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Transmission grind


Jordan Botha

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Jordan Botha

Hi all, 

 

I am new here and I hope this is the right place for my post. 
 

I bought a 2016 750x about 3 or so months ago. Put on just under 6k km’s since then. 45k km’s total mileage. 
 

About a month and a half ago the bike started grinding gears. It grinds when going into first occasionally(from stationary), it also grinds on other gears especially when at higher rpm’s. 

6th gear always grinds, and sends an intense vibration up my entire foot. 
 

Anyone else had similar issues? Wondering it it’s maybe the clutch.

 

Regards,

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Rocker66

Hi Jordan welcome to the forum. Sorry to read about your problem. I’m sure that some of the more technically minded will be along to help you.

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Jordan Botha
1 hour ago, Rocker66 said:

Hi Jordan welcome to the forum. Sorry to read about your problem. I’m sure that some of the more technically minded will be along to help you.

Thanks for the welcome :thumbsup:

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trisaki

Drive chain too tight ? 

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Jordan Botha
40 minutes ago, trisaki said:

Drive chain too tight ? 

Can you elaborate? How would this cause my clunking and grinding transmission? Had no idea this was even possible 

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MatBin

Welcome along. Is this a manual or DCT version?

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davebike

Too tight chain is a posibility 

If the chain is too tight  it pulls on the output shaft from the gearbox and can cause issues  mostly noise and viberation but proloned overtightning kills chains and can kill the gearbox output bearing

With the chain freshly lubed 30/40mm free play  my go to guide is the chain should nearly be able to tutch the swing arm seen=m rather loose  but get two mates to sit on the bike and see how littl free play is left !!

 

Is it manual or DCT? 

 

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trisaki

As above but find the tightest part of the chain  first and adjust  the chain on that tight spot 

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Steve Case

With a name like Botha you in UK or RSA?

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Jordan Botha
13 hours ago, MatBin said:

Welcome along. Is this a manual or DCT version?

 

6 hours ago, davebike said:

Too tight chain is a posibility 

If the chain is too tight  it pulls on the output shaft from the gearbox and can cause issues  mostly noise and viberation but proloned overtightning kills chains and can kill the gearbox output bearing

With the chain freshly lubed 30/40mm free play  my go to guide is the chain should nearly be able to tutch the swing arm seen=m rather loose  but get two mates to sit on the bike and see how littl free play is left !!

 

Is it manual or DCT? 

 

It is manual. 
 

wow this is extremely helpful. I will have a look and hope that that is the problem! Should be a lot easier and cheaper to fix than replacing a clutch:D

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Jordan Botha
2 hours ago, Steve Case said:

With a name like Botha you in UK or RSA?

RSA unfortunately, good spot though! The surname gives me away that quickly? :sweat:

Couldn’t find a nc750/700 forum anywhere else besides this one. 

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Steve Case

Not really a problem, but I doubt there are many people on this forum who are neighbours and will be able to pop round to have a look.

 

Get the bike upright then get a ruler  and measure the play top to bottom at points around the length of the chain, I look for an average of 35mm play (30mm min, 40mm max) as my chain has a couple of tight spots on it

 

Also have a look and make sure its not dry.

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Grumpy old man

Hi Jordan and welcome to the forum.

Hope it's just a tight chain and you've sorted it in time.

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Jordan Botha

 

Measured it and it averaged around 25mm. Would this be tight enough to cause my stated issues?

 

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Andy m

Welcome to the forum. 

 

25mm on the stand might be less as the swing arm moves. Slacken if off until you can pull it clear of the rear sprocket teeth, clean and adjust back to 35mm. You always want to pull a chain into adjustment, so if it goes tight you need to go back and start again. While you have the ruler out measure from the middle of the axle to back of the swing arm. Lets make sure the axle is straight in the fork of the arm, using the little markings can, be awkward enough to go out by a couple. The chain running on an angled sprocket will make a bit of a fuss. 

 

Andy

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Grumpy old man
1 hour ago, Jordan Botha said:

 

Measured it and it averaged around 25mm. Would this be tight enough to cause my stated issues?

 

If that's while the bike is on the side stand or centre stand either way it's too tight, slacken it.

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Xactly
1 hour ago, Grumpy old man said:

If that's while the bike is on the side stand or centre stand either way it's too tight, slacken it.

My thoughts exactly.

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Jordan Botha

Thank you for all the help gentlemen! Looks like I have some work to do over the weekend. 

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SteveThackery

Can someone explain again?  I still don't see how a tight chain can cause the gears to "grind".

In fact, what does "grind" even mean?  And when does it grind?  

 

The only time I've ever heard bike gears make a grinding noise is when changing into 1st from neutral, and that's caused by clutch drag.  So exactly what are we talking about here?  And how can the chain affect it?

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davebike

If the chain is tight enough the chain goes compleatly tight as the suspention comprsses and  the bike/riders weight is carried though the chain , This load the bearing in the sprocket carrier and the output rearing in the gearbox overlaoding them 99/100 times the Sprocket carrier bearing fails first (good design ) but the loaded gearbox bearing can cause nasty noise. In very bad cases it fails grinding is now missalined gears ! add an oil leak as the output oil seal quits !

 

IN 40+ years I see only one do the gearbox bearing and I cannot remember what bike it was so long ago !

I seen meney sprocket carrier bearing fail some I sure due to too tight chains

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Steve Case

Hi Steve, maybe the sound he described was wrong. Possibly more GER-CHUNG-KA and the gear box slips unwilling into another gear.

 

Who said being facetious....

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Xactly
41 minutes ago, Steve Case said:

Hi Steve, maybe the sound he described was wrong. Possibly more GER-CHUNG-KA and the gear box slips unwilling into another gear.

 

Who said being facetious....

I don’t really know what is meant by a grinding sound either…no doubt just me. To me gearboxes either clunk (eg when putting into first gear and in higher gears on BMWs etc with engine speed clutches), rumble or whine (when bearings are worn) or grate (when clutch doesn’t disengage fully or dogs/selectors are worn). 

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Steve Case

Not sure it matters, he got the point across and the information he needed.

 

Oh yes the BMW gearboxes clunk amongst other things, maybe I should reopen my thread worstest gearboxes ever....

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Andy m

No need for a thread, very simple, did Bavarian Tractors have the worst gearbox?, yes, job done 😁

 

I was imagining more of a rumble/whine in the OP description. The clunk as the dry clutch unsticks or the dogs force the cogs off the 1920's style splash lubricated shaft I would expect to be described as a clunk? 

 

Andy

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Steve Case

My favourite was the way the GS used to stick between 5th and 4th as I peeled off the M1 onto the long sweep of 15a at around 80mph!

 

Oh my sainted underpants... Or is that stained!

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