Cotter pin wear

[a101960]

Just changed out my kick start cotter pin, because the crank had a small amount of play. Bit of a b*gger to knock the old one out! All went well until it was about three quarters of the way out and from there on after it was quite a battle. Are they all like that sir? Anyway the new one went in easily enough, and everything is nice and tight now, so a new cotter pin resolved the problem. Luckily there was no visible wear to either the shaft or the lever. However, I will make sure that I keep an eye on things in the future. Maybe the old pin metal was a bit soft, or is the cotter pin designed to be a sacrificial component to safe guard against damaging the shaft and lever? This leads me on to a couple of questions:

1) Despite the fact that I had to knock the old cotter pin out, I fitted the new pin by just pulling it through by tightening up the nut. I know that it is now after the event, and therefore it is a bit late in the day to ask, but should I have knocked it through and just tightened it up with the nut?

2) Should the cotter pin be regarded as a consumable and be renewed periodically ( obviously do not want any damage to occur either on the shaft or the kick start lever).

John

[bsa-bill]

all cotter pin are not of the same taper, thickness or length, I've found it difficult to get correct ones to fit our kick starts, Kick start levers may be wrong as well of course.
I just give then a little tap to seat them and tighten the nut on

[Butch (cb)]

I thought you used to be able to buy them plain and file your own flat/taper on to them? They are quite soft for sure. My experience is that once you have them moving they pretty much drop out. They're bicycle technology really, used to hold the cranks on on cheaper/older machines. They last for years in that application without maintenance - and with a lot more 'kicking'.

[RichardL]

John,

This is quite a coincidence, just yesterday you were talking about an oily exhaust issue very similar to mine. Now I can say that, just last week, I had the exact same loose kickstart crank and stuck cotter pin issue as you. I was beating like crazy on the loosened nut with very slow and difficult movement. It got to a point where it wasn't moving anymore while using sane hammering force after applying some heat. I was starting to worry about fracturing the gearbox cover so I grabbed the back end of the pin with a Vise-Grip pliers and I was able to twist and pull until it finally let go.

Once out, I compared the shape of the old pin with the new one from SRM. The old one had a slower taper on the flat and, apparently, had to be pulled through further to do the job. Thinking about it, the whole concept creates and depends on friction between the top half of the pin and the kick crank. With the slower taper, more surface area is subject to the friction. Also, we may find out later that the faster taper is faster to release the pressure.

Richard L.

[Butch (cb)]

Pulled through further - nut bottomed out on threads?

[RichardL]

I can't quite recall if it got pulled through further over time or if it was like that when I first installed it. I was using washers riding on the surface of the crank above the counterbore. In any case there was no pin sticking out fhe back end of the crank, so, lots of "I'm stuck in here and I'm not coming out. Nah, nah, na, nah, nah."

Richard L.

[duTch]

 I won't be saying anything constructive or otherwise here, but I do hear what you are saying re; slow/long taper...makes sense that a steeper taper will release easier.
 I think I debated this with myself when I had to deal with same, but the details are flushed away*conf*, except to say the replacement went in like a bug in a rug...is that how it goes??
 Not sure if I used a stainless pin and/or anti-seize compound though, but now am curious..

 To go retrospect, I discovered the joys of cotter pins and left hand threads on the bicycle at about age eleven....thanks to "help" from a neighbour...(use a bigger hammer)!!! Needless to say I don't regard helpful neighbours well 

[bsa-bill]

I have assumed (possible wrongly) that the taper on the pin should match a taper on the shaft, without taking a kickstart lever off I can't verify that there is a taper on the shaft.
However if there is then the tapers should match , if there isn't then the steepness of the taper will matter not an awful lot as it will contact the shaft at one small point only.

If I have time today (got things to do in the big city) I'll examine a shaft, or maybe someone already knows the answer

[orabanda]

I have found it necessary to match (fit) the cotter pin on nearly every occasion.

The essential requirements are a file, a dab or two of bearing blue to confirm the taper bears across most or all of the shaft, and a little patience. If you don't have the faces matched, it is possible to shear the pin because of excessive loading on the pin.

Finish off with a cup of tea; its the most fun you can have on your own!

Richard 

[RichardL]

Richard,

So, "cup of tea" is what it's called in your quaint Australian slang?

Richard L.

[orabanda]

Others might call it a Swan Lager.

[Gerry]

Hi all, Gotta get my pennyworth in here... I had the same problem, Loose crank to shaft on the A10. Fortunately a few scientific hammer blows with brass drift and a loosened nut got it out ok. With regard to the taper on the cotter pin am I wrong in saying the taper will match up with the flat in the shaft no matter whether steep or shallow angle of taper, as I see it the crank will move around the shaft until the cotter taper and the flat in the shaft are parallel. Come on guys, let me know how much my senility has stuffed up my reasoning....Gerry

[muskrat]

No one here is senile Gerry. Some may be a little confused or eccentric.

[bsa-bill]

let me know how much my senility has stuffed up my reasoning....Gerry

No Gerry I can see the logic in your thinking (was going to say I get your drift but thought better of it  )

Now think your right up to a point except that as the pin has a back to it that engages the back of the hole in the kickstart lever, will there be a limit to how far the lever can rotate to accommodate the taper, - now you've got my brain chugging slowly up hill

[Rocket Racer]

I recently had to drill one out, it wasnt coming out otherwise, put up one hell of a fight