This is how you build a reliable 74cc two-stroke 5-speed engine. A year ago, I uploaded a video called "Tomos 74cc APN4/4L 5 Speed Engine Build Timelapse". Back then, I did not realize slamming a Puch 74cc Airsal cylinder on a Tomos APN engine would be so problematic and expensive ;)
Setup is a Puch 74cc Airsal kit, Dellorto PHBG 21mm, custom intake manifold, custom exhaust pipe and carbon fiber muffler, MVT premium inner rotor ignition system and a Rito crankshaft. I changed the original L17 bearings with solid 6203 crank bearings. Finally, my Tomos Revival Café Racer project is a reliable moped
I have a Tomos Apn4 5speed engine with welded transfers and redone to fit a Puch PSR 70cc kit. (Puch Shop Racing) But im dissapointed with the power output. its got a super wide power band and without that two stroke ompf and ketchup effect. The bike is used for classic moped rallys on weekends. So no need for long term reliability (used total runtime 8h per year) Setup is as follows.
-Tomos Apn4 engine with 5th gear added
-Brand new Top Racing Crankshaft
-Transfers welded up and portmatched to fit PSR 70cc Puch cylinder
-Minarelli AM6 flywheel and whole ignition system timed at exactly 15 degree BTC
-19mm Dellorto Black Racing carb with 19mm intake (plug brown)
-80km driven PSR 70cc (TCCD?) with little porting, Piston skirt at intake shortened 1.5mm, exhaust port has been widened 2mm total and from top of port to gasket surface 25mm so around 175 degree timing.
-Exhausts i got 2 different ones. One is a Homoet P6 replica that i fabricated to exact dimensions but has a 15mm centerbleed stinger from belly. Second is a AM6 Metrakit Thrower welded to fit my moped, removed stock 17mm stinger and put a 15mm stinger instead , advertised powerband for the stock pipe is 7500-11000rpm.
Top speed i got now is 69kmh, torque is high at 5000 rpm but after 8000rpm it lacks ompf.
I got 5 gears so its not a problem to keep it in powerband if i did more exhaust timing than whats usual on 1/2 gear puchs. Does anyone see anything wrong with my setup? Im guessing more spark timing to say 18 degrees and probably more exhaust timing (say 185 degree?) would do the trick?
I have read so many threads on this forum but sense i have a kind of hybrid engine i thought it would be best to just make a new thread explaining my setup and what would be best to do.
This is how you build a reliable 74cc two-stroke 5-speed engine. A year ago, I uploaded a video called "Tomos 74cc APN4/4L 5 Speed Engine Build Timelapse". Back then, I did not realize slamming a Puch 74cc Airsal cylinder on a Tomos APN engine would be so problematic and expensive ;)
Setup is a Puch 74cc Airsal kit, Dellorto PHBG 21mm, custom intake manifold, custom exhaust pipe and carbon fiber muffler, MVT premium inner rotor ignition system and a Rito crankshaft. I changed the original L17 bearings with solid 6203 crank bearings. Finally, my Tomos Revival Café Racer project is a reliable moped
I have a Tomos Apn4 5speed engine with welded transfers and redone to fit a Puch PSR 70cc kit. (Puch Shop Racing) But im dissapointed with the power output. its got a super wide power band and without that two stroke ompf and ketchup effect. The bike is used for classic moped rallys on weekends. So no need for long term reliability (used total runtime 8h per year) Setup is as follows.
-Tomos Apn4 engine with 5th gear added
-Brand new Top Racing Crankshaft
-Transfers welded up and portmatched to fit PSR 70cc Puch cylinder
-Minarelli AM6 flywheel and whole ignition system timed at exactly 15 degree BTC
-19mm Dellorto Black Racing carb with 19mm intake (plug brown)
-80km driven PSR 70cc (TCCD?) with little porting, Piston skirt at intake shortened 1.5mm, exhaust port has been widened 2mm total and from top of port to gasket surface 25mm so around 175 degree timing.
-Exhausts i got 2 different ones. One is a Homoet P6 replica that i fabricated to exact dimensions but has a 15mm centerbleed stinger from belly. Second is a AM6 Metrakit Thrower welded to fit my moped, removed stock 17mm stinger and put a 15mm stinger instead , advertised powerband for the stock pipe is 7500-11000rpm.
Top speed i got now is 69kmh, torque is high at 5000 rpm but after 8000rpm it lacks ompf.
I got 5 gears so its not a problem to keep it in powerband if i did more exhaust timing than whats usual on 1/2 gear puchs. Does anyone see anything wrong with my setup? Im guessing more spark timing to say 18 degrees and probably more exhaust timing (say 185 degree?) would do the trick?
I have read so many threads on this forum but sense i have a kind of hybrid engine i thought it would be best to just make a new thread explaining my setup and what would be best to do.
No comments:
Post a Comment