Schwinn High Timber hi speed build

reed ported cylinder
 

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Wow that's a lot of changes to the cylinder. I'm pretty sure thats going to make a big difference. I can't wait to hear what that does for you.
 
biknut... 32 has been the fastest ive been able to go. I dont know why, i guess i misread someone's post and had jetted my carb to 72. Today i got a new NT carb and moved the needle to the center position. I put my 66 jet on the new nt carb. Hopefully if its not raining tommorrow i can tell you how it went.

So to recap:
bicycle
Schwinn High Timber 26" bike 21 speed
26 1.95 kenda tires
cloud nine big cushion seat
origin 8 low rise bars

engine
Dax F80 engine
Arrow ported reed cylinder body
fuel/air
Nt carb jetted 66 with c clip in middle position
SBP heavy duty air filter
electrical
ngk b6hs plug
SBP spark plug boot
drivetrain
36T sprocket
spring chain tensioner
exhaust
stock pipe with 1" cut off of stinger
exhaust wrapped header

estimated top speed:36.7
achieved top speed:32.8
goal: 36mph flat out
 
it went... bad. New carb didn't seat right so i had an air leak right off the bat. Chain stretched some more and spring stretched some more. so chain kept jumping up and jamming into engine housing. when i did get it to start air leak symptoms prevented me from checking engine power. I know this thing can pull so i really hope to get some good things out of this engine this month.

ordered a gasket set and 68 jet and a head bolt kit, when i get everything dialed in right, i want to try the 50cc hi hi head again. with a much cooler b8 plug
 
today's run i moved my needle back to the middle position, and changed the jet to #70 jet. i ran my bgf expansion chamber, and i still top out at 30 on flats.
 
graydog8josh said:
today's run i moved my needle back to the middle position, and changed the jet to #70 jet. i ran my bgf expansion chamber, and i still top out at 30 on flats.
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On all my bikes a 70 would be way too rich. Usually I end up with a 66, and the needle clip in the next to the top for NT carbs. If it's a speed carb the needle clip likes the top position more.
 
i don't know you're having trouble getting to 36 mph. All my 80s would do 36+ stock with just a 36T sprocket.
 
me either. I had the clip at the 2nd position and it had no power. so i moved it back to the middle. i had the 66 jet and it ran really hot and it wasn't going any faster. with this it seemed to run better but when i get to 28-30 WOT it starts oscillating like, it will pull and then release and pull and release. also, ive found that it runs smoother with the choke partially on until it warms up.
 
graydog8josh said:
me either. I had the clip at the 2nd position and it had no power. so i moved it back to the middle. i had the 66 jet and it ran really hot and it wasn't going any faster. with this it seemed to run better but when i get to 28-30 WOT it starts oscillating like, it will pull and then release and pull and release. also, ive found that it runs smoother with the choke partially on until it warms up.
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That sounds like 4 stroking, which usually indecates too rich.

You've made sure you're not starving for fuel I assume? Gas cap vent is good? Float level is not set too low? Petcock flows well? How many miles are on the engine?
 
i dont know how to set my float level. I recently cleaned the petcock that was my problem last week it was filled with paint. theres about 400 miles on this engine. I am pretty sure the gas cap vent is okay and when i push the prime i can see flow.
 
If you adjust the float level too high gas leaks out. Too low and it's can starve for fuel at high speeds. Yours is probably ok.

Are you running a reed valve, and high compression head?
 
that i shouldnt need to jet. Im guessing that means whatever worked before should work. Before i got the reeds i was running 66 jet 2nd clip position.

let me make sure i understand this:
the second position is like this on the picture, right?
 

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graydog8josh said:
that i shouldnt need to jet. Im guessing that means whatever worked before should work. Before i got the reeds i was running 66 jet 2nd clip position.

let me make sure i understand this:
the second position is like this on the picture, right?
Click to expand...

Yeah that's right.
 
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