Sure, when you destroke a motor you're reducing leverage but that is due to the fact that you're decreasing the displacement of the cylinder and thus making a smaller engine. The main reason that oversquare engines can make more high rpm HP is that the engines can be designed to withstand the higher rpm that a more radical camshaft design and cylinder head design can take provide as the shorter stroke bottom end can tolerate more revs as can the piston to due the slower piston speed of a shorter stroke engine.
In other words more radical valve timing and breathing can be used which wouldn't provide much advantage to a longer stroke engine that couldn't rev near as high in any event. When you make a multicylinder oversquare engine of the same displacement you can really cut your piston speed at a given rpm and the crank has a short throw which will really allow it to rev if it is given adequate valve timing and cylinder head design, just as the Jap multicylinder bikes are set up to do.
However, you could take one of their multicylinder bikes and design a strong low speed power bike by modifying the cylinder heads and camshafts for better breathing at the same rpm as our Sportster engines. At that point the multicylinder bikes would cease to be the gazillion rpm screamers as currently designed, and they wouldn't make near as much peak HP, although they still might be able to rev a bit higher simply because things wouldn't fall apart if they did so.
Anyway, I have no more time now until likely tomorrow. You might want to go through Aaron's recent posts of the last month or so and you will find something on this. A short stoke motor can make more reliable high rpm HP before it falls apart and that is why Ralph and I have been talking about it.
The power band of a hp cc motor is NOT going to be in the same place as an 80hp Motor One last point Case in point, say you built two bikes, an 80HP and an 80HP , the rider will probably be casually riding closer to his peak TQ powerband -which will come at a much lower rpm band, than the rider who has the 80hp who might need to keep his RPM's up near just to produce that power.
I have been wrong before, but I thought that moving the crankpin further out on the flywheel increases the leverage produced by the combustion pressure, the same way a longer wrench increases torque. So, the same pressure exerts more force, because it now has more leverage during the portion of the stroke when the crankpin is horizontal where all the propulsion occurs.
As far as reliability is concerned, My high compression 80 never had any bottom end issues. It had I toured on it and everything. I did one set of heads that were pretty radical valve job wise right on the edge and.
This motor was more peaky than when it was milder, but not to the point of being unfun to ride. I do know that it would result in a higher rpm torque band, and would reduce low end power compared to a stock stroke version. I think peakiness is more tied into the cam profile relative to the motor. You could build it to have a broader power band, or not.
As far as RPM range, you can only spin one of these motors so fast. Racing motors will hit k for breif periods of time, but they will not last long like that. You are best staying under , for longevity From what I know any motor with as much mass to it's reciprocating assembly as either stroke version will be limited in it's safe redline.
If you build with an eye towards higher RPMs, short stroke or not, you will be taxing the crankpins ability to harness all of that wieght which destroking will not reduce.
My point was the higher rpm bikes jap are built and designed to spin that high via multiple smaller parts, and that is not the case with a two valve sportster motor. So basically I'm saying that piston speed is only one element of a high RPM motor, and sportsters will always lack some of the other elements. I beileve that a street motor should be built to run in the RPM range which allows the design to retain some reliability, which in the case of an XL is or less.
If you stroked it beyond stock you wuold likely want to lower this. The question is can you build a reliable, fun, 80 hp, cc motor in this rpm range, and I think you can! LOL a Turbo! But why would anyone waste money hot rodding an for the street, when a simple 3. PS- some of my posts in this thread may sound contradictory, as I'm talking of two distinctly different ways to produce power -ie: one way and probably the best for the street is just a simple big bore kit, and my second way is just mainly fantasy- and thats the short stroke higher revving XL motor, and to the best of my limited knowledge on this subject- I believe no one on this forum has ever even short stroked an XL motor for the street?
The short stroke will hurt the torque A 3 inch stroke chevy is very peaky and the torque sucks thats 1 reason everybody builds the ,gobs of torque. The stock has a good rod ratio for tq and hp at 1. Ya know if you mounted that bad boy in a sidecar with some pipe bending skills!! The short stroke will hurt the torque. I'm afraid that it's not that simple. You can make more power with the same displacement simply due to the fact that the short stroke engine can be made to rev safely for a longer period of time.
