Dual point timing

[Davidb]

I am luck enough to have dual points on my 61 FLH.

First time timing anything, read extensively about how to time the first cylinder and I am confident in this procedure but the fly wheel that I have does not have a rear timing mark. read the book about the 95885-61 tool to get the cylinder on compression stroke at 7/16" BTDC to adjust the points for the rear cylinder. I do not have the tool and looks like it will be difficult to find.

A couple of questions since I am a newbie at timing

1) How can I determine position of 7/16" BTDC for second (rear) cylinder without this tool. I am worried about the angle and do not know if a straw or pencil will be accurate. without removing the head of course
2) How do you adjust the points on the rear cylinder if the lobe is not in contact with the points after you lock down the timing for the 1st(front) cylinder. It appears that the points for the rear cylinder are fixed and cannot be adjusted or moved around the circumference of the upper timing plate. So if the rear cylinder points are in a fixed position why do you need to set it to the dimension indicated in the manual. Why not just gap the points like the first cylinder when the lobe makes contact

I have not tried to time yet but hope to in the next couple of days or at least get it static timed, for now

Thanks

Davidb

[1950Panhead]

1) How can I determine position of 7/16" BTDC for second (rear) cylinder without this tool. I am worried about the angle and do not know if a straw or pencil will be accurate. without removing the head of course

You Can't.

2) How do you adjust the points on the rear cylinder if the lobe is not in contact with the points after you lock down the timing for the 1st(front) cylinder. It appears that the points for the rear cylinder are fixed and cannot be adjusted or moved around the circumference of the upper timing plate. So if the rear cylinder points are in a fixed position why do you need to set it to the dimension indicated in the manual. Why not just gap the points like the first cylinder when the lobe makes contact

The only practical way to do this without the tool is a degree wheel.
Remove primary cover, attach degree wheel to crankshaft, rotate crank 157.5 degree past front points opening, rear points should open here.
Jerry

[RUBONE]

The primary failing in the original H-D dual point ignition is the inability of accurately timing the rear cylinder. It is done by changing the point gap, not moving the point assembly as you found out. Therefore the dwell angle is never at the optimum for the engine. The timer can be modified for true dual point timing if you have the desire to do it.

[58flh]

As JERRY & RUBONE stated!--A degree-wheel would be needed to ACCURATELY find position of piston!.--& you already know as RUBONE said about ADJ. -POINTS for rear-cyl.--It actually turns out you will be running at different dwells for each cyl.--(Dont get discouraged its an easy fix to get propper gap-settings for the rear!-By simply modifing the plate.)--The dual-Point is HDs REAL Single-Fire IG.///I say real as its always on single!-Aftermarket Single-fire set-ups go to Dual-Fire for start-up!-(not all but most of them!).With a factory TRUE Single-Fire You dont have to look for that comp.-stroke on front cyl!.-You just simply find any compresion on the kicker & just relax your leg from that 9-o-clock position & its running!.I take-it you have a manual!--Follow its instructions for now-until you get the rear set of points to ADJ. properly to .022///You probably get .018 on the rear points.-I would set the front to .018 also!--Plug-gap at .025 & INDEX THEM!.As long as you have no intake leaks she should run quite well!.-Its best to have both cyl. at the same gap so point/dwell will be the same time!--By closing-up the gap to .018 your actually letting more Voltage build-up in the coil,& that makes for a VERY nice Spark!.--I know alot of guys running tighter gaps!--The motors just respond better & run nice!.--Also PROPER COPPER WIRES & 4 to 5 ohm coils must be used!,for a proper Funtion of the system.---Respectfully----RICHIE

[kitabel]

A device that threads into the plug hole will help - if you can determine the thread's angle (from vertical). An old spark plug with the center drilled out and a long rod accurately placed through the center (concentric) can give you a fairly good eyeball guess by simply holding a protractor nest to it with the bike vertical.
The distance a tool goes down into the cylinder varies by the cosine of the thread angle, so its movement will always be more than the actual piston travel.
7/16" is correct for 74 OHV motors (but not for 61 or 80 OHV).
The procedure is:
1. find TDC.
2. insert the tool until it contacts the dome.
3. with a ruler or caliper on the rod, rotate the flywheels forward, until
4. the rod has moved the correct distance: the actual distance × the cosine of the thread angle. E.g., if the thread angle is 45° (I don't know), multiply the rod travel by .707 etc. To get rod travel from a known advance position, divide by .707 or multiply by 1.414.

Very important: there is a popular myth that the distance the piston moves in a specific period of flywheel rotation is exactly the stroke length divided by 180°, times the number of degrees.
E.g.: 74 OHV stroke is 3.96875", ÷ 180 = .022" per degree, times 35 = .772".
This is always completely wrong.

[1950Panhead]

A device that threads into the plug hole will help - if you can determine the thread's angle (from vertical). An old spark plug with the center drilled out and a long rod accurately placed through the center (concentric) can give you a fairly good eyeball guess by simply holding a protractor nest to it with the bike vertical.
The distance a tool goes down into the cylinder varies by the cosine of the thread angle, so its movement will always be more than the actual piston travel.

Kitabel, you are on a tangent here.

Very important: there is a popular myth that the distance the piston moves in a specific period of flywheel rotation is exactly the stroke length divided by 180°, times the number of degrees.

The piston comes to a dead stop at tdc, starts to accelerate, reaches maximum velocity half way down, starts to deaccelerate, comes to another dead stop at bdc.
Jerry

[Davidb]

Thanks for all the insight, I will try it in a couple of weeks as I am waiting on some parts and let you know.

I did static time the front cylinder last night and took a guess at the rear for now.

David

[Panacea]

My rear points wound up being set to .018 on my 64. This thread has me considering checking the rear cyl. timing with the timing lite just for S&Gs...