How fast can your 80cc really go?
- Thread starter freshwater
- Start date
- Status
My 80cc will go 43mph on the flats and 30mph going up steep hills. I have done numerous mods. I changed to a 36t sprocket to start. Port matching the intake and exhaust is a must. They are so far off it's not funny. Also my muffler has been modified slightly because I really don't want to make it louder than it is. Remove the endcap and cut the long tube off as short as you can. This doesn't make it much louder but allows for a more smoother path out. Change plug to NGK and plug wire to a good performance 7mm wire. Lastly, this mod gave me 5mph up steep hills and really put the power in my bike. Remove your carb and intake manifold and put your piston to TDC. The piston shoud completely open your intake port to the top of your port. My engine had 1/4 to 1/3 of the port still covered at TDC. Take a scribe and mark on your piston the amount that is still showing. Remove head and cylinder, cover and tape up the crankcase opening and rod. With a dremmel tool, remove all that material from your piston that you marked. Smooth the edges of the piston that you just cut with a small file and assemble. You will be amazed how much more power you will gain. You will probably need to adjust your carb needle and give it more fuel. Mine runs so good, starts so good, idles so good that I am done working on it.
mine goes so fast I can catch myself racing around the block
my 70cc is the fastest at 38mph I pussed out used a gps for reading the speed.
80cc bushed is 31 mph 44 tooth rear sprocket
70cc bushed is 38 mph 36 tooth rear sprocket
70cc needle bearing wrist pin 34 mph 44 tooth rear sprocket
50cc needle bearing wrist pin still in the break in stage but should be about 30 to 32mph on a 44 tooth rear sprocket
my 70cc is the fastest at 38mph I pussed out used a gps for reading the speed.
80cc bushed is 31 mph 44 tooth rear sprocket
70cc bushed is 38 mph 36 tooth rear sprocket
70cc needle bearing wrist pin 34 mph 44 tooth rear sprocket
50cc needle bearing wrist pin still in the break in stage but should be about 30 to 32mph on a 44 tooth rear sprocket
I did 70.9kmh or 44.3mph on the flat two days ago, I finally put a speedo on.
Mods include:
I have increased the compression by machining the head and also removing the gasket between the barrel and crankcase, use silicon to seal there.
I have removed the small area of the piston skirt that slightly covers the inlet port when the piston is at TDC.
I have match ported both the inlet and exhaust ports and removed the casting burrs in the intake manifold.
I have ground a 45 deg edge of the top of the piston at the exhaust port. Don't grind down to the top ring.
Running a NGK plug.
My rear sprocket is 22 tooth however the wheel is a 20" x 4.5" Stingray spoiler, the tyre diameter is 500mm. These tyres have a large profile, the rolling diameter is about half way between a normal 20" and a 26" tyre.
I run the pull start and centrifical clutch kit and it pulls really well of the line and the top speed is excessive. I run the tall gearing not for the speed but for the nice quiet low revs when I am cruising.
Engine is sweet, starts first pull and idles well.
Cheers,
Matt.
Mods include:
I have increased the compression by machining the head and also removing the gasket between the barrel and crankcase, use silicon to seal there.
I have removed the small area of the piston skirt that slightly covers the inlet port when the piston is at TDC.
I have match ported both the inlet and exhaust ports and removed the casting burrs in the intake manifold.
I have ground a 45 deg edge of the top of the piston at the exhaust port. Don't grind down to the top ring.
Running a NGK plug.
My rear sprocket is 22 tooth however the wheel is a 20" x 4.5" Stingray spoiler, the tyre diameter is 500mm. These tyres have a large profile, the rolling diameter is about half way between a normal 20" and a 26" tyre.
I run the pull start and centrifical clutch kit and it pulls really well of the line and the top speed is excessive. I run the tall gearing not for the speed but for the nice quiet low revs when I am cruising.
Engine is sweet, starts first pull and idles well.
Cheers,
Matt.
Attachments
1000W, I JUST BOUGHT A BLACK SCHWINN STING RAY CHOPPER YESTERDAY FOR 75 BUCKS, VERY CLEAN. IT IS SMALLER THAN I HAD THOUGHT. MY 285 + LBS LOOKS LIKE OVERLOAD OR OVERKILL!! DID YOU MAKE YOUR MOTOR MOUNT? WHAT ABOUT THE REAR HUB.? I KNOW YOU CAN BUY THE NEAT PARTS, BUT THAT GETS THE TOTAL INVESTMENT UP PRETTY HIGH= FOR RESALE. THE SPOKES LOOK A BIT THIN. THEY WERE NOT MADE FOR MOTORS, SURE ARE "PURRRDY" THOUGH. ENJOY YOUR RIDE. LATER RON 
DID YOU MAKE YOUR MOTOR MOUNT? WHAT ABOUT THE REAR HUB.? I KNOW YOU CAN BUY THE NEAT PARTS, BUT THAT GETS THE TOTAL INVESTMENT UP PRETTY HIGH= FOR RESALE. THE SPOKES LOOK A BIT THIN. THEY WERE NOT MADE FOR MOTORS, SURE ARE "PURRRDY" THOUGH. ENJOY YOUR RIDE. LATER RON
I went to do this the other day, and it turns out my motor (from zoombicycles.com) doesn't have this issue. That's a nice plus.
