Go Back   Horizons Unlimited - The HUBB > Technical, Bike forums > Yamaha Tech
Front sprocket came lose Front sprocket came lose
Register FAQ Calendar Today's Posts
Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
Photo by George Guille, It's going to be a long 300km... Bolivian Amazon

I haven't been everywhere...
but it's on my list!


Photo by George Guille
It's going to be a long 300km...
Bolivian Amazon



Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 28 Aug 2018
Registered Users
HUBB regular
  
Join Date: Nov 2017
Posts: 45
Front sprocket came lose
I just had a wild idea to go from 15 front sprocket to a 14 because why not and I mostly drive off ...

When I tried to unscrew the nut holding the sprocket I was surprised that the the nut came lose with my fingers !!!

The safety retaining washer was in place (sort of) but how can this happen ? I've seen the person who tighten it with an air wrench and I said it will never cause problems that was maybe 5k km before maybe less.

I've changed the sprocket the shaft was in pretty good condition and I've tighten it with a good wrench that I have and I've bent the safety locking washer.

Is this a nut that I have to check regularly ? I don't want to mess up my gearbox shaft because of this ...

Really intrigued what could have happened ? It wasn't tight in the first place ?
Reply With Quote
  #2  
Old 28 Aug 2018
Registered Users
Veteran HUBBer
  
Join Date: Feb 2012
Location: Milan, Italy
Posts: 562
the nut just keeps the sprocket in place axially speaking, it doesnt help transmit any of the torque, the splines do that. other bikes have some times just a slotted plate keeping the sprocket in place, not even a nut pressing...
as long as you used the locking washer so the nut cant unscrew, you are good.

on my race bikes where i change sprockets often, i have the nut drilled so i can use safety wire instead of a new washer every time. i snug them up with a wrench but the nut is always hand tight when i have to remove it.
Reply With Quote
  #3  
Old 28 Aug 2018
g6snl's Avatar
Contributing Member
Veteran HUBBer
  
Join Date: Aug 2011
Location: Home in Essex GB
Posts: 563
I'm no expert but I would say it wasn't done correctly in the first place, it's the only logical explanation. Tight nuts and a lock washer / tab washer or similar is pretty trouble free, when done correctly. Just because you see someone use an air wrench doesn't mean its tight. Torque wrench and manual brut force is the best way to check. I would bet you will never have this happen again, you will make sure
Of course I may be wrong and happy to be corrected...
__________________
Regards Tim

Learning my craft for the big stuff, it won't be long now and it's not that far anyway
Reply With Quote
  #4  
Old 28 Aug 2018
Grant Johnson's Avatar
HU Founder
Veteran HUBBer
  
Join Date: Dec 1997
Location: BC Canada
Posts: 7,231
In theory, there are two basic designs here.
1: Big nut with a locking tab to absolutely hold the sprocket tight and in place

2: loose sprocket, with a bit of metal and two bolts to keep the sprocket from coming off.

My experience has been that if you have type 1, the nut should be TIGHT always, as the shaft splines will wear excessively if not. With type 2, I believe the shaft is harder, and the sprocket heat treating may be less in the center, so that it wears and not the shaft.

To get the big nut tight, first step is to make sure that it's tight up against the splines by rotating the rear wheel backwards, so that under acceleration the sprocket is tight against the splines so LESS likely to TRY to loosen the nut. Less force under deceleration. Then make sure the nut is tightened to FACTORY SPEC torque not just an air gun which may or may not do the job. Then bend the tab washer over thoroughly, tightly, and it should be tight forever.

Others may well have different experiences!
__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com
Reply With Quote
  #5  
Old 29 Aug 2018
Registered Users
HUBB regular
  
Join Date: Nov 2017
Posts: 45
Quote:
Originally Posted by Grant Johnson View Post
To get the big nut tight, first step is to make sure that it's tight up against the splines by rotating the rear wheel backwards, so that under acceleration the sprocket is tight against the splines so LESS likely to TRY to loosen the nut. Less force under deceleration. Then make sure the nut is tightened to FACTORY SPEC torque not just an air gun which may or may not do the job. Then bend the tab washer over thoroughly, tightly, and it should be tight forever.
This is what I've done myself today ! I've tighten the nut as hard as I could with a 30 cm long key then bend the tab washer over it.

I will check it after a while to see how it is !

I think the air gun is was bad or not adjusted properly for torque since I had this problem on the rear axle also ... same gun same guy ...

I was missing the safety wire in the rear axle nut and the bolts at the end of the swing arm.

I will test all important bolts and nuts tomorrow because I don't want to have any problems.

L.E. I just re-read your post and figured out that the nut might be in the wrong way placed !?

