1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Pantah 500 Sl Clutch.

Discussion in 'Technical Help' started by Pantah Nick, Aug 21, 2017.

  1. Slowly working my way through the issues on the Pantah, has anyone experience of clutch slip. I'm told there was a new clutch pack fitted prior to sale.
    It slips when cold and improves as the engine warms, but still ocassionally slips when pulling in 4th or 5th.
    I am happy to replace the clutch pack but have seen anecdotal write ups of inserting an extra plate etc. I was informed that over servicing the oil level can be a cause so that's