Topic: Power Arc Ignition w/ VOES

[banzaibob]

I posted a thread about a month ago pertaining to an 849cc Cycle X kit that was pinging and knocking loudly.  I even talked to Ken at Cycle X and he steered me toward a solution.  The bike has been re-jetted several times finally settling on 130 main jets but it still has a pretty good knock at low rpm's, with modest to large throttle settings.  BTW, performance other than that is outstanding, lots of acceleration. 

I'm thinking about one of their Power Arc ignitions BUT I think a real solution would be using it in conjunction with a vacuum operated switch.  The rpm range I'm having trouble with is from 2000 to 4000 with about 35% or greater throttle settings.  My guess is that when the throttle opens under those conditions, the vacuum is low enough to effect the usage of a VOES effectively. 

My questions would be pretty general:  Anybody have any decent ideas about this subject?  How would one hook it up?  Are there any variables?  Has anybody done this/doing this? 

[dave500]

lower the compression,use a thicker head gasket.

[banzaibob]

Removing the engine from the frame and installing a thicker head gasket to lower the compression is impractical in this case.  I like the power and would rather try simpler solutions like upgrading the ignition to something that I could program or fine tune to give it even more street-able performance.   

[dave500]

ok,take the edge of the early ignition advance,are you running points now?you wont really lose any true power lowering the compression,,that or use a longer overlap cam to reduce the effective compression?a programmable ignition will probably help you get around it without going into the mechanical side of things,try and use only proper quality fuel aswell.

[Terry in Australia]

What fuel are you using mate? My first BMW R100RS would ping like buggery on 91 RON, was better with 95 RON, and the pinging all but went away when I upgraded again to 98 RON.

My 836 with 12.5:1 RC pistons, MJR stage III head and Megacycle 125/75 cam hates 91 RON, but runs well on 98 RON Shell Optimax fuel. I just run a Dyna S ignition and Dyna 3 Ohm coils with no problems, but a Dyna 2000 would be my choice if I wanted to be able to run different programs. Cheers, Terry.

[K3Owner]

Terry's got it. Engines need higher octane at low RPM load and knock will be even worse in higher gears. If you're running the best premium there is, your options are race gas or thicker gasket. Stronger spark would be a waste of money if our current system is healthy. There's also an assumption that your timing is not overly advanced.

That VOES idea takes me back to the old adjustable distributor vacuum switch use in modifying GM cars. Those were the days...

[banzaibob]

I'm running pump gas, 91 octane.  I've also tried raising the needles in the carb one notch, it didn't help so I put it back.  I have a Dyna S on it right now.  I've tried stiffer springs on the advance to where full advance was 3300 rpm instead of 2500.  It didn't work.  I'm under the impression that the Power Arc AND the Dyna 2000 both can accommodate a vacuum switch, true? 

I'm using this bike as a performance tourer, no racing.

[K3Owner]

Hi Banzai,

Locate the highest octane available and fill an empty tank. This is for troubleshooting and not necessarily daily riding - at least not now   . 91 is still to low for a high compression engine. Anything stronger? Sunoco usually has 93 available or higher if you're near a track. Our little Sunoco out here used to have 95 - no more.

There are also boosters you can buy that can move it up a couple of notches. Truly sounds like octane and it's cheaper troubleshooting than pulling the engine to replace a gasket. I use 91 in my 550 stocker...

Good luck!

[Xnavylfr]

The DYNA 2000 would be a good choice!! It is programmable to adjust the timing curve.  As like others said HIGHER octane.  If you are near a SMALL airport you may be able to buy some 110-115 octane AVGAS.  This gas is LOW LEAD ,so mix a gallon to 5 gallons of 91 octane, this will give you about 100 octane leaded gas. I had to do this mixology  for a 12.5:1 engine I built!!


