Small frame clutch woes from the season...

[nerdspeed]

In the three or four years I raced, I never blew up a clutch. (knock on wood) What seems to be the main point of failure??

[j2]

I raced all last season without blowing up a clutch, but had to hold back and tailor the way I rode due excessive slippage. Patrick and Dayn bikes both put out more power than my setup from last year, so in building a new and hopefully faster engine... we have been trying to come up with the best clutch combo for holding strength and longevity. what clutch did you use?

[nerdspeed]

Specifically I used a surflex 4 plate standard cork clutch with a Polini spring. I would wear out the plates faster than street riding, but it never blew up on me.

[j2]

I was using the three plate polini aluminum plates with a polini spring, when I took them apart there wasn't much cork left, and considering the beating I put on them they held up ok. I just couldn't really nail full throttle.. had to ease into it.

[Dayn]

4 plate = 1.5 days on the track
3 plate = .75 days on the track

Not acceptable. It's a PITA to have to change the clutch after every day (or portion thereof) on the track and particularly frustrating when the actual points race is on the end of the last day of the weekend, meaning your clutch is on it's last legs at that point. More so when you work your way to the lead an then your clutch lets go resulting in a DNF.

A clutch that will last the weekend would be nice, a clutch that would last the season would be better. I'm working on a solution but if it doesn't pan out I'll spring for a Falc clutch to be done with it.

[j2]

which 4 plate were you using days? pk xl2?

[Dayn]

Malossi for the PV type. Uprated spring.

[paddyfitz]

I ran the xl2 for a few dates @ PARC. 12 springs & 4 carbon plates. Murder on the hand for a clutch that never stopped slipping - but kept my front end down!
Finally actually grenaded on me while on a test run around the neighborhood.
Out of funds, cobbled together the single spring w/ 4 plates in for the last cpl rounds @ Mac. It was like a barbecue in my motor. Apocalypse flavor. Rolled into the pit w/ smoke literally billowing out of the side of my bike.
Gonna try the Falc plates as they say they are better at not... barbecuing?
Given the amount of $ I spent on numerous clutch configurations last year, I too am willing to look at what the Europeans say works.

[Dayn]

Yeah I was thinking of trying the Falc plates too. Aluminum & dry. From what I was reading on motorcycle clutches in general, the dry clutch like the Falc seems the way to go. they don't swell when they get hot and they shed heat faster as there is no oil for it to collect in.

I'm going to try my assembly. Aluminum basket and plates with my aluminum spring holder. Hopefully it will be good at shedding heat even with oil and have enough spring pressure to hold with 8 springs. I also noticed that all the single springs I tried became coil bound before the 2 parts of the spider came in contact with each other. I designed my spring system to allow the clutch to completely release by not being the limiting factor in travel, hopefully this will keep it from dragging and again help with the heat issue.

Patrick do you think those Falc plates will work in a PV style clutch?

[j2]

I ordered a few sets of plates. the newfren xl2 clutch comes with fiber plates. Sip also has "race" plates, and then the "race evo" plates. they are all slightly different in color and come with different strength springs. Patrick, which ones were you using?
Also when I tried to add the cosa springs inside my xl2 springs I they were binding on each other before full travel.

[paddyfitz]

Dayn - Falc plates are designed to work around an XL2 inner bell/spider. I put it together a few days ago. Required some manufacturing/finessing to fit into a normal primary... so I got a DRT.
Still a little bit of fitting, measuring and trimming, but looks real purty.

J2 - The race evo ones were not yet available last year, so I was using the Malossi/SIP race brand. I didn't have any trouble with springs binding. Everything compressed fine - it just wouldn't hang on.

I did run the DRT outer plate setup w/ 5 plates in Seattle on the single spring and had pretty good success, but made me realize I was ready for a bit more power across the board.

[j2]

the race evo ones look pretty stout, and the springs that come with that one are quite a bit stiffer than the ones that came in the standard xl2 clutch. I would say nearly double the strength.

[mikekoch]

One thing I am noticing is that the stamped steel top plates I've found scrounging around in my garage, from SIP, DRT and other sources, are all deformed. I do not have a PK style outer plate to measure but I would guess the same problem exists there. Those of you who have one laying around: drop a straight edge on the friction side. I am finding that they're all conical and in the wrong direction. This causes the friction area on the outer plate to be greatly reduced (pressure is only applied to the inner 25% or less). Obviously this will also affect the rest of the stack.

At the moment I don't have time, but will be looking at making a jig to compress and reform outer plates. Once that's done, I'm curious about heat-treating them to increase rigidity. Might turn them into pretzels or grenades, but also might help!

In the meantime I am running a PK outer friction plate in my PV clutch to help center the load on the inner plates. Crossing fingers...

Mike

[paddyfitz]

Nightmare week of bike building for me. Yesterday at the track was the first run on my setup this time. (XL2, falc plates, DRt outer plate, 12 springs of varying strengths). No sign of slippage & my woodruff key survived the whole day. Didn't kill my hand. Big ups on that setup.

[j2]

5 plates still? if so what combo of steels thickness worked?