Just how wide is a Wide Pedal Crank?

cachehiker

cachehiker

New Member
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.
 
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.
 
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.
 
cachehiker said:
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.
Click to expand...

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
 
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
 

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jimraysr said:
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
Click to expand...

Hi jimraysr. Where did you get your cranks?
 
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
 
Thanks Jim.

Your right about the time used for just finding all the stuff that will play nice together. Can be maddening.:eek:
 
jimraysr said:
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
Click to expand...

Hi Jim, Nice pedal cranks you have.
I don't see these on Spooky Tooth's online parts list. (only the one piece crank set) Did you have to call Spooky's for them?
 
Yes, I did call him to get them. May have been ones left over for a 4 stroke build? Anyway he seemed pretty down on the GruBee 4 stroke kits back then (18 months ago) as he like a lot of dealers has gotten stung with transmission / clutch problems. He didn't say anything directly about them, but was very hesitant to sell me a transmission, fearing a kickback? I got what I paid far and knew the possible problems.

The transmission I got from him, like the one in my kit, the clutch has the wrong size keyway, which didn't match the engine or the idler bushing? eventually I got the proper one from Bicycle Engine. So I have a spare transmission and two clutches. when I need a clutch, I will mill the key slot wider or step a key to fit it? No biggie.

Anyway after seeing the GruBee belt drive, I am glad I have a transmission for a future build.

Back to your question, maybe he has an other set of wide cranks and the sprocket?

Jim
 
Thanks for the info Jim.

I have a Walmart Schwinn Point Beach 7 speed with a ZoomBikes 66cc 2 stroke and a Sick Bike Parts shifter kit on it. I want to use a pull starter and need wider crank arms for that.

I just ordered a pair from "GasBikeShop - RuiHong Enterprises Ltd." I'll find out how well that outfit does business soon enough. They were $28 with the shipping.
 
I got a pull start for the 48cc that I was given. Took a little juggling with washers and nuts to get the moving part to clear the mag frame, but now, it looks good. The only place I found the pull start was Zoombicycles. They suggest changing the China rope. Other engine parts I needed came from Gasbike.net / KingMotorBikes (same outfit.) They both acted like business, businesses and gave good service.

Good you found the cranks. I looked for several weeks.

Jim
 
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