Xnavylfr(CHUCK)

[banzaibob]

In actuality, I am resisting the urge to use av-gas or additives.  I am trying to make this thing run on what I can find readily available.  My performance parameters are basically pulling hills at 85mph.  I have no problem keeping a bottle of reliable octane booster in a saddlebag but I would like to work this out so I won't have to worry in case I get stuck way out in the boondocks somewhere. 

[Xnavylfr]

If you can find it ? Look for some gas without ethanol(ALCOHOL) I know there are SOME company stations that still sell it!!  I know that it's supposed to be EARTH friendly and GREEN but I think that is all BS!! They add it so you get LESS gasoline with a WATER based additive at a higher price, so they make MORE money!!!

CH3CH2OH  You see the H2O=WATER

Xnavylfr(CHUCK)

[nokrome]

 I think the lite pinging on those 850 kits is pretty common, I was having the same issue running the power arc system on the lowest advance curve (33.5 deg. total advance) on my 850 with 91 octane. There was a member here (coyote ?) that was successfully running a VOES system on his 850 with the power arc but im not sure of the details. I have been running 100LL avgas with excellent results but thats very inconvenient for long rides. Im not sure that a VOES system would help here because that would only serve to advance the timing at higher RPMs (up to about 43.5 deg. total advance on the power arc).
  I think that a thicker head gasket would be one solution but would like to hear other ideas.

[banzaibob]

Basically, I would be looking for all of the devices to work in concert when the engine is pulling a heavy load at lower rpm's.  So far the performance above 4000 rpm appears to be stellar.  In fact, I have it geared tall so 4000 rpm = 70mph. 

[banzaibob]

I had a 2001 HD Road King Police 88 cu. in. twin cam fuel injected that had a similar but not as severe problem.  At 2200 rpm or less you simply could not give it decent throttle or else it would knock pretty harshly.  I bought a first generation Power Commander, the one that you plugged the cord into the the serial port of your computer.  The software controlled 7 parameters including spark advance/retard on an X-Y axis graph (advance/throttle position).  All it took was about 1 or 2 degrees of retard in the right slot and presto!, it made you feel like a genius.  No more BB's in a boxcar! 

Is there anything out there in the aftermarket besides Dyna and Power Arc? 

[nokrome]

there are other electronic ignition units but i think that dyna and power arc are the only ones for these bikes that have programmable curves

[banzaibob]

I know that certain models give you a choice between per-programed curves but are there models that allow for programming your own individual curve via software on your computer? 

[Silverback]

IMO the only way to properly use the power arc is with a VOES. The Dyna S system is permanently advanced, compared to stock points. After experimenting with these on my 850 kit, I found the stock points to be best and even more reliable with the Hondaman transistorized ignition. Terry's advise is paramount. Increase the octane and work to get the carb tuning better. I learned my lesson with running low octane fuel with a higher compression piston on the Relay Rally. My pistons melted while running extended periods down the highway. Should have taken my own roads home instead of trying to hustle with the other riders. BTW, what carbs are you using? Advance tuning procedures might be required if your running stockers. My 850 pulls like a banshee with CR29s. No pinging whatsoever! Keeps breaking tach cables at about 9500.

[Retro Rocket]

there are other electronic ignition units but i think that dyna and power arc are the only ones for these bikes that have programmable curves

The ignition is NOT THE PROBLEM, high compression and low octane fuel = knocking, as has already been said, lower the compression {i know you don't want to do this and I wouldn't either} or run higher octane fuel, its that simple..... I had the same problem with a car of mine, went to higher octane, just like Terry said earlier, and the problem was gone for good, I got better gas mileage as well....

[Cqyqte]

I posted a thread about a month ago pertaining to an 849cc Cycle X kit that was pinging and knocking loudly.  I even talked to Ken at Cycle X and he steered me toward a solution.  The bike has been re-jetted several times finally settling on 130 main jets but it still has a pretty good knock at low rpm's, with modest to large throttle settings.  BTW, performance other than that is outstanding, lots of acceleration. 

