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Thread: Can anybody explain to me?

  1. #1
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    Can anybody explain to me?

    Can anybody explain to me why the two cycle is not more popular in dirt racing?

    I know for a fact that you can buy a K71, with the clutch and the exhaust included, take it out of the box and run it. It doesn't need work on the clearances, it doesn't need a new rod, it needs nothing, and all of the engines are competitive with each other. There are no better heads, there are no better cams, there are no better clutches, nothing has to be added, nothing has to be done. Bolt it on the kart and go race. I had an HPV back in the 90s, and that's exactly what I did. I bolted it on a kart and raced it. Me and an engine builder friend of mine did tear it down some, just to see what was up. Every measurement, without totally disassembling the engine, we could make was right to the spec. A truly "bolts on" out-of-the-box competitive engine.

    The only reason, (actually two things) that I can think of for the engines failure in the marketplace was; 1: because of the big disparity in the exchange rate between the euro and the dollar at that time, they got a little expensive on the initial purchase. 2: the shops couldn't make big money blue printing the engine. There was no need to blueprint! There was no advantage to having a blue printed engine.

    I would be real interested in anybody's idea on why this engine did not succeed.
    From the desk of Al Nunley 512-630-6215
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  2. #2
    I do not know why that particular engine didn't succeed back in the day Al, but my opinion why HPV isn't real popular anywhere now and Yamaha is declining rapidly revolves around manufacturer support. IAME sponsors series, gives engines away as prize packages, gives automatic entries to World Finals and Grand National races and quite often has representatives at all the bigger races. Rok does the same thing. Rotax was doing the same thing, until they priced themselves out of the market and alienated their customers with mandatory upgrades that were unreliable and over priced. Briggs seems to be in tune with their customers too, last season for the very first year of the AKRA Sprint Series, Briggs gave away brand new in the box Inverter generators at every race in a random raffle. Any participant that entered a Briggs powered class was automatically entered in the raffle at each race. Briggs gives away engine packages to class winners at the end of the season.I think the same goes for tires too, if the manufacturers don't support the racing series the series switches brands to a manufacturer that will support them. When is the last time Yamaha or HPV sponsored a race series and gave away prizes to the competitors? It may happen, but I haven't seen it on the east coast lately. PRD were a real popular TaG engine option here for a couple years, and now they are pretty much extinct too like the Rotax. I think it's just a sign of the times, and the way racing operates these days.

  3. #3
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    it pays no money

    can race two cycle for $200 to win

    or race any weekend in 4cycle for from $5000-$50,000 to win

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    Quote Originally Posted by Sjg22 View Post
    it pays no money

    can race two cycle for $200 to win

    or race any weekend in 4cycle for from $5000-$50,000 to win
    That's fine, if you are "trying" to make money racing,, I got in to racing because I like to go as fast as I possibly can, not follow the bumper in front of me, long live 2 strokes!!!!

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    Current and future regulations will put the two stroke out of the mainstream compettition. I don't feel that is the reason for its decline though. I think the demise of your local kart shop and everyone shopping online has made it tough to get your two stroke engine parts. And now nobody works on their own engines. Back in the day building your engines used to be part of karting, it was father son type of deal, a family sport. It is not anymore. But mostly I feel the old school kart engine manufacturers like IAME, Yamaha and alike have priced themselves out. The cost of a KT is ridiculous compared to its original, and the European motors are even more. The whole TAG thing was a joke to me also. Too high of cost and all the reasons mentioned above. I would bet if the two stroke manufacturers could compete on cost with Briggs you might see a difference? 4 strokes are also easier to race/maintain for the non engine builder or tuner also. If stock classes is your thing, LO206 is awesome, kinda like Kt classes were back in the 80's. Karting has changed and I don't see the 2 stroke making a comeback with the current technology of the Mx 4 stroke. They are lighter and more powerful than ever. I used to be a 2 stroke guy but now a 450 is my favorite. I wouldn't go back.

