Drag Bike Questions

theamusingnerd

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Hello! I am building a drag bike. So far, I have a Dax RT carb, I am putting a tuned pipe on it and a Puch 70cc head. Do you think a 50cc head would be better? My only concern is that in Phoenix, we can only get up to 91 octane gas. Also, what size rear sprocket should I go for? I can't decide between a 40, 39, and a 36. I need the best compromise between acceleration and speed.
 
You can get some avgas, 100 octane stuff is about $6 a gallon and contains no ethanol. It's leaded, but the lead content is lower than typical leaded street gas
 
depends on what power the engine is making. I like using 40 tooth sprockets personally.
 
major lack of info!

what engine are you going to run? primary redux ratios if it isnt a standard HT? what size tyres are you running?

port work, what have you done, and what RPM have you tuned it for? is the pipe also tuned for the same rpm? are you geared to allow it to reach such an rpm?

yarda yarda... shifting or single speed?

wouldnt worry about compression ratios and octane if its only doing short runs, if it detonates...who cares? pistons are cheap.

reed valve or piston ported? what size intake? does the carb match the intake? a bigger carb on the standard intake is still restricted by the intake.

standard HT id go 39 or 40, if its on 26" wheels...
 
major lack of info!

what engine are you going to run? primary redux ratios if it isnt a standard HT? what size tyres are you running?

port work, what have you done, and what RPM have you tuned it for? is the pipe also tuned for the same rpm? are you geared to allow it to reach such an rpm?

yarda yarda... shifting or single speed?

wouldnt worry about compression ratios and octane if its only doing short runs, if it detonates...who cares? pistons are cheap.

reed valve or piston ported? what size intake? does the carb match the intake? a bigger carb on the standard intake is still restricted by the intake.

standard HT id go 39 or 40, if its on 26" wheels...

Standard HT engine. Port matched. Extended intake. It will have a bicycle motor works expansion chamber and a Puch 70cc hi hi compression head. Dax RT Carb. Single speed. Also, I am planning on driving too, as I will have to get it to and from the track and everything.
 
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Maybe you should return to a short intake tract since the extended one focuses power at lower rpm instead of at high rpm like a race bike needs.
 
Maybe you should return to a short intake tract since the extended one focuses power at lower rpm instead of at high rpm like a race bike needs.

Although I need good acceleration as I am drag racing. I also need to clear the frame. If you think it would help a lot, I can make it work.
 
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