Topic: Power Arc Ignition w/ VOES

[Cqyqte]

No problem, first thing my Mikunis were not drilled for a vacuum sync port so that had to be done first.  There is a dimple in the casting just ahead of the manifold lip (engine side rubber boot flange) on the left side of both carbs.  I drilled and tapped for a 5mm vacuum barb on each one (only one vacuum port is necessary, but I did both carbs so I could vacuum sync them).

In preparation for installing a VOES I connected a set of vacuum gauges and afixed them on the handle bars so I could read them as I rode.  Then I preceded to go for a boot and made a mental note of the vacuum level on the gauges just before the pinging began as I accelerated or throttled up going up hills.  In my set up it appeared that the pinging could be heard when the vacuum hit 4.5 inches of Hg.

Knowing this I searched out a source for a VOES that had a trigger point of 5 inches which would be just before the critical moment before pinging could be heard.  Drag Specialities sells 2101-0010 a VOES set to function at 5 inches of Hg vacuum.  It comes with a mounting bracket as well.   Now the VOES is a switch that is either open or closed and is set to change at a specified vacuum level.  The contacts are N.O. when at resting state, and when the vacuum increases the contacts close when the predetermined level is reached (in my case 5 inches of Hg).   Which means before I start the bike the switch is open, once idling the switch is closed, cruising along at 40 mph the switch is closed, accelerate to 60 mph and head up an incline and when the load on the motor builds and the vacuum drops below 5 inches the switch opens.

I found a place to hang the VOES and then ran a vacuum line from the VOES to one of the sync barbs on one carb, I left the sync barb on the other barb covered.  Now I run a PowerArc ignition that has 4 different ignition maps, all selected by grounding or ungrounding two different wires.  In my set up I run map 2 (Brown wire grounded) so I attached one lead from the VOES to a ground source and the other end to the Brown wire off the PowerArc ignition.  So when the VOES has vacuum above 5 inches I am running on Map2, when the vacuum falls below 5 inches I drop down to Map1 (a less advanced mapping).   Now the neat thing is that when starting the bike or pulling away from a stop sign the vacuum drops below 5 inches and the ignition advance retards to Map1 and the bike starts easier and doesn't fall flat on its face if a don't have my revs high enough when I roll away from a stop.  And when in top gear approaching a hill I can give more throttle without any pinging or having to drop down a gear, she just pulls happily up and over the crest.  When the vacuum recovers the VOES jumps back to Map2 without me sensing a thing.

Now if you run Map3 you will need to put a relay into the mix triggered by the VOES so that when the vacuum is high the Blue wire is grounded and when the vacuum drops below 5 inches the Blue wire becomes ungrounded and the Brown wire gets grounded.  You do this by having the VOES control the state of the relay, you ground the common contact of the relay and attach one side of the relay coil to the VOES, the other lead from the VOES to ground.  Then attach the other side of the relay coil to +12v and then attach the Blue wire from the PowerArc to the N.O. side of the relay contacts and the Brown wire to the N.C. side of the relay and you are done..... now go ride.

[Cqyqte]

Here's a Pic of Ken from CycleX test riding my bike with the VOES on Hwy 51 and a better pic of the setup....

[chewbacca5000]

Here's a Pic of Ken from CycleX test riding my bike with the VOES on Hwy 51 and a better pic of the setup....

Geez that bike is feakin awesome!  Make me want a hard tail.  Is that a cycle x frame?  Very nice bike.

[Cqyqte]

It's for sale, need money to fund new builds 

[Cqyqte]

Yes the frame is original Boxer Pro frame, which I don't think Ken sells anymore.  Their current frame has some minor differences. 

[chewbacca5000]

It's for sale, need money to fund new builds 

So sad.

Yeah I am in the same situation will have to sell some so I can do my next project.

[nokrome]

   I understand how running a VOES will help you take advantage of the full range of advance curves available on the power arc but if you are already running the least advanced curve (both sensor wires ungrounded, 33.5deg. total advance) then I dont see how this will help with the pinging issue. Am I missing something?

 Retro Rocket:
     the base gaskets that I have are approx .018" thick, how much could it potentially lower your comp ratio by running two of them?

