Topic: Difficulty Setting Points Timing

[M 750K6]

Today I took off my points plate, to check the auto-advance. Everything reassembled, I have been setting the static timing, using a light bulb.

I set 1 and 4 OK, but there is very little anti-clockwise adjustment left. When I came to 2 and 3. On max adjustment, the light comes on before reaching 'F'. It is about 2 degrees advanced, I'd guess.

With the plate for 2 and 3 tightened up, I slightly advanced 1 and 4 and that left 2 and 3 slightly less advanced. Now they are both about 1 degree advanced (light coming on just head of the 'F' Mark), with no further adjustment for the 2 and 3 plate and very little left on 1 and 4.

Am I doing something wrong here? I did wonder if the points cam / nuts were not properly seated, from checking the auto-advance. I removed them and reassembled with no change.

[bryanj]

WHAT BIKE

[robvangulik]

His username is 750K6m, I wonder....

[M 750K6]

Hi, Yes, a UK spec CB750K6.

[newday777]

A couple of possibilities.
Points advancer springs are stretched and need clipping 1/2 turn off the end and rebend the end to clip on the pin.
Or your advancer shaft is bent from someone using the 22mm nut with spark plugs in place, compression will cause you to turn hard enough to bend the shaft. Put a dial indicator on the shaft to test. It has to be straighter the .006 runout. Fine tune it with light taps of a hammer on the nuts.

[bryanj]

Just cos its his user name dont make it the bike he is working on

[M 750K6]

A couple of possibilities.
Points advancer springs are stretched and need clipping 1/2 turn off the end and rebend the end to clip on the pin.
Or your advancer shaft is bent from someone using the 22mm nut with spark plugs in place, compression will cause you to turn hard enough to bend the shaft. Put a dial indicator on the shaft to test. It has to be straighter the .006 runout. Fine tune it with light taps of a hammer on the nuts.

Thanks. That's interesting. I've not been removing the plugs and I very much doubt previous owners would have. I'll see if I can borrow a dial guage. If not, is it easy to remove the shaft, does it just unscrew off the end of the crankshaft, once the advancer is removed?

So I understand. Is a bent shaft potentially causing the points cam to come in early = overadvanced. If it is the cause, and straightening it sorts out 2 and 3, once straight, does it have a knock on effect of also increasing the amount of adjustment available to 1 and 4? Because I am already very close to the end of adjustment here also.

[BenelliSEI]

Are you using a timing light with the engine running or using a clip on 12V. light and checking static timing?

[newday777]

A couple of possibilities.
Points advancer springs are stretched and need clipping 1/2 turn off the end and rebend the end to clip on the pin.
Or your advancer shaft is bent from someone using the 22mm nut with spark plugs in place, compression will cause you to turn hard enough to bend the shaft. Put a dial indicator on the shaft to test. It has to be straighter the .006 runout. Fine tune it with light taps of a hammer on the nuts.

Thanks. That's interesting. I've not been removing the plugs and I very much doubt previous owners would have. I'll see if I can borrow a dial guage. If not, is it easy to remove the shaft, does it just unscrew off the end of the crankshaft, once the advancer is removed?

So I understand. Is a bent shaft potentially causing the points cam to come in early = overadvanced. If it is the cause, and straightening it sorts out 2 and 3, once straight, does it have a knock on effect of also increasing the amount of adjustment available to 1 and 4? Because I am already very close to the end of adjustment here also.

The advancer shaft does screw on, but no need to remove it. Set up dial indicator to find the high and low point. With the nuts on the shaft and dial to the high point,  use light taps on the nut to push towards the low spot so it straightens out. Anything under .006 is within spec. I straightened one to .000
When it is bent, the advancer which has a cam in it, pushes one or the other points too far, changes the dwell and advance. Very important to be straight so the advancer works properly.

[M 750K6]

Are you using a timing light with the engine running or using a clip on 12V. light and checking static timing?

The latter.

[seanbarney41]

Don't forget the basics!  Point gap affects timing, so point gap needs to be set first.  Sometimes you have to run the outer limits of point gap.  Remember you want .012-.016 inches.  Also, if your points plate can shift slightly slideways when the retaining screws are loose, adjustments are NOT purely affecting degrees of timing.