Yes, A HP will not have to rev near as hard as a 80 HP in order to accelerate as quickly. Don't forget that it also increases the displacement of the motor whenever the crankpin is moved out. If you decrease the size of bore proportionally in order to maintain the same displacement at the same time, power output isn't going to change quite so much. The lack of torque of a Pushing the RPM high to get all the horses ponies it can provides is exciting And what an incredible sound with my supertrapp mufflers!!!
Saturday afternoon, I came back to the circuit after 3 weeks of freezing weather. Under RPM, i haven't got enough power to fight against "rice roadsters" The EXACT same cylinder pressure will equal higher torque output is the crankpin is further outboard from the centerline of the crank. How much, I can't say, but some is a given. This is regardless of displacement. Torque is produced by cylinder pressure, it does'nt care what displacement caused it. A small motor with "x" pressure will equal the torque output of a big motor with the same pressure, unless the leverage you send it to is increased.
Also the pistons will dwell at tdc and bdc longer, with a stroke increase, giving the burning mixture longer to push on the piston.
All of this theory is only somewhat applicable in practice, and every combination is influenced by a buncha variables including rod length to stroke ratio, bore to stroke ratio, airflow potential, cam timing, compression ratio, cooling abilities, ad ifinitum.
The will be more like hp. Some combos are "happier" than others, even if the theory goes against it being so. If you're talking about the old c. Z28 motor 4 inch bore w 3 inch stroke you're also adding 81 ci of power producing displacement if the same bore engine is stroked out to c.
I believe that the differences in power output wouldn't be too great between two motors of the same displacement with similar camshafts and valve timing, etc. Yes, there would be some difference in powerband characteristics between the two motors but not anywhere near as much as there would be once the shorter stroke motor was optimized for reving and higher peak HP output by using different cylinder heads, valves, valve springs and camshafts, etc. Anyway, it's been a good discussion.
It has been a good discussion. It's good to talk and debate about this stuff, because it keeps one thinking critically, and keeps ones knowledge fresh on the mind. This particular discussion seemed to be more about starting with an and developing it as much as possible, so I figured using the crank and cylinders you already have made sense.
Yeah, this has been a good thread. Just shows ya there are lots of opinionated.. No disrespect meant to anyone. Myself I'm goin with a shorter stroke and bigger bore So, I got that goin for me..
Don, That will smoke a up to a point where the will get on the pipe and the will just run out of air,given the same cam and heads. Qusstion is by that time is it too late to catch that ? If the guy driving that car is better than the guy,said will never catch him Now does the share the same crank as a ? Now ol38y if ya go 4x3 that would give you CC but the rod ratio needs to be about 1. Rocket, You're a good man and I always enjoy your posts! I have little disagreement with anything that you have said in this post except that I think that an set up in a similar way as a may like holding higher rpm a bit better due to less reciprocating weight.
Of course there is no substitute for cubic inches! As you have implied, generally a bigger motor putting out the same HP has the advantage of a broader powerband. Of course with smilar heads and camshaft that will still be making more peak HP than the due to it's larger displacement. Even if you detuned the to make the same peak HP as the , it ought to smoke the as it should have an even broader powerband.
I have been eagerly watching your Stage 1 carbed 80 HP project! Ralph, Look at my earlier post where I discuss speaking to Dan at Naliins' about this An X1 Lightning gets hp out of a reliable streetable production bike by basically using the the same bottom end components as the early You can bolt the Lightning top end on an earlyy and get hp but I think you will only get in the high 90's on a due to the fact the has heavier flywheel than the ones shared by the Buell's and the 's this changed on the later models.
As stated in my earlier post if you want to get to above 80 and above it will involve a "full race" rebuild. In addition one thing to consider is since the piston speed should be the same for both motors that should be the same so that is not a real factor but the Buells and early 's will be be MORE reliable at higher RPM's than a regular due to significantly lower rotating mass due to lighter flywheels and pistons The smaller bore motor will be more peaky and need higher rpms to make the same HP as a larger bore motor.
The 80 HP will have to rev significantly higher and stay at higher revs just to make the same amount of power that the 80 HP makes at low and midrange revs. The same is still also true if compared with the HP although the HP will be peakier than the 80 HP I think it could be done. She wont be much fun to ride on the street though.