The nut has a groove on one side and is flat on the other side. I put the nut the way I've found it with the groove towards the sprocket ?! and now it holds the sprocket in place ... should it lock it self on the axle or on the sprocket ?

The design seems to be no.1 from your example and I think it's correct the way I've mounted it.
Reply With Quote
  #6  
Old 29 Aug 2018
Registered Users
Veteran HUBBer
  
Join Date: Oct 2016
Location: Devon, UK
Posts: 794
I've changed plenty of front sprockets over the years and never found one that was loose. However I can certainly see how it could work loose even if it was properly tightened at initial fitment. If there is excessive clearance between the sprocket and the splines, either because the splines are worn or the sprocket is hardened at the teeth only, then it would be possible for the sprocket to slip a few degrees round on every acceleration and braking. This will wear the abutment faces causing the sprocket to become loose, and given that there is very little elasticity in the bolted-up assembly, even a tiny amount of wear will result in looseness. That's why you should always have a secondary locking method such as a serviceable tab washer installed and properly fastened.
Reply With Quote
  #7  
Old 29 Aug 2018
xtrock's Avatar
Registered Users
Veteran HUBBer
  
Join Date: May 2013
Location: Norway
Posts: 1,325
Its not a problem when you torque it 110nm and use lockwasher all ears.
Last edited by xtrock; 29 Aug 2018 at 23:28.
Reply With Quote
  #8  
Old 30 Aug 2018
Registered Users
Veteran HUBBer
  
Join Date: Aug 2015
Posts: 489
Quote:
Originally Posted by xtrock View Post
Its not a problem when you torque it 110nm and use lockwasher all ears.
exactly, who tightens nuts with air wrench...
Reply With Quote
  #9  
Old 31 Aug 2018
Grant Johnson's Avatar
HU Founder
Veteran HUBBer
  
Join Date: Dec 1997
Location: BC Canada
Posts: 7,231
Quote:
Originally Posted by tremens View Post
exactly, who tightens nuts with air wrench...

you'd be amazed, that one especially - holding it is difficult, so an air wrench is quick and easy and SHOULD be extremely tight - though no idea what the torque is set to!
__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com
Reply With Quote
  #10  
Old 31 Aug 2018
Registered Users
Veteran HUBBer
  
Join Date: Aug 2015
Posts: 489
Quote:
Originally Posted by Grant Johnson View Post
you'd be amazed, that one especially - holding it is difficult, so an air wrench is quick and easy and SHOULD be extremely tight - though no idea what the torque is set to!
exactly, you don't know what torque is applied, bad idea.
I changed many time xt660 and ktm front sprockets. You need to have torque wrench for this, and it's not that difficult, just sit on the bike and press the rear brake while tightening the nut. You really don't want that sprocket come off during ride...
Reply With Quote
  #11  
Old 1 Sep 2018
Registered Users
HUBB regular
  
Join Date: Nov 2017
Posts: 45
Quote:
Originally Posted by tremens View Post
exactly, you don't know what torque is applied, bad idea.
I changed many time xt660 and ktm front sprockets. You need to have torque wrench for this, and it's not that difficult, just sit on the bike and press the rear brake while tightening the nut. You really don't want that sprocket come off during ride...
Thanks all guys for answering I will check it after a few more kms I hope with no problems... I just can't check it before each ride it's annoying

I applied quite some force that I was turning the engine will have to have someone help me with the brake.

I just don't want it to come off ... during
Reply With Quote
  #12  
Old 1 Sep 2018
Grant Johnson's Avatar
HU Founder
Veteran HUBBer
  
Join Date: Dec 1997
Location: BC Canada
Posts: 7,231
If it's turning the engine and you have NOT got the brake on, it's nowhere near tight enough.

You can do it alone.
I believe the sprocket is on the left side on your bike. Instructions assume it is.
  1. Put in 1st gear.
  2. Get the socket and bar on the nut, and stand on the OTHER side of the bike,
  3. step on the brake pedal,
  4. reach across and tighten.
  5. REALLY tight, or better with a torque wrench!!
You may need to reposition the wrench a time or two as it all "winds up" as you put pressure on it.
__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com
Reply With Quote
  #13  
Old 1 Sep 2018
Registered Users
Veteran HUBBer
  
Join Date: Aug 2015
Posts: 489
additionally helps pushing bike's front wheel against the wall while on brake.
Reply With Quote
  #14  
Old 1 Sep 2018
Registered Users
Veteran HUBBer
  
Join Date: Oct 2016
Location: Devon, UK
Posts: 794
A piece of wood through the spokes braced against the swinging arm always worked for me. If it's in top gear it won't bend the spokes.
Reply With Quote
Reply

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 Registered Users and/or Members and 1 guests)
 

