Author Topic: How important is a cush drive?  (Read 1481 times)

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Offline Mantree

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How important is a cush drive?
« on: October 24, 2021, 08:57:53 PM »
I am currently working on a new rear end for my 750 and am planing on using a harley rear wheel. This wheel has no cush drive as the sprocket os bolted straight to a flange on the hub. Now I was under the impression that the cush drive was just to make the bike ride a bit smoother but I was told that I would trash my trans in short order without it. Is this true or or will I be fine without it. I just put a fresh trans in and plan in eventually building a race trans and overboreing the engine at sompoint down the line.

Offline Terry in Australia

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Re: How important is a cush drive?
« Reply #1 on: October 25, 2021, 02:00:35 AM »
I'd be very careful mate, if it was originally a belt drive Harley (most were) the belt acts as a cush drive, and my 1973 Sportster has a cush drive on the engine sprocket, and I'm pretty sure, another one on the rear wheel. I wouldn't risk it. My Suzuki GS1000 had a special rubber mounted front sprocket as well as a cush drive in the hub, to try to reduce vibration back thru the gearbox. I suppose there's only one way to find out for sure, but it could get expensive. ;D
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Offline low-side

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Re: How important is a cush drive?
« Reply #2 on: October 25, 2021, 02:23:56 AM »
I ran a Morris mag without cush drive - for about 5 minutes.  It was surprisingly harsh and couldn't have been doing the bike any favors so I installed a Morris cush drive which was essentially nylon bushings riding inside oversized bolt holes in the sprocket and over spacers on the bolts.  That was just enough that I was confident that it wasn't damaging the drive sprocket bearing.

Offline Alan F.

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Re: How important is a cush drive?
« Reply #3 on: October 25, 2021, 09:43:02 AM »

Nobody is gonna die or grow a third eye, if they dont have a cush drive.. :o
 Besides, if it were important, then why didnt the shafty have it.. Eh??..EH??

 Should cost 200 or less to convert the wheel, basically a big lump of aluminum, with a register lip, and a bearing bore.. and 2 bolt patterns in it.. piece-of-cake..

http://forums.sohc4.net/index.php/topic,62108.0.html
« Last Edit: October 25, 2021, 09:45:22 AM by Alan F. »

Offline pekingduck

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Re: How important is a cush drive?
« Reply #4 on: October 25, 2021, 09:56:40 AM »
The sprocket has a great deal of leverage, and without the cush drive you will likely tear the sprocket bolts out of the wheel.  Dirt bikes get away with it because they have less torque and weight to deal with, and there are usually more bolts set out at a larger diameter.  But they still break hubs.

Offline grcamna2

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Re: How important is a cush drive?
« Reply #5 on: October 25, 2021, 11:00:21 AM »
The sprocket has a great deal of leverage, and without the cush drive you will likely tear the sprocket bolts out of the wheel.  Dirt bikes get away with it because they have less torque and weight to deal with, and there are usually more bolts set out at a larger diameter.  But they still break hubs.

I would think that also contributes to rear spoke breakage.
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Offline slikwilli420

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Re: How important is a cush drive?
« Reply #6 on: October 25, 2021, 03:39:05 PM »
You guys are over thinking this. I'm running a dirt track hub on my race bike with well over stock power and sticky race tires. Never broke a spoke or had any other damage to the rear wheel. I don't have a lot of time on my other race bike but it makes 94 at the wheel and again no broken pieces.
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Offline Mantree

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Re: How important is a cush drive?
« Reply #7 on: October 25, 2021, 04:11:26 PM »
The sprocket has a great deal of leverage, and without the cush drive you will likely tear the sprocket bolts out of the wheel.  Dirt bikes get away with it because they have less torque and weight to deal with, and there are usually more bolts set out at a larger diameter.  But they still break hubs.