  6. #6
    Well said Kevin. The only problem with the KT's was, even when they were blueprinted, there were fast ones and slow ones. They were not all equal. The whole having to blueprint thing got too expensive for most people too. The HPV KPV thing worked for a while.
    Little things like buying a 100cc IAME piston is over $150 here but I can buy an Asso Werks piston from England for under $50 delivered. Or I can get a top fuel piston for about $100 here.... I agree the UAS guys with their 450s are onto something good. In fact the dirt racing in general seems to be doing a lot better than pavement if Bob's is to be believed.

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    Quote Originally Posted by moebiusgold View Post
    Well said Kevin. The only problem with the KT's was, even when they were blueprinted, there were fast ones and slow ones. They were not all equal. The whole having to blueprint thing got too expensive for most people too. The HPV KPV thing worked for a while.
    I agree with you on the KT, that cast in liner does not give you consistent cooling between engines. The best KT I ever tested on my dyno, had the highest EGT reading I had ever seen on my dyno, and as I was told, that engine won a lot of races.
    Mike Burris' dad once told me about a KT he had blueprinted and just could not get it to put out the horsepower of the other nine engines he had done at the same time. He cut the barrel in half, lengthwise, removed the liner, and found a big void in the casting just above the exhaust port. Suspicions confirmed!!
    From the desk of Al Nunley 512-630-6215
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    I raced 2 cycle open back in the early days of dirt racing and street racing. Rn a 100 cc Komet built by Mark Dismore,Loved the speed and lack of problems.When the 4 strokes took over I tried them, hated it. At one time I had 8 karts and sold everything because there was not any 2 cycle stuff running around me. I would get back into if there was a nice field of 2 stokes. I won lot of races with that little motor including 2 B&S State championships. Didn't have $1500 in the motor and only put a piston in it one time. Miss those days

  9. #9
    helmet painter and racer Ted Hamilton's Avatar
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    The IAME KA100 would be PERFECT for a fun oval class. 22hp, TaG, one piece pipe, easily tunable carb. Also, $2600. But 50 hrs. run time before major rebuild. I wonder how many hours a top shelf clone or Briggs gets these days? Amortizing the engine cost over the several years it would last, might not be a bad deal after all.

  10. #10
    4 Cycle Advanced User rainman's Avatar
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    Ted, I think that engine is a good thing but to my knowledge it is basically a detuned version of a reedjet with a clutch and I doubt you can put 50 hours between rebuilds. It will need a piston kit way before that hours IMO. Still a great deal but hasn't been successful in other places they have tried (Australia for example).

  11. #11
    helmet painter and racer Ted Hamilton's Avatar
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    25 Hours on top end. Aussie reviews vary. It is a 100cc reedjet.
    If you consider hours on motor per event, it's sobering. 8 lap warmup (14 second laps) x 2 = 4 mins. 12 lap heat - say, 10 mins. 25 lap feature, say 15 mins. So, 30 mins actual racing run time per event. That means you could run several UAS seasons before any major service.... Also, I'd love to see how it would do in DD format...sans starter.

  12. #12
    a two stroke can NEVER be competitive to a 4 stroke on price. The added machining time required to turn 15k is too much. Not to mention you can't use aluminum rods (cheaper to machine) and have to have a two piece crank means more costs.

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    Quote Originally Posted by manyfunnies View Post
    a two stroke can NEVER be competitive to a 4 stroke on price. The added machining time required to turn 15k is too much. Not to mention you can't use aluminum rods (cheaper to machine) and have to have a two piece crank means more costs.
    Designe a four stroke, 100 cc's, that can turn 15,000 RPM and produced 22 hp and see how much it costs! Even 200 cc's, 12,000 RPM and produced 18 hp.
    From the desk of Al Nunley 512-630-6215
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    Quote Originally Posted by manyfunnies View Post
    a two stroke can NEVER be competitive to a 4 stroke on price. The added machining time required to turn 15k is too much. Not to mention you can't use aluminum rods (cheaper to machine) and have to have a two piece crank means more costs.
    i think you have that backwards, there are a ton more parts in a 4 cycle. Pound for pound, horse power for horse power the 2 cycle is the winner. Less parts to make, and assemble.

