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Discussion Starter · #1 ·
anyone know which style of engine typically has the best power to weight ratio, the v or the inline? I'm thinking of building an off-road/on-road bike and was trying to figure out which engine would be the lightest fit with out sacrificing power. what about v twin vs v4? Im imagine at equal displacement the twin would be lighter, but would the power coming out of the four offset its weight to place it in the running as well?
 

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There's way too many ways to build a motor to answer that question with any kind of authority. Look no further than the differences between a boat anchor Harley 883 and the Ducati Panigale 1199 for proof just inside the V-Twin category.

If I had to guess, I'd say that a highly strung thumper is going to have the best power/weight ratio. V engines tend heavier for the same cylinder count because you need twice as much of everything on the top end (blocks, heads, cams).
 

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UnicycleMode
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I think this question boils down to, "How do you want it to handle?". :thumbsup:




Best power to weight ratio is by far a 2 stroke 500cc single, but, you sacrifice low end torque and ride-ability in a huge way to run an engine like that. Other options are what sort of bigger engine really sorts out a dual sport. CF Mag had a trio of Ducati swapped Cagiva dual sports converted to supermoto's that really highlighted what your asking about. I would start there and work out from that point if I was going to answer your question in detail.

Best beginning would be a SV650 or NT650 engine mated to something dual sport oriented... and why not just buy a V-Strom or a Versys at that point? See what I'm saying? It's extremely subjective to how a rider prefers a bike to handle. I am cool with a 435lb dual sport/adventure machine, most are not into that sort of weight to wheelie up and get over a log or power it through a rock garden.


Not to say "just buy a dual sport or supermoto", but I guess that is kinda what I'm saying. Find the fasted thing built for the purpose or expect either a heavy, or hard to ride bike using a street bike engine or a hard tuned offroad engine. The factories have honestly done a pretty damn good job giving us platforms for adventure bikes in the past 10 years or so.


Just my 2 pennies on the matter. :thumbsup:
 
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I would look at this from another angle ..... first decide what you want from the engine in terms of HP & torque then find the lightest engine that will deliver what you want

For the best power to weight ratio a 500cc 2 stroke has to be hard to beat not because they are overly powerful but because they are light, from your post that wouldnt suit what you are after but worth mentioning as an example
 

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sickboy
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4cups is right, its best to decide how much power you want then pick an engine from there... but for what its worth...

Honestly the best power to weight ratio is a cr500 motor as they only weigh 55 lb's and easily make 60+ Hp with very minor tuning and up to 100hp if you wanna run methanol and such. But as ratty said, it has its drawbacks.
Pretty much MOST (not all) high performance bike motors from the past 6 years or so have right about a 1:1 power/weight ratio weither it be a twin, inline 4 or single.
Ducati 1098 (twin) is 160hp and the engine weight is right around 170lb's.
2006 cbr1000 (I4) - 160hp - 160lb's
sxv550 motor (twin) - 70hp - 75 lb's
crf450r motor (single) - 50-55hp - 65lb's

get my point, any newer HiPo motor is damn close to 1:1, The real key to a fun good to ride bike is having the correct power to weight ratio of the entire bike. You dont want a 160hp in a bicycle frame, itd be too much power to ride which makes you tired and sloppy, especially offroad. Personally, id say if your building a enduro/tracker type build for cruising threw town and the ability to hit some fire roads or power line trails id try and keep it under 300lb's and make sure its over 50Hp and you will have tons of fun with it.
 

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Look up Aprilia RS250

mine is less than 240 LBS, and has 69 HP at the rear wheel
Will beat a CR500 in any road frame
Actually a picture of a RGV/RS250 engine is to the left of these words

Probably not the best for off road though.....


http://www.gizmag.com/go/2542/
 
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What about the KTM 990-1290 v twins? Anyone know how heavy they are? The make great power and torque.
 

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Will Tig For Food
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Look up Aprilia RS250

mine is less than 240 LBS, and has 69 HP at the rear wheel
Will beat a CR500 in any road frame
Actually a picture of a RGV/RS250 engine is to the left of these words

Probably not the best for off road though.....


http://www.gizmag.com/go/2542/
FFS that sounds like all kinds of nasty track weapon...:rock:


I was a dirty-biker for years and maybe I'm bias, but a plated 450 honda that's modified was my version of maximum pavement fun.