[TwoTired]

If you disable the points springs, how much lateral play do you have between plate and engine mount bosses with the mount screws loosened.  Any play there changes the point gap when setting the point gap, and therefore the timing, as the plate moves relative to the point cam when the springs are enabled.

The engine mount bosses were machined to a tolerance.  The points plate also has a diameter size tolerance (as originally built when new).  Manufacturers loosen tolerances to save money on parts outside of inspection tolerances to keep their profits up at your expense.  Too many buyers “assume” the parts they buy meet OEM dimensional specification.  They seldom check, and never make a defective product claim to effect sales profits.  Manufacturers then loosen acceptance tolerances even wider.   Each one thousandths the points plate undersized that the plate is made,  it another thousandth of error setting applied to the points gap. And that, in turn, effects the timing position of the plate relative to crankshaft position.  The solution is to alter the plate fit with near zero tolerance to the engine mount bosses, or add shims during the adjust period when the screws are loose to keep it from moving under point springs forces while being measured under points gap or timing adjustment.

[M 750K6]

Thanks, I will look again at these areas. I did set the points gap first. I use metric, so 0.2 to 0.3mm, I set them between 0.25 and 0.28, a loose 0.25, tight 0.28mm.

I didn't look for play in the plates, but I did notice the main points plate was a tight fit.into the bosses machined into the engine case, when I put it back in, but that was with the points springs fully engaged.

I took it for a ride this afternoon. I have been struggling with 1 and 2 running rich and booging down on WOT. I have replaced the needles and jets, going back to the old ones the bike came to me with. I checked the auto advance and reset the points and timing. I only did about 10 miles, as it was so cold. Initial impressions are the bike seems happier and now only bogs down under WOT below 3,000rpm. But I need to get it fully warmed through and do a longer ride.

[bryanj]

Gap SHOULD be 0.35mm or 14 thou

[Tracksnblades1]

Thanks, I will look again at these areas. I did set the points gap first. I use metric, so 0.2 to 0.3mm, I set them between 0.25 and 0.28, a loose 0.25, tight 0.28mm.

I didn't look for play in the plates, but I did notice the main points plate was a tight fit.into the bosses machined into the engine case, when I put it back in, but that was with the points springs fully engaged.

I took it for a ride this afternoon. I have been struggling with 1 and 2 running rich and booging down on WOT. I have replaced the needles and jets, going back to the old ones the bike came to me with. I checked the auto advance and reset the points and timing. I only did about 10 miles, as it was so cold. Initial impressions are the bike seems happier and now only bogs down under WOT below 3,000rpm. But I need to get it fully warmed through and do a longer ride.

You’ll need to set the points according to Honda’s specs first…then timing…then check points again…then timing again..
Don’t try to correct improper ignition with carburation adjustments…

They make feeler gauges called “go” “no go” that can help one verify their settings…
Example the “go” part of the feeler gauge is .014 thousandths and the “no go” part is .016 thousandths…

Depending on your vision a magnifying glass may help you determine if the points have to “open up” to insert the correct size feeler gauge..

It’s hard to convey to someone without knowing their experience how important it’s is to make certain “positive” the ignition is spot on before moving to the carburetors…..excepting perhaps the obvious gas is running on the floor before…

In reference to the 3000 rpm and below bog, How fast are you snapping the throttle open?
The 76k has no accelerator pumps so a very rapid low rpm wide open throttle opening can result in a bog even when properly tuned and jetted.  Honda moved to pumper and cv carbs to satisfy emissions and drivability concerns…

Verifying your ignition is spot on first can save you a lot of mis diagnosised carburetor headaches.

[M 750K6]

Gap SHOULD be 0.35mm or 14 thou

Damn. I checked my Haynes manual beforehand. I'll check that again when I'm in the garage, but i just checked the Honda handbook online and you're right, it is 0.3mm to 0.4mm. So that's a cock up. Will that be the cause of my timing adjustment issue?

[M 750K6]

Thanks, I will look again at these areas. I did set the points gap first. I use metric, so 0.2 to 0.3mm, I set them between 0.25 and 0.28, a loose 0.25, tight 0.28mm.

I didn't look for play in the plates, but I did notice the main points plate was a tight fit.into the bosses machined into the engine case, when I put it back in, but that was with the points springs fully engaged.

