VOES Switch Explained

[Hoople]

I was under the impression that grounding the blue wire actually lets it run up to 35 advanced.
Thanks

Yes, the VOES switch is suppose to be normally open which would mean removing the wire FROM ground would retard the timing. So you are correct with the logic state of the VOES switch. So ask Gary how much spark advance will be removed from the 35 degrees when you remove the Blue wire from ground. Also confirm if spark advance are steps and not a curve. The manual was not clear regarding any of these points.

I am guessing the blue wire is responsible for maybe 5 to 7 degrees. That would put you around a more realistic number of 28-30 degrees of total advance.
Just a guess.

 

[cacasal]

It jumps from 25 to 35.
The active voes will open at the pre set value and retard the ign 10 degrees from the total advance....back to 25.

 

[Hoople]

Good work on getting the info. The ignition timing is in-fact "stepped" and the VOES retards the timing a fixed 10 degrees or in other words inhibits the system from going into level 3 advance.

This is what I would try. Use the big twin setting of 5 degrees cranking. I would select a higher RPM value for the "switch over" from 2nd level to 3rd level. Maybe something in the 2750 to 2900 range. 25 degrees of advance is plenty to carry you from idle to 3000 RPM. Then find a new switch or adjust your present VOES vacuum switch to retard the ignition back to 25 degrees at a value of maybe 7.5 in/Hg. I know that is more than a stock setting, but your going to need a pretty high number or else your engine will knock due to having 35 degrees of advance while at partial throttle. Remember, at light engine load cruising speeds above 3000 RPM you will have 35 degrees of advance. When you crack the throttle you want VOES to kick in immediately or I am sure you will hear engine knock. 5" of HG is getting close to having to be at wide open throttle for VOES to retard the timing. If you test ride the bike and hear engine knock, INCREASE the value from say 7.5" to 9" /HG. This way the VOES will be More sensitive and kick in earlier. Remember that the setting of VOES will have no effect on the performance of the bike while under WOT.

So to answer your original question, I would use a higher Vacuum switch setting than stock. The higher the number the more sensitive (kicks in sooner) VOES will be.

 

[cacasal]

Hoople....regarding one of your original questions: My dynamic compression is: Front = 160 PSI. Rear= 155 PSI. I wonder what compression the pistons are. The motor was assembled when purchased. With SE heads, it could be stock or High Compression.

 

[Hoople]

Those PSI numbers are workable. 160 PSI is not an amount that will cause you concern with your advance and it will be plenty to have good power. I would bet the theoretical PSI or compression ratio (squish area vs total cylinder volume) is much higher and the intake lobe cam shaft profile/timing is relaxing that number. That is expected.

Since you have made more than 1 change to your engine, I would temporarily disable VOES (remove and tape blue wire). That will give you 5 degrees at cranking, then a hop to 25 degrees with no hop to 35 degrees. Put the bike through its paces and see if you experience any issues with knocking with VOES disabled. If it runs clean, enable VOES and experiment with the vacuum switch setting. If it does not run clean with VOES disabled, enabling VOES would just make it worse. 1st Get the bike to run knock free & clean with VOES disabled. Since VOES is disabled for the test runs, you may experience excessive popping on de-acceleration. Just disregard that for the time being.