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Old January 23rd, 2012, 09:04 AM   #1
Nemesis
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Check your Front Sprocket Nut!!!

This past weekend @ the track, I downshifted just before a turn and got nothing but false neutral so obviously I shifted one gear up (never down) and again nothing but false neutral. So I pulled into the dirt and had the crash truck pick me up.

When I got to the pits, we discovered the nut & washer holding the front sprocket was completely gone and the front sprocket was barely hanging off transmission shaft.

The next day, Rexbo's front sprocket nut came off as well. Luckily for him, his nut fell into his belly pan but he still lost the washer.

I was thinking of drilling a hole through the end of the shaft rod and safety wire it but that's gonna prove to be a bit difficult. So I think I'm just gonna lock tight and RTV seal the damn thing.

So, my suggestion to you guys is if you race/track or have a lot of miles on your bike keep an eye on your front sprocket nut. May want to re-torque nut or do what I suggested above.
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Old January 23rd, 2012, 09:21 AM   #2
jdoucet93
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And the list of ninja 250 quirks continues to grow...
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Old January 23rd, 2012, 11:42 AM   #3
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The front sprocket should have a toothed washer that the edges fold up around the nut. Pain to use since it gets "folded" and has to be frequently replaced, but locks the sprocket nut down. I've seen a lot of track bikes that quit using this style washer or just don't fold it, but I still do for peace of mind.
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Old January 23rd, 2012, 11:44 AM   #4
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I used the same washer and bent/locked the washer to the nut...but maybe that was my problem--using the same old washer. Maybe I needed to replace mine every time I swap sprockets.

I just ordered a nut & washer and will RTV the damn thing.
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Old January 23rd, 2012, 04:36 PM   #5
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Quote:
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I used the same washer and bent/locked the washer to the nut...but maybe that was my problem--using the same old washer. Maybe I needed to replace mine every time I swap sprockets.

I just ordered a nut & washer and will RTV the damn thing.
Probably - I would guess the bend will weaken/break.
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Old January 23rd, 2012, 11:54 PM   #6
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Quote:
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When I got to the pits, we discovered the nut & washer holding the front sprocket was completely gone and the front sprocket was barely hanging off transmission shaft.
Nemesis - glad that's all that happened. did you get that false neutral because there is some protection built into the bike, i.e. the bike was engineered to shut down once the sprocket worked it's way out to a dangerous position?
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Old January 24th, 2012, 07:18 AM   #7
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Nemesis - glad that's all that happened. did you get that false neutral because there is some protection built into the bike, i.e. the bike was engineered to shut down once the sprocket worked it's way out to a dangerous position?
Sarcasm will get you nowhere....well, maybe a response but that's about it!
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Old January 24th, 2012, 10:19 AM   #8
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Sarcasm will get you nowhere....well, maybe a response but that's about it!
howdy! no sarcasm at all - it was a legit question. maybe it's a dumbass question but, no, I was not being sarcastic. coming into the pits and seeing my front sprocket hanging off like that would scare the piss out of me. You said that you were hitting false neutrals so I'm genuinely curious if that was some kind of default that was engineered into the bike or whether it just happened to be a coincidence. - thanks amigo!
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Old May 28th, 2013, 03:42 PM   #9
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Agreed. This happened to me yesterday.
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Old May 28th, 2013, 03:57 PM   #10
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howdy! no sarcasm at all - it was a legit question. maybe it's a dumbass question but, no, I was not being sarcastic. coming into the pits and seeing my front sprocket hanging off like that would scare the piss out of me. You said that you were hitting false neutrals so I'm genuinely curious if that was some kind of default that was engineered into the bike or whether it just happened to be a coincidence. - thanks amigo!
It wasn't a false neutral, the sprocket was off, so it was "neutral".
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Old May 28th, 2013, 04:11 PM   #11
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It wasn't a false neutral, the sprocket was off, so it was "neutral".
Thanks for the pertinent information!
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Old May 28th, 2013, 04:13 PM   #12
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Thanks for the pertinent information!
Well, if he really didn't get it, figured I'd just explain the obvious.
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Old May 28th, 2013, 06:11 PM   #13
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I safety wire mine
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Old May 28th, 2013, 06:13 PM   #14
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Why always shift up on a false neutral and not down?
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Old May 28th, 2013, 07:00 PM   #15
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rpms dear Watson. this way you don't over rev.
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Old May 28th, 2013, 07:54 PM   #16
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rpms dear Watson. this way you don't over rev.
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Old June 1st, 2013, 07:40 AM   #17
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Was giving my bike a once over on my day off and discovered mine to be hanging on by a thread or two. My bike is strictly a fun commuter as of right now, so even if you dont track the bike it can still back off.
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Old June 1st, 2013, 08:01 AM   #18
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Why always shift up on a false neutral and not down?
When your tires are really hot on the track and say you get a false neutral or you just loose track of what gear your in. Always upshift, downshifting causing a over rev is not good for the engine but more importantly... at pace can get your bike out of sorts real quick like.

