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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
    Comments compliments criticisms and questions always welcome.
    If the data does not support the theory, get a new theory. (Al Nunley)

  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

  4. #4
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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!!!!

  5. #5
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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.

  7. #7
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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
    Comments compliments criticisms and questions always welcome.
    If the data does not support the theory, get a new theory. (Al Nunley)

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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.

  13. #13
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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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    If the data does not support the theory, get a new theory. (Al Nunley)

  14. #14
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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

  16. #16
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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.

  17. #17
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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.

  19. #19
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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
    Comments compliments criticisms and questions always welcome.
    If the data does not support the theory, get a new theory. (Al Nunley)

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