What would you recommend? Shaft drive versus chain? New versus old air versus liquid cooled.
Cost versus performance? What is the best bang for the buck? HP versus torque?
I always thought that the motor form a Vmax would be a good starting place or something from a gold-wing but I am sure others have good inside in to this.
Discuss
I don't recall numbers, but off the top of my head I recall hearing that Goldwing engines are heavier than you'd think, eating badly into the "lightweight bike engine" thing. OTOH, they are already shaft drive, I believe they have an electric reverse facility, and for a bike engine they're huge displacement.
When it comes to that approach to the bike engine thing, I'm curious about the 2.3 liter (!) triple from the Triumph Rocket III. No reverse, but the other advantages of the Goldwing remain.
Then there's the latest BMW 6-cylinder engines. Transverse, but shaft drive.
I think the simplest answer for a lightweight racer is Hayabusa. It's been done a lot, much is known about handling oil pans and drive setups (you can run in longitudinally with a shaft adapter that replaces or mounts to the output sprocket, or run it transversely with chain drive). I think this is probably the most hp/$, and they'll put up with forced induction to ridiculous power numbers. While they're somewhat less-often used, similar things could probably be said for the giant Kawasaki and Honda uber-sportbikes.
If you have the $$$, go to Quaife and get one of their boxes that more or less mounts to a transverse bike engine and provides a torque sensing diff and a reverse facility. But its a couple thousand dollars, IIRC.
In the end, most of your questions can't be answered by "what's the best powerplant", as they also affect packaging, or get caught up in what you're trying to achieve. Do you need reverse, or is the only place it ever has to maneuver the grid of an autocross? How heavy (i.e. will it be no fun to drive with a peaky engine). I do think you're not going to find something with a good specific output by modern standards that's air cooled, and even if I'm wrong there, getting airflow to it in a car doesn't sound like any fun to me.
EDIT: And of course, this is all the stew in my head after a bunch of reading. Take it with salt, I've never built a bike-engined car.
My dad has a shaft drive BMW with the 4 cylinder that is horizontal, but only to one side.
In reply to RossD:
The K100; I think they actually used that in a junior open wheel class promoted by BMW at some point.
The hyabusa (sp) is popular. What engine is used in the dwarf cars.
I have started seeing BMW S1000RR motors for around 3k. 180hp. 
Dwarf cars are shaft driven with a starter motor for reverse.
I'm planning on wedging a CBR929 into the front of my wife's Mini. Since it will be FWD, I'll probably go with chain drive. One big expense there is the diff; chain-drive LSDs start at around $800.
What sort of car is this? I would only use an air cooled motor for a critter like this:
They generally don't have the same power output as liquid cooled, and create more cooling issues if you try to put them inside the bodywork.
In reply to MadScientistMatt:
Morgan 3 wheeler.
As always, 'it depends'. Is the car going to be street driven? Yes? Then reverse is a must, unless you want to be like some Isetta owners who are always having to ask passersby to shove their car. Not street driven, i.e. race car only? Reverse is not so essential.
motoiq said: Endurance racing a bike-powered car gives Alex Vendler a uniquely experienced perspective on this peculiar form of hybrid, though, and it only took three or four destroyed gearboxes for him figure out that while their engines are surprisingly robust, sportbike gears simply aren't beefy enough for car-sized loads.
http://www.motoiq.com/projects/mazda/project_mazda_miatabusa.aspx
Dave Coleman's ongoing project: Adapting a 'busa motor to mate to a Miata transmission. More horsepower, rear weight bias.
No help here, but considering sacrificing my triumph daytona 955 for it's engine/trans since I've put shamefully few miles on it - 148hp, better torque than japanese liter bikes and infinitely better sound. seems like oiling issues ate an engine or two on Per's LeGrand - with bike oiling not made with the same forces in mind as car oiling.
One thing to remember is that bike transmissions are geared differently than cars. First gear is more like a car's 2nd gear which makes starting from a standstill more of an issue. Usually a bike's first gear will carry you to 60+.
Also bike clutches are designed to be slipped enough to carry the weight.
If you adapt them to a car tranny the cranks can become an issue as there's more whip built into the system. If you'll note a lot of the adaptation to the Miata tranny is jackshaft supporting the output shaft of the Hyabusa.
And as oldtin pointed out oiling is another issue since the bike engine is designed to lean into corners.
I'd recommend new, liquid cooled, shaft drive would be nice but who am I fooling, anything other than chain drive on a BEC is a monstrous amount of work.
And don't even try driving with the stock sump on anything but a Yamaha I4, you'll starve it real quick. "Professionally made" BECs usually use a dry sump system.
It depends on a lot of things:
1) Front (shaft drive) or rear-engined (chain drive)?
2) On-road (liquid cooled) or off-road (air cooled)?
3) Street-driven (reverse needed) or track only (no reverse)?
4) Low-grip (baffled sump) or high-grip (dry-sump)?
etc...
Some guys in FSAE recommended this book as a good starting point. It's very specific to rear-engined formula race car, but a good primer.
