Timing @ RPM?

What RPM does everyone run at when adjusting the timing? I have the stock Lucas points on a 75 - Commando and my manual says to set it at 28 deg while running it at 3000 rpm (to advance the timing). I cannot get it anywhere close to 28 degrees at that RPM! It is way advenced at 3000 RPM. All it has gotten me is blue pipes! I set it to 28 degrees at 1000 RPM and it seems much happier (I set the eccentric left cylinder that way too). Is my manual way out of touch or is my bike? :?

Now I need to decide if I want to order some "Blue-job" or headerwrap. :|

Captain B said:

What RPM does everyone run at when adjusting the timing? I have the stock Lucas points on a 75 - Commando and my manual says to set it at 28 deg while running it at 3000 rpm (to advance the timing). I cannot get it anywhere close to 28 degrees at that RPM! It is way advenced at 3000 RPM. All it has gotten me is blue pipes! I set it to 28 degrees at 1000 RPM and it seems much happier (I set the eccentric left cylinder that way too). Is my manual way out of touch or is my bike?

Click to expand...

Many of us use now use some form of electronic ignition system, so those timing @ RPM figures aren't going to be any use to you, but 28 degrees BTDC at 3,000 RPM for points should be correct, as that is past the RPM where the points ignition should have stopped advancing.

Captain B said:

I cannot get it anywhere close to 28 degrees at that RPM! It is way advenced at 3000 RPM.


I set it to 28 degrees at 1000 RPM and it seems much happier (I set the eccentric left cylinder that way too).

Click to expand...

Can you give more details why you cannot seem to get the ignition timing close to 28 deg at 3,000 RPM? Are you running out of adjustment, or does the engine run badly, or refuse to run?


Setting to 28 deg. BTDC at 1,000 RPM would make it even more over-advanced at 3,000+ RPM?

Are you using a 12V strobe conected to a separate power supply other than the bike's own battery?


Does your strobe have an adjustable advance control? If so, it must be set to Zero degrees.

Have you checked the alternator rotor and timing degree scale marks for accuracy by checking with the MkIII's crankshaft timing aperture below the timing cover?

Can you give more details why you cannot seem to get the ignition timing close to 28 deg at 3,000 RPM? Are you running out of adjustment, or does the engine run badly, or refuse to run?

The timing mark is all the way off the scale to the right (advanced position) at 3000 rpm even with the timing all the way retarded.

Setting to 28 deg. BTDC at 1,000 RPM would make it even more over-advanced at 3,000+ RPM?
Yes, it becomes advanced at 3000 rpm at this setting, but seems to run "OK".
Are you using a 12V strobe conected to a separate power supply other than the bike's own battery?
Yes.

Does your strobe have an adjustable advance control? If so, it must be set to Zero degrees.
I don't know. I'll check. :wink:
Have you checked the alternator rotor and timing degree scale marks for accuracy by checking with the MkIII's crankshaft timing aperture below the timing cover?

??? :? ??? I'm going to have to look that one up. ??? :? ???

Captain B said:

The timing mark is all the way off the scale to the right (advanced position) at 3000 rpm even with the timing all the way retarded.

Click to expand...

If you are running out of points plate adjustment, then the auto advance unit probably needs to be removed from the camshaft taper and repositioned? (see "Ignition Timing Procedure- Engine Static" in your manual, Section C )

This is my timing light: (#3551) - no advance control.
http://www.equus.com/product_info.php?p ... egory_id=1

It does not say anything about a neg ground system. The manual says this:

"Your timing light is designed for use on all 12-
volt negative ground vehicles equipped with
conventional breaker point, and electronic
ignition systems or with DIS (distributorless
ignition systems). "

... Maybe it could be the issue, but the light seems to work fine (it's just reading really advanced at 3000 rpm)

(edit)

How many degrees difference should the timing change from 1000 to 3000 rpm?

Captain B said:

(edit)

How many degrees difference should the timing change from 1000 to 3000 rpm?

Click to expand...

If you have the correct auto advance unit (you'd have to extract it and check the numbers on the back?) I think the total advance range is 11 degrees (that's 11 camshaft degrees = 22 crankshaft degrees ) .


[Edit] Correct AAU range should be 12/24 degrees not 11/22 degrees.

hi captain,i would forget the strobe for a while and go back to basic static timing 28 deg fully advanced btdc,or if LAB,S numbers are correct 12/24 i make that 4 deg fully retarded btdc(crank) this basic setting should get you to within 2 or 3 deg either way of where you want to be,then strobe it ,if there is a much bigger difference it could be the strobe light but i cant think why, all a strobe does is freeze the moving timing mark on the rotor,all this is assuming that the marks on the rotor and timing degree scale are correct

Just a thought....you are holdingb the auto advance cam at full advance when you set the points statically??? There is a special washer for this!

The strobe is working fine. When I point it at the mark and have someone rev it the mark moves from where ever it is to off the right side of the gage. If i set it at 28 @ 1000 (the middle of the slotted adjusters) it moves slowly off to the right to just past the gage. If I set it to a full retarded it moves just to the edge of the gage (well past 28) and if I advance the timing to the other end of the slotted adjusters the mark will progress untill the edge of the trapazoid like metal block with the timing mark on it is off the edge of the gage when reved to 3000.

