This is a homage to the old school. An introduction to the newbies on how to tune the old school way. Proof that you don't need big bore kits or fancy pipes to go fast. All you need is some 50cc stock parts and a whole lot of two-stroke know how.
I rebuilt the ZA50 motor on my old school Hawaiian style cafe racer Puch Maxi. I restored it back to its original incarnation to the version my cousin owned back in the 90s. This is the version we were blasting anyone and everyone with. Back in its day, this setup was pulling at least 50mph plus easy. I recall one time taking down a fleet of Yamaha Jogs in a straight away stretch from Sand Island to Kakaako Park town bound (Hawaii peeps know what I'm talkin' about!).
The cylinder:
One-over 50cc Magnum bore with L-ring piston. Didn't do any additional work on the ports or timing. The original port work that were done by our Puch guru's are already proven. I can't tell you any specifics, measurements, nor numbers. But I can tell you it kicks ass!! They never wrote any of that shit down. Everything they did was done by "feel". If you got your butt kicked, you went back to the drawing board and ported it again until you got it right!! And believe me, this set up was done right!!
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| Port work proven to kick your ass!! |
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| Intake |
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| Exhaust |
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| 1-Over |
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| Butt wooping port timing |
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| No machining..Hand filed down head |
Modified clutches:
I don't know what they did to these clutches but it kicks ass!! The perfect stall to engage ratio. I blew away a modified Honda Elite Dio off the line back in the day. Don't know how short they cut the springs or how lightened they are but no need to touch'em!!
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| Was that you I just passed? |
Top end, J-pipe, carburetor, ignition on:
Buttoned up the top end and mounted the exhaust manifold and carburetor. I scored a clean, undinged, J-pipe exhaust manifold. I still had the original custom manifold from a washing machine (I think?) paired with a Bing 17mm carburetor. Stock ignition on. Old school stock parts to blow your kit away!!
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| Stock! |
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| Stock!! |
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| Stock!!! |
Re-Mounted:
Looking like the original build. Added the modified Magnum exhaust it had before. Went old school 18x32 gearing on stars rims no pedals. This bike sure brings back memories...
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| Enjoy da Stock!! |
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| Stock!!! |
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| Stock!! |
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| Stock does not Suck!!! |
This 50cc "modified" stock set up is the reason why I'm such a two-stroke enthusiast. This is an example of two-stroke tuning at its purest. Getting everything out of a tiny 50cc motor by pure two-stroke know how and ingenuity. Anybody can buy a kit and slap it on to go fast. But it takes skill to squeeze 50mph+ speeds out of a stock 50cc displacement. And I always believed that a "modified" stock Puch has the greatest potential to do just that. Back in the day in Hawaii, it was so difficult to find big bore kits and modified parts. Tuners had to relied on their ingenuity to make their available parts go fast. This bike has all stock parts that came from different stock Puchs. But with the know how, we made this bikes scream.
So here is my homage to all old school two-stroke tuners out there.
Happy Tuning!!
This is a homage to the old school. An introduction to the newbies on how to tune the old school way. Proof that you don't need big bore kits or fancy pipes to go fast. All you need is some 50cc stock parts and a whole lot of two-stroke know how. 
Awesome post! Luv it ! Miss my bikes! So many memories flying fast and free. In tune with your machine. No cares, no worries. 1 focus, fly. Boys and their bikes extreme. Crackle pipes screaming through a quiet valley raining terror in flight! You have no idea how much your passion honors me. Pushes are a huge part of my being, in my DNA.Thanks bro keep tuning to scream that tiny Greman motor bike. The famous Island flyer, Puch moped.
ReplyDeleteI'm cut from the same cloth as you. This is one of my favorite bikes. Pure 50cc two-stroke modding at its finest. Who needs a big bore right?
DeleteHey there! This is a really awesome build and I'm hoping to go to a 17mm carb like you on my Magnum with a ZA50. Would it take much to get it dialed in if I did a 17mm intake and just aaftermarket exhaust? I'm not trying to get too crazy with any other mods. Also, what size jet did you need for this to run well? Thanks!
ReplyDeleteIt is very easy to dial it in with the parts you mentioned. I have a 72 jet in my Bing 17. Let me know how your go!! Thanks.
ReplyDeleteThanks so much for getting back to me with the info! I haven't secured a bigger carb just yet but I'm looking for one. Happy riding :)
ReplyDeletePorting 2 strokes is an art, just like tuning an instrument. It's called tuning because most results you get when all parts are tuned with each other. Starting with an extra strong crankshaft with needle bearings on the small end. Than use both carter halves to match the transfer ports so there are no obstructions, and the transfer ports are as wide as possible without compromising the gasket space too much. Any leak in this will prevent the entire project from runnnig at all so be very careful not to take away too much from the very start. Make extra transfer ports with a 'dremel': start with a small 1 in the middle, that's deep where it meets the hole in the piston right under the L-ring and gets less deep towards the sparkplug; max length should be no more than the existing transfer port length. This way we can give the airflow direction. It should point towards the sparkplug. Try water to test the flow through the transfers. Light also works: looking from the spark plug side we should be able to see light shine through the sideway transfers.
ReplyDeleteWhen the extra transfer port we made is a match, we first are going to see if it works, before adding more ports (if needed). Next, the inlet. It should be made bigger towards the crankshaft, as much as possible. This way, it opens quicker. Understand how the piston works like a valve opening and closing the holes in the cylinder named ports. Next, get a wider exhaust bend so the extra exhaust gases can exit the cylinder easily. The exhaust port should not be tinkered with too much. 1 mm wider, and maybe 1 mm higher, but no more as we compromize our compression. Now we got to get a bigger carb, bigger inlet pipe, and maybe electronic ignition. Every time we make a change in the engine setup, we want to try the effect, this is how we learn. I've been very lucky to have many friends who gave me their old cylinders etc, so I could experiment a lot. If you're able to weld your own expansion exhaust, there are fast ones cold Homoet P4 and P6. Use those measurements. Enjoy, and if you want to go faster get a Kreidler 5speed close ratio engine block, put Van Veen stuff on it, and start your racing career.
Hope this helps to shed some light on the dark art of porting 2strokes.