Clutch - deep rear sprockets

[Knowledge]

I have been researching clutch sprockets all night, and I'm not too sure that I have made much progress.

I recall someone saying to me that they had identified a "lightened" rear sprocket that was deepened to allow more plates to be fitted. The thing that was really interesting was that the sprockets could be picked-up for less than £40. However, most performance sprockets cost nearer £100.

The closest I have found are the Atomic sprockets at $50 from ScootsRS, but are these any good? Are they deeper for the clutch basket, as well as the ears of the friction plates?

I saw some Atomic parts being used in a sprinter at York at the weekend and it was good for 90+mph machine.

Your thoughts on performance sprockets, from any supplier, please.

[DaveTomo]

I have been using one of the scootrs/atomic deep rear sprockets for the last 3 years or so, been bob on. One of the of things that drew me to it, was the hardened center so could use the needle bearings. Can't remember how much but I'll say about £38ish at the time (maybe less) from a very nice man in Blackpool . I was expecting a little fettling or maybe fitment issues,but to be fair it fitted well. Like I say I've had it fitted now for a few years ,haven't checked it since the beginning of this year, but when I do give the engine its annual overhaul this winter I'm not expecting any problems.I've used various clutch set ups with it, standard 4 plate, LTH 5 plate & as has been in the last 2 years the readspeed 5 plate with MB springs. In fact I want to buy another as the one I have is a 46 and I'd like to get a 47 to alter the gearing slightly, but as far as I'm aware they don't have any in stock.When I contacted them a few months ago via email they told me they were working on another design which would be available "soon". So going on my own experience being used in a Ron Moss fettled rapido 225, I've found them to be very good.
PS yes they are deeper I also have fitted their atomic clutch spider as well, with a standard SIL GP pressure plate

[Knowledge]

Excellent reply. Just the sort of detail I wanted. Nice one Dave.

[peter357bikes]

hi Martin..i use one from the very nice man in Blackpool too on my RT225. Works well but I had to fettle the basket a bit as they are very sharply edged.

[corrado]

I've recently replaced the clutch in my Imola engine, though It's still on the bench at this stage. Using an Italian deep sprocket, Atomic spider, Atomic pressure plate and 6 BGM red plates and mixture of different steels to get the correct clearance. All seems fine but the retail costs are around £40 more than an AF road 6 plate so it's a bit of a no brainer now to just fit the AF ones in future. I'm using one in my RB sprint engine and had no issues at Elvington with it despite doing about 30 runs on the day.

[rossclark]

I think I have an atomic one under the bench somewhere. I'll have a look and post a pic if I can find it.

One thing I noticed though was that the atomic spider was too short for an MB deep sprocket so would have locked when tightened.

[Norrie Bodge]

lads sorry to revive this oldish thread
but!!!
before i fit my Atomic tall clutch spider & Atomic clutch pressure plate
also with the Readspeed 5plate clutch kit.... do i need a deeper crown wheel?

cheers

[Knowledge]

I don't know the answer, but I will be interested in the answer.

For starters, have you sat a standard clutch spider next to an Atomic spider to see if there is much difference in height (and done the same with the clutch pressure-plates - original and Atomic)?

If they are all similar heights, then there maybe nothing to worry about, but I suspect there will be some fettling to be done.

(I have ordered an Atomic spider this week, but the pressure plates are out of stock )

[martyn dwane]

i bought an Atomic 47T deep sprocket a few years back ,probably when they first came out, it was deeper but hadn`t been machined where the clutch "ears" sit, so a club mate machined it for me. Mine came direct from Scotrs, so wasnt realy feasable to send back. No probs with it now.

[Norrie Bodge]

I don't know the answer, but I will be interested in the answer.

For starters, have you sat a standard clutch spider next to an Atomic spider to see if there is much difference in height (and done the same with the clutch pressure-plates - original and Atomic)?

If they are all similar heights, then there maybe nothing to worry about, but I suspect there will be some fettling to be done.

(I have ordered an Atomic spider this week, but the pressure plates are out of stock )

ive tried it & dont look good, its too proud.... im gonna need a fancy machined crownwheel

i will take clutch back out in morning & compare, think a std pressure plate going in?
but then with a std pressure plate, will the 5plate reedspead clutch fit in??

[Knowledge]

Norris,

How many plates have you got there? What is the combined thickness of all the plates (I think 14mm is standard?

When you have stripped the clutch, lay the Innocenti pressure plate and the Atomic on a flat surface and take a photo from the side, to illustrate the difference in height.

Good luck.

Martin

[Norrie Bodge]

its a Readspeed 5plate clutch kit & all plates thickness including top plate = 19mm

heres the Atomic on the left compared to std pressure plate

[berniek]

Norrie - looking at your pic I am unsure as to what you mean when you say "its too proud"

your top cork is well within the crown wheel with no danger of it popping, your top steel plate looks ok to me, the top plate does not need to be within the confines of the crown wheel. I would think that as long as you are getting seperation on the compressor then your set up looks ok?

[Norrie Bodge]

I cannot get the side casing on with the atomic one fitted m8
The depth difference of the atomic 1 is say 5mm deeper than std

[berniek]

Ok, not trying to teach you to suck eggs, but is it a case of having to grind away the kickstart shaft to stop it fouling? Skim the casing to allow the shaft to pull through further (and take up with shims on the outside)? or a combination of both?

Good luck

[Norrie Bodge]

It's not the kickstart m8
With the Atomic mate, when I try fitting the side casing
The clutch brass is rocking on the Atomic clutch pressure plate
With it being 5mm deeper! I Must need a machine crownwheel m8?

When I say proud... Look at 1st pic m8
How the Atomic pressure plate is protruding so when side casing is fitted its tight against brass pusher

[dscscotty]

Use thicker steels/top plate it'll draw it down, the 5 plate does not have enough over all depth, (you can fit 5 standard thickness plates in an atomic clutch) and is allowing the pressure plate to protrude.

[Knowledge]

So what you are saying Scotty, is that there currently aren't enough plates in the stack to allow the pressure plate to sit at the correct height?

I guess you can keep inserting thick and thin plates into the clutch until there is the minimum space between the underside of the pressure plate and the bottom of the bowl of the sprocket. This way, you can fine-tune the height of the top of the pressure plate.

What is this minimum clearance? Does anyone know?

Martin

[Norrie Bodge]

Use thicker steels/top plate it'll draw it down, the 5 plate does not have enough over all depth, (you can fit 5 standard thickness plates in an atomic clutch) and is allowing the pressure plate to protrude.

cheers on the reply scotty i see what you are saying
so i can add a standard steel & cork in there m8 would that do it? or do i need another thin steel & cork

& as Martin says What is this minimum clearance?

[Knowledge]

I just found this picture of the spider, taken from the ScootRS website. http://scootrs.com/category.cfm?category=7



It looks like the total height of the new spider is the same as the original Innocenti item, so this should not be an issue. Shortly, I will have one of my own, so I can take some measurements to confirm this.

Martin