ZZR1100 front sprocket has moved outwards?

[Mrflashy]

I have a Zzr1100d engine in a race car and I suddenly lost drive when changing down at high speed, when inspecting, the rear chain is now loose and the front chain sprocket is 1-2cm further out and the nut is rubbing on the sprocket cover housing. If you try to select a gear and pull the clutch out, I get no drive just a revving engine like being in neutral.

What could the cause of this be? The shaft still turns with the chain/sprocket when rocking the car on the driveway, and no other signs of damage.

Many thanks

[Nobby the Bastard]

Sounds like a fucked gearbox. No point trying to work out what in the gearbox is fucked, the whole engine Will need stripping anyway.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stinkwheel]

Obvious and easy one would be that the nut has come undone and the sprocket is no longer properly engaged on the splines.

Compex and annoying one would be that either the mainshaft has snapped, a gear has let go or the bearing has walked out of the crankcase
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Nobby the Bastard]

[Mrflashy]

Thanks all. There is a small possibility that this is a loose nut now it's been mentioned, as if I keep rocking back/forth occasionally the shaft stops turning when the sprocket is still turning, putting a bit of pressure with a pry to push it back on it starts turning the shaft again.

Will remove the cover and inspect the outside and feedback!

[Nobby the Bastard]

Have you considered just taking the casing over the sproket off?

If it moves with a pry bar applied it's not a loose nut.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stinkwheel]

If the nut is unscrewing itself, the way they used to prevent this (other than the obvious properly tightening/thread-lock etc) was to use a grub screw into the sprocket.

You get an M6 cheese head screw, these usually have a 10mm head diameter. Measure 5mm away from one of the flats of the main sprocket nut on the sprocket and drill and tap an M6 hole in the sprocket (some sprockets actually already have these).

Once you've tightened the main nut down, take it a little either way until a flat is adjacent to the screw hole and screw the cheese-head in. Use a good spring washer and loctite, I'd suggest a nord-lok washer. Then you have a good mechanical lock preventing it happening again and because it's offset somewhat, is less prone to precessing out.

Old pre-unit brit bikes use this as it's very difficult to do up the mainshaft nut particularly tight for a variety of reasons. They don't come undone, even if they are barely past finger tight
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Pete.]

Broken output shaft is common on bike-engined carsbecause the larger mass of the car means that the engine is at peak torque for longer (because the larger mass needs more time to accellerate through peak torque). Many people fit an outboard support bearing and in fact they make a stronger shaft for the Hayabusa engine for this very reason and strengthened case bolts too as they sometimes burst the cases.

Only way you're going to find out is have it apart.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Mrflashy]

[Mrflashy]

Thanks all for the detailed advice, makes perfect sense to have a better fixing for the nut, and to be aware of the gotchas with bike engined cars. Luckily for me it didn't cause any safety issues for me as I was around 10,000rpm when I lost drive!

[Nobby the Bastard]

It's not the nut thats the problem....

The shaft that the sproket is on has busted something further upstream because the bearing supporting the shaft is not up to the stress of hauling a car.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[stinkwheel]

You'll very quickly know when the cover comes off anyway, either the nut or the broken shaft will fall out.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Nobby the Bastard]

[WD Forte]

Cant he just weld the sprocket on?
I'm sure its been done before
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bikers smell of wee

[Mrflashy]

Thanks all, prize goes to stinkwheel, the sprocket was sitting completely off the spline, and the nut had wound all the way off, the only thing stopping the nut from falling off was friction against the sprocket cover itself.

The previous owner appears to have used a smaller and wider sprocket which rendered his attempt of using the locking tab washer useless as it wasnt sitting on any splines.

I have refitted it by hand, put the car in gear and the output shaft is binding and halting the car from moving forward/back as expected.

Needs more checking as others have mentioned to ensure no further damage.

[Pete.]

That's a result for you. Bike engined cars often get geared down with a smaller sprocket because usually 1st gear is too tall for the job. The downside is that you lose some speed at the top end.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

Wow, that's a dinky sprocket. What is it 13 tooth? Grub screw trick wont work on that.

If you can't get the tabbed washer under it, it's likely to happen again.

If there's enough thread, you could try a nordlok washer, those things are remarkable. Better than anything else that isn't a physical mechanical lock like your tabbed washer or lockwire. Including nylok, loctite and double nuts.

My other thought would be milling/surface grinding the outside face of the sprocket so you can get the splined washer on and the nut on properly. Only reason I can think of to use a fatter sprocket would be to get the chain line and that's determined by the inside face.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Pete.]

High strength threadlock on the nut threads. When you want it off, cook it with a blow torch and it'll come loose easy as anything.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Mrflashy]

14 tooth, the acceleration is immense as it's a Powertec tuned model with keihin FCRs too.

I might use both threadlock and a nordlok washer, don't fancy chances with this again!!

Thanks again all. I will report back if it turns into something more nasty when it starts up and moves again

[MCN]

If you are able to 'develop' the project, then look at fitting a Slipper Clutch.

I read your first post and considered, as Pits did, that the 'car' is a heavier lump to decelerate than the donor bike by a large margin.
Therefore, the drive train is being overloaded.

A slipper Clutch almost eliminate harmful 'back-torque' from the road reaching the engine.
It's because the engine cannot be pushed around much more than designed limits that something has to give. The weakest link in the chain being the drive sprocket.

Thread Lock and a Nord Lock washer may hold the sprocket on but the extra energy will ossiblybbe pushed elsewhere.
A rear wheel or burst chain is fine. A minced gearbox or a mashed bottom end, rammed push rod into an up coming piston.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.