Evo engine on rushmore frame??
Elite HDF Member
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From: Santa Clarita
Joe12rk is correct. If you doubt him, do a little research on the subject on this or other forums. It's been well explained any number of times, and I believe the wasted spark explanation to be true in large part. There are a couple of other factors but it's the wasted spark that's the biggest deal. Change the OEM ignition on a pan, shovel, or Evo from dual fire to single fire and you too will be a believer. It will run a bit smoother but will no longer have the classic 'potato potato' idle.
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From: Canada
[QUOTE=Veekness;16251051There are a couple of other factors.[/QUOTE]
I would love to know what those other factors are.
The sound is determined by crank design and vee angle. In a harley engine its a bit of a mismatch as we know. Like a flat plane V8 crank vs a 90 degree crank changes the sound. The engine goes from alternate bank firing to what would seem random and in Harleys case the mismatch of crank vs vee angle means there's a pause then a double hit. Knowing engines intimately and based on what you just explained, the different ignition just makes it run better so it sounds different. A carb needing a signal from an engine with a lot of overlap will run like crap (essentially sounding cool like a muscle car) but EFI that engine (vacuum signal is now moot) and it'll run smoother and ignition will take it up a notch again.
If they are physically the same configuration meaning vee angle and crank pin location then only a cam and engine management can effect the characteristic we're talking about.
I would love to know what those other factors are.
The sound is determined by crank design and vee angle. In a harley engine its a bit of a mismatch as we know. Like a flat plane V8 crank vs a 90 degree crank changes the sound. The engine goes from alternate bank firing to what would seem random and in Harleys case the mismatch of crank vs vee angle means there's a pause then a double hit. Knowing engines intimately and based on what you just explained, the different ignition just makes it run better so it sounds different. A carb needing a signal from an engine with a lot of overlap will run like crap (essentially sounding cool like a muscle car) but EFI that engine (vacuum signal is now moot) and it'll run smoother and ignition will take it up a notch again.
If they are physically the same configuration meaning vee angle and crank pin location then only a cam and engine management can effect the characteristic we're talking about.
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Joined: Jun 2012
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From: CT/FL
I would love to know what those other factors are.
The sound is determined by crank design and vee angle. In a harley engine its a bit of a mismatch as we know. Like a flat plane V8 crank vs a 90 degree crank changes the sound. The engine goes from alternate bank firing to what would seem random and in Harleys case the mismatch of crank vs vee angle means there's a pause then a double hit. Knowing engines intimately and based on what you just explained, the different ignition just makes it run better so it sounds different. A carb needing a signal from an engine with a lot of overlap will run like crap (essentially sounding cool like a muscle car) but EFI that engine (vacuum signal is now moot) and it'll run smoother and ignition will take it up a notch again.
If they are physically the same configuration meaning vee angle and crank pin location then only a cam and engine management can effect the characteristic we're talking about.
The sound is determined by crank design and vee angle. In a harley engine its a bit of a mismatch as we know. Like a flat plane V8 crank vs a 90 degree crank changes the sound. The engine goes from alternate bank firing to what would seem random and in Harleys case the mismatch of crank vs vee angle means there's a pause then a double hit. Knowing engines intimately and based on what you just explained, the different ignition just makes it run better so it sounds different. A carb needing a signal from an engine with a lot of overlap will run like crap (essentially sounding cool like a muscle car) but EFI that engine (vacuum signal is now moot) and it'll run smoother and ignition will take it up a notch again.
If they are physically the same configuration meaning vee angle and crank pin location then only a cam and engine management can effect the characteristic we're talking about.
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From: Canada
Couldn't agree more that ignition will change the sound because it makes it run better but its not the Evo itself that is the cause. I dont have an old bike and no desire to but I've done enough electromotive distributor-less conversions on old carb'd exotic cars and it changes the sound, makes it more fun to use. Wasn't trying to start a debate honest, just wanting to learn about them and what made the Evo special. So the bottom line is a better ignition system makes it run better but its not wasted spark that changes the sound which was what I originally questioned, because it cant. Its a hotter spark, more complete combustion - technology makes it run better effecting the charm shall we say. I can make my 103 run rough and sound like an EVO but at a cost, it would be a step backwards. But the OP can get that sound for sure without an engine swap.
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From: CT/FL
no, it's a good discussion.
if we are talking evos, mine has electronic ignition but set for dual fire. it sounds like the shovehead did with points. and by sounding alike or changing the sound, I am talking about potato potato vs thump thump thump like a triumph etc
if we are talking evos, mine has electronic ignition but set for dual fire. it sounds like the shovehead did with points. and by sounding alike or changing the sound, I am talking about potato potato vs thump thump thump like a triumph etc
Last edited by Joe12RK; May 19, 2017 at 01:55 PM.