Somebody needs to develop a decent turbo setup for a 450 single and retire young
 

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FFS that sounds like all kinds of nasty track weapon...:rock:


I was a dirty-biker for years and maybe I'm bias, but a plated 450 honda that's modified was my version of maximum pavement fun.

Somebody needs to develop a decent turbo setup for a 450 single and retire young
Turbo for the mx/dual sport/supermoto 450s?:party-smiley:

Yes please. That would be bonkers.
 

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Discussion Starter · #10 ·
I see my thread attracted several offroad enthusiast. Sorry I was out of pocket for a couple of days, my gsx-r project is getting way more complicated than i had anticipated. this bike is a future build i've got in mind, and because the field is wide open i wanted to try to go ahead and start narrowing things down. I think i'm wanting something a little more for the street than you guys are imagining. I live in mississippi and as the suzuki i have in my shop will testify, the roads are shit. I'm looking for an engine that will hang with the big boys, at least til say a buck twenty, and can be geared so that it has plenty of pepp at all ranges. I've always been a fan of low end torque over horsepower and generally favor a v4 setup but i want a bike that i can handle easily on rough roads, gravel and mud (my house is on stilts in the middle of a flood zone). So not so much a looking-for-adventure bike, as it will be a driving-to-work-is-an-adventure bike. that being said, you don't grow up in the south and not take ur car/truck/bike thru the woods at least a time or two so i don't want a street bike with mud tires either. in the meantime, I've going to get a 750 interceptor in a few days, Im gonna c what i can do with that. I've never tried this type of project so i figured since it was cheap and already run down, it wouldn't be a bad start for now.
 

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Take whatever street bike you want, swap over some dirt bike forks with heavier springs, and jack up the rear end. Toss on something like a Dunlop D616 or Avon Distanzia and go to town.
 

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Discussion Starter · #12 ·
i was thinking of cutting the rear end completely off :Evil_smile:. i'm gonna c what else i can trim off too, it weighs 523 lbs. I'm ready to get my hands on it and get started. I've been checking out test ride videos all week and its a pretty sweet sounding bike. after i'm done with it tho i'm gonna go for something a little more agile. thinking of starting that project from the ground up provided my welding skills improve by then.
 

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Will Tig For Food
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I see my thread attracted several offroad enthusiast. Sorry I was out of pocket for a couple of days, my gsx-r project is getting way more complicated than i had anticipated. this bike is a future build i've got in mind, and because the field is wide open i wanted to try to go ahead and start narrowing things down. I think i'm wanting something a little more for the street than you guys are imagining. I live in mississippi and as the suzuki i have in my shop will testify, the roads are shit. I'm looking for an engine that will hang with the big boys, at least til say a buck twenty, and can be geared so that it has plenty of pepp at all ranges. I've always been a fan of low end torque over horsepower and generally favor a v4 setup but i want a bike that i can handle easily on rough roads, gravel and mud (my house is on stilts in the middle of a flood zone). So not so much a looking-for-adventure bike, as it will be a driving-to-work-is-an-adventure bike. that being said, you don't grow up in the south and not take ur car/truck/bike thru the woods at least a time or two so i don't want a street bike with mud tires either. in the meantime, I've going to get a 750 interceptor in a few days, Im gonna c what i can do with that. I've never tried this type of project so i figured since it was cheap and already run down, it wouldn't be a bad start for now.

Everything you're saying is exactly a built super to the T. 1-120 is no problem if it's geared correctly.

Modded out 525 that's feather light VS lot's of shit that's 100 lbs heavier...
 

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BLACK BELT
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Reposted from another thread. Seems appropriate.


RZ350/Banshee Engine with 535cc cylinders + 10mm stroker crank.

This dyno was done when making the pipes. Further tuning brought the HP up to 120.

The engine is reliable and weighs 75 lbs.



The stock engine can be modded up to your needs. No need to go with aftermarket cylinders, unless you want big HP.

EDIT: In case you don't know, this is a two cylinder two-stroke engine used for street and dirt.
 
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