Think really peaky jap bike! Yeah well I wish somebody would get with it, hey they can take it to Daytona and win the domestic class Wyotec down Daytona. I bet this don't happen:laugh:laugh:laugh:laugh:laugh:laugh:laugh. Of course it maybe possible to extract 80 hp from an cc motor, but it's not going to be easy- nor very streetable or practical.
Hell, I don't even think anyone on this entire forum has a streetable making over 65 HP! It would be waste of time and money. I think he would have some success, as A hot , with no other change than the bore reduced to 3" should still be somewhat stout.
Also obviously you would'nt want an exact clone minus bore. A little less cam, slightly smaller valves,jets, etc might be beneficial, but the same basic idea, anyway. Yeah, a colossal waste of money.
Even with the stage 2 heads and such mentioned before, it's unrealistic. Even if you're only asking for 80 hp,you're asking to double the HP. Let's say the newer sportys run in the 65 hp range, just for an average. That would be like expecting to get hp out of your stage 2 Ain't gonna happen. See where I'm going, here. It's really not much of a stretch. The roadracers were all in the mid 60s, and they had to use stock compression and head castings.
Those bikes were totally streetable, and long lived. An has no rpm penalty from a it will spin at least as fast , it will have a WAY more stable bore, and probably hold more combustion heat in via the thicker liners. Thus using more of it to push down on the piston. The only downside other than shrouding from the close bore walls, is displacement. I say to the OP, do it and see for yourself. But a streetable and long lived 65 HP with a fairly broad powerband is a far cry from a more peaky and has to rev that long stroke motor more to make any power 80 or HP HP also being discussed in this thread, if it were possible that a reliable HP could be built.
I think a streetable long lived hp is possible, therefore It seems like a streetable long lived 80 hp should be. A at 1. An at 1. I kmow that the smaller bore has drawbacks other than displacement over the , but it also has advantages. It seems to me like there should be close to 15hp in headwork, compression, and wilder cams.
Tonight I'll plug it in to my Acellerator II program it's a hassle, because I have to borrow an external floppy drive The Accellertor II has been percent optimistic against dyno runs on the three bikes I've compared. How can i have a 80 HP ? A stock , for the french market, has only 50 HP at he crank Should I change the cams, make a flow bench to my heads? Will my sportster stay as reliable as today?
I would like to upgrade a few more my engine but without future engine troubles I would suggest porting your heads, checking if you have room for conversion valves, and if so install them. Also raise the compression to at least I think it's interesting that you got 65 without cams or headwork. The penalty for going hotter is slightly reduced longevity, and a mildly higher powerband.
It might be a good idea to find early ''89 heads with the bathtub chambers, and mill them to attain the compression. Also at this level of developement, intake and exhaust choice will be way more critical. I like two into one pipes, with the biggest mufflers you can find, and Mikuni 42's. And btw, how did you get that Crank HP measurement? That may be low but 65 is awfully high for those upgrades, IMO. On a dyno bank. Unfortunatly, when my old computer died, I've lost all what I had on the hard disk I don't have a scanner A few month ago, a dealer opened a few miles away from where i live.
I'll go there for a new dyno I've made a few mods since the last dyno recording. I thought my bike was running better since I've modified the ignition wiring wiring. I came back to a separated ignition module, like on my XL after I've burnt 2 integrated ignition modules The bike goes faster to high RPM. About the crank power, it has been calculated about the number of chain links, front and rear sprocket I had. I have a 21 teeth front sprocket, a 48 teeeth rear one and chain links.
He said the loss of power will be worse with a belt secondary transmission Is that true? A stock french provides 38 HP at the rear wheel I'll be waiting to see your NEXT Dyno print out then, and until then- I'm highly skeptical about those claims:rolleyes:. Like I said, the numbers may be low but, the bike was never tuned on a dyno. It was just a base run before I did a conversion. Then, we have a different story. The after dyno was 76 hp and 80 trq.
Lets see if i can put this into something i can understand being more of a Chevy kinda guy. Lets say an is a V8 or Even seeing a dyno run print out is only mildly informative, as they are only really comparable to bikes run the same dyno. I used to work for a guy that would tweak the ambient temps, and run bikes in different gears to minimize before numbers and maximize after numbers.