I took it for a ride this afternoon. I have been struggling with 1 and 2 running rich and booging down on WOT. I have replaced the needles and jets, going back to the old ones the bike came to me with. I checked the auto advance and reset the points and timing. I only did about 10 miles, as it was so cold. Initial impressions are the bike seems happier and now only bogs down under WOT below 3,000rpm. But I need to get it fully warmed through and do a longer ride.

You’ll need to set the points according to Honda’s specs first…then timing…then check points again…then timing again..
Don’t try to correct improper ignition with carburation adjustments…

They make feeler gauges called “go” “no go” that can help one verify their settings…
Example the “go” part of the feeler gauge is .014 thousandths and the “no go” part is .016 thousandths…

Depending on your vision a magnifying glass may help you determine if the points have to “open up” to insert the correct size feeler gauge..

It’s hard to convey to someone without knowing their experience how important it’s is to make certain “positive” the ignition is spot on before moving to the carburetors…..excepting perhaps the obvious gas is running on the floor before…

In reference to the 3000 rpm and below bog, How fast are you snapping the throttle open?
The 76k has no accelerator pumps so a very rapid low rpm wide open throttle opening can result in a bog even when properly tuned and jetted.  Honda moved to pumper and cv carbs to satisfy emissions and drivability concerns…

Verifying your ignition is spot on first can save you a lot of mis diagnosised carburetor headaches.

Yes, thanks. I'm OK in the workshop, but definitely no expert. Keen to learn. A good reminder to be more systematic.

Slightly in my defence, here's the recent history, which led to my original question:), I bought my bike knowing it was only running when the choke was out. Once that was sorted, I found a considerable leak from the head (once the oil warmed up) and a sheared head bolt at the front centre. I had the engine out last month to cure the oil leak and refurbished the valve oil seals etc. I'm a few hundred miles on and all now appears fine there.

However, even before the work, I was running rich on 1 and 2. I had checked out the points and ignition timing and so was working on it either being the carbs, or being due to the leaky head. First, I thought it best to sort out the head. However, once back together, I still had the rich running. Mainly on cyl 1, but a little on 2 also. I also had a bogging down on full throttle. I felt this suggested fuel, rather than ignition. At the moment I'm hopeful I've cured that. I've gone back to the needles and jets the bike came with, as I back checked and found that the needles in the refurb kit were thinner than the originals.

I was asking about the ignition because I had forgotten to check the auto-advance, before I put the engine back in. That's why I had to go back to the points and timing. Also, I thought it might help to rule the auto advance out of the bogging down issue.

I will re-do the points at the correct gap setting. My dumb mistake. Go over the timing again and then iterate, to make sure. But, I'm encouraged by your comments about my bogging down issue. I don't normally ride this way, but I was snapping the throttle open as quick as I could, just to check whether I'd solved my problem... Seems I may not really have a problem 

Sorry for the long reply, probably because I was stung by being so dumb about the points gap. Better to find out now though. Thanks for the help.

Martin

[Tracksnblades1]

Thanks, I will look again at these areas. I did set the points gap first. I use metric, so 0.2 to 0.3mm, I set them between 0.25 and 0.28, a loose 0.25, tight 0.28mm.

I didn't look for play in the plates, but I did notice the main points plate was a tight fit.into the bosses machined into the engine case, when I put it back in, but that was with the points springs fully engaged.

I took it for a ride this afternoon. I have been struggling with 1 and 2 running rich and booging down on WOT. I have replaced the needles and jets, going back to the old ones the bike came to me with. I checked the auto advance and reset the points and timing. I only did about 10 miles, as it was so cold. Initial impressions are the bike seems happier and now only bogs down under WOT below 3,000rpm. But I need to get it fully warmed through and do a longer ride.

You’ll need to set the points according to Honda’s specs first…then timing…then check points again…then timing again..
Don’t try to correct improper ignition with carburation adjustments…

They make feeler gauges called “go” “no go” that can help one verify their settings…
Example the “go” part of the feeler gauge is .014 thousandths and the “no go” part is .016 thousandths…

Depending on your vision a magnifying glass may help you determine if the points have to “open up” to insert the correct size feeler gauge..

