| Author | Message | ||
     Mudshuvel319 |
I know this forum is inherently V-twin-dedicated, but I have a question about 4 cylinder engine orientation. Basically, why don’t we see transversely-mounted 4 cylinder engines on bikes? Obviously in earlier days air flow was necessary for cylinder cooling and carburetor air intake, but with almost all modern 4 cylinders featuring fuel injection and water cooling, these aren't really issues. The current longitudinal engine position makes the bike wider, decreasing the mass centralization and increasing the frontal area and drag. I know larger 4 cylinders like the Hayabusa 1300 or Ninja ZX-14 would be tough to fit transversely between the front of the frame and the seat but the smaller 600s and 750s aren't prohibitively wide. Does the current configuration create just enough air cooling to make the transverse mounting appealing? I know this is kind of a dumb question but I’ve bounced it off of a few friends with bikes and none can offer a reasonable explanation. Thanks! -Dan (Message edited by mudshuvel319 on February 05, 2009) | ||
| Spiderman |
Well I can not tell you the full reason or even if this is true... But for expense and tolerance wise it is easier to transfer energy from the crank and trany to tire in a line vs having to set up some way to transfer the energy transversely from the motor to the rear tire like you would see on a car or BMW motorcycle... | ||
| Rubberdown |
BMW did it for years with the K series. | ||
| Mudshuvel319 |
The BMW configuration makes sense because the drive shaft would line up perfectly with the engine crank. I guess other manufacturers might find it difficult or inefficient to transfer the power via belt or chain drive. | ||
| Hexangler |
I own an '85 BMW K100. Engine has always smoked on start up due to oil seepage past rings in "pancake" motor. (edit: My Beemer is an '85 not an '89) (Message edited by hexangler on February 06, 2009) | ||
| Androidgobotron |
http://www.motoczysz.com/main.php?area=07C1_tech | ||
| Jaimec |
Ummm... aren't 98% of the four cylinder motorcycle engines out there transversely mounted?? The only longitudinally mounted fours I can think of are the old Honda GLs, the current Honda ST, the old BMW "K" engines and going back even farther you have the four cylinder Indians (didn't an English company build a replica) and Curtiss designs. There may be others but that's all I can think of at the moment. The new BMW "K" engines are all transversely mounted. Only the K1200LT has the old longitudinal engine. | ||
| Rubberdown |
Your right Jaimec!  | ||
| Mudshuvel319 |
Jaime, you're correct; I reversed the terminology. I mean to ask why there aren't more longitudinally mounted 4 cylinders. And I never saw the Moto Czysz before. That's pretty cool. | ||
| Ft_bstrd |
Longitudinal mounting requires a longer wheelbase wrecking handling responsiveness in a sport bike. Transverse mounting provides for a more compact wheelbase. | ||
| Spatten1 |
Wide is not the problem. Long is the problem. Designers look for the shortest front to back engine because for handling and acceleration longer swingarms are the goal. That is why they stack transmissions now rather than putting the countershaft behind the mainshaft. Anything to shorten the engine front to back is preferable. | ||
| Spatten1 |
Jeremy, saw your post after posting mine, you are correct! | ||
| Spatten1 |
BTW, now that BMW is building their first competitive sportbike, they are using a transverse mounted 4 banger for the first time. They also dropped para and tele-lever and are using standard suspension like the Japanese bikes. | ||
| Hughlysses |
In addition to the other points, the designers also want the mass of the engine as far forward on the bike as they can get it for handling and "wheelie resistance". A longitudinally mounted engine makes that difficult. | ||
| Ft_bstrd |
There are also some nasty feedback from a shaft drive which would be the preferred structure for converting longitudinal power to the rear wheel. It adds weight and driveline lash the worst of these being weight. | ||
| Rubberdown |
Let's see....BMW HP2 air-cooled twin with paralever and shaft drive was 4th and 5th in last years Daytona 200. Yeah, that configuration must suck! My experience on the track with those and similar bikes has been very good. Just expensive to throw down the track. (Message edited by Rubberdown on February 05, 2009) | ||