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    Quote Originally Posted by Skeet View Post
    i think you have that backwards, there are a ton more parts in a 4 cycle. Pound for pound, horse power for horse power the 2 cycle is the winner. Less parts to make, and assemble.
    Agreed

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    Quote Originally Posted by alvin l nunley View Post
    Designe a four stroke, 100 cc's, that can turn 15,000 RPM and produced 22 hp and see how much it costs! Even 200 cc's, 12,000 RPM and produced 18 hp.
    Realistically, who would want a 100 cc 4 stroke that turns 15000? You can essentially buy a big 4 stroke off the shelf that makes 60ish hp and turns around 12000. It's apples to oranges. Both platforms make power in different ways. But rpm, hp, and all the numbers aside, I choose a 4 stroke for ease of maintenance and reliability in the "open" community. I've seen too many stuck pistons and simple little things that just will not let a 2 stroke run consistently at its peak. A small crack in the pipe does whacky stuff to a 2 stroke. A little weather change makes them finiky. Too hot, you stick. Not enough oil mix, you stick. Too cool, you're down on power. My liquid cooled 4 stroke just does what it does every time I drive it. Change the oil every 3 races and keep gas in it.

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    Quote Originally Posted by Ted Hamilton View Post
    The IAME KA100 would be PERFECT for a fun oval class. 22hp, TaG, one piece pipe, easily tunable carb. Also, $2600. But 50 hrs. run time before major rebuild. I wonder how many hours a top shelf clone or Briggs gets these days? Amortizing the engine cost over the several years it would last, might not be a bad deal after all.
    Its the $2600 initial cost that stops most people. It would me. I don't have that in my 450.

  18. #18
    4 Cycle Advanced User rainman's Avatar
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    Quote Originally Posted by manyfunnies View Post
    a two stroke can NEVER be competitive to a 4 stroke on price. The added machining time required to turn 15k is too much. Not to mention you can't use aluminum rods (cheaper to machine) and have to have a two piece crank means more costs.
    Wrong again. I spent much more money the seasons running my stock flathead than I do in a regular season running my stroker 131cc Sudam in UAS. We are talking 45-55 hp vs something between 10 and 15 hp. You rebuild a stock engine every 8 -10 races (classes I mean, not even races) if you want to be competitive. That's my Sudam. One of my 100 cc has like 10 races on asphalt and 2 days on dirt making close to 30 hp and no work on that. It might need just a piston kit with pin which is less than $150 or I can wait till it just messes up the piston and still be cheaper than a rebuild for a 4 cycle, and much more simple to do it yourself than messing with valves. Don't get me wrong, I loved racing stock classes too and supporting stock 4 cycle builders who treated me great, especially Hi Tech or my good friend Jr Wilburn.

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    Quote Originally Posted by manyfunnies View Post
    a two stroke can NEVER be competitive to a 4 stroke on price. The added machining time required to turn 15k is too much. Not to mention you can't use aluminum rods (cheaper to machine) and have to have a two piece crank means more costs.
    I just noticed this, maybe you're not aware of the fact; you can take a Parilla 100 cc, out-of-the-box, bolt it to your kart, add a pipe, and turn 15,000 RPM. Absolutely no problem whatsoever. And if you run direct drive, on the average Sprint track, you turn 8000+ out of the corners and maybe 16,000+ at the end of the straight, and that was better than 30 years ago that I did that. That engine makes in the neighborhood of 22 hp, out-of-the-box (I don't know what machining you're talking about) and the operating RPM range is near two times plus what a four cycle would use. Obviously that means a much lower gear ratio.

