What kit is good for me?

toxanadu · Jan 29, 2009

Hello everyone. wondering if you can help me out picking out a kit.

BACKGROUND:
This bike is for training for our bike racing team. We need a bike to comfortable hold around 35mph for hours. We will be drafting behind the motor. we originally wanted a electric bike so we are not sucking exhaust fumes, but getting that speed and distance is 1 big expensive battery. we are hoping we can point the exhaust down, so we can avoid inhaling fumes. we are concerned about holding speed, rather than acceleration. this bike is for open roads(the flatest we can find)and on our velodrome.

WHAT WE NEED:
motor kit that can comfortable hold 35mph. maybe quick burst of 40mph. acceleration is not a concern, holding speed is what is important.
Budget is a concern. the lower the better.
over gear the bike to hold speed?
we need a reliable motor, as we will be using 2-3x per week.
I think the motor in a frame is better for center of gravity, as our veldrome is 44 degrees of banking.

your thoughts on what kit is good for me?

thanks!

brisbane_boy · Jan 29, 2009

hey mate, I would recomend a 2 stroke if it going to be for extended amounts of time. the only problem would be u will have more exhaust fumes from the 2 stroke. but the 4 stroke would be alot more expensive. A 2 stroke happy time with a few minor mods would be able to do 35-40mp/h.
Im not that in the know of four strokes as some other ppl on this forum so maby they can help out a bit more.

Finfan · Jan 29, 2009

A 2-stroke with a shifter kit would probably do the job for you. They don't really put out that much exhaust. The shifter kit is a bit more expensive and you will need somebody with some mechanical know how to assemble and maintain.

MB-Monkey · Jan 29, 2009

i would agree an 8 speed rear hub, a shifter kit and a well modded 2 stroke would do the job. my advice would be to take it to a hot rod shop have them port and polish it for you it would not cost very much as it is a small job.

as far as exhaust goes use a good synthetic oil and it would be negligible.

Reliability... well any motor you run for hours on end is going to have problems the nice thing about the two strokes is they are inexpensive so buy 2 kits have them both modded that way if you have a failure you can be up and running in less than an hour.

Clotho · Jan 29, 2009

The bike you are describing is called a Derny.

Derny

The guard on the rear wheel is to prevent contact with the bicycle wheels drafting it.

They can be purchased here: Derny Sport UK

They are a bit pricey but they are known to be very reliable. One thing to note is that the engines are about 98cc. This should give you some indication as to what you need for power. I would be looking for something in the 6hp range.

If I was to build a bike for your application I would chose a Morrini motor or one of the larger rear rackmount kits. The Chinese kits are innexpensive but your application would be running it WOT the entire time and I am not confident that it will hold up to that in the long term. I have noticed that most Derny style racing in North America seems to use a small motorcycle or a moped for the Derny.

toxanadu · Jan 30, 2009

Thanks for the replies.

Clotho, yup, we are looking for a derny. I am planning to put a roller on the rear so we can bump into the bike.

The way i have been reading, I think i should stay away from the cheap chineese motors for reliability. I e-mailed thatsdax and he recommended, the titan kit.

anyone with a titan kit, have problems with the rack mounted engine? do you think the extra weight will be a problem on a 44 degree banking velodrome? I was still thinking on a 36t ring for high speeds.

Bikeguy Joe · Jan 30, 2009

I am not sure a Titan or any other chinese motor kit is going to hold 35 mph for long periods, most won't go 35, period.

I would suggest a purpose built Derny, or a modified scooter. (not a chinese scooter, a Honda, or a Yamaha.

urace4me2 · Apr 12, 2011

I had a honda helix scooter that I mounted a cheap trunk mount bike rack to, then modified the rack to hold a PVC roller. It worked great. The rack/roller mounted to the rear trink lid using bungy chords. We motorpaced with it a few times then I sold it to another racer. I suggest the scooter option, then find a way to make a roller.

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What kit is good for me?

toxanadu

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brisbane_boy

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Finfan

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MB-Monkey

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Clotho

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toxanadu

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Bikeguy Joe

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urace4me2

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