| Spatten1 |
Shafts also eat up horsepower, not acceptable on a sportbike. Anyone else notice that that new Guzzi Greaso puts out more RWHP than the 1200 XB. I believe it is a 4 valver, but still air-cooled. | ||
| Ducbsa |
new Guzzi Greaso puts out more RWHP than the 1200 XB. Are you sure it's not BHP (Brochure Horse Power)? | ||
| Spatten1 |
It was magazine tested. | ||
| Indy_bueller |
I believe another factor is the torque effect of the spinning crankshaft. The bike would be twisted over toward one side or the other when the RPM went up. This I believe is the reason behind the V-4 design of the MotoCzysz. | ||
| Jaimec |
The SV1000RR is NOT the first time BMW used a transverse 4. The K1200S is the first bike they built with a transverse four... about four years ago. | ||
| Jaimec |
Torque effect can be eliminated easily in a longitudinal engine. Honda did it first in the GL1000 (the original GoldWing) and BMW copied the idea in their K-series. Essentially, spin an equal mass in the opposite direction from the crank/flywheel. Apparently, they did not do this in the "R" series bikes because that torque effect was "expected" and considered a desirable characteristic. MotoGuzzi is the same way but if you REALLY want to experience torque effect, take a Boss Hoss off it's sidestand and hit the starter button. That damn thing felt like it wanted to throw me to the ground on the right!! Can you high side a motorcycle standing still? You might be able to on a Boss Hoss! | ||
| Kowpow225 |
I saw the guzzi you're referring to. Was also running 11.0:1 compression. Pretty impressive on an air cooled lump. | ||
| Bombardier |
I own an '83 K100 and it is a very impressive bike and was well deserving of its praise when it was produced. The engineering and castings are things of beauty on this bike and as German tradition requires all produced with a huge safety ( read heavy ) factor. Probably the most adept description of its power output would be 'turbine like'. They too subscribed to a similar philosophy of having components serving more that one purpose. The driveshaft assembly is contained inside the swing arm on a single sided arrangement. The engine and transmission acts as a stressed member and has the swingarm attached to it. Also of note is that it uses a dry single clutch plate which can be exchanged for one from a Volkswagen if stuck for a spare. Also it is fuel injected which was not a common thing for that era. Hex, the smoke at startup can be minimised by parking the bike using the centre stand or a wheel stand on the front wheel at home. | ||
| Slaughter |
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| Bombardier |
Hey Slaughter where did you get that picture of my K bike?!?!?!  | ||
| Slaughter |
Wikipedia - I was looking up Henderson. http://en.wikipedia.org/wiki/Henderson_Motorcycle | ||
| Bombardier |
Betcha his prostate is long gone by the look of the seat. | ||
| Jaimec |
Bombardier, my old K100 stopped smoking once it was broken in. As I recall, that was somewhere around 50,000 miles. I LOVED that bike. I had a 1985 model (first year in the States). It was stolen almost ten years to the day after I bought it with 158,000 miles on the odometer. That one still hurts, it was never recovered. Probably the most reliable vehicle I EVER owned. Despite APPEARING complex, it was actually quite easy to work on, too. I still miss that bike. | ||
| Teddagreek |
1949 Indian inline 4 My neighbor and I have talked about this before. They did have some heat issues...  | ||
| Bombardier |
My only issue is the valve clearance procedure - Ensure engine is at 20 deg C before adjusting valve clearances via shims. A very small window of opportunity where I live. | ||
| Jaimec |
Bombardier... as long as all engine components are at the same temperature, you're fine. I let the bike sit overnight before doing the valves. The newer 16v K-Bike valves (like on my K1200LT) may require less adjustment, but the complexity involved SUCKS. I wish they kept the old shim-over-bucket architecture. It's not like the bikes had stratospheric redlines that would spit shims for crying out loud! I'm not sure how the LATEST K engines are serviced. I do know they use a finger follower (a la Formula 1) to actuate the valves, but I don't know if it's a shim-over, shim-under or (horrors) a shim-is-the-bucket design (like mine). |