[banzaibob]

The carburetors are stock with stock pilot jets, needles, slides, etc.  Main jets are #130.  Air screws are turned out maybe 2 turns (they are tuned to the idle). Stock air box with a foam element and cut outs at the air intakes.  I do not remember specifically what the gearing is but it is tall with at one one added tooth to the counter shaft.  It also has a tall Continental 130/90-17 touring tire on the rear. 

In tuning this bike, I have been doing one thing at a time.  When I first retarded the timing and put on heavier advance mechanism springs I do not feel as if the main jets were rich enough.  Subsequently, the rattling and pinging was not effected.  The only thing that appears to have lessened the pinging is richer main jets.  During my last test ride ( over a week ago) it appeared that the rich jets may have fouled a plug.  However I am trying to determine whether or not I over-fueled it in feeding it wacky throttle.

I have seen the dual carb conversions kits in action and they are stunning.  The acceleration is way cool.  However my reasons for all the performance mods on my bike are to make it pull those long hills in the Ozarks at 90mph.  Reliability and predictability are paramount.

I have another 836 that I built that has garden variety pistons that I picked up off of E-Bay.  Just got back from a 1500 mile jaunt over the weekend and it did exactly what I want this one to do; haul ass for hours at a time.  Picture is included.  Also included is a picture of a diesel motorcycle that I built for #$%*s and giggles (168mpg).

[nokrome]

BTW the PDF that I attached to my previous post contains 4 separate pages, scroll between them to see the 4 different curves available on the power arc.

[ccmclane]

Thank you Cqyqte that was very helpful.

No problem, first thing my Mikunis were not drilled for a vacuum sync port so that had to be done first.  There is a dimple in the casting just ahead of the manifold lip (engine side rubber boot flange) on the left side of both carbs.  I drilled and tapped for a 5mm vacuum barb on each one (only one vacuum port is necessary, but I did both carbs so I could vacuum sync them).

In preparation for installing a VOES I connected a set of vacuum gauges and afixed them on the handle bars so I could read them as I rode.  Then I preceded to go for a boot and made a mental note of the vacuum level on the gauges just before the pinging began as I accelerated or throttled up going up hills.  In my set up it appeared that the pinging could be heard when the vacuum hit 4.5 inches of Hg.

Knowing this I searched out a source for a VOES that had a trigger point of 5 inches which would be just before the critical moment before pinging could be heard.  Drag Specialities sells 2101-0010 a VOES set to function at 5 inches of Hg vacuum.  It comes with a mounting bracket as well.   Now the VOES is a switch that is either open or closed and is set to change at a specified vacuum level.  The contacts are N.O. when at resting state, and when the vacuum increases the contacts close when the predetermined level is reached (in my case 5 inches of Hg).   Which means before I start the bike the switch is open, once idling the switch is closed, cruising along at 40 mph the switch is closed, accelerate to 60 mph and head up an incline and when the load on the motor builds and the vacuum drops below 5 inches the switch opens.

I found a place to hang the VOES and then ran a vacuum line from the VOES to one of the sync barbs on one carb, I left the sync barb on the other barb covered.  Now I run a PowerArc ignition that has 4 different ignition maps, all selected by grounding or ungrounding two different wires.  In my set up I run map 2 (Brown wire grounded) so I attached one lead from the VOES to a ground source and the other end to the Brown wire off the PowerArc ignition.  So when the VOES has vacuum above 5 inches I am running on Map2, when the vacuum falls below 5 inches I drop down to Map1 (a less advanced mapping).   Now the neat thing is that when starting the bike or pulling away from a stop sign the vacuum drops below 5 inches and the ignition advance retards to Map1 and the bike starts easier and doesn't fall flat on its face if a don't have my revs high enough when I roll away from a stop.  And when in top gear approaching a hill I can give more throttle without any pinging or having to drop down a gear, she just pulls happily up and over the crest.  When the vacuum recovers the VOES jumps back to Map2 without me sensing a thing.

Now if you run Map3 you will need to put a relay into the mix triggered by the VOES so that when the vacuum is high the Blue wire is grounded and when the vacuum drops below 5 inches the Blue wire becomes ungrounded and the Brown wire gets grounded.  You do this by having the VOES control the state of the relay, you ground the common contact of the relay and attach one side of the relay coil to the VOES, the other lead from the VOES to ground.  Then attach the other side of the relay coil to +12v and then attach the Blue wire from the PowerArc to the N.O. side of the relay contacts and the Brown wire to the N.C. side of the relay and you are done..... now go ride.

