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Slipper Clutch: Yoyodyne vs STM

Coyote

Coyote

Member
Joined
Nov 14, 2002
Location
Redwood Road
Moto(s)
2008 R6, 2021 KTM 450SMR, 2010 KTM 450 EXC, and 2006 KX65 Minimoto
Name
Neil
Besides a $130 price difference (Yoyodyne - $795 and STM - $925) what are the differences between the Yoyodyne Slipper Clutch and the STM Slipper clutch?
 
I can't even figure out how a slipper clutch works! But I sure do love my STM
 
I think for the oil-bath japanese clutches, the STM is an Evo style with a big central outer nut and a single flat central spring, while the Yoyodyne uses 5-6 coil springs and the nut is inside and just holds the hub in place. I've used both types on my Duc and I like the multiple-spring version better, because you can get at the clutch plates without removing The Big Nut every time. Don't know how well either of them work on a japanese bike.
 
I use Yoyodyne, no problems, my buddy uses STM, no problems. Both work great. So I'd get the cheaper one?
 
I've used both Yoyodyne and STM as well. Also Bucci, and Ducati Performance. Mostly in racing conditions, but some street time as well. We've experimented with all sorts of stack heights, directions of the beveled plates, and even combinations of worn friction plates combined with new - all new plates - or all worn plates. One trait they all consistently have is a real crappy launch. They lock up on you when you REALLY get in it. You can't pull back and burn it again, like a standard clutch, so once you go a bit too far, you're done. Left with a real nice elevated view of the rest of the pack leaving you behind. This is true on all but the YOYODYNE . That thing gets you going like the Jolly Green Giant just smacked you in the ass with a huge croquet mallet. You can pull back on it to burn more, or stay in it all the way to lock up - just like a good standard clutch. Yoyodyne sells two different friction plate sets - one for the track, one for the street. The street one feels nice and soft on regular launches, but you'll kill it in a race. Also, the Yoyodyne has given us the most consistent rear wheel drag on decel, and the best wear. We only changed one clutch pack this season, and only because we thought we should - not because we needed to.

You can throw three downshifts at once on the Yoyodyne, and then dump the lever, under REAL hard braking. You will not skip the rear tire....

Oh, yeah. Somehow the Yoyodyne slipper is the least expensive too. Go figure.

Good luck,

GoGo
 
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Yoyodyne rules

1487605-yoyodyne_slipper.jpg
 
I had a STM. It worked great slipping but for some reason I could never get a good start with it all year long.
 
Great feedback, especially yours GoGo. Thank you.
 
GoGo said:
I've used both Yoyodyne and STM as well. Also Bucci, and Ducati Performance. One trait they all consistently have is a real crappy launch. They lock up on you when you REALLY get in it. You can't pull back and burn it again, like a standard clutch, so once you go a bit too far, you're done. Left with a real nice elevated view of the rest of the pack leaving you behind.
GoGo
Click to expand...

Well, of course I read this AFTER I already bought the DP slipper made by Bucci. So, any words of wisdom or am I screwed for starts now? Also, any comments on install and plate set up/stack height for this particular slipper? Maybe I should just return it??
 
I'm not kidding, bother, I nailed ONE start with the Bucci in three seasons on it. Most installs on them were done by the guy who imported them at the time, Supermoto International. We always had a problem with launches, and he was trained by Mimo Bucci himself. In 03 we used Bucci again, but installs were done by a different crew. Same resluts.

Freddy asked me to test the Yoyodyne slipper at Ohio a few years ago, during an AHRMA weekend. AHRMA ran their weekend as doubles at the time - same schedule Saturday to Sunday. I had the Bucci in for Saturday, Yoyodyne in for Sunday. Saturday's Bot Open I had to come from the back, made it to second by lap five. Sunday's Bot Open we had the same grid. Got the hole shot from the back row. No bullshit.

We also tested Yoyodyne's street pack that weekend. It felt real smooth, but we roasted it on the first launch. It did come back though, after half a lap. Probably overheated. Their race pack wears like iron.

