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Thread: Two Questions: Exhaust and RPM
12-04-2006 #1mrsaxman99 Guest
Two Questions: Exhaust and RPM
1) What is a good/safe way to bend the exhaust pipe. I need a good 15 degree bend on it to get it out of the way of my left pedal. I know you need to remove it from the engine, but then can you just bang it with a hammer???
2) has anyone figured out a good equation for getting accurate engine RPM based on Speed (using a 26" tire and 44 tooth sprocket)? I will probably go to the trouble to figure it out exactly once I get mine up and running.
12-04-2006 #2motorbicycle Guest
About the muffler, I just put it in a vise and pulled and pushed on it with my hands. It is fairly weak so it should bend. Keep doing this until you get the right bend.
12-04-2006 #3davidsis Guest
I do not get the RPM question. seems like you only have one selection High. RPMs on mine with 26" tires at 25 mph is crazy high.
12-04-2006 #4gone_fishin Guest
do not bang on that pipe with a hammer, any place you ding it is gonna rust much faster (inside too)
use wood blocks inside and outside your curve, and have patience, work the bend a lil at a time, moving slowly along to avoid a sudden kink...that's my 2-pennies worth 8)
12-05-2006 #5bird Guest
heat the pipe up with a propane torch while its in a vice and then bend it. it works alot better i did this on one of my pipes. the pipe might blue where u heated it up tho.
12-05-2006 #6Dr. J. Guest
To get an accurate RPM indication, you might consider the Sportech Mini-Tach. You can get them for two or four stroke motors. Search the Internet and look for the best price. I had one on a Cushman a few years ago and it worked great.
12-05-2006 #7mrsaxman99 Guest
Cool I'll try heating the pipe.
Audgidog, use wooden blocks inside and outside the curve, and then bend by hand I assume you mean?
Davidsis, I am talking about simply using bicycle speed to determine RPM. you can do the math...20mph -? bicycle tire rotations per minute, then just divide out the ratios till you get to the crank of the engine. Do this so you can just have your speedo on your bike and know that 20mph = 4k rpm, 25mph = 5k rpm, etc...
anyone know the gear ratio on the crank side of the engine...when I briefly looked at it, looked close to 3:1...i'll pull the cover and count teeth.
12-05-2006 #8gone_fishin Guest
yup, using heat with wooden blocks should make for a fairly easy & clean bend 8)
don't forget to wear some gloves :?
hehe, you're lil RPM/science project reminds me of a technical drawing i did for physics in high school...i used pulleys, gears, levers, etc...had about 30 or so components with a mechanical mad-vantage of something like 28,000:1 :P
12-05-2006 #9davidsis Guest
12-07-2006 #10bird Guest
the oldschool mechanical speedometers that hook up to the front wheel also tell you how many rpms your bikes running. they are cheep to like 20 bucks