Join Date: Jul 2016
Location: Seattle, WA, USA
Mystery of the Clutch Springs
I usually don't start new threads, maybe because I'm too busy answering other folks threads.
My question: Is there anyone who knows what is the condition of the 6 Springs on the back side of a new or low miles the Clutch Basket on a K-40? That is, are they all nice and tight in there Pockets or are they rattling around like all the older ones I've seen to date.
Let me clarify: Most of us K-40 riders have experienced the K-Bike Clutch Chatter in various degrees and attempted fixes from a set of Barnette Plates to complete factory replacements ($$$) with varying degrees of success.
The factory did a major update to the Clutch with the introduction of the 1300 including:
Hard Anodizing the entire Basket in an effort to get a harder surface on the Slide Grooves where the Plates ride in order to reduce wear. That's why 1300 Baskets are black. I have worked on a number of 1200 clutches and seen these grooves so badly warn and galled that the plates were seized in the basket.
The Oiling of the whole mechanism was reworked also to help with the wear factor. This can be seen in the relocated Oiling Holes in the Hub, a different ratio in the Oil Pump Drive, and an added Slot in the Release Push Rod (total=2).
The Plate Stack got a Conical Ring and Steel Thrust Washer added between the back of the Hub Face and the 1st Steel Plate. This required a different 1st Fiber Plate in order to clear the new Ring. All this was to aid in Plate Release when pulling in the Clutch. Note: this means, don't try to jam a 1200 Plate Stack into a 1300 Basket and Hub
Also the Oil Pump Drive Gear engagement was changed from a series of Dowel Pins to a pair of slots but this was done just to ease assembly.
Even though the 6 Springs on the back side of the Basket I mentioned previously are seen by many as part of the problem, they have remained the same on the entire run of the model as best as I can determine. It is these Springs that take the brunt of the impact when the Clutch develops Chattering and it is assumed that is why they become so loose in their Pockets. The problem with this observation is that there are 2 Smaller Springs that remain snug in their Pockets on all the Baskets I've seen, 1200 and 1300 alike. This shouldn't be possible unless the Spring Spacing is set up like this in the first place.
I asked the Service Manager at the local Beemer dealer if the Larger Springs rattle in their Pockets on a new Clutch Basket and he couldn't recall. He said the one guy they had that might know had recently left. Further more; the factory doesn't rebuild Clutch Baskets so there isn't a Replacement Set of Springs available. Besides, you can't just unbolt the Back Plate off the Basket; It's Riveted with Tapered Rivets, no less.
Being a retired machinist I can make my own rivets and I have sourced springs of any size and pressure range I might need but I have to first know what the restoration parameters should be or at least determine if the factory set the Larger Springs up with that much slop (at least .140"). So has anybody ever seen the backside of a new or low miles Basket?