[Cqyqte]

   I understand how running a VOES will help you take advantage of the full range of advance curves available on the power arc but if you are already running the least advanced curve (both sensor wires ungrounded, 33.5deg. total advance) then I dont see how this will help with the pinging issue. Am I missing something?

 Retro Rocket:
     the base gaskets that I have are approx .018" thick, how much could it potentially lower your comp ratio by running two of them?

Sorry missed the line "lowest advance curve", what number plug are you running with your setup?

[dave500]

i had to have the combustion chambers milled out to lower compression on a 500 engine i built with xl125 domed pistons,the stockers are flat topped,no ignition tuning solved it,yours may get worse as it accumulates a little carbon?

Why not mill the pistons or use 2 base gaskets Dave..?

the machinist didnt want to do the piston crowns as they might be too thin,id have needed four base gaskets mick the amount that was removed!!

[nokrome]

   I understand how running a VOES will help you take advantage of the full range of advance curves available on the power arc but if you are already running the least advanced curve (both sensor wires ungrounded, 33.5deg. total advance) then I dont see how this will help with the pinging issue. Am I missing something?

 Retro Rocket:
     the base gaskets that I have are approx .018" thick, how much could it potentially lower your comp ratio by running two of them?

Sorry missed the line "lowest advance curve", what number plug are you running with your setup?

  D8EA, i experimented with cooler plugs at one point but they fouled out right away

[banzaibob]

Thanks, Cqyqte.  The info is very helpful. 

Let me take this in another direction if I could.  Does anyone make a device or a "black box" that would eliminate the need for the centrifugal advance?  I'm very satisfied with the Dyna S units I have used in the past so since we are talking about mapping simple electrical impulses to advance and retard the spark wouldn't it stand to reason that that functional could be "digitized?" 

Wouldn't the only parameters the digital device would have to consider would be vacuum pressure (VOES) and rpm?  I am WAY far away from being an electrical engineer but I cannot believe that someone hasn't thought of such a device for the CB750 SOHC. 

[Silverback]

Oh, but they do!
http://www.dynoman.net/ignition/dyna2000.html

Get your wallet out!

So, did you ever try the higher octane? Try retarding your Dyna S?(Yes you did, missed that.) Try stock points?

I just built an 836 motor for a customer with lightened crank/rotor, heavily modified head and more. The Dyna S was pinging badly. Stock points cured it!
Just sayin'!

DYNA 2000 FEATURES:

FULLY STATIC TIME-ABLE- You can set the timing accurately to the desired value without having the engine running.

INDEPENDENT 1/4 2/3 CYLINDER TIMING- The Dyna dual sensor crank trigger uses one sensor for cylinders 1 & 4 and the other cylinder for 2 & 3 allowing you to accurately set the timing for each cylinder pair.

BUILT-IN STATIC TIMING LIGHT- An LED light built into the Dyna 2000 ignition module allows you to monitor the crank trigger signal status and easily set the ignition timing.

FIVE DIFFERENT ADVANCE CURVES- You can advance slowly to dial out pinging on high compression motors or bring the advance in quickly on quick revving motors or select a curve in between to maximize the performance of your combination.

FOUR DIFFERENT RETARD MODES- The Dyna 2000 is an ideal solution for turbo or nitrous combinations.

TEST MODE- System check out and troubleshooting is a breeze with this feature.

SAFETY INTERLOCK INPUT- You can keep your side stand safety switch functional or hook up a theft prevention switch, or activate a shift lever kill for road racing.

BROAD RANGE REV LIMITER- The Dyna 2000 rev limiter is adjustable from 8500 to 16,000 rpm to let you run in any range you want.

DIGITAL TACH OUTPUT- Your tachometer will run smooth and accurate, even at the rev limit.

HIGH ENERGY- An innovative dwell control scheme maximizes spark energy all the way to 16,000 rpm! The Dyna 2000 can be used with 2.2 ohm or 3 ohm coils.

EASY MOUNTING- The Dyna 2000 ignition module has built in frame saddles to make mounting anywhere a breeze.

COMPLETE WIRING HARNESS- The Dyna 2000 kit includes a complete wiring harness to simplify installation.

