ok I have seen only one in a old artical but I am aquiring 4 aisin amr500 roots type superchargers they pump 500cc of air per revolution any one here ever put a blower on a cb77 or cb72 engine? and how would i lower the compression ratio? thicker head gasket? anyway just thought i would throw it out there:)
James
supercharger
Wow, that sounds like a never ending project. You can lower the compression by using a thicker gasket, but usually people opt for shortening the stroke. Especially when adding in extra pressure.
although it's been done with carb setups before, superchargers as well as any sort of forced induction take a ton of tuning. Kind of like what Vince is going through with the 350cc setup only it would be 10x more difficult to tune it in because of the varying air flow. Something like that is really only reliable with a fuel injection setup and ECU where you can change the flow of fuel through the RPM range unless you're just doing high speed runs at wide open throttle. I would imagine swapping in a larger engine would be less of a hassle and more reliable. Here's a supercharged CB77 with partial info of how it was done: http://www.flickr.com/photos/53591907@N ... otostream/
There seems to be a demand for those with the early VW Beetle crowd. Perhaps you can make a few dollars flipping them to those guys. It's basically a trap just like finding a good deal on a non-running bike. You keep thinking "man, this is such a great deal" and by the time you're done, you've spent twice what a new bike costs if you're lucky :-) James,
In regards to lowering the compression, I'm building a little rat bike (CL) trying to use up a bunch of mis-matched , left over, and "unusable" parts such as Broke fin cyl's and heads and super badly pitted sleeves that won't clean up at .100 over. I've come up with 63.5 MM pistons readliy available on the cheap , $20 each with pins and rings. Got mine here: http://cgi.ebay.com/ebaymotors/ws/eBayI ... AUS%3A1123 Pin dia is 15mm and the height look to be spot on. Flat on the top and a bunch shorter than stock, but pretty much all the modern stuff is anyway. I haven't done any calculations or anything but I'd imagine it would get it down to around maybe 7:1 or so. The cyl's should end up at around .060 wall and with the lowered compression and way detuned engine I'm not really that concerned. Not gonna take this one to the drags. If I'm not mistaken these are also available in 62mm as well which would put you at around .090 wall. My old Flathead 45" Harley with cast iron heads was 3.75:1 . My racing heads were 5:1 . The old saying was that the 45's never ran good , but they always ran. Mark
I'd like to turbocharge and fuel inject a 305 and I even have the turbo and EFI, although not all of that hassle is necessary to get a basic forced induction setup to work IMO. A draw-through supercharger would be the simplest as there would be little to no extra electrical overhead and jetting the carburetor wouldn't be much different than a naturally aspirated engine. I think getting the advance curve set up would be the most hassle. To lower the compression, I would look for flattop or even dished slugs if they exist and avoid castings if at all possible. Shortening the stroke is probably the most painful way to reduce static compression ratio and it costs displacement and quench at the same time. Plus, if short-stroke cranks aren't available for the engine, it's not really an option anyway.
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