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Front Sprocket Nut Goooaaann! And Thread Stripped!


Annaz

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Yep my bargain YZF750 bike is showing me some pain already.

I thought this was just a common fault on later YZF's and FZS's but I is wrong, the nut has come off (looked like it may have been a bodge to start with) and the shaft now looks like it wants machining and re-threading.

So the question is how easy is it to remove the layshaft? and can it be done insitu or is it engine out time?

Cheers

A

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new front sprocket and judicious use of an arc welder, whats to lose? best way it buys you 20,000 miles, worst way you get involved in the strip down you are already contemplating

beaten to it

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Just one question?

Are you a welder? Lol

Haha! not a real welder no but I have a mask :lol:

I'll sort some pics out, a thousand words etc

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Being realistic I think it's 'cattle trucked' I don't think there's enough meat to machine it down and re-thread it and maintain a confident amount of strength.

I've got another motor arriving later in the week, which I'm going to use for the rest of the Summer, hopefully, and if we get one!

So I'm going to search for a decent secondhand layshaft/output shaft (whatever you call it) there must be some half dead motors out there with what I need still intact.

Then I plan to refresh the engine over winter to use next year.

I'm wondering how much of a job the shaft removal will be? (ooh-er missus etc) I have been told is fairly straightforward

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Now see i thought that Mike but i did not put that on here as i would be worried about it working loose. How would you overcome that as it normally has a locktab? I did think of a left hand thread, or red loctite.. Its not the sort of thing you want flying off really is it lol..Just interested to know really as i would rather replace the shaft.

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The thread doesn't need to be left hand ( unless the bike has a reverse gear) and drilling and tapping would be a nce way round the problem.

But look at the nut that was on the bike, when did that last hold the sprocket on? It matters not now the engine is out but it's a cheap old bike and any competent welder could have fixed it for a tenner.

By the time the engine has come out and been replaced with one of dubious parentage, or the old one stripped and repaired a cheap bike just started to get expensive

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The thread doesn't need to be left hand ( unless the bike has a reverse gear) and drilling and tapping would be a nce way round the problem.

But look at the nut that was on the bike, when did that last hold the sprocket on? It matters not now the engine is out but it's a cheap old bike and any competent welder could have fixed it for a tenner.

By the time the engine has come out and been replaced with one of dubious parentage, or the old one stripped and repaired a cheap bike just started to get expensive

I suppose the internal thread idea would be a fix but I'd be a tad paranoid of it failing. I have had an idea though, I reckon I could re-thread, fit a fatter locknut and drill 'n' tap for an m6 grub screw at 90deg , to hold it on it's worn shoulder (I've seen this done on a blade IIRC) With a new lock tab washer I could be on a winner?

As regards the engine of unknown parentage, yes it's an expensive luxury but I will at least not miss out on as many sunny rides out, as long as it doesn't knock, rattle and burn the lube. Time will tell.

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