[NOT FOR NOVICE]
When your comfortable with the rear stepping out and getting wiggly, you can dump one extra gear down into hairpin corners, for extra fun factor. But you have to be going in hot and late on the brakes. It's FUN in the dirt too.
[/NOT FOR NOVICE]
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Old June 1st, 2013, 09:50 AM   #19
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once i accidentally dropped to 2nd instead of 3rd at turn 2 CCW at chucky. you already are lifting the rear before turn in, so with the extra rear pull, it slid out like i knew what i was doing. i felt like a badass until i totally ****ed the apex and almost rode into the dirt on the exit.
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Old June 1st, 2013, 10:06 AM   #20
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Yep, I seem to go way wide most of the time trying dumb crap like that. But when I go wide like that, my front sprocket nut is still as tight as my bunghole. hahahahahahaha
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Old June 1st, 2013, 10:36 AM   #21
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I didn't lose the sprocket, but I came in from practice at Roebling Road (fast, flowing track in Savannah with about a 3/4 mile front straight) to find the countershaft nut lying in my bellypan.

Sometimes I wonder if those "imagine what could have happened" moments are scarier than an actual crash.

The lesson here is that, if it's a racebike, it's worth your time to check everything before turning a wheel on the track.
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Old June 1st, 2013, 10:56 AM   #22
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Seriously does no one safety wire?
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Old June 1st, 2013, 12:01 PM   #23
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No way to safety wire it?
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Old June 1st, 2013, 01:11 PM   #24
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Mine wired right up. I snap a pic soon.
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Old June 11th, 2013, 09:06 AM   #25
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Mine backed off again, and this time shes gone. What size and thread pitch is the output shaft? I cant find anything that will fit.
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Old June 11th, 2013, 12:44 PM   #26
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Nobody?
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Old June 11th, 2013, 03:53 PM   #27
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I don't know but I would think that that would be a case where you might be best to just get the real thing at a dealership rather than trying to improvise.
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Old June 11th, 2013, 04:36 PM   #28
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Someone has posted it but I cannot search for you right now. Seriously...put the lock washer on AND wire the thing. Mine never move. Makes me wonder what's going on with thosr who have posted here. Should you usr some blue loctite if u cannot wire? Mind u I am not one to push the blue goo but sometimes. ...
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Old October 21st, 2013, 08:21 AM   #29
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TTT.
Not sure why this came off. I put a new sprocket on about 6k miles ago. Super lucky this didn't happen at freeway speeds. My bike has had a super sh***y week
I hope nearby dealer has this in stock.
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Old October 21st, 2013, 11:59 AM   #30
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Quote:
Originally Posted by jdoucet93 View Post
And the list of ninja 250 quirks continues to grow...
This list public somewhere?
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Old October 11th, 2022, 01:26 PM   #31
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I see no mention of the washer from the people who caught it in time. Did anyone find their washer intact but flat? Broken? It shouldn’t be possible to find it with the bends in place around the nut. I mean, it’s not like it would shear every locking tooth before the fatigued bends fail.
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Old December 14th, 2022, 09:31 AM   #32
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I had the same locking mechinisum on my honda 90cc back in the late 1960's and 1970's
and what would happen is the washer would sheer off the tab that goes down into the spline and the bent over part for the nut would be unaffected... and it came off frequently
my cure was to take the nut off and flatten the washer and then use a punch to make deep divots in the washer that go into the spline area all the way around the washer
and really bend more metal from the washer into the splines of the sprocket shaft
I then put the nut back on and torqued it and bent 2 or 3 parts of the washer over the nut....... that cured the silly thing coming off.....
in your cases I think I would buy a NEW washer as they do need replacing periodically
and add punch marks or cut the washer with a chisel to make a few new tabs to go into the splines blue lock tight it and then torque it all down and finally bend over the washer for the nut in 2 places one on the flat and then at the corner of that bend so the corner of the nut is captured this is easy with a real sharp chisel as you can cut the fold
which allows that to be done. think over Kill as that is what is needed !
safety wiring is my next choice but that would take a tiny drill and drilling into the splines I think which I don't care for...... alternately you could double nut it if there is enough room on the sprocket shaft.
.....
Bob.......
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