Finally! I got the right Main Jet on this HS142F with an NT carb. I used a #76 jet that i bought from sick bike parts, e-clip of the needle is at the top (leanest) and using the SBP airfilter originally used on the stock carb. It idles great and pulls hard, ( i weigh 240lbs and easily pulls however top speed is still questionable since im using a 5:1 gearbox and a 50T rear sprocket. Im gonna change back to a 44T and see what happens.
Finally got it to work!
- Thread starter docjph83
- Start date
Will'smotobikes19
Well-Known Member
50T is pretty big I recommend a 41 or 40 tooth.
JerboaJohn
Well-Known Member
sweet,,, luv the exhaust. keep us posted on what it's like with smaller sprocket, if it can still pull good
Timbone
Well-Known Member
I was wondering if you could use a NT carb on a 4 stroke. Thanks!!!
MotorBicycleRacing
Well-Known Member
Have you counted the teeth on the sprockets in that gearbox?
How many teeth on the front and back sprocket in that gearbox?
How many teeth on the sprocket going to the back wheel?
If you give us all the tooth counts we can do the gearing calculations.
Gearbox Inner Sprockets
Front 6T, Rear 41T
Drive Sprocket 10T
Rear wheel sprocket 50T
MotorBicycleRacing
Well-Known Member
Are you sure you counted teeth right?
8000 rpm redline on 26.5" dia tires with 50 tooth is only 18.5 mph
8000 rpm redline on 26.5" dia tires with 40 tooth is only 23 mph
8000 rpm redline on 26.5" dia tires with 36 tooth is only 25.6 mph
8000 rpm redline on 26.5" dia tires with 30 tooth is only 30 mph
thanks! how about take off? would I need to pedal start it if i use a 40T and below sprocket
Timbone
Well-Known Member
My 140cc 4 stroke motor has a decent carburetor but the butterfly valves (throttle and choke) are attached to chinsy plastic parts that lean against one another. Using a simple NT would make things so much simpler in terms of hooking up the throttle cable.I’m using an NT on this build.
I have a set of jets! I have a .75 and a .80 - I’ll put in the .80 and see if I can get a start!