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From: Canada
Ill read up more about the Evo but there must be shortcomings or they wouldn't have moved on right? Emissions or maybe displacement limitations so they started fresh.
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From: Santa Clarita
If you're looking for technical knowledge, hellonewman, it's just as easy as reading Donny Peterson's books on the subject. There are several. I used to believe that the evo was the best engine Harley ever built...until I read his book on the Twinky. Now I'm a believer.
As for those other factors, over the years I've read enough on the subject to satisfy myself that there ARE other factors, but also to have come to the conclusion that the single fire versus wasted spark is the main reason. Honestly, if you're curious enough about it, you can start looking into the subject your own self...to me, it's like who gives a rip? Believe or don't believe. And I've also read that it's not practical...nor is there the technology available...to give the Twinky the 'potato potato' idle.
But I tell ya...Joe12RK seems to have the same information I do, would do ya well to believe him!!!
But back to the subject of this forum...only an idiot with more money than common sense would seriously want to replace their Twinky engine with a blockhead...take a step back in time and GET an evo-engine scooter to start with. Believe it or not, back in the day, blockheads were just as dependable and made outstanding power, and they didn't go crash all the time cuz they didn't have ABS. I've become a believer in ABS...but it's not all that, either.
As for those other factors, over the years I've read enough on the subject to satisfy myself that there ARE other factors, but also to have come to the conclusion that the single fire versus wasted spark is the main reason. Honestly, if you're curious enough about it, you can start looking into the subject your own self...to me, it's like who gives a rip? Believe or don't believe. And I've also read that it's not practical...nor is there the technology available...to give the Twinky the 'potato potato' idle.
But I tell ya...Joe12RK seems to have the same information I do, would do ya well to believe him!!!
But back to the subject of this forum...only an idiot with more money than common sense would seriously want to replace their Twinky engine with a blockhead...take a step back in time and GET an evo-engine scooter to start with. Believe it or not, back in the day, blockheads were just as dependable and made outstanding power, and they didn't go crash all the time cuz they didn't have ABS. I've become a believer in ABS...but it's not all that, either.
Seasoned HDF Member
Joined: Jun 2015
Posts: 8,055
Likes: 8,080
From: Canada
If you're looking for technical knowledge, hellonewman, it's just as easy as reading Donny Peterson's books on the subject. There are several. I used to believe that the evo was the best engine Harley ever built...until I read his book on the Twinky. Now I'm a believer.
As for those other factors, over the years I've read enough on the subject to satisfy myself that there ARE other factors, but also to have come to the conclusion that the single fire versus wasted spark is the main reason. Honestly, if you're curious enough about it, you can start looking into the subject your own self...to me, it's like who gives a rip? Believe or don't believe. And I've also read that it's not practical...nor is there the technology available...to give the Twinky the 'potato potato' idle.
But I tell ya...Joe12RK seems to have the same information I do, would do ya well to believe him!!!
But back to the subject of this forum...only an idiot with more money than common sense would seriously want to replace their Twinky engine with a blockhead...take a step back in time and GET an evo-engine scooter to start with. Believe it or not, back in the day, blockheads were just as dependable and made outstanding power, and they didn't go crash all the time cuz they didn't have ABS. I've become a believer in ABS...but it's not all that, either.
As for those other factors, over the years I've read enough on the subject to satisfy myself that there ARE other factors, but also to have come to the conclusion that the single fire versus wasted spark is the main reason. Honestly, if you're curious enough about it, you can start looking into the subject your own self...to me, it's like who gives a rip? Believe or don't believe. And I've also read that it's not practical...nor is there the technology available...to give the Twinky the 'potato potato' idle.
But I tell ya...Joe12RK seems to have the same information I do, would do ya well to believe him!!!
But back to the subject of this forum...only an idiot with more money than common sense would seriously want to replace their Twinky engine with a blockhead...take a step back in time and GET an evo-engine scooter to start with. Believe it or not, back in the day, blockheads were just as dependable and made outstanding power, and they didn't go crash all the time cuz they didn't have ABS. I've become a believer in ABS...but it's not all that, either.
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Joined: Nov 2013
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From: Santa Clarita
Well, there ya go, hellonewman! That's probably one of the threads I read on the subject. Lots of good info in there...certainly the higher idle speed makes sense. Back in the day, it was a matter of pride for many pan or shovel riders to get the idle just as low as it would go...like you could easily hear each jug hit individually...
Seasoned HDF Member
Joined: Jun 2015
Posts: 8,055
Likes: 8,080
From: Canada
Well, there ya go, hellonewman! That's probably one of the threads I read on the subject. Lots of good info in there...certainly the higher idle speed makes sense. Back in the day, it was a matter of pride for many pan or shovel riders to get the idle just as low as it would go...like you could easily hear each jug hit individually...