SETTING TIMING ON 74 850

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Littlefeat69

Littlefeat69

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WHEN I WAS GIFTED A BASKET CASE 74 850 THE ALTERNATOR ROTOR AND STATOR WERE OFF THE BIKE AS WERE THE POINTS AND AAU, ALONG WITH OTHER PARTS. 6 MONTHS HAVE PASSED AND NOW READY TO THINK ABOUT SETTING THE VALVES AND GETTING THE RIGHT ( AS IN WHICH ONE ) PISTON IN POSITION TO SET THE TIMING SO I CAN GET A ELECTRONIC IGNIYION SET UP. I KNOW I HAVE OPENED MYSELF UP A BIT, SO I AM READY
 
EI are virtually all wasted spark so you can time them to either piston as both sides fire every 360 degrees.

Having CAPS on is shorthand for shouting when on forums.
 
There are 2 timing marks on your alternator rotor. The one to use is opposite the keyway. You can tell which cylinder is about to fire by putting your finger over the spark plug hole and feeling for compression.
And yes, using caps is rude.
 
Well, I just learnt something. No, not that most electronic ignitions are wasted spark, i installed a Lucas Rita on my T160 in the early eighties (never given an ounce of trouble despite what we hear of Lucas) but the etiquette of when to capitalise and when to use lower case. But seriously, it is fascinating how various unwritten rules and conventions have grown around internet communication. My big worry now is how many people I have inadvertently offended by flaunting the ‘done thing’ through my ignorance. And here I was thinking that I actually had a measure of civility
regards al.
 
kommando said:
EI are virtually all wasted spark so you can time them to either piston as both sides fire every 360 degrees.

Having CAPS on is shorthand for shouting when on forums.
Click to expand...
is not one on compression and the other on exhaust..im guessing
 
Littlefeat69 said:
is not one on compression and the other on exhaust..im guessing
Click to expand...
Yes only 1 on compression other on exhaust. Wasted spark because both plugs fire at same moment, every 360 degrees, only one is igniting the fuel on the compression stroke cylinder, while other spark eats exhaust smoke.

Have you checked the timing chest side to ensure crank to cam timing is correct?
PS there is a workshop manual file in the technical information thread of this forum (its a sticky thread at top of forum listings). Timing (both mechanical and ign) are covered there. Also, you should confirm timing scale on outer primary cover inspection opening are accurate. Use a timing scale disk on the rotor to determine true TDC and confirm the scale guage on the cover. Lots reported as being out a few degrees.
 
Tornado said:
Yes only 1 on compression other on exhaust. Wasted spark because both plugs fire at same moment, every 360 degrees, only one is igniting the fuel on the compression stroke cylinder, while other spark eats exhaust smoke.

Have you checked the timing chest side to ensure crank to cam timing is correct?
PS there is a workshop manual file in the technical information thread of this forum (its a sticky thread at top of forum listings). Timing (both mechanical and ign) are covered there. Also, you should confirm timing scale on outer primary cover inspection opening are accurate. Use a timing scale disk on the rotor to determine true TDC and confirm the scale guage on the cover. Lots reported as being out a few degrees.
Click to expand...
Thank you
 
SETTING TIMING ON 74 850
SETTING TIMING ON 74 850
 
i have ordered both and thanks...now comes the knowledge part...timing side piston or drive side piston to start with
 
The degree wheel shows the piston at TDC.
Set your engine rotation to peak TDC and then set your wheel to zero.
Upon initial setup rotate the crank/engine clockwise from zero to a reading of 28 degrees before TDC and then set the initial spark signal accordingly.
It makes no difference which cylinder you set it for, as Tornado said both cylinders are firing.

The second pic shows a simple tool to locate TDC and adjust accordingly.
You can use a dial indicator to find a more exact TDC location by inserting the dial indicator probe through the spark plug opening to find the top of the piston at its max height but the method shown will bring it in very close to where it should be.
 
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As mentioned in other threads on piston stops vs dial indicators, since the amount of piston linear movement up/down barrel diminishes significantly as it approaches TDC, using a piston stop can actually give more accurate measurements, since it halts piston motion further away from TDC. You take a disk reading at stop point, then rotate crank opposite direction until piston drops, comes back up to stop again. Take that disk reading and divide by two to determine precise tdc on disk. Now turn crank 28 deg BTDC and set ign timining.
 
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