On Honda RS125's and TZ250's from about 95 on there is a micro-switch that cuts the ignition when you shift........simply push down on the shifter without ever lifting (they are GP shift pattern which is opposite road bikes)
Now for older 2 strokes you can simply hold the throttle wide open and put pressure on the shifter, just as the bike starts to fall off the power band on the top end, the bike will slide into the next gear. A buddy used to use the same technique on his open class motocrosser.
One final thought I remembered this morning: there is some 60's hillclimb car that used multiple Aerial 2 stroke engines, something like 8 or 12 of them, on that note my ultimate bike engine would be a pair of Yamaha TZ750 top ends to make a V8 1500cc 2 stroke.

Tom

http://www.youtube.com/watch?v=4OSFUC3-ars

It's not a datsun..... still CRAZY but. My parents own a Goggo Dart, and this is MADNESS. They are dangerous enough already!! Might help with the conversion to datsun!!

Hahaha, Tim

thanks dazza for clearing that up i always wondered

if you do go ahead with it make sure you post up pics in the project section i'd like to see how it goes

lethal john: drag bikes use an air shifter with an ignition interupt (unloads the gearbox during the shift) so you dont close the throttle
change down with foot lever
prob not of much use in a road race setup

the driver is a big variable when it comes to durability

Quote:
what else would you expect from an online forum? or the majority of car enthusiasts? it seems to be the one field of interest where blokes like to think they know everything and like to think they don't need to be taught mechanical knowledge or get taught how to drive. seriously there are not many other sports out there were even the lowest least competitive teams don't have coaches etc.

it's funny, there's always a lot of opinions about 'this won't last' 'that will break' from people who haven't done the conversion themselves. there are a couple of road legal rallycars (toyota starlets) just that I know of personally here in NZ with bike motors and they go very, very well. I also know of one being fitted to a datsun as we speak, so it's not exactly unchartered territory.

Yeah I could listen to that all day. If I were going to use a bike engine though I'd be using the big 6 cylinder buggers from the Valkyrie, Goldwing, NOT TRIUMPH ROCKET CRAP, Suzuki thingamabob.

A couple of things to comment on:

First the gearboxes are quite durable, the biggie is to treat them properly, in the sports racer it was chain drive so that probably takes some shock load out. Once I left the pits I never used the clutch pedal again. Left foot brake and match RPM's. Now I do have quite a bit of bike racing experience so that likely helps. I'd always have some one warn me about grenade the box with clutch less downshifts but never had a single gearbox issue. NOW guys who run Radicals have had issues with this; partly I believe because for many of them are guys with money who can afford a high end race car but have never raced before so they tend to be rough with the box, the other is that these cars use a gear drive to the rear end and the manufacturer advises against this practice and the motors are often heavily modded.

Clutches aren't an issue with the Yamaha's, in contrast on my Honda 1 2 5 GP bike clutch plates only went one full day of practice and one race day plus they would only tolerate one race start (when you gear a 125cc bike for 130 first gear is like using third gear to take of in a 1200)

In the sports racer I slipped the clutch as little as possible (I do this in all track cars), I'd go chuggin down the pit lane at 1/4 throttle then once the car was up to about 35 MPH roll on the throttle. It's sort like Viper guys complaining about weak axles........well when you light the tires for 150ft then the suddenly hook up, mmm yea that might break something.

As for bike motored dirt cars we have Micro Midgets with 600cc bike motors 3/4 midgets with 750cc bike and engines and Mini Sprints with 250cc motocross 2-stroke engines hung on the side driving a quad style axle.

Finally while the bike motor would be cool from a cost stand point a Rotary conversion will net more power and would be a lot easier BUT wouldn't a Ducati powered 1200 make a glorious sound.......yummy

Tom

yeah they're mini nascar style cars built in america. on closer inspection of your chassis they are obviuosly not the same, i just saw the basic suspension design and the winters quick change and thought it might be one. that is a winters quick change in yours isn't it? i wanna get one for my ute, they used to be like 3 grand then the dollar changed and it's more like 6 now