    Lap times, all things being equal, are achieved with the horsepower under the usable curve. I don't know if you're aware what that means, but the usable curve of the Perilla is twice that of your four stroke.

    And where did you get the idea that a three piece crankshaft creates more expense to operate. They're a lot more expensive, on initial cost, than a four stroke, but in most cases, they last the life of the engine, other than an occasional new crankpin. Not always.

    Perhaps you should study up on two cycles??
    From the desk of Al Nunley 512-630-6215
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  20. #20
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    Quote Originally Posted by alvin l nunley View Post
    Designe a four stroke, 100 cc's, that can turn 15,000 RPM and produced 22 hp and see how much it costs! Even 200 cc's, 12,000 RPM and produced 18 hp.
    I can build a Briggs animal that will make that 22hp at half the rpm of the 100cc 4 stroke you mentioned, with twice the cc's and half the cost of the 2 stroke, and be reliable for at least a full season of racing before needing rebuilt, and even then the rebuild would only consist of new rod bearings and rod bolts, piston and rings, lapping the valves and replacing the valve springs basically....$200 or less total rebuild cost. Not sure what you were getting at with that post Al. Most of the 2 strokes i race against all end up having to pull off the track before even finishing a 20 lap feature because of some type of problems, usually either stuck piston or broken belt on the belt drive setup....while the little 4 strokes are still going, and are usually the only ones left on the track. I love the sound of the 2 strokes and the smell of the exhaust, i grew up riding and racing them, but when it comes to plain reliability, cost and dependability, it is hard to beat a 4 stroke. The only real advantage on a racetrack that i can see with a 2 stroke would be the power to weight ratio....they weigh less and make more power in stock form. But at the same time, can usually build a 4 stroke that will easily compete with the 2 stroke for less money and more reliability.

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    It's just my 2 pennys worth but, not many people understand how to adjust a 2-cycle carb, let alone just plane tune the engine. If you don't know how to do these things you end up with a stuck piston, burnt bearings or many other things. Lots more to it than just opening the box, bolting it on then go racing. Sure, you can by a builder prepped 4-cycle, just bolt it on and go racing. Kinda takes the fun out of it for me. If I ever am forced to quit racing 2-strokes, I QUIT!

    Whatever you decide to bolt on, just remember this. GO HAVE FUN!!!

    Brian #89

  22. #22
    4 Cycle Advanced User rainman's Avatar
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    Quote Originally Posted by W5R View Post
    I can build a Briggs animal that will make that 22hp at half the rpm of the 100cc 4 stroke you mentioned, with twice the cc's and half the cost of the 2 stroke, and be reliable for at least a full season of racing before needing rebuilt, and even then the rebuild would only consist of new rod bearings and rod bolts, piston and rings, lapping the valves and replacing the valve springs basically....$200 or less total rebuild cost. Not sure what you were getting at with that post Al. Most of the 2 strokes i race against all end up having to pull off the track before even finishing a 20 lap feature because of some type of problems, usually either stuck piston or broken belt on the belt drive setup....while the little 4 strokes are still going, and are usually the only ones left on the track. I love the sound of the 2 strokes and the smell of the exhaust, i grew up riding and racing them, but when it comes to plain reliability, cost and dependability, it is hard to beat a 4 stroke. The only real advantage on a racetrack that i can see with a 2 stroke would be the power to weight ratio....they weigh less and make more power in stock form. But at the same time, can usually build a 4 stroke that will easily compete with the 2 stroke for less money and more reliability.
    Good luck trying to get 22 hp from a 4 cycle and doing that cheap. Just the parts to get that power will cost you more than a stock 2 cycle. Besides a stock reed 2 cycle from the late nineties will get you 26-28 hp stock on gas and will be completely reliable running the needles reach which everyone can do. Even more, the last 100 cc water cooled reeds on gas from the early 90s were close to 35 hp stock on gas and you can find one for $500 now in perfect shape barely run. A top stock clone from a good builder, not junk, will be in the $1,500s range and will need freshening every 8-10 outs if you want to be competitive here in the South East. I have run both 2 and 4 cycles and know better, I am not talking about something I haven?t tried like some people that have never run a 2 stroke and talk about the cost without any knowledge. Running a 2 stroke carb is easy if you run it reach on gas, more complicated on methanol if you try to run it lean which is not necessary.

