How Do I install PIn in Small the Gear.


Local time
3:38 PM
Jan 20, 2008
Sydney, Australia
How Do I Install this Pin into the Small Gear ??

Hi All,

My motor has had a failure...again.
(been motorless 3 weeks now)
The Clutch no longer engages the motor.
I have a 70 CC 2 stroke Chinese motor.

On The right side of the bike, when in sitting position.
There is a large cover plate for the bikes gears.
After undoing the five screws,
there`s two large cogs that sit inside this plate.

With clutch engaged and pushing the bike forward.
The smaller cog goes round and round, and the bolt that goes into
the cog stays still.

The motor does not try to start when the clutch is out.

My supplier gave me a small pin (for want of a better word) that goes in there.
I have tried to install the Pin, but could not work out how it would install.

On the small axle, that the cog goes on, there is slot in the axle.
On the under-side at 5 0Clock, there is a small slot that this pin i guess would go into.
The pin looks like a half a coin, but its twice as thick as a coin.
Looks like a half moon shape.
It's about 7-8mm long and about 2.5mm thick.

The slot is the same length as the pin. The small cog has
a slot for the pin. I tried the pin in the cog and it fits.

I tried to get the pin to fit into the cog and then put
it onto the axel, but no way I could see would make this work.
I tried this for about 30 mins to no avail.

I tried to insert the pin directly into the axle, but it would not fit.
It seems like its like 0.25mm thinner.

There has to be a way around this issue.
Someone else must have seen this.

If I've managed to break this pin,
then someone else must have and has managed to fix it.

I've thought of filing down the pin, so it will fit into the slot.
but I only have one, and unlikely my supplier
will send me another without causing grief.

So, I thought I'd ask if you knew how to fix it.
Have you seen this.

All help appreciated.
I'll take some pics if anyone needs it to help clarify.:cool:

Best regards,

Will Start
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I might have missed this but,,, Has this engine ever ran for you?
For lack of a better word, this coin shaped object is called a woodruff key, they sometimes appear in hex shapes also.
Have you checked to see of the slots where this key goes are both clean, and empty of all broken pieces?
DO NOT file anything down until you confirm that you either have the wrong replacement part or your engine is damaged where this part goes.
Pictures will help us, to help you.

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As Papa said, make sure the keyways are clean and undamaged. If everything is the way it should be, it will have an interference fit (tight) in the shaft, and the gear should be slightly looser. The idea is to insert it (fully seated) in the shaft, and slide the gear onto the shaft and over the key. If the gear has been spinning on the shaft, there is a good possibility that metal has been dragged into the keyway. Good luck.

I know about that key you speak of. Try to picture how it works and you may have better luck. As you are pushing the clutch into place, the key gets pushed backwards. Thing is that as it gets pushed back, it raises upwards,and ends up being too big/tall/high and this is why you are having probs.Make sure it is very clean, also make sure that the slot that it fits into is also clean. As you place the key into the slot, keep it tilted with the end closest to you low enough for there to be room for clutch to slide over it.If you can just get it into place, a small tap with a hammer may help, along with the tightening up of the nut. This is a hard one to help you with in a post-sorry.
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Woodruff Key Install response, and video of install.

Hey All,

Thanks, Papasaun , ibdennya and cooltoy .

I read each of your posts.

Thanks for the woodruff Key term,
better to call a thing by its proper name.

This bike has been running, on and off for about 4 months, and I've
solved more issues than I thought I'd ever have to.

I saw a picture of the item in another post, so I now know my supplier is telling the truth.

I will see if I can degrease the axel, and if that makes any difference.
Also check for a build up of steel etc.

I'll take photo's of everything, just for the record.

I wrote that earlier,
now I have sucessfully installed the key.

I took pictures at each stage, and created a short vid of the install.
music and all.

This is on topic, and if you watch closely, shows the key inserting into
the slot. I used a pair of pliers to push it in.