It’s hard to convey to someone without knowing their experience how important it’s is to make certain “positive” the ignition is spot on before moving to the carburetors…..excepting perhaps the obvious gas is running on the floor before…

In reference to the 3000 rpm and below bog, How fast are you snapping the throttle open?
The 76k has no accelerator pumps so a very rapid low rpm wide open throttle opening can result in a bog even when properly tuned and jetted.  Honda moved to pumper and cv carbs to satisfy emissions and drivability concerns…

Verifying your ignition is spot on first can save you a lot of mis diagnosised carburetor headaches.

Yes, thanks. I'm OK in the workshop, but definitely no expert. Keen to learn. A good reminder to be more systematic.

Slightly in my defence, here's the recent history, which led to my original question:), I bought my bike knowing it was only running when the choke was out. Once that was sorted, I found a considerable leak from the head (once the oil warmed up) and a sheared head bolt at the front centre. I had the engine out last month to cure the oil leak and refurbished the valve oil seals etc. I'm a few hundred miles on and all now appears fine there.

However, even before the work, I was running rich on 1 and 2. I had checked out the points and ignition timing and so was working on it either being the carbs, or being due to the leaky head. First, I thought it best to sort out the head. However, once back together, I still had the rich running. Mainly on cyl 1, but a little on 2 also. I also had a bogging down on full throttle. I felt this suggested fuel, rather than ignition. At the moment I'm hopeful I've cured that. I've gone back to the needles and jets the bike came with, as I back checked and found that the needles in the refurb kit were thinner than the originals.

I was asking about the ignition because I had forgotten to check the auto-advance, before I put the engine back in. That's why I had to go back to the points and timing. Also, I thought it might help to rule the auto advance out of the bogging down issue.

I will re-do the points at the correct gap setting. My dumb mistake. Go over the timing again and then iterate, to make sure. But, I'm encouraged by your comments about my bogging down issue. I don't normally ride this way, but I was snapping the throttle open as quick as I could, just to check whether I'd solved my problem... Seems I may not really have a problem 

Sorry for the long reply, probably because I was stung by being so dumb about the points gap. Better to find out now though. Thanks for the help.

Martin

👍

You know what they say…”Timing is everything”…

Since you’re checking on your advancer:
Attached is Honda specification for timing..6* at an idle and the advance to 40* is all in at 2500 rpm..
I would check what the rpm ranges that yours starts to advances at and where it reaches full advance at..
Remember this rpm range if riding at rpm levels within this start and full advance range. They tend to perk up at this rpm with little additional throttle input..

The 40* advance tells you the cylinder head’s combustion chamber shape is not very efficient (not to many where then)..
I would make sure you realize the 40* total. Some say don’t worry about idle timing, but I would if it’s less than 6*..

Myself, I would rather limit the total to 40* to run the initial timing where I want it…makes two up low rpm stop light launches easy..

What gearing do you plan on running? 
What type of continuous speed is allowed across the number 2 big pond…?  Oil cooler..?
We’re allowed 80mph on a few interstate here. Makes em turn em if you’re running stock final gearing…

[M 750K6]

Thanks.
Stock gearing. 70mph is our limit on motorways / dual carriageways, 60mph on unrestricted single carriageways, although local politicians are doing what they can to reduce the amount of roads this applies to.

Not much need for an oil cooler for nearly all the year here!

[M 750K6]

It was the points gap. Points plate adjustments are still biased to anticlockwise, but able to set them with adjustment to spare.

Thanks for spotting my error and the help.

[bryanj]

Have you seen the uk site?

[HondaMan]

If you disable the points springs, how much lateral play do you have between plate and engine mount bosses with the mount screws loosened.  Any play there changes the point gap when setting the point gap, and therefore the timing, as the plate moves relative to the point cam when the springs are enabled.

The engine mount bosses were machined to a tolerance.  The points plate also has a diameter size tolerance (as originally built when new).  Manufacturers loosen tolerances to save money on parts outside of inspection tolerances to keep their profits up at your expense.  Too many buyers “assume” the parts they buy meet OEM dimensional specification.  They seldom check, and never make a defective product claim to effect sales profits.  Manufacturers then loosen acceptance tolerances even wider.   Each one thousandths the points plate undersized that the plate is made,  it another thousandth of error setting applied to the points gap. And that, in turn, effects the timing position of the plate relative to crankshaft position.  The solution is to alter the plate fit with near zero tolerance to the engine mount bosses, or add shims during the adjust period when the screws are loose to keep it from moving under point springs forces while being measured under points gap or timing adjustment.

