whole points plate assembly is cheaper than individual points and condensers.

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(76)_750_FOUR%2c_JPN%2c_VIN%23_CB750-2540001_TO_CB750-2575894/POINTS/b3d05c73-22e7-4620-b018-132301d96b6e/80fb05af-446d-41cb-a88f-21b6993df839/y

[rotortiller]

The whole points setup can be mickey mouse due to shifting sloppy timing plate or non-conforming points. My advice is to get as close as you can to correct timing with the spec'd point gap and then alter the point gap to fine tune to the "F" mark. Another reason to change to electronic ignition. I would expect you to be within .004" of what the manual says for range and the bike will run fine that way, just check the full advance with a strobe in case you need to tweak a small compromise.

[bryanj]

Sorry you are wrong, back in the dealership i worked for using Honda parts, whilst needing care and practice it was always possible to get both points gap to 14 thou and timing spot on the F mark then in future on that motor all that was needed was to set the gap correct at service

[rotortiller]

i worked for using Honda parts

byranj,

I said no-conforming parts. When a part is made incorrectly it usually causes an issue. Most of us know about points with the incorrect geometry that often cause setup problems.

[njlantis]

Next question is what make of points have you got and how worn are the nylon heels?

The points are brand spankin new from 4into1.com

4into1 sells Chinese junk points and condensers.

Get them from Honda
The whole points plate assembly is cheaper than individual points and condensers.

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(76)_750_FOUR%2c_JPN%2c_VIN%23_CB750-2540001_TO_CB750-2575894/POINTS/b3d05c73-22e7-4620-b018-132301d96b6e/80fb05af-446d-41cb-a88f-21b6993df839/y

I have actually tried to order the points plate assembly from these guys and they said it was discontinued, I also tried to order the individuals from them and they said those were discontinued as well

[cooldrum]

On Ebay JTMarks motorcycle parts may have what you need. Check them out . Keep us posted

[HondaMan]

The 'exact' problems with the Chinese-made parts are:
1. The condensors are junk, out of their boxes. They are made incorrectly: I have taken a couple of them apart to see why they are so poor, and that's the reason. They are supposed to be a thickly-waxed (or polymer-coated) paper sheet in between 2 thin sheets of copper, rolled up to about the size of the can: they are aluminum foil in both of the ones I disassembled, wrapped up in dry paper, with loose wires laid into the winding as the connectors. Absolute garbage.
2. The Daiichi China points geometry has always been 'off' such that the points gaps are impossible to set correctly. I've posted many times about how to try to fix them up, similar to the above post, but it involves bending [something] on the points to make them spatially correct for the timing. It's almost as if they designed them to fit something else similar (like maybe the Yamaha 750 triples?) and then sold them as Honda parts. Dunno about that...but, I ran a set of them on my own 750 for several years, just to see if they would work, attached to the Transistor Ignition which stopped them from wearing. They did fine for the duration of that test, but I have TEC units in place for this year's riding.
3. The Daiichi whole-points-plate assembly has an undersized baseplate, too: it must be pushed upward (like with a small screwdriver blade in the lower mounts) to get the points within adjustment range, even with the rebending of the points base arm.

They can be 'made' to work (except the condensors), but they don't come out of the box running.

[njlantis]

On Ebay JTMarks motorcycle parts may have what you need. Check them out . Keep us posted

I looked this guy up and it looks like he does have a plate assembly available however it's listed as part number 30200-300-154 compatible up to 77'. My bike is a 78 and the oem part number for my bike is 30200-300-015. It seems no different visually but I'm not sure if there is any differences non-visually. I also found an assembly from Z1 parts https://z1parts.net/ignition-contact-breaker-69-78-honda-cb750-750k-750f/

The one from z1 is listed to be compatible with both part numbers

[bryanj]

All the fours use the same item

[njlantis]

All the fours use the same item

Great, any indication on if z1 has reliable parts? the one I found on ebay is double the price

[HondaMan]

All the fours use the same item

Great, any indication on if z1 has reliable parts? the one I found on ebay is double the price

Honda's own points are expensive these days, but worth the $$, IMHO. If you combine them with one of my Transistor Ignitions they will likely outlast the bike, too.

Those units from Z1 are something I've only seen once (in someone else's 750 engine I rebuilt) and they seemed to work, but all they had to do for me was run the engine for 1 pint of fuel before I sent it back to its owner, about 10 minutes' worth.

[cooldrum]

Honda's own points are worth the extra $.  They are made more sturdy than the import ones and hold their adjustment. Quality is equal to the price for parts.  I've ordered from JTMarks and the quality is good in what they sell.

[njlantis]

Hello Everyone,

Figured I would post an update on this. I ordered a new points plate assembly and with the new one I was able to set the static timing dead on with some adjustment and (after I realized I had the wires from the points plate mixed up) the bike started right up. Last year I was having difficulty with the bogging out/stalling under load, backfiring, and struggling to rev-up even in neutral. I had it narrowed down to weak spark on 2 of the cylinders OR timing was incorrect. This new points plate assembly solved all of those issues, who knows if it was a bad condenser or if I just never had the timing right before, but now the bike has plenty of power and I was actually able to drive up and down the road for the first time.

That being said, I am now chasing a new issue with the idle. When I start the bike it will idle normally around 1200 RPM  but if I give it even a little bit of throttle the RPM's "hang" and get stuck around 2500-2700 RPM. When this happens I can't get the RPM's to drop even by adjusting the idle screw.

I have read that this is possibly a symptom of a vacuum leak so I sprayed starter fluid on all of the airbox boots and carb boots to confirm that everything was sealing properly. I also read that this could be a symptom of a lean mixture so I adjusted the idle mixture screw from 1.5 to 1.75 turns out to try and richen up the idle mixture but experienced the same thing.

If you are interested in reading up on everything I've done to the bike to this point then here is the link to the thread from last year. A basic summary is that I checked all valve clearances, set cam chain tension, resistance tested all ignition components, did a compression test on the cylinder, replaced the float valves and set the heights using the clear tube test, and tore down the carburetors to make sure all jets and channels were free of clogs.

http://forums.sohc4.net/index.php/topic,193224.0.html

Open to any advice to chase this issue! Just want to ride the damn thing!

[M 750K6]

I don't know factory settings for a K8 air screw. It is 1 turn out only on a K6. Have you checked all slides are fully returning?

[scottly]

When I start the bike it will idle normally around 1200 RPM  but if I give it even a little bit of throttle the RPM's "hang" and get stuck around 2500-2700 RPM. When this happens I can't get the RPM's to drop even by adjusting the idle screw.

If you slow the engine down by slightly slipping the clutch with the bike in gear, will it stay at 1200 RPM until the next time you give it throttle? If yes, the advancer springs may be too weak, allowing the advance to happen too soon, and not returning to the F mark until the engine is forced to slow down.