Cooltoy, I also used a wrench and hammer. Held the wrench over the cog,
and lightly tapped it in.

The bike would then start, after about the usual 10 minute peddle=strain/session.
So I guess next stage is looking for HOWTO's
on making your bike start easier.
As this bike takes me at least 1km to get going,
and then conks out after about 2km of riding.

I have a video, made from the pics I took.
I will have to put it on UTUBE,
as it won't upload through here.
Also the pics themselves won't upload.

I'll post that link when its done.


Will Start.
The bike would then start, after about the usual 10 minute peddle=strain/session.
So I guess next stage is looking for HOWTO's
on making your bike start easier.
As this bike takes me at least 1km to get going,
and then conks out after about 2km of riding.

If you solve that one, let me know. :) I personally have a three page list of things that don't help.
Most excellent news on your motor!
These 2 stroke motors are a very simple design, and the expectations are very high that they work. But like most things today, and yesterday, some can be very troublesome. Some motors are just "perfect" right out of the box, some are not.
I believe that by sticking to the basics you can figure out what is wrong with your motor. Basics,,, Air, Fuel, Spark. Check each one and verify that it is indeed performing as it should be. When trouble shooting it is all to often to just start replacing items when quite often all that is needed is a simple cleaning or adjustment.
Fuel, verify that you are indeed providing a unrestricted flow of fuel to the carb. Small impurites have been found in tanks and carbs that will and do cause problems.
Air, verify that you are indeed providing a seal at the intake and carb connections, and that the seal at the cylinder is solid. Choke working properly and the carb is assembled correctly. (clip on needle and the slide works correctly, float and needle valve functioning)
Spark, verify that you are indeed using a spark plug that provides a good spark And that it is gapped to the correct size.
These are the basics that seem to be over looked at the factories and are not caught in QC.
What seems like the correct "fix" with these engines is often one of the basics! With a search of this forum you can find a vast amount of info and specs for all three of the basics.
Please keep us informed of what you find as this does add to the info available. Already we have seen several members reporting on, Junk in the tanks, bad gaps on plugs and weak spark, leaking intakes. All these factors will add to your motor not functioning as expected.
Also when trouble shooting the electrical system don't be afraid to disconnect the kill switch for a test, some of these units have proven faulty, as are some of the connections in the electrical system.

The assumptions we made today, are the problems we discover tomorrow.

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Good points papasaun.Thats the thing with 2 strokes, is it getting gas, is it getting air and is there a spark.
If I were you "will start", I would pull the sparkplug first to see if it sparks,You would do this by leaving s/p hanging on top of head , so that you can see spark.
A great way to find fuel probs. is to get one of those spray bottles from a dollar store and fill with your mixed gas/oil. Take off air filter and as you are starting the engine spray fuel into carb. If it starts, you can spray,spray,spary to keep it running. If this helps it run, you know it's fuel probs.This would be better if you had a pull-start but maybe you could get a pal to help,running beside you spraying the bottle, or even better, just pushing you. This will almost always start the motor if you have fuel probs.
If all of this is of no help, I would next make sure the wires are OK,you could have a short or some other stupid ,goofy thing that you overlooked.
As I think of your post I have to ask myself why you were messing with the key, was there a bad misfire/backfire? Could this have caused a timing issue?
I will wait for more info,good luck! Also, did you use fuel filter, if not , do it!
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I agree Norman, I too would like to see more members asking for help. It makes it more fun to be here. I'm into free to air (FTA) satilites and man, that is about as fast paced as you can get. There are many times that you have 1500 members on at once asking "why did I lose channels" or whatever and before you know it , you have been on line for 10 hours. Thats what I love,helping others, while learning at the same time.
I really want to see this guy get his bike running and know that "we" can do it!
Hi Thanks for all the encouragement. I have a new carbie, that I am going to try,
once I get my vid on YOUTUBE, you'll see why I wish to switch Carbs. Probably do the
upload on the weekend.

The carb may settle the bike down, who knows.


Will Start