One thing I will say about the Bucci is it's made out of real nice materials. I went to Italy and actually met Mimo Bucci a few years ago. Real nice group of people he has. Their clutch basket is actually poured into a mold which is basically the shape of the basket already- then it is machined from that shape, instead of simply from a block of billett. Their idea is that the basket is stronger if it is formed out of the original shape. Also, the Bucci is offered with titanium spring posts, or steel. The Bucci rarely hopped on decel.

Stack heights were the same I believe, but I personally didn't do the install work on the Bucci. I remember we experimented in a range of 34 - 36mm. Best lauch we had was when it was worn out.

Best I personally can suggest to you is if you want consistent strong starts, you know where to get em'.

Good luck, brother,

GoGo
 
Sorry, never had the pleasure.

Basically, if you don't have a problem with rear wheel hop when you're jammin on the brakes - and you don't struggle with the thing locking up before you tell it to on launches, you're stylin'.

If it aint broke, don't fix it.
 
Hmmm... I remember sliding on my a$$ in T7 at Sears Point in May and wondering if a slipper clutch would've helped my failed banzai braking attempt... :rant :cry
 
afmotorsports said:
Hmmm... I remember sliding on my a$$ in T7 at Sears Point in May and wondering if a slipper clutch would've helped my failed banzai braking attempt... :rant :cry
Click to expand...

:laughing Considering how long you told me you stayed WFO, I don't think so, Alex! :laughing

But stack height made a huge difference with my STM Evo. It had to be between 36.0 and 36.5 mm to work well, and it worked better but wore out more quickly on the low end of that range. This meant a lot of plate swapping as the clutch wore - I have a thick stack of spacers with various thicknesses in my garage, and I mic'd the stack before every weekend and set it to the right thickness. Pain in the arse. It would feel grabby on launches if it was too thick, but if it was too thin or if I really burned it up in practice, it would start slipping on the gas even with my 748 motor driving it. It completely fried about 2 laps into a race at Thunderhill a couple years ago, leaving me cursing and watching everyone fly by as I tried to nurse it home. After two years of use and abuse, the clutch was seriously banged up and I retired it to my street bike, where it now enjoys a liesurely life. :laughing

My current STM 6-spring clutch is much easier to work on and should be less sensitive to the stack height, but I realized after running it all last year that I'd installed one of the parts backwards, so that it actually wasn't slipping. Explains some of the wheel hopping and fishtailing I occasionally had. :p At least it's still new. :laughing Moral is, make sure you know what you're doing when you install it and set it up, and if you're not sure then ask someone who is.

I know Desmotosport has experimented quite a bit with different friction plates and found what they think works best, so that's another variable that will effect how well any particular slipper clutch works.
 
Thanks for all the the valuable advice guys.

I've got a Yoyodine coming in this week and was wondering if i should let a pro install it or try to get it done with my somewhat mechancially inclined friends. :laughing

If you think better to go with a guy who knows what he is doing, who would you reccomend (on the peninsula prefferably).

Thanks!
 
So I've been waiting over 4 weeks for the yoyodyne to come in from backorder for my 04 GSXR 750, and I just called and he said he has no idea when he'll get them. I'd like to get the Yoyodyne based on what I've read here so far but it looks like the STM may be the only option for now.

How well does the STM work on an 04 750, primarily for launching? It sounds like they both slip okay, launches are the only real difference.
 
both myself and carol have a yoyodyne slipperclutch (with race plates) in our 996 and 998. we installed them ourselves with the help of our rent-a-husband and all went well. you need a airtool to get the big nut off and we don't have that (yet).
the clutches are working fantastic. i am not fast at all but have always very good starts. i had to get used to it a bit but now they are good again. i also had to get used not to blip so much anymore. those habits are hard to unlearn.
i would go with yoyodyne anytime. he is the best :)
corien
 
Make sure you get the extra adjustment steels,and if oem makes different thickness steels,I would get several of each size.I have installed Yoyodyne and STM,both are a great product,but clutch pack thickness is very important for either one to work correctly.....Robbie
 
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