I got fired for fronting him off for this he later went out of business, in debt and in disgrace, thankfully. The road racers had a large number of dyno runs for a bigger input pool, so you can kinda approximate what they came up with from a comparision standpoint. Yeah this ought to be interesting. The mythical 80HP and now the lost dyno sheet. Albeit down 65 rwhp. Why do ever thing I see on the is that it is so undered powered.
It seems to me that my keeps up with any traffic and them some. On top of that it gets real good gas milage. The only thing is that I have never been on a bigger bike so I don't know the differance. Reynoldston; nobody to my knowledge said the isn't a nise little motor for daily comutes and " keeping up with traffic " IT IS!!!!! It's just not a great candidate for a 80 rwhp platform. That's the debate anyways. Because most of the s are running around with 50ish horsepower, with just an aircleaner, jets and pipes, these guys think 80 is out of the question at least with streetability, and longevity.
Personally, I think it's possible, with head work, compression and cams, and of course proper choice of intake and exhaust parts. I think that a lot of our debate has to do with personal preferences and what we would be willing to put up with or find acceptable as a ride. I'm not saying that a 80 HP can't be built. I'm saying that it won't have the same power characteristics as a milder built or a 80 HP or even a wilder HP as that larger displacement is still going to add power across the full range even if the motor is just as wild and peaky.
The wilder 80 HP long stroke engine is gonna have to wind more before it starts to make as much power and it's gonna have to stay somewhat wound if you want to have any power on tap with the flick of the wrist. Is that practical? Does it decrease reliability on these long stroke engines? What's acceptable to some isn't acceptable to others I suppose.
If it were a bigger bore and shorter stroke, the process to get there would be much simpler. Even the CBRRR suffered from a narrow, cc size bore, hurting it's top-end hp potential when modified. Come on! It's all about more power,we need more power! Compared to most cars, your is pretty snappy. If you had that machine in , you would be one of the local kings of the road.
Today however It's not that an is by any means "underpowered", it's that we can have more and want more. Let me add something and no i cant upload the dyno chart cause im dumb. Dyno operator shut it off at ,well the DTT is set at and the bike still pulls to the rev limiter.
Maybe it already makes 80 HP? On the same dyno bank, I put my Four Honda. On the manual, it was given for 48 HP at the crank. The dyno bank said 37 HP at the rear wheel at rpm. I have many doubts, now. Are european and american dyno banks the same? How my can have as HP as a ? The has been the best bargain out there from H-D! The is not underpowered for a lot of things.
I just wouldn't want one with much less power over it's broad stock or stage I powerband and that's what anyone is going to get if they try to make a very peaky 80 HP screamer out of one. It will make all of it's power at high revs which will have to be used to make any. Except that the cc Ironhead Sportster of had 55hp and weighed a lot less than today's Blockhead Sportster.
It WAS the king of the road, bar none, in Buez Convert it to newton meters! You're coirrect about except for possibly a Norton.
The Sporty was one mean bike! However the 55 HP was measured at the crank if my memory is correct. Also, the Iron s were given quite a bit more gear for better acceleration than the EVO ones of today. Today's is so much better in many ways. The cold wind rushing on the face.
No sounds around you but the sound of the engine humming. People feel like on top of the world! Harley-Davidson is a major motor-bike company originally launched in the US. It was launched in and it is said to be one of the companies that survive the great depression.
The difference between and Sportster is that Sportster has spoke wheels whereas the Sportster has alloy wheels. Spoke wheels can be used for off-road, bumpy riding because of their shock-absorbing properties. The bike is distributed in India with the help of Hero Motor corp. Hero and Hardley ventured together into the Indian market.
The Sportster is also known as Iron The edges towards the high-end motorcycles. The price tag is high for the average Indian. In the U. A, the is considered to be cheap and an easy way to get a Harley bike for yourself. The Sportster is sold as a cruiser. The weight of the bike is kg. The engine of the Sportster is cc, it packs a punch. It has 6 gears.
From Harley-Davidson. Blacked-Out Look. Black on the throwback round air cleaner cover. Chopped fenders, to show off a little rubber and black front forks with gaiters to add a little old-school nostalgia. Street Inspired Paint. These are tough finishes, as mean as the meanest street. The combination of a lowered front and rear suspension together with a low, narrow solo seat—just Tuck and Roll Seat.
Machined 9-Spoke Wheels.
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