Not to worried about bolts ripping out as they are 5/16 bolts with nuts on the back of the steel flange. I don't thing I could rip mounting bolts out with under 150hp so the little 750 engine shouldn't have any problem. The has a cush drive on the primary so that reqly just leaves the transmition

Online bryanj

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Re: How important is a cush drive?
« Reply #8 on: October 25, 2021, 05:08:33 PM »
I think your skeletal construction would hate the removal of that cushdrive
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Offline Terry in Australia

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Re: How important is a cush drive?
« Reply #9 on: October 25, 2021, 05:15:46 PM »
Yep, as much as I respected Frank, I didn't always agree with him, and the same for anyone else who says you don't need a cush drive, you do, full stop. Manufacturers don't go to the expense of designing and installing a cush drive if you don't need one. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

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Offline dusterdude

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Re: How important is a cush drive?
« Reply #10 on: October 26, 2021, 03:15:56 AM »
My opinion,harleys dont need/use a cush drive due to the design of their hubs.honda used a cush drive because a)the way the hub is designed and b)they didnt want the hub to take a beating.

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Offline Kevin D

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Re: How important is a cush drive?
« Reply #11 on: October 26, 2021, 04:59:13 AM »
I’d like to point out that Honda had recalls and upgraded the cush drive on the K1 from its original design as part of the chain breakage improvements.
The 1st photo is borrowed from the SOOC forum with the softer holed damper on the right.
The 2nd photo from CMSNL is the later design with larger damper on the pull side small damper on the rebound side.

On by dirt bike, my 11 hp SL100, I broke several of the cush drive sprocket carrier bolts. That bike took a thrashing. Here is an unmolested/restored SL100 up for auction recently:

[/url]
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Offline Terry in Australia

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Re: How important is a cush drive?
« Reply #12 on: October 26, 2021, 06:41:19 PM »
Thanks Kev, I'll have to check my K0 hubs and see what dampers are in them. I can't stand that Kaplan guy, I've watched some of his video's on YouTube and I think he's a poser, and a shark. He does get some nice bikes in, but occasionally he gets some real dogs and thinks that engines with big end knocks just need a little tuning, and painting over rust is "restoring". I wouldn't buy anything from him. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline Mantree

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Re: How important is a cush drive?
« Reply #13 on: October 26, 2021, 09:10:04 PM »
My opinion,harleys dont need/use a cush drive due to the design of their hubs.honda used a cush drive because a)the way the hub is designed and b)they didnt want the hub to take a beating.

Sent from my SM-G973U1 using Tapatalk

Just wondering what the difference you see is. I know the harley hub is beefier since they whent the old fashioned under engineered over built but is there any other design differences to support this? Maby the longer spokes flex more?

Offline dave500

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Re: How important is a cush drive?
« Reply #14 on: October 27, 2021, 12:25:14 AM »
my 87 yammy TT600 has no cush drive,the same year XT600 has with the same motor,all early year TTs have no cush drive but all the XTs do,with the same motor,the TT has a couple more ponies,you might get away with it on a smooth 4 cylinder but i wouldnt do it.

Online newday777

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Re: How important is a cush drive?
« Reply #15 on: October 27, 2021, 05:42:01 AM »
My opinion,harleys dont need/use a cush drive due to the design of their hubs.honda used a cush drive because a)the way the hub is designed and b)they didnt want the hub to take a beating.

Sent from my SM-G973U1 using Tapatalk

Just wondering what the difference you see is. I know the harley hub is beefier since they whent the old fashioned under engineered over built but is there any other design differences to support this? Maby the longer spokes flex more?
Longer spokes do flex more.
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Offline Shtonecb500

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Re: How important is a cush drive?
« Reply #16 on: October 27, 2021, 07:21:15 AM »
Thanks Kev, I'll have to check my K0 hubs and see what dampers are in them. I can't stand that Kaplan guy, I've watched some of his video's on YouTube and I think he's a poser, and a shark. He does get some nice bikes in, but occasionally he gets some real dogs and thinks that engines with big end knocks just need a little tuning, and painting over rust is "restoring". I wouldn't buy anything from him. ;D