If you are running out of points plate adjustment, then the auto advance unit probably needs to be removed from the camshaft taper and repositioned? (see "Ignition Timing Procedure- Engine Static" in your manual, Section C )

Click to expand...

I would like to do this, but cant find it anywhere in the manual. This seems like the only thing to do. Does it require a puller to get it off?


Oh and... Where can one get the "special washer" to do this? (edit) nevermind - found one)

Captain B said:

I would like to do this, but cant find it anywhere in the manual. This seems like the only thing to do. Does it require a puller to get it off?

Click to expand...

There was a factory extractor tool available, but the AAU can be released from the camshaft taper by removing the 1/4" AAU retaining bolt, and then screwing a 5/16" - 24 (5/16 UNF) bolt into the AAU spindle. Then tap the 5/16" bolt head gently UP-DOWN-LEFT-RIGHT with a hammer until the AAU loosens from the taper.

Set the crankshaft to 28 degrees BTDC with the timing side cylinder on its compression stroke (easy on a MkIII as it has a 28 deg timing slot in the crank that lines up in the timing aperture below the timing cover @ 28 deg. BTDC) with the AAU locked at the fully advanced position (bobweights fully out) adjust both the the AAU and points plate positions so the timing side points start to break in the middle of the back plate adjustment slot range. Follow your manual's instructions for static timing.

L.A.B. said:

[the AAU can be released from the camshaft taper by removing the 1/4" AAU retaining bolt, and then screwing a 5/16" - 24 (5/16 UNF) bolt into the AAU spindle. Then tap the 5/16" bolt head gently UP-DOWN-LEFT-RIGHT with a hammer until the AAU loosens from the taper.

Click to expand...

Sweet! I can do this with an extra bolt from my old beancans!

8) Thank you sincerely for helping a guy who has minimal experience in these matters. I am learning this as I go. I know these questions must seem obvious and even completely misdirected to you all. That's the price some new guys pay for trying to learn (looking like fools), but if that's what it takes... I'm down. The Norton hook is set and I'm being reeled in.
So, please humor me again. I'm already generating questions.

You don't even need the bolt or hammer. You can stick in the shaft of the toolkit screwdriver and do the same bumping routine. I just use the heel of my hand gently and it usually rocks right out.

batrider said:

You don't even need the bolt or hammer. You can stick in the shaft of the toolkit screwdriver and do the same bumping routine. I just use the heel of my hand gently and it usually rocks right out.

Click to expand...

That worked out well Thanks!

Here's what I did:

After getting the left side piston to top dead center I looked at the points. It was still open. (I just realized that this whole time I was saying the timing was very advanced... nope. retarded ...my bad).

I noticed that there is a thin etched line that seems like it lines up with where the points are full open (for checking the gap?---.015, I re-set that too while I was at it.) and then there is a thicker/wider one which seems to be where the points are firing (it's width seems to indicate the duration of the spark). So,with that in mind I used the above screwdriver trick to set the advance in a position where the plug would fire right a 28deg (when fully advanced). I havn't tried to start it up yet though due to the weather. I'll see what happens tomorrow.

Captain B said:

After getting the left side piston to top dead center I looked at the points. It was still open. (I just realized that this whole time I was saying the timing was very advanced... nope. retarded ...my bad).

Click to expand...

The points will be open at TDC (on the firing cylinder) as they should have started to open at 28 deg, BTDC, with the AAU set to full advance if the ignition timing is correct?

From what you described previously " The timing mark is all the way off the scale to the right (advanced position) at 3000 rpm even with the timing all the way retarded." that does indicate the timing was over advanced, not retarded?

Captain B said:

I noticed that there is a thin etched line that seems like it lines up with where the points are full open (for checking the gap?---.015, I re-set that too while I was at it.)

Click to expand...

Yes, the points gap is set when the points heel aligns with the etched mark (that is mentioned in the manual instructions)

Captain B said:

and then there is a thicker/wider one which seems to be where the points are firing (it's width seems to indicate the duration of the spark).

Click to expand...

I think it's just a screwdriver slot?

Captain B said:

So,with that in mind I used the above screwdriver trick to set the advance in a position where the plug would fire right a 28deg (when fully advanced). I havn't tried to start it up yet though due to the weather. I'll see what happens tomorrow.

Click to expand...

Don' t forget you need to rotate the crank 360 degrees, and adjust the points for the other cylinder to 28 deg. BTDC if you didn't do that?

Once you have both points sets opening at approximately 28 deg BTDC, the AAU can be unlocked, and the engine started and strobed (on both cylinders). Any coarse adjustment can then be made by moving the points backplate, and fine adjustment can be done by moving each individual points sub-plate (10CA points assembly-1973-on)

Yeah, I wasn't thinking right it was advanced. I seem to have temporarily for got that the timing mark on one side moving counterclockwise. moves clockwise on the other side .

I repositioned the advance mechanism and rechecked the point gap and now it is OK. The advance mechanism no longer lines up like the book describes, but it works.