  23. #23
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    Quote Originally Posted by rainman View Post
    Good luck trying to get 22 hp from a 4 cycle and doing that cheap. Just the parts to get that power will cost you more than a stock 2 cycle. Besides a stock reed 2 cycle from the late nineties will get you 26-28 hp stock on gas and will be completely reliable running the needles reach which everyone can do. Even more, the last 100 cc water cooled reeds on gas from the early 90s were close to 35 hp stock on gas and you can find one for $500 now in perfect shape barely run. A top stock clone from a good builder, not junk, will be in the $1,500s range and will need freshening every 8-10 outs if you want to be competitive here in the South East. I have run both 2 and 4 cycles and know better, I am not talking about something I haven?t tried like some people that have never run a 2 stroke and talk about the cost without any knowledge. Running a 2 stroke carb is easy if you run it reach on gas, more complicated on methanol if you try to run it lean which is not necessary.
    I grew up riding and racing 2 strokes, and 4 strokes both. I build my own 4 strokes for open racing, and compete in RWYB with an open small block. I had an open predator that i had less than $800 in total, that would run up front against a field of 2 strokes in RWYB without a problem. Last season i switched to the Briggs Animal, a little more expensive to build, but still cheaper than buying a 2 stroke, unless we are talking about MX based 2 strokes like the CR250 or 125's.

    22+ hp can be had with a 212cc predator engine ($90-120 max) with stock bore and stroke, using a big valve head with decent port work ($200-250), good cam and springs ($125-130), billet flywheel and rod ($200) and tilly carb/intake manifold ($150-200), spending around $800-850 total with no machine work other than the big valve head....this is assuming you can build your own engines like most like to do, and buy a big valve head to bolt on, either way it is easily done for $1000 or less. What 2 stroke kart based engine can be bought for $1000 or less and be race ready for that kind of money and will actually compete? The guys i know using Sudams and other kart based 2 strokes have quite a bit more than $1000 in them, and are still behind me on raceday, so what gives?

    I have thought about going with a 2 stroke for RWYB racing honestly, but i see guys having too many problems with them and having to pull off the racetrack before a 20 lap feature is over and that is what deters me from using one. I believe if i do make that switch, i would go with something like a Cr250 or 125 with a little work done to it personally. I have one friend who has ran a mostly stock Cr250 for a couple of seasons, with the stock transmission setup still on it and stock carb and has literally dominated the RWYb racing with it last season. He switched it to methanol this season and has already stuck the piston twice trying to get it right on the methanol, he finally gave up and switched back to the stock carb and on gas, and i dont blame him one bit for that. I didnt say what i said earlier to start an arguement at all, so please dont take it as that. I was just making a point that some can build the 4 strokes to make good power without spending a ton of money on them, you just have to know what you are doing and what parts combinations work well together, that does take some time to learn. Guys are making 20+ Hp with stock bore and stroke predators and have been for some time now, usually with well built heads on them and big lift cams and ratio rockers, using tilly carbs. Im not saying you can just take it out of the box, add these parts and have 20+ hp, there are things that need to be done along with the parts, but anyone can do those things once they learn how these engines work. I have spent alot of time in the shop and on the racetrack trying different things to see what works and what does not, because i am not just out there to have fun, im out there to compete also, that is where the fun is for me in racing. I love the sound of the old CR500's and wonder just how wicked one of those would be on a kart, if it could even be hooked up on the small tracks where i race...that would be one wild ride, and would be legal for RWYB. I have absolutely no interest in the stock clones, i refuse to pay the kind of prices they are going for right now, and honestly am glad i do not have to race in the southeast...no way i would want to spend that kind of money on engines, let alone the kind of tire bill it requires to compete down there no matter what class you are racing, to me it is just ridiculous honestly and has gotten out of hand in the southeast.