Boy, Lloyd, if THAT isn't the truth now!
Not just for the points plates, either. This is where using OEM Honda parts can help: they have been holding a tighter 'spec' line for the parts they still offer.

Martin:
Don't be surprised to find the sparkplugs changing colors for a while if the bike sat for a long time before you got it. A pattern I see almost 100% with the 750 (and almost that much with the smaller SOHC4 engines) is that of the engine fouling sparkplugs in 2 cylinders, usually sequentially in the firing order, after the bike gets 'reawakened' and ridden more than the previous owner. This often comes from the simple rust that builds up on the intake valves that were sitting open for months on end. The valves [strongly] tend to re-wipe themselves clean with some spirited riding (i.e., stay above 4000 RPM for long periods) and all is well again. For this reason I often use lower chain gearing if I have to ride in-town for long periods of time: on my K2 (same gearings as your K6) I will use a 17T front sprocket for extended in-town use, an 18T (aka "stock") sprocket for mixed hiway/city use, and sometimes a 19T front sprocket here in America when traversing places like Wyoming, Utah, or other States with long stretches of 80+ MPH speed limits - although, not all stock K6 engines can pull the 19T sprocket to top speeds like 100+ MPH without some help. My K2 now has a K6 cam in it, but it also has increased compression and breathing, making the difference 'up there'.

[M 750K6]

Yes, I'm going to ride it and see. But I did put a couple of thousand miles on it, trying to dial in the carbs, before I took the engine out. I had the cylinders checked and honed and I lapped the valves in, as I was there. They didn't look bad, but I didn't want to regret not doing it!

I replaced the needles and jets as part of getting the bike to run, when I first got it. So, I never rode it with the old (can't say if 'original) needles. Certainly, the general rich running looks to have been due to the Keyster brand replacement needles I installed, which were visibly thinner than the ones the bike came with. To be sure it wasn't an illusion, I dropped both the old and the Keyster needles into a gap (like a slot guage) in my Vernier callipers. The old ones were a fatter profile and stopped in the gap about 2mm higher than the Keysters. I switched them back and after nearly 70 (very cold) miles today, that particular problem seems to be gone. I don't yet know if the plug fouling on 1 and 2 is also sorted.

It was taking about 150 miles for plug #1 to soot up 1st and misfire. So a bit early to know if that has also gone away. I was just too cold to check after I'd washed and dried the bike! I'll look tomorrow. But it ran perfectly. I enjoyed my ride. I live on the coast and these blue sky, low sun rides can be serene, despite the chill. Also, the bike seemed to be happy to be out with me  .

[HondaMan]

Also, the bike seemed to be happy to be out with me  .

Yep, there have been times when my 750 was the only pal I had! One of those times is captured in my book.
It's been a great friend, and for longer than anyone else I've known: the others are all gone now!

[Redline it]

Today I took off my points plate, to check the auto-advance. Everything reassembled, I have been setting the static timing, using a light bulb.

I set 1 and 4 OK, but there is very little anti-clockwise adjustment left. When I came to 2 and 3. On max adjustment, the light comes on before reaching 'F'. It is about 2 degrees advanced, I'd guess.

With the plate for 2 and 3 tightened up, I slightly advanced 1 and 4 and that left 2 and 3 slightly less advanced. Now they are both about 1 degree advanced (light coming on just head of the 'F' Mark), with no further adjustment for the 2 and 3 plate and very little left on 1 and 4.

Am I doing something wrong here? I did wonder if the points cam / nuts were not properly seated, from checking the auto-advance. I removed them and reassembled with no change.

i've had trouble on occasion getting the 2 pairs of cylinders timed, using a timing light and a dwell meter set up on a 400f 76 to do both at once. after setting #1and4 then trying 2&3 that was off and moving it's plate i'd get the F mark in view and traveling towards the case mark, but quite a ways away from it, still moving the plate, the F mark would disappear, and it'd run like crap, after few times of that, and i wasn't sure which way it was traveling when it disappeared, so i started then on #2&3 first, only i set it Off as much as i needed it to go or half the distance that it was lacking to go, trying it per manual. and doing that, then setting #1&4 put both of them right on. something to do with the play the plate has. i tried shimming it once before that a pain to do though. i either did it that way or i started back on 1,4 but left it out of time as much as or half i can't remember, the distance that the 2,3 points would be off when the f disappeared.