I'm thinking about one of their Power Arc ignitions BUT I think a real solution would be using it in conjunction with a vacuum operated switch.  The rpm range I'm having trouble with is from 2000 to 4000 with about 35% or greater throttle settings.  My guess is that when the throttle opens under those conditions, the vacuum is low enough to effect the usage of a VOES effectively. 

My questions would be pretty general:  Anybody have any decent ideas about this subject?  How would one hook it up?  Are there any variables?  Has anybody done this/doing this? 

I run with a VOES on my 849cc set up with twin Mikunis.  I run on the first advance map with the PowerArc ignition and the voes retards it to the factory map from the start and then anytime the vacuum drops below 5mm HG on the vacuum scale.  Works like a charm and I run regular fuel and don't have to drop a gear when climbing hills.  The biggest improvement was found accelerating away from stops, cured that fall flat of the face launch if you don't wind her up first, which everyone said was caused by carb settings....NOT.

[ccmclane]

I run with a VOES on my 849cc set up with twin Mikunis.  I run on the first advance map with the PowerArc ignition and the voes retards it to the factory map from the start and then anytime the vacuum drops below 5mm HG on the vacuum scale.  Works like a charm and I run regular fuel and don't have to drop a gear when climbing hills.  The biggest improvement was found accelerating away from stops, cured that fall flat of the face launch if you don't wind her up first, which everyone said was caused by carb settings....NOT.

Cqyqte can you describe how you set that up?

[nokrome]

I posted a thread about a month ago pertaining to an 849cc Cycle X kit that was pinging and knocking loudly.  I even talked to Ken at Cycle X and he steered me toward a solution.  The bike has been re-jetted several times finally settling on 130 main jets but it still has a pretty good knock at low rpm's, with modest to large throttle settings.  BTW, performance other than that is outstanding, lots of acceleration. 

I'm thinking about one of their Power Arc ignitions BUT I think a real solution would be using it in conjunction with a vacuum operated switch.  The rpm range I'm having trouble with is from 2000 to 4000 with about 35% or greater throttle settings.  My guess is that when the throttle opens under those conditions, the vacuum is low enough to effect the usage of a VOES effectively. 

My questions would be pretty general:  Anybody have any decent ideas about this subject?  How would one hook it up?  Are there any variables?  Has anybody done this/doing this? 

I run with a VOES on my 849cc set up with twin Mikunis.  I run on the first advance map with the PowerArc ignition and the voes retards it to the factory map from the start and then anytime the vacuum drops below 5mm HG on the vacuum scale.  Works like a charm and I run regular fuel and don't have to drop a gear when climbing hills.  The biggest improvement was found accelerating away from stops, cured that fall flat of the face launch if you don't wind her up first, which everyone said was caused by carb settings....NOT.

  details please

[scottly]

I'm running pump gas, 91 octane.  I've also tried raising the needles in the carb one notch, it didn't help so I put it back.  I have a Dyna S on it right now.  I've tried stiffer springs on the advance to where full advance was 3300 rpm instead of 2500.  It didn't work.  I'm under the impression that the Power Arc AND the Dyna 2000 both can accommodate a vacuum switch, true? 

If slowing the mechanical advance had no effect, I doubt your problem can be solved with a vacuum switch. With the stiffer springs installed, did you try retarding the initial timing?
I think you also mentioned that you had the bike geared higher? What are your sprocket sizes?

[Terry in Australia]

Here's a really interesting article I read a few years ago about increasing octane via fuel additives. It's not all snake oil, but some of the better known additives do next to nothing.

When I was a kid I worked as a "Bowser Boy" at a gas station that sold Toluene for race cars, but back then it was known as Methyl Benzine, I didn't realise that it was the same product until I re-read this article. Cheers, Terry.

http://www.fueltechexperts.com/2008/08/08/octane-boosters-which-is-best/

[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?

[Retro Rocket]

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..?