Hi All, I Bought A 10 Motor Kit Close Out On E Bay A Few Months Ago. 7 New Engines In The Box And 3 Used Motors. One Has The Cyl Off, The Piston Is Scoured, The Cyl Looks Good. Where Can I Get A 49 Cc Piston And Ring ?? Good To Do The Mods As Its Allready Apart. I Think TheY Are Grubee Spitfire?? Ron
NEAT TIMES I am only using the rear wheel and tyre off the stingray, the bike is a custom frame, see here. http://motorbicycling.com/f26/two-stroke-cruiser-2916-5.html
Cheers,
Matt.
Cheers,
Matt.
GOOD DAY, MATT, I THINK I REMEMBER YOUR PICTURES WHEN YOU WAS BUILDING THE FRAME, YELLOW AND DIFFERENT COLOR PIECES!! NOW ALL YOUR EFFORT IS PAYING OFF. ( DOES "GOOD DAY" MEAN HELLO OR GOODBYE??) MAYBE I USED IT INCORRECTLY!! HOW ARE THE BLUE MOTOR MOUNTS DOING THEIR JOB? GREAT IDEA IF THEY GET THE JOB DONE! YOUR MACHINE LOOKS GREAT. THANKS FOR THE PICS. HAS BEEN T SHIRT WEATHER FOR SEVERAL DAYS.l RON
) MAYBE I USED IT INCORRECTLY!! HOW ARE THE BLUE MOTOR MOUNTS DOING THEIR JOB? GREAT IDEA IF THEY GET THE JOB DONE! YOUR MACHINE LOOKS GREAT. THANKS FOR THE PICS. HAS BEEN T SHIRT WEATHER FOR SEVERAL DAYS.l RON
No such thing as an 80cc engine kit out of Asia. but.. I can cruise 35-38mph on my 69cc F80 with a 36T at 9000 feet. Thanks..
Ok, finally installed a CatEye speedo yesterday.
So, I hit 35 on cruise, 37.5 with 8gram nitrous shot from my homebuilt nitrous kit, (anyone wants instructions? seriously, its easy and I feel it is very controllable, total cost is about $40).
With pedaling all out and nitrous shot, 39.1.
Port matched intake and exhaust. 36t sprocket.
Specialized Hardrock Sport, 80cc RAW, stock carb and exhaust.
I work at Spookytooth Tucson now, so any questions or ideas let me know.
I am designing a custom tuned pipe, going to upgrade the carburetor, and find a bigger nitrous canister.
look out at the deathrace! I'll be on the bike that looks like a stealth fighter.
Andyinchville: I need a smaller sprocket Bike+rider= 180lbs and I know my engine has the power i can cruise 30 uphill... Call us back at Spookytooth in Tucson!
So, I hit 35 on cruise, 37.5 with 8gram nitrous shot from my homebuilt nitrous kit, (anyone wants instructions? seriously, its easy and I feel it is very controllable, total cost is about $40).
With pedaling all out and nitrous shot, 39.1.
Port matched intake and exhaust. 36t sprocket.
Specialized Hardrock Sport, 80cc RAW, stock carb and exhaust.
I work at Spookytooth Tucson now, so any questions or ideas let me know.
I am designing a custom tuned pipe, going to upgrade the carburetor, and find a bigger nitrous canister.
look out at the deathrace! I'll be on the bike that looks like a stealth fighter.
Andyinchville: I need a smaller sprocket Bike+rider= 180lbs and I know my engine has the power i can cruise 30 uphill... Call us back at Spookytooth in Tucson!
Was clocked at 45mph today by friends 50cc scooter, which I out ran out of the hole and uphill...Dax 80
all these reports give me hope for my project. i was thinking that i was going to have a **** of a time getting up to 45mph but it seems like its completley within reach.
especially because i have been having a lot of long email conversations with a two stroke authority who used to race Krindler GP bikes and holds a current two stroke world record. hes been helping me systematically break the tuning process for this engine down to a science. im even thinking about offering a complete top end upgrade kit if our findings yield good results.
ive also talked to my uncle whos worked with boats as a hobby all of his life and is real handy at working with fiberglass about making a GP style fairing. any one interested?
especially because i have been having a lot of long email conversations with a two stroke authority who used to race Krindler GP bikes and holds a current two stroke world record. hes been helping me systematically break the tuning process for this engine down to a science. im even thinking about offering a complete top end upgrade kit if our findings yield good results.
ive also talked to my uncle whos worked with boats as a hobby all of his life and is real handy at working with fiberglass about making a GP style fairing. any one interested?
sPOOKYTOOTH TOP ENDand cns carb ,long pipe,and long plastic intake runner[gas can nozzle]cut to 5"...36tooth rear....ported...26" tires...='bout'42 on the flat ...32 uphill and catcha car for the draft and did 50+ and LET OFF,Quickley ; oh yeah, took a bunch off the head and used ultra thin head gasket,expansion chamber is about 48" long,with a 1"by18"long header pipe...phat
Last edited:
- Status
