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Discussion Starter · #1 · (Edited)
This project is to put a Z1 one ring piston into modded Cag reed port cases with a lightened 12mm stock Cag crank. The crank stock is 396g now it's 346g, if you look close you can see the knife edges on the rod to cut thru the air. Everything on this engine has to be light. Looking for 12 to 13,000 rpms and high compression. It's going into a Razor Rocket PR220 frame, modded and lengthend 6 to 12", it's very light also. I got the crank from Hugh @ SDscooters in Texas. He has 3 more 35 & 45grams lite $25 shipped. The rod crank pin has been spot Tig welded so it can't twist or come out. Still have alot of work to do.
 

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Seems like a good project......I cant see rhyme or reason to the crank though other than the tig welded pin and here are my reasons behind it.......

The engines are already designed for lawn equipment....The crankcase volume is large to begin with utilizing a non-fcc crank;- now that crank is so shaved its gonna add even more volume with the counterweight thats missing....

To build hp ya gotta take the volumetric crankcase area and deplete the area with things like fcc's or crank stuffers n such......

If ya blueprint the case and cylinder thats gonna add even more crankcase open volume aswell as installing the ADA.....Crankcase pressure is gonna be weaker than a stock engine in the end

Now if you take the weight of the piston w/ring.pin,pinbearing and clips its gonna tip the scales at 70-75 grams.....The 12mm pin is gonna be the substantial addition to some of the weight.....

Unless you can get the whole piston assembly lighter by 22.5 grams to compensate which would be an amazing miracle youre gonna get alot of load vibrations at high revs not to mention that you may experience a loss of momentum at high speeds when going up slight inclines and hills...

In my experiences in engine building you never do two things to the rod.....you never polish the rod and you never knife edge the rod.....I see the later of the no-no's....

If your looking to enhance the revs of an engine designed to deliver industrial rpm's your increasing load on the rod.....A mirror polished rod cant absorb oil needed to help keep it cool....The rod snaps from overheating and meltdown fatigue and a knife-edged rod fails because its strength has been grinded away combined with the increased load from the extra rpm's....

If you put the crank in half of the crankcase and spin the crank youll see theres very little of the crankrods middle mass that offers any resistance while spinning its full cycle.............

I hope the engine turns out like you expect but I already know how its gonna turn out..........Good Luck..
 

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Discussion Starter · #3 · (Edited)
Yeah, I hear ya. I was thinking about all the space inside the cases, already. Not going to open up the cases at all, only around the area above the main bearings. Haven't looked at stuffing or filling in the case area yet.
The Z1 40mm one ring piston has a 12mm pin bearing that don't fit the Cag rod, so I am using a12mm Cag rod bearing and it is the only 1 ring piston I know of that will fit the 40mm Cag cylinder. I took very little material off the rod, just enough to point to the center edge.
It's just an experimental engine, if I can't make it work, I keep the cases and build another engine,lol. I am ordering the Billet Cag cases from Germany next week, for the F1 engine 49cc Cag engine that will use a 12mm FC crank.
It's winter 30 degrees or coolder outside, not much fun for pocketbikes.
 

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Discussion Starter · #5 ·
I just got another Z1 40mm piston kit with rings, bearing, pin and clips, but you need a 12mm Cag rod bearing, cause the Z1 is 12mm ID but too small OD, from hkmotos for $12.95 shipped.
Have many mm is the 50cc Polini piston?
 

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Discussion Starter · #7 ·
The problem with the Z1 40mm piston in the 47cc cases and 40mm cylinder is you need a .150" cylinder spacer to raise it up so the piston is at the top and not sticking out the top,lol.
Have to look at the 50cc Polini piston to see how tall it is from the pin hole to the top. But then you would need a 10mm crank.
 

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Discussion Starter · #9 ·
Re: V1 40mm One Ring Piston in Cag cases and FC 10m FC Crank

Worked on this engine today, which started w/ a Z1 40mm 1 ring piston, 12mm pin, and light crankshaft 12mm pin, w/ CF reeds & 603 Walbro carb.
Alot has changed, have a 10mm FC balanced crank w/ 40mm Husqvarna 1 ring piston, 299 gram flywheel, w/ key & 219 gram 2 shoe, drilled arms adjustable racing clutch, which I had to cut a slot for a key.
Will post more photos of the engine and parts soon. Got a 4 reed box intake w/ Polini reeds form a member here and a modded Cag 603 alum intake modded to fit the box opening, w/ a 16mm copy carb and boost port.
 

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