Total Motorcycle Community Forums

Hey Man

I´ve been designing a motorbike using 3d cad programs for a lot of years now as a hobby.
It has 2 1985 Kawasaki KX500 engines side by side.
I would like some info from people who have experience of joining engines together (drag bikes, hillclimbers e.t.c.).
What is the best way to join the engines, welded crank?, joined after gearbox with chain?

Cheers Man

Hillclimbers and dry lake racers usually run the engines inline rather than side by side. They couple them with chains or gears.

Don't weld the cranks together if you run them side by side. I work with much larger engines that are often trained together at the crankshafts. You must have some type of coupling that will allow for slight misalignment and thermal growth variations between the cranks or they will break something... hopefully just the weld between cranks, but you could bust the cases on one or both engines.

You will also need to design in some way to vary the mounting position of one or both engines to allow you to align them, as well as providing access for a set of dials or a lazer-alignment sensors between the 2 engines.

Coupling your prime movers with chain or gears eliminates the need for such extreme accuracy and allows for changes in relative position due to heat or frame twisting as well.

Hi Buzzz

Thanks for the info.
This is a bike which will probably not see the light of day outside my computer monitor, but I am designing it with a high level of realism.
I´m definately having the engines side by side for looks more than anything else.
There is about a 50mm gap between the engines, so there is enough room to fit some kind of chain coupling system like you suggested to do away with extreme precision.
Could you show me a diagram or photo of such a coupling.
I have spent ages searching the net, but have found no photos or info about this subject.
I need a good idea of how the drive is joined so I can model the parts in 3d.
How about using both gearboxes and running short chains to the rear of the bike that are joined together on one shaft that has a sprocket for a chain to the rear wheel?

Cheers again for your experienced reply

I'll dig around and see if I can steal...I mean find.... some pics of a lakebed racer's driveline later tonight.

The easiest way would be to run a short drive chain off of each motor's countershaft sprocket back to a common jackshaft, and run the final drive chain from that jackshaft to the rear wheel. If you have room behind the motors to mount the jackshaft...... luckly your engines are pretty short and compact in that dimension.

What kind of chassis will it be? Streetbike, roadracer, off-road or what? Just curious...

I also happen to be a dirty open-class 2-stroke mean..... I just love 'em.

I have a year old brit mag with a feature on This guy:

http://uk.zn1300.com/

He took two Inline six Kawasaki engines and made a v/12 out of them. It is possible to make a combiked case for the two jugs. But it would also be a bit more challenging for your stroker engines. This is obviously an old article because the magazine I have shows the final product. But you should note, the article says this guy can build a 5-cylinder Kwak H-2 "Blindfolded" ... It can be done

Might as well shoot for the moon if tho you are just doing conceptual designs

I saw this one on Ebay a few weeks ago. It doesn't look very pratical, but it's a great conversation piece.

http://cgi.ebay.com/ebaymotors/Kawasaki ... dZViewItem

BuzZz wrote:I'll dig around and see if I can steal...I mean find.... some pics of a lakebed racer's driveline later tonight.

Cheers for that, I really need to see a few different solutions so I can choose the one thats suits me and the bike.

BuzZz wrote:The easiest way would be to run a short drive chain off of each motor's countershaft sprocket back to a common jackshaft, and run the final drive chain from that jackshaft to the rear wheel. If you have room behind the motors to mount the jackshaft...... luckly your engines are pretty short and compact in that dimension.

I take it this means I am using 2 gearboxes which means connecting the gearshift lever to both, or using a hydraulic shifter.

BuzZz wrote:What kind of chassis will it be? Streetbike, roadracer, off-road or what?

I took the dimensions for the bike off my current KX500 streetbike (www.craighood.com). It has the same seat height same wheelbase, lights are in the same position e.t.c. I designed the frame myself and actually made most of it by hand a few years ago. It is made from 47mm dia. stainless steel. I did intend building this bike and at one point had a gpz600r engine and wheels from a cbr1000h, but lack of funding and interest made me sell them.
The frame was actually designed to fit perfectly around the gpz600r engine, but 2 kx engines also fit in there nicely.
I also intended having the gpz exhausts run through the frame.
I still like this idea so have decided to keep the exhausts going through the frame. This means I have straight pipes on a 2 stroke, so I also intend adding a supercharger (or 2) to compensate for the loss in power through not having expansions.
I´ve found loads of debate about 2 stroke superchargers and turbos on the net, some people saying it cant be done.
I saw a website a while ago showing an RD350LC turbo (the turbo was in the top box).
A supercharger would be less hassle design wise.

Cheers again for the replies guys

Wow, I love that KX. Freakin' Cool!!!

I still haven't got time to find you any pics yet, sorry. Busy weekend and all....

That chassis sounds cool, the bike would be a blast to ride in real life.

And turbos on 2-stokes is no only possible but almost common. Snowmobilers have been doing it for years. They are also fussy to tune and very prone to meltdown. Some serious hill climbers swear by them, but they think nothing of wrecking and rebuilding their engines every other time out too, so......

Hi again Buzzz

Glad you like the KX

I think the jackshaft at the back of the engines is a good way to go.
Does this shaft have any kind of give in it to handle recieving different power from each engine?
Or is this difference taken up by the small chains going from the jackshaft to the engines?

Cheers

If you have the room, cogged belts and pulleys might be a good alternative....but engine sync is still going to be critical. The cushdrive in the rear hub will help damp any shock loads to some extent, but the tighter the synchronization between the 2 drive units, the better. Not just for shock loads, but you don't want the engines fighting against each other under acceleration or something like that.

How can you ride that KX like a civilized person?
I have *ahem* more than a little *ahem* road time on a CR-500 with full knobbies. Put good street tires on that thing and I can't imagine riding it in anything like a legal manner.