Cushion drive?

[hmurphy]

Hey,

how important is cushion drive? Would it be an issue to eliminate this? I am putting a rather wide rear wheel inbetween a very narrow swing arm gap so space is at a premium. No sprocket carrier bearing is possible unless I become a millionare and find a huge block of aluminium to make a new sprocket carrier.

This wheel will be powered by a 125cc 2 stroke motor. Will it be really bad for the gearbox? I have seen a couple other buckets without cushion drive but I would like to make sure it's not too likely it will ruin the gearbox or something else.

Cheers

[Bert]

Glen's one seems to work ok..

I've had a few issues with mine (but thats due to lack of engineering skills). seems to be holding fine now.

[speedpro]

I don't know the motors but it should have a cush drive as part of the clutch. Others seem to have gotten away with it. As an example of bikes without cush drives - McIntosh bikes using McIntosh rear wheels don't have a cush drive. The sprocket mounts directly to the wheel.

I've found that it can be hard on the cush drive in the back of the clutch so just keep an eye on it. You're looking for springs coil binding or the cush mechanism could bottom out on the rivets (after the coil-bound springs have shattered).

[bogan]

I don't know the motors but it should have a cush drive as part of the clutch. Others seem to have gotten away with it. As an example of bikes without cush drives - McIntosh bikes using McIntosh rear wheels don't have a cush drive. The sprocket mounts directly to the wheel.

I've found that it can be hard on the cush drive in the back of the clutch so just keep an eye on it. You're looking for springs coil binding or the cush mechanism could bottom out on the rivets (after the coil-bound springs have shattered).

it is a very common mod on the bros/hawks to make a cush drive eliminator never heard of problems attributed to it, an added benefit is it reduces a significant amount of unsprung mass.

I don't see it being an issue on the anti-chatter springs on the back of the clutch, especially with the relatively low power of buckets. For example I just rebuilt my clutch basket on the bros with new anti-chatter springs, 6 50kg/mm springs, with bout 4mm movement either way, and the springs bottom out on their own coils before hitting the plastic region of deformation. If only the original set were designed so well I wouldn't have had to do it! Another thing to note is I was noticing a large amount of driveline slack when going from power to engine braking so you should notice if they are wearing out before any real damage is done.

[SS90]

As Speedpro said, there has been plenty of bikes with out cush drives in the rear wheel over the years.

High mileage bikes (1998 to 2004 T series Triumphs (Speed triples and Daytona's) where really bad for breaking the clutch cush drive springs at 80,000 km) for example.

A 125 2 stroke is not really going to have the torque to smash rear cush drives, nor really destroy a clutch hub in a short time, so I would say go for it.

Obviously make sure that it is all central (I am sure you are aware of that)

I know of plenty of buckets with ample power that have no rear wheel cush drives, and never had a problem in years of running.

[gatch]

How big is the sprocket carrier ? 110 OD ?

[marsheng]

Anything bigger than a 120 width on a 125cc road bike is going backwards. There will not be enough heat generated in the rubber to make the tyre work. An RS125 with 45+ hp uses 120x70x17.

[quallman1234]

An RS125 with 45+ hp uses 120x70x17.

Fair comment, however New Zealand 125gp bikes are all around the 40 mark at the wheel.

[hmurphy]

Yeah but my FXR150 has about 50 or 60 hp at the wheel.

Problem is solved now though, going to attempt to run a bearing. Might be a close one.

Thanks for all the help though! Good for future reference for sure

[gatch]

Anything bigger than a 120 width on a 125cc road bike is going backwards. There will not be enough heat generated in the rubber to make the tyre work. An RS125 with 45+ hp uses 120x70x17.

Ha, my spada bucket project has a 140 tire as standard. I'll be using that till I can get something skinnier..

Might have to buy tire warmers..

[TZ350]

- McIntosh bikes using McIntosh rear wheels don't have a cush drive. The sprocket mounts directly to the wheel.

Also

1960's and early 1970's Yamaha Road Racers that I remember, didn't have rear wheel cush drives.

And neither did K Roberts TZ750 Dirt Tracker.

The sprocket was bolted directly to the rear wheel hub.

[F5 Dave]

Also

1960's and early 1970's Yamaha Road Racers that I remember, didn't have rear wheel cush drives.

And neither did K Roberts TZ750 Dirt Tracker.

The sprocket was bolted directly to the rear wheel hub.

A bike known for it's extreme ridability.
Also dirt is a cushdrive.

[TZ350]

Also dirt is a cushdrive.

That's true, dirt is a cushion of sorts...........

how important is cushion drive?

The TZ750 road racer also didn't have a cush drive, wasn't 100% sure before, needed to check a spares manual..........

So I guess a bucket doesn't need a rear wheel cush drive if there is a cushion in the clutch..........