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Author Topic: Front Sprocket Removal  (Read 1269 times)

Cloud

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Front Sprocket Removal
« on: April 10, 2015, 10:12:29 PM »


Is there a technique to removing the sprocket retaining nut?

I've tried the chain and in-gear method, and turning the nut just drives the bike forward. I've also tried wedging a socket between the sprocket and the stator case, but with all the power I can give, I'll just end up cracking the stator case and pushing the socket through the aluminium. Is there a way I can put serious torque on the nut to get it undone, without breaking anything?

I'd really like to avoid getting the grinder out in such a delicate space, particularly as I don't think I have a replacement nut.

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Cloud

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Re: Front Sprocket Removal
« Reply #1 on: April 10, 2015, 10:18:17 PM »


Ah, didn't see this on mobile!

I'll give this a go.
> https://www.youtube.com/watch?v=PvtmJjpUqm8

I'll have to put the rear wheel, axle, pivot shaft and chain back in place. What a ball-ache.
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Joss

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Re: Front Sprocket Removal
« Reply #2 on: April 10, 2015, 11:04:28 PM »

The best bit of advice in that video was the one thing he never used.. heat.
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serp

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Re: Front Sprocket Removal
« Reply #3 on: April 11, 2015, 12:27:47 AM »

I now have an electric impact wrench which does the job nicely but before that what I did was to remove the cover and ride down to the local car shop with my socket and have them put the impact on it then tighten it back down by hand for the ride home.
And of course be sure to fold back the locking washer first.
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Codeh002

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Re: Front Sprocket Removal
« Reply #4 on: April 11, 2015, 02:45:19 AM »

Impact wrench is your friend here, I can get mine off by simply putting the bike in gear and hitting it for about 2-3 seconds.

Works like a charm.
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umop-ǝpisdn

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Re: Front Sprocket Removal
« Reply #5 on: April 11, 2015, 06:38:11 AM »

FYI

Torque spec for the front sprocket nut is circa 100Nm.

The 250cc makes, what? 30Nm tops?

A better idea would be to put the bike in neutral and with the chain still on and tight to the back sprocket, get someone to hold the bike while you use the impact wrench.

The gearbox is not designed for the kinds of torque you're subjecting it to.
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Cloud

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Re: Front Sprocket Removal
« Reply #6 on: April 11, 2015, 09:26:28 AM »


Yeah, it crossed my mind after I'd gone to bed last night, my arm produces way more torque force than my engine can.
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Cloud

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Re: Front Sprocket Removal
« Reply #7 on: April 06, 2016, 03:42:35 PM »


Wow, nearly a year to the day and I'm back again at the same problem.

Put the new chain on, slotted a fence post through the rear wheel, to stop it turning, 3ft breaker bar with aluminium pipe extension on the end, blowtorched the nut until it was glowing (worried about baking the bearing on the output shaft) gave it a huge heave, and something broke.

I think it was the fence post.

But the nut is still in place.

I think this is it, I think if I want to replace the sprocket, it's a split gearbox and new output shaft kind of job.

Fxxk.
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Joss

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Re: Front Sprocket Removal
« Reply #8 on: April 06, 2016, 04:17:30 PM »

You could split the nut with a grinder...

It will come off with heat and oil, warming and cooling.
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umop-ǝpisdn

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Re: Front Sprocket Removal
« Reply #9 on: April 08, 2016, 04:34:13 AM »

I used a battery operated impact driver. Soooooo easy. <-- I realised after re-reading the previous sentence that if my mind was in the gutter, I may perhaps see others floating by.

Used a screw driver to bend the locking plate back a little, then put the socket over the nut and used a rubber hammer to tap the locking plate the rest of the way. Then I put the bike in neutral, back wheel on the ground, front wheel pressed against a wall. Left hand on handlebar to keep the wheel pointing at the wall and let the impact wrench do all the work.

6 seconds later, nut was off with no damage to anything.
« Last Edit: April 08, 2016, 04:37:11 AM by umop-ǝpisdn »
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