[Retro Rocket]

Retro Rocket:
     the base gaskets that I have are approx .018" thick, how much could it potentially lower your comp ratio by running two of them?

I don't know but i have seen gaskets doubled up for that use as well as spacers made up, once you reduce the comp ratio of the head, thats it, its permanent....

[Silverback]

Just to add, when tuning carbs the RPMs are secondary to throttle position. I simply put a piece of tape on the inside of the grip and mark the throttle positions on it.
You mentioned that richening the needles had no effect on the ping, but did it effect anything else? If no, then you might want to move it two clip positions. All of the positions are there for a reason. Don't be afraid to use the extreme settings if that's what gets your tuning right. 130 seems a bit rich for the main and could be compensating for an overly lean needle position. A tight motor will pull lots of fuel through the main.
Just throwing ideas out there for you. Another option: Do a plug chop at the point of pinging. This method is very informative, although a bit tedious.

[banzaibob]

I understand how throttle position actuates the different circuits of the carburetor.  RPM quite often is meaningless, especially with engines that are not under load.  For the sake of this discussion, I'm talking about 3rd, 4th and 5 gear, not lugging the engine but not quite on the pipe either; 2500-3800rpm.  I would have to assume that once the flame front of the burning fuel achieves it's mystic relationship with the speed of the engine (above 4000rpm) all becomes well. 

The needle position right now is back to where I started, on position #2 from the bottom.  I put it on the #1 position with 130 mains and had a plug fouling problem.  HOWEVER, I remember that I had some float control issues that caused some flooding.  It is all worked out now.  I may go back and revisit raising the needle a notch.  It would almost appear that the knocking is at the throttle position where the needles and the main jets would overlap.

 

[scottly]

  For the sake of this discussion, I'm talking about 3rd, 4th and 5 gear, not lugging the engine but not quite on the pipe either; 2500-3800rpm.
 

2500 rpm is lugging, especially with 12.5-1 compression, IMHO.

[scottly]

       the base gaskets that I have are approx .018" thick, how much could it potentially lower your comp ratio by running two of them?

Adding an .018" (compressed) base gasket would add about 1.5 cc to the chamber volume.

[Silverback]

I thought the 849 kit was 10.5-1. Not really high compression. Same as a standard 836 kit.
My vote is to try stock points and work on the carb tuning. 3rd, 4th and 5th gear issues are indicative of a tuning issue.
Really hope you get this sorted as the 849 can be a fun motor.

Ignition can influence pinging. That's why modern cars have knock sensors, to retard timing when knocking is detected.

[banzaibob]

That is what I have, the 849 kit.  I bought it from them about 3 years ago, assembled the engine and then had to let it sit due to other projects.  When I finally assembled the bike about 2 months ago and started having the pinging problem I called Cycle X to see if they had a record of what I had actually bought (thinking that I might have received high comp pistons unknowingly).  They stated that their inventory and sales records don't go back that far.

It is not uncommon for any bike to find itself at 2500 rpm driving on residential streets and other light duties.  In my opinion how a bike behaves with light throttle application and low engine speed is pretty important to overall drive-ability.  My theory on this entire matter is that if it knocks and pings around the neighborhood and church parking lot, its going to give me 100 times that amount of grief on a dirt road in the middle of a hot desert. 

I'm going to do a compression test later on today just to see where I'm at on this.  I'll post the results.

[Retro Rocket]

Don't expect much at 2500 rpm guys, its no wonder you have knocking, change gears and use the rev range properly.. Why kit the engine if you plan on running around just over idle speed....?

[banzaibob]

I don't plan on running it at just over idle speed.  The bike is being built as a performance tourer AND as a touring machine it has to be ready for any and all conditions.  As a bike that will supposedly carry me far into the boondocks I DO NOT want to get stuck out there because I didn't work a potentially disastrous (but maybe simple to solve) problem beforehand. 

[Terry in Australia]

I'll be interested to see how this works out. Retarding your ignition isn't ideal, and prolonged pinging will eventually destroy your engine. Reducing your compression ratio or using higher RON fuel are the two obvious "fixes", (to me at least) but if you can get a VOES gadget to negate doing anything else, you've successfully outsmarted just about every mechanical engineer currently working in the automotive industry. Cheers, Terry.