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Josey H11D

400hp/liter

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This is just a question. Not planning a build anything like that. Does anyone know if its possible to achieve 400hp/liter out of a single cylinder 125cc 2 stroke? Naturally aspirated no nitrous

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It’d probably be difficult with a manufacturer’s already existing 125cc 2 stroke motor.

I would think that it would take a well balanced engine with light parts (read expensive metals to get the strength you’d need) to reach the RPM necessary for 50 hp with a 125cc thumper.

I have heard of a Yamaha TZ250 (twin cylinder street going two stroke) getting to almost 100 hp.  However the power band was almost non existent.

Please report back if you’re able to do it.

   Greg

Edited by gregsportster

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An Aprilia RS125 GP machine is in the ballpark. I believe the last version they produced was close to 50hp at the crank. The KTM 125 GP machine Márquez rode in 2010 was in the high 40s as well.

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9 hours ago, Studhaeuser said:

Its done all the time in road racing and karting. 

Is it? What motor has 400hp per liter naturally aspirated?

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1 hour ago, Zinergy said:

Is it? What motor has 400hp per liter naturally aspirated?

1000cc's is a liter, a 125 is an 1/8 of a liter so 50hp is his goal.  125cc shifter karts can exceed that, so yes it's doable but not really ridable.   

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Is it? What motor has 400hp per liter naturally aspirated?

Let’s see here,
1 liter is equal to 1000 cc
Or
1 liter is equal to 61 cubic inches.

I don’t think you are going to see 400hp from a engine that size.

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5 minutes ago, kxlubber said:

A friend told me a story about building a 400hp 1L NA EFI motor in between projects at work, but he worked at ILMOR.

He's only talking about building up a 125cc 2 stroke engine so he wants to hit 50hp which has been done many times.  If you could build a v-8 2 stroke that shared the same basic engine build and the same bore to stroke relationship as the 50hp 125's have you would have a 400hp 1 liter engine.  

You'd probably need about 13-15k rpm or higher redline though.

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51 minutes ago, MentalGuru said:

1000cc's is a liter, a 125 is an 1/8 of a liter so 50hp is his goal.  125cc shifter karts can exceed that, so yes it's doable but not really ridable.   

Theres the math that should have been in the original post.  You have laid out the equation.  The OP should thank you.  

Dyno charts of 50hp 125cc 2 strokes?  Lets see them

Edited by WRider995
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He's only talking about building up a 125cc 2 stroke engine so he wants to hit 50hp which has been done many times.  If you could build a v-8 2 stroke that shared the same basic engine build and the same bore to stroke relationship as the 50hp 125's have you would have a 400hp 1 liter engine.  
You'd probably need about 13-15k rpm or higher redline though.

I missed that he was talking about 2stroke. TT and wine
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6 hours ago, gregsportster said:

I have heard of a Yamaha TZ250 (twin cylinder street going two stroke) getting to almost 100 hp.  However the power band was almost non existent.

the street version is the TZR250. And wouldn't get close to 100 hp without some serious magic, and being a literal time bomb.

The TZ250 is (was) the production race version. I raced them for many years, and never came across one that had 100 hp. Even the one that won the AMA National championship with Rich Oliver aboard. (his was pretty close, with a power band unrideable for most people).

 

Edited by Hammy-56

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1 hour ago, MentalGuru said:

1000cc's is a liter, a 125 is an 1/8 of a liter so 50hp is his goal.  125cc shifter karts can exceed that, so yes it's doable but not really ridable.   

I get what you are trying to explain but that's not how engines work so it makes it a goofy question to ask that way. There are many other variables when increasing engine size such as increased mass vs rpm etc.

I have seen 125cc shifter karts with 70hp but that doesn't mean if you built the exact same engine but 8 times larger that it would make 560hp. It wouldn't.

Edited by Zinergy

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14 hours ago, Josey H11D said:

This is just a question. Not planning a build anything like that. Does anyone know if its possible to achieve 400hp/liter out of a single cylinder 125cc 2 stroke? Naturally aspirated no nitrous

Wheres my flynrod?????????????????

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14 hours ago, William1 said:

Yes, but the engine would not last long and it would be hard to ride, basically a drag bike engine. It begs the question, why? BTW, Nitrous is the lazy mans way to power.

He didn't ask about anthingnrideable............

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