Just how wide is a Wide Pedal Crank?

cachehiker · #1 (**permalink**) 07-11-2008, 05:10 PM

The title says it all.

I'm looking at mounting a 4-stroke with a centrifugal clutch in the frame. I assume the wide pedal cranks are provided to ensure the crankarms miss the sides of the engine. Anyway, has anybody actually measured the Q-factor of these cranks?

I'm looking to motorize a ten year old GT with a standard UN-72 square taper bottom bracket. It's a triple crank that would be converted to a single ring in the front. I already have a much wider bottom bracket that I could use to put the crank arms out another half inch or more but I need to know how wide is wide enough.

Scotty · #2 (**permalink**) 07-13-2008, 09:28 AM

I guess it depends on the design and engine placement. I run a wide bb, 127mm, but this doesnt clear the motor. I placed the motor forward and higher so the cranks clear. Most frames dont have room for the motor in this space so you may need an x/large frame or custom made.

cachehiker · #3 (**permalink**) 07-13-2008, 10:55 PM

If 127mm doesn't clear the motor for you, I'm pretty sure I won't make it either. It looks like I can fit a 48cc 2-stroke in there if I can find a clutch actuating mechanism that I like. I don't want two levers on the left side and since I'm a cyclist first, I don't want to get used to braking solely from the right.

ocscully · #4 (**permalink**) 07-14-2008, 01:22 PM

Quote:

Originally Posted by cachehiker

The title says it all.

I'm looking at mounting a 4-stroke with a centrifugal clutch in the frame. I assume the wide pedal cranks are provided to ensure the crankarms miss the sides of the engine. Anyway, has anybody actually measured the Q-factor of these cranks?

I'm looking to motorize a ten year old GT with a standard UN-72 square taper bottom bracket. It's a triple crank that would be converted to a single ring in the front. I already have a much wider bottom bracket that I could use to put the crank arms out another half inch or more but I need to know how wide is wide enough.

The Optional Wide 3-piece crankset offered from GRUBEE and other vendors are designed to clear the Honda GXH50/Clone motor and its attendent gearbox. This set-up is 9.5 inches wide. The wide crankset is designed to clear this with what ever square tapered BB your bike has for its existing crank set. The wide crankset is also a single 44t sprocket. Just changing to a longer spindle isn't even close and would cause chain line problems for the pedal side as well if you could find a spindle long enough.

ocscully

Just

jimraysr · #5 (**permalink**) 07-14-2008, 01:58 PM

My Honda GXH50 plus a GruBee gear box is 232mm (9 1/8") at its widest point. Below the bulge for the bearings it is only 222mm (8.75")

My three piece peddle set clears 229mm (9")

The one piece that I could not use is 225mm (8.75")

I just installed the wide cranks yesterday on the 38mm (1.5”) factory lower bracket. The one piece crank requires a 51mm (2”) lower bracket to fit through and use the bearings that come with it.

The attachment is a picture of the new wide cranks. Jim

MotorbikeMike · #6 (**permalink**) 07-23-2008, 08:24 PM

Cachehiker, contact me if you like, I have Rotary clutch handles (match the old-style throttle)

Mike

Dan · #7 (**permalink**) 10-19-2008, 10:09 PM

Quote:

Originally Posted by jimraysr

My Honda GXH50 plus a GruBee gear box is 232mm (9 1/8") at its widest point. Below the bulge for the bearings it is only 222mm (8.75")

My three piece peddle set clears 229mm (9")

The one piece that I could not use is 225mm (8.75")

I just installed the wide cranks yesterday on the 38mm (1.5”) factory lower bracket. The one piece crank requires a 51mm (2”) lower bracket to fit through and use the bearings that come with it.

The attachment is a picture of the new wide cranks. Jim

Hi jimraysr. Where did you get your cranks?

jimraysr · #8 (**permalink**) 10-20-2008, 02:31 AM

Spooky Tooth. Think they were $20. Just the two cranks that fit on the square spindle of the lower bracker. The type that have internal threads for a removal tool and are retained by a bolt into the spindle. Good Luck.

Trying to find these parts often seems to be the most time consuming part. Guess I am going to have to buy a minil beer keg and make my own round tank to go behind the seat?

Jim

Dan · #9 (**permalink**) 10-20-2008, 06:05 AM

Thanks Jim.

Your right about the time used for just finding all the stuff that will play nice together. Can be maddening.