The guys that really really bother me is the moto phg guys or whatever, some bike shop out of Pittsburg. There are always only 2-3 people driving up their prices on the #$%* bikes they build to stupid prices....they list the bike they pump the number up on each one. I dont get it. I would never buy a #$%*ing bike from them  and i dont really get how they even sell anything.
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Offline MauiK3

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Re: How important is a cush drive?
« Reply #17 on: October 27, 2021, 08:26:25 AM »
Cush drives are important.
As I've mentioned before, I used to work on nuclear submarines.
For a long time, through several class ships, they have had cush drives, albeit of a type that is elegant and very effective. They work on the same general ideas as those on our bikes, keep the shocks and noise from going either up or down the drive train.
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Offline Terry in Australia

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Re: How important is a cush drive?
« Reply #18 on: October 28, 2021, 04:58:36 AM »
Thanks Kev, I'll have to check my K0 hubs and see what dampers are in them. I can't stand that Kaplan guy, I've watched some of his video's on YouTube and I think he's a poser, and a shark. He does get some nice bikes in, but occasionally he gets some real dogs and thinks that engines with big end knocks just need a little tuning, and painting over rust is "restoring". I wouldn't buy anything from him. ;D

The guys that really really bother me is the moto phg guys or whatever, some bike shop out of Pittsburg. There are always only 2-3 people driving up their prices on the #$%* bikes they build to stupid prices....they list the bike they pump the number up on each one. I dont get it. I would never buy a #$%*ing bike from them  and i dont really get how they even sell anything.

I don't know if I've seen them mate, but yep, there are a lot of dodgy (sketchy) shops around. Not too long ago here there were little "Custom" shops popping up all over the place building/modifying custom bikes. Most of these turkeys didn't know one end of a spanner from another, and I was called on to fix one CB750 that they had returned to the owner after charging him several thousand dollars for some very poor repairs.

It came to me with a massive oil leak and was running on 3 cylinders. I took a look at the invoice that he'd just paid, and could see that the bulk of the new parts and work that they'd said they'd done, was fiction. To add insult to injury, the bike had been sitting in their shop for a couple of months, and I think he only paid them to get his bike back. I had his bike back to him and running like a swiss watch in under a week as he was heading to Vietnam to work teaching English to the locals. There was nothing wrong with it that any half arsed mechanic couldn't diagnose and fix, but these turkeys didn't have a clue. Luckily for some, most of those shops have long since closed their doors, but there are still a few around, sadly. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline pekingduck

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Re: How important is a cush drive?
« Reply #19 on: October 28, 2021, 01:02:37 PM »
I know little about H-Ds, but a lot of H-D big twins had a spring-loaded damper on the crank, and many Sportsters had rubber mounted engines.  Those, along with belt drive, reduces the need for a cush drive, but I think they all have cush drive now.

Offline Mantree

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Re: How important is a cush drive?
« Reply #20 on: October 30, 2021, 04:26:45 PM »
Ok so I have a plan I think. I'm going to make a disk similar to a wheel spacer that ypu see pepol put on cars 5 countersunk holes to bolt to the hub flange and 5 large holes which will have ducati cush drive bushing pressed into. I just need to get access to the tooling to cut the disk and a press to press in the bushings.

Offline Terry in Australia

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Re: How important is a cush drive?
« Reply #21 on: October 30, 2021, 04:32:29 PM »
That sounds like a much better idea mate, well done. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline wolf550

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Re: How important is a cush drive?
« Reply #22 on: October 30, 2021, 05:25:19 PM »
I will be interested to see how yours comes out.
I was able to purchase pieces of a front wheel to rear wheel conversion from mister Ricky Racer
and this was a part that I wanted to include in the setup when I get to it one day

http://forums.sohc4.net/index.php?topic=48511.0

http://forums.sohc4.net/index.php/topic,111520.0.html

it would be something to keep me busy
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