Pedal/motor clearance interference, necessitating pedal shaft extension replacement?

[nimblebee]

Idea of adding kickstart or a pull cord start addition to motor is appealing, but it always runs into the same problem: pedal width distance is too narrow to clear motor with these additional accoutrements.

Park Tool has video identifying what type of crank bicycle has, which would serve as a starting point to determining what crank extension kit to order.

Alternative would be getting out the grinder and welder to add extensions to whatever you've got to work with?

Not locating any ideal pedal shaft extension kit, another potential method of extending crankshaft using adapters as pictured has possibilities.

Basically, something needed that would fit end of pedal crank shaft, extening length of shaft, and have correct end pedals could fit into?

If commercial product, for whatever reason, wouldn't fit, one could locate correct threaded coupler/bolt combination which could be cobbled together.

 

[nimblebee]

Took a look at crank and pedal setup on motorized bicycle. Was hoping for 3-piece crank, because that would be the easiest to work on, modify & to be used with shaft extensions.

Welding extra length on shaft would be saving me some time, money & having to wait for parts, thereby avoiding time spent trying to figure out what shaft extension kit would play nice & actually fitting what frame set-up bike's using.

Doing a lot of work today on my day off with the motorized bicycle and weather cooperating, I'll revisit removing pedals/crank later on today.

One thing I've been able to determine for sure: quite a bit of clearance is needed, provided by shaft extension to prevent pedals striking pull start kit, which arrived via post today.

With different accouterments already welded into bike frame, I'm not having any current clearancing problems nor parts shifting about, but definitely shaft will have to come out an inch and a half or two inches to be able to clear everything pedals could whack, if adding kickstart and pull start kit.

Motorized bicycle kits are fun for those who like to customize, invent, and experiment. Thankfully parts are readily available and quite reasonably priced.

Anyone that desires a "trouble-free" jump-on-it-and-ride convenience, is probably going to find themselves dissatisfied with a motorized bicycle, as it's being a maintenance-hungry machine, always needing tinkering/tuning.

 

[nimblebee]

Located forum post by chappie wrenching4fun, managing to weld extension into his pedal crankshaft, providing sufficient clearance to avoid pedal arm striking motor:

W

Post in thread 'Way Back Machine'

Jan 30, 2025

It warmed up a bit today so I ventured into the shop to work on the Wayback Machine. Since the GHX Honda sits low in the frame and is a little broad in the beam, the pedals wouldn't clear the flywheel shroud. My solution was to extend the pedal shaft. Note from the photos that the key slots were held in alignment by a long piece of keystock during welding while an angle iron jig held them perfectly straight. I welded a bead from one side of the slot to the other so I didn't have to re-cut the slot. The splice probably isn't as strong as the rest of the shaft but I don't expect that to be a...

• wrenching4fun

• 

EZL innovated by using oxy acetylene torch to heat & form metal enough to avoid pedal arms hitting motor, without having to add aditional extension piece onto shaft.

Post in thread 'Phatmoto Right Pedal Striking Engine Pull Starter Solution'

Sep 23, 2021

After a crash, I'm guessing that the crank arm is bent... Remove the crank arm & bang it straight with a hammer.

I had worse clearance problems on my 212cc bike and even though I had the extended pedal shaft on the bike neither pedal would clear
the CVT housing or the engine. That was 2 years ago and I had a Oxy/Act torch but I ran out of Oxygen so I did manage to heat and
bend the pedal arms using a propane torch and used a lot of persuasion using a heavy hammer after heating them. The Oxy/Act
torch would have made it a lot easier since it could get it hotter for bending. I...

• EZL

• 

Good to know alternatives, if fail locating appropriate fitting shaft extension kit. I get by with welding, but they're strong welds, not pretty: more like chewing gum mixed with peanut brittle.