Will this bearing last? Dirt bike

Jimi Gray · Mar 26, 2023

Hi all I’m currently in the early stages of designing an electric start system for my Dirtbike (Kawasaki KDX200) using a bendex style set up. The bendex has to be mounted the wrong way, the bendex will engage the engine via a gear attached (bolted) to the flywheel (see photos) but due to it having to be mounted the wrong way I’ll need to put a smaller gear in between the flywheel and the bendex to reverse the rotation and turn the engine in the correct direction. This small gear would be constantly spining with the engine when it’s running) I’d use a sealed bearing mounted onto a shaft. So my question is would this sealed bearing last under constant motion and spinning at the same RPM as the engine? Keep in mind the gear is very small so there would be a lot of stress on the bearing only stress from the RPM of the motor. Cheers images bellow

(photos of are of the bendex fully extended downward to show it engaging the small gear)

TugboatEng · Mar 26, 2023

Yes. There are lots of bearings of the same type within the engine and provided you're is not loaded during normal operations it will exceed the life of those other bearings.

Can you find a starter that does not require a support bearing?

Can you find a starter with a roller clutch so it can stay engaged with the primary gear at all times?

As a fellow dirt bike rider, e-start on a KDX? That bike will start itself with a stiff breeze on the kick starter.

Jimi Gray · Mar 26, 2023

In order to remove the use of a a chain and starter sprag clutch which requires oil to use and also adds extra moving parts
. I’ve decided to use a bendex as it can be run dry. The only “load” on the bearing will be that of the engine spinning. As for the kick start yes absolutely these bikes start unbelievably easy, but I ride enduro so I cant count the amount of times I’ve had to actually get off my bike to kick start it. In this situation an E start set up would be amazing it seems like as long as the shaft is the correct size and has good tolerances. The bearing is pressed in straight and is lubed properly it will last. Thanks for the reply.

XR250 · Apr 18, 2023

Didn't Kawasaki have a 2 stroke engine in the 70's that used the flywheel/stator as a motor for electric starting?
As someone with an XR250R (imagine that), I feel your need for the magic button.

XR250 · Apr 18, 2023

Seems like there would be a bunch of drag with that small gear always spinning. Can't you reverse the direction of the starter somehow?

SwinnyGG · May 11, 2023

XR250 said:
Can't you reverse the direction of the starter

This is the path I'd be wanting to take.. starter motors are DC devices, it can be done. The changes needed are straightforward, how easy it is depends on the specific construction of the motor you're using.

The easiest solution would be to find a starter motor that turns the right direction. Starter motors are cheap.

Jimi Gray · May 11, 2023

https://www.eng-tips.com/userinfo.cfm?member=XR250

Yes I’ve luckily found a bindex which spins the correct way so no need for that silly idle gear and bearings set up so now I can just use a starter motor and bindex. That’s all Ill need so it’ll remove the extra moving parts. This is a far better set up and should last forever.

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