supercharged two-stroke

Am I completely crazy? I have seen small motorcycle superchargers on ebay for not much money, there is plenty of room in the frame of my GT250 with a smaller battery and the airbox gone.

DKW had that one their racing two strokes pre-WWII. IIRC it got banned as it worked rather well...

The one complication I can think of is driving the pulley. Would driving it off the drive sprocket work? It would only produce boost when in gear and underway but would the supercharger choke off the engine in neutral since it wouldn't be spinning?

A good tuned exhaust works like a supercharger if sized properly. I'm thinking a supercharger would cause problems when both intake and exhaust ports are open.

Think older diesel bus, and there you are, two stroke supercharged (though most were turbocharged).

Whenever the engine is running--idle to full throttle--the supercharger lobes are spinning.

I like where this craziness is going.

Any better way of driving the pulley than the drive sprocket?

EvanB wrote: Any better way of driving the pulley than the drive sprocket?

Well you need a rotating assembly to spin a supercharger soooo:

• drive it off a wheel or tire? (mostly kidding here) -dive it off crank or cams?

Shoot i dunno just throwing stuff that spins out there. This is tricky

Well 2-strokes don't have cams so that is out. Spinning it off the crank is a possibility but how to get at the crank without the oil spilling out as it runs?

First thing you'll have to do is redesign the pipe. They're made to operate at a given EGT and exhaust pressure ratio.

Gordon Blair's "Design and Simulation of Two-Stroke Engines" contains all the stuff you'll need to draw up a new pipe. Remember that you'll want to have a more "friendly" powerband with more power, and that all the parts will be under more stress so you'll want to design around a lower rev limit.

Drive it with a synchronous belt off the front-gear if it's a centrifugal blower that has to turn many tens of thousands of RPM. Press the front-gear off the crankshaft, fixture the pulley concentric to it, drill holes, then press in oversize dowels to hold it in position. If it is a Roots blower you can drive it off the flywheel as the speeds are lower. Remember that you want peak boost early because your power peak is lower relative to the rev limit and the rev limit is lower. You will either switch to a dry clutch for this or wish you had, because you don't want to hope your Grassroots gearbox seal will keep oil off that poor, overworked rear tire that is the only thing keeping you out of the cemetary.

You will need more fuel at all stages of the game and you might discover that the crankcase sealing isn't good enough. If you get discouraged think about just putting a bigger engine in there; a CR500 plant is hardly any larger than a CR125.

I know you guys are talking about blowers, but here's a 2-stroke turbo project. Its a pretty interesting build thread. Guy took a direct injected Aprilia scooter motor, converted to port injected, bored up to 70cc and added a turbocharger. Build thread here:

http://www.apriliaforum.com/forums/showthread.php?t=185518&highlight=turbocharged

Its an ongoing build. He just recently got it put together and out on the road. He's only up to running 1.9psi boost, but the scoot is getting up to 75mph which will earn you godlike status in scooter circles...

Take a look at snowmobiles! there crap loads of blown sled in snow land. But why bother just get a bigger bike.

I didn't know you could turbocharge a single piston engine, Its always been told it doesn't work well

EvanB wrote: Am I completely crazy?

Yes which is why your on this board. Do It!!!!!!!!!

Am I completely crazy?

Yes. Now that we have that settled.

Do you like this bike? Would you be sad if you killed it? If so don't mess with it. Go get a moped and play..Remember 70's vintage cadys had HUGE air pumps for the exhuast? Well they did i forget what one i used but added one to a 5hp briggs as a kid. Found i had to presureize the gas tank too. After dabbling in alky powered 2 stroke karts i got a moped and got it to run on alky then worked my way up to 3.5% Nitro for the life of me i could not get it to run well over 3.5% tried 5% once and well lets say the motor went BOOM...that putting it mildly. The 2 inch long section of the con rod that stayed on the crank cut the motor in two. This was after the clutch let go and parts came out the side... Later i tried a RD350 on Alky. got that to work great with some lectron carbs. Mpg's sucked for the road...not much fun waiting for the gas can to come. Once i tried ram air on the RD and found at 55mph the funnels were so efective the exhust back pulse was not efective enough to push the charge back in...SQUEEK. So experiment yes but not on anything you like.

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I like it a bit, I just got it though so I'm not too attached and wouldn't be sad if I killed it.

I should probably just work on making some expansion chambers fit and some mild porting first.