The oiling issues are one reason I've limited myself to Yamaha R1's. Well, that and I don't want the XS getting pissed off.
A lot of bike transmission failures in car apps happen because there are rubber shock absorbers in the average road bike rear wheel to lessen shock loads, they are usually referred to as 'cush hubs' and a lot of people eliminate those from a car drivetrain. The same thing happens with pure dirt bikes that are converted to dualsport, since there are no springs, rubber etc in the drivetrain to absorb sharp shock loads transmission failures can occur.
Some bikes, such as my XS, have springs in the clutch hub to accomplish this. If so then it's not a big problem. It seems the R1 shares this design, if so I can eliminate an elastomer damper from my drivtrain design.
If you were to be front engined than maybe the yamaha FJR1300 might be an option as its shaft drive,very tq'y and has a wide ratio gear box that would be a little more relaxing.I owned one for a summer and while not as rev happy as my modded FZ1 it was still decent,gear driven cams sound wicked as well. I've not had any issues with the 2 R1 powered cars of mine,to beef the clutch up simply add a 2nd oem clutch spring(more of a concave disc) right on top of the original for double the clamping force.I use the clutch for all shifts as a precaution in the awd car for the reasons Curmudgeon mentions but in the much lighter rwd autox car I only use the clutch for downshifts and the 1st to 2nd gear shift-easy to catch neutral on the way thru with no clutch. No issues with oiling either,both running a simple/cheap baffle plate and a slight overfill.The suzukis and kawi's have earrned a rep for going boom in cars without much more effort to the oiling set-up.
If you can find one the Kawasaki Kz1300 was 6 cylinder water cooled shaft drive. Made about 120hp in 79. The last ones came with FI.
Chain drive in a ar would be a maintenance pain, just buy a adapter and hang a drive shaft. If your streeting it get a two peice driveshaft with center bearing. This will help keep you safer as driveshafts will spin close to second crittical speed if it is one long unit a center bearig type will up the critcal speed. center bearing units also let you move the shaft to gain some room too.
Go modern water cooled FI as thee cheap and plentiful now and they make gobs of power BUT you'll need steep axle ratio (the result...higher driveshaft speed) Older air and oil cooled motors make more low end torque bt there down on overall power and relibility would be lower in a street car as the weight is hgher.
Dwarfs weight in at 1250 with drive after the race.
Most 04 and up EFI motors are able to hack the ECU for tuning theres even sites showing how to do it yourself or add ons units like power comanders.
44
Bear in mind too that motorcycles weigh500 - 800 lbs. You won't get the performance we all like unless your car weighs near that.
914Driver wrote: Bear in mind too that motorcycles weigh500 - 800 lbs. You won't get the performance we all like unless your car weighs near that.
Keep in mind late model big bore bikes are geared for over 170mph-dropping that down combined with the close ratio 6 speed will still be much quicker in 1300lb car than you think.
Depending on the application, a liquid cooled snowmobile engine and clutch set could work well without oiling issues or weight penalties.
Many of the newer engines and ECUs will run in reverse. That is how many newer sled provide a reverse gear rather than a mechanical reverse.
HP numbers can climb over 150 without much work (if any required), and oil injection avoids the need to premix.
My race car had a GSXR1000 for the first season, and I swapped in a GSXR1300 Hayabusa for the second. The car weighed about 1260 w/ driver and post-race fuel load last season and will be closer to 1200 this year.
W/ a 17t countershaft sprocket and 45t on the (Quaife) diff, the car launches w/ authority, and there's less slipping the clutch at the beginning of the friction zone to get off the line than in most conventional cars. If I'm not in a hurry I shift before 10k rpm. Clutchless upshifts, rev-match on single downshifts. For multiple downshifts where a slow corner follows fast section, once I'm on the brakes I clutch and bang the lever the correct number of times, counting aloud in my helmet.
Regarding changes from stock configuration, I'm using a flat-bottom flapper baffled aluminum oil pan, windage tray (which deletes the balance shaft) and trimmed wiring harness from Rilltech Racing . I'm running a low-profile breather cover and clutch cover brace and springs made by APE, an upgraded clutch pack, probably from Barnett, and block-off plates on the EGR ports.
It pulls like mad. sounds great, and is low-maintenance. BTW - most bike-engine cars that need reverse do it electrically or w/ a quaife reverser box.
My dwarf car has an r1 engine with a drive shaft. The gsxr's make more power, but costs more. You cyan get pretty much everything needed for it to run in a car for about 1500-2000. Hybusas cost a lot more, but do have more power. I think the r1is the best bang for the buck cause they are not fast enough for the dwarf car guys, and have better oiling than others.
I assume you are talking this http://en.wikipedia.org/wiki/Yamaha_YZF-R1
There is good info re the motors and what not if you scroll down. Looks like on 06 or so would be a reasonable choice. I wonder how much a wrecked bike would be? I am thinking insurance auction or something. As long as I can get a title with it. Hummmmmm 180 hp out of the box.
There is always the option of adding a turbo to a bike motor if you need / want more power but that is way way down the road.
Keep the info suggestions coming I have learned a tone from this thread so far.
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