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
yamaha xt600E 2002 front sprocket bolt issue derayon Yamaha Tech 6 3 Sep 2017 09:07
Tenere 1VJ front sprocket svakak Yamaha Tech 13 19 Aug 2012 16:25
KLE500 A3 Front sprocket issue... Orlow Kawasaki Tech 2 14 Aug 2012 21:44
XT600E/4PT: RFI - max.rear sprocket size with 14T front sprocket and standard chain Bigfoot 2 Yamaha Tech 8 26 Jun 2012 14:07

 
 

Announcements

Thinking about traveling? Not sure about the whole thing? Watch the HU Achievable Dream Video Trailers and then get ALL the information you need to get inspired and learn how to travel anywhere in the world!

Have YOU ever wondered who has ridden around the world? We did too - and now here's the list of Circumnavigators!
Check it out now, and add your information if we didn't find you.

Next HU Eventscalendar

HU Event and other updates on the HUBB Forum "Traveller's Advisories" thread.
ALL Dates subject to change.

2024:

Add yourself to the Updates List for each event!

Questions about an event? Ask here

HUBBUK: info

See all event details

 
World's most listened to Adventure Motorbike Show!
Check the RAW segments; Grant, your HU host is on every month!
Episodes below to listen to while you, err, pretend to do something or other...

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

"Ultimate global guide for red-blooded bikers planning overseas exploration. Covers choice & preparation of best bike, shipping overseas, baggage design, riding techniques, travel health, visas, documentation, safety and useful addresses." Recommended. (Grant)



Ripcord Rescue Travel Insurance.

Ripcord Rescue Travel Insurance™ combines into a single integrated program the best evacuation and rescue with the premier travel insurance coverages designed for adventurers.

Led by special operations veterans, Stanford Medicine affiliated physicians, paramedics and other travel experts, Ripcord is perfect for adventure seekers, climbers, skiers, sports enthusiasts, hunters, international travelers, humanitarian efforts, expeditions and more.

Ripcord travel protection is now available for ALL nationalities, and travel is covered on motorcycles of all sizes!


 

What others say about HU...

"This site is the BIBLE for international bike travelers." Greg, Australia

"Thank you! The web site, The travels, The insight, The inspiration, Everything, just thanks." Colin, UK

"My friend and I are planning a trip from Singapore to England... We found (the HU) site invaluable as an aid to planning and have based a lot of our purchases (bikes, riding gear, etc.) on what we have learned from this site." Phil, Australia

"I for one always had an adventurous spirit, but you and Susan lit the fire for my trip and I'll be forever grateful for what you two do to inspire others to just do it." Brent, USA

"Your website is a mecca of valuable information and the (video) series is informative, entertaining, and inspiring!" Jennifer, Canada

"Your worldwide organisation and events are the Go To places to for all serious touring and aspiring touring bikers." Trevor, South Africa

"This is the answer to all my questions." Haydn, Australia

"Keep going the excellent work you are doing for Horizons Unlimited - I love it!" Thomas, Germany

Lots more comments here!



Five books by Graham Field!

Diaries of a compulsive traveller
by Graham Field
Book, eBook, Audiobook

"A compelling, honest, inspiring and entertaining writing style with a built-in feel-good factor" Get them NOW from the authors' website and Amazon.com, Amazon.ca, Amazon.co.uk.



Back Road Map Books and Backroad GPS Maps for all of Canada - a must have!

Your ad could be here, on EVERY page of the HUBB, or the whole website, or as many as you like!

New to Horizons Unlimited?

New to motorcycle travelling? New to the HU site? Confused? Too many options? It's really very simple - just 4 easy steps!

Horizons Unlimited was founded in 1997 by Grant and Susan Johnson following their journey around the world on a BMW R80G/S.

Susan and Grant Johnson Read more about Grant & Susan's story

Membership - help keep us going!

Horizons Unlimited is not a big multi-national company, just two people who love motorcycle travel and have grown what started as a hobby in 1997 into a full time job (usually 8-10 hours per day and 7 days a week) and a labour of love. To keep it going and a roof over our heads, we run events all over the world with the help of volunteers; we sell inspirational and informative DVDs; we have a few selected advertisers; and we make a small amount from memberships.

You don't have to be a Member to come to an HU meeting, access the website, or ask questions on the HUBB. What you get for your membership contribution is our sincere gratitude, good karma and knowing that you're helping to keep the motorcycle travel dream alive. Contributing Members and Gold Members do get additional features on the HUBB. Here's a list of all the Member benefits on the HUBB.



All times are GMT +1. The time now is 12:39.

Contact Us - Horizons Unlimited Motorcycle Travellers Website - Archive - Privacy Statement - Top