  24. #24
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    Stock gas burning Leopards make around 30hp and have a huge range pulling very strong from 7 to 17K. If turned up to 17K they are good for 12 hours without any service at all. Limit the peak rpm to 16,400 and they go 20 hours plus without touching them. They are no longer the "current" choice for TAG racing so entire engine packages including the whole exhaust and cooling system are going for $1,000 or less.
    You can bump the power about 2hp by switching to an alky carb and running methanol and even more power can be gained by using a better pipe. I don't understand why they are not more popular with the circle track racers in the southeast. They are easy to find and easy to run. Best performance for the money in karting.
    Steve O'Hara

  25. #25
    4 Cycle Advanced User rainman's Avatar
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    I think Steve post is a good answer to the question. You can get a good used 100 cc reed for way under $500 if you know where to look for them. I bought an even faster air cooled rotary Italsistem that was basically like new, stock bore, and on my asphalt chassis and direct drive configuration is faster than most modern water cooled 125 TAG engines. I paid $400 for it. I don't know in what dyno you get 22 hp on a predator built with less than $1000 but I had built some open clones too and not only they cost money but they are even weaker than a 2 cycle. I have at least 10 races on my reed PCR and hadn't touched anything on it, and obviously it has more than 22 hp. I don't dislike 4 cycles, I just don't think they are cheaper and even if rods and cranks are way cheaper for 4 cycles I have only broken one rod and 2 cranks in way over 20 years racing and only one of the cranks was on a stock 100 cc. The rest was on my open 131 Sudam and after several seasons.

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    There are true stock appearing clones/honda/predators that are at 20hp or more Rainman. Check out Poboy's Greasy Nails Club on facebook, you'll see builds on there, with dyno sheets to back them. I know everyone isnt going to be able to build the same way or the same power, thats completely understandable. Im not talking about just buying parts and bolting them together, it takes knowing what parts work best together just like you would with a 2cycle. It gets harder to get more power once you get past a certain point, and from there your power only goes up in tenths of a hp increments instead of half of a hp increments, in my opinion. i was that kid in the garage who would tear engines apart just to learn how they worked, and see if i could put them back together right, i learned early on how to work on my own stuff, and was lucky enough to have a dad who could work on or build anything, and i learned everything from him. Im good friends with some of the best small engine builders in the country and i have learned alot from them just since ive been in kart racing, im thankful for that, and for this great site because i learn something new everyday here also.

  27. #27
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    Quote Originally Posted by W5R View Post
    There are true stock appearing clones/honda/predators that are at 20hp or more Rainman.
    There are 100cc 2 strokes that can exceed 22 HP right out of the box, just add a pipe. Oh, and they have a usable RPM range of 8000 - 16000 plus with no clutch!!
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    Bench racing can be fun!
    Usually the horespower goes up....

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    Quote Originally Posted by flattop1 View Post
    Bench racing can be fun!
    Usually the horespower goes up....
    you don't believe 22 HP out-of-the-box?
    From the desk of Al Nunley 512-630-6215
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    What does the usable rpm range have to do with anything? Those 100's that are making 22hp on a pipe are probably quite peaky and make "usable" power from 12000-16000 with the peak power at 15000ish. A 4 stroke, also making 20ish hp will likely be very peaky as well. It will probably build "usable" power from 5000-10,000 with peak around 8500. So we're still talking about the same 4000-5000 usable rpm sweep. Either way, final gearing is going to determine how it applies that power. On the same track, they will require very different ratios because of that rpm difference but essentially the same results. Each platform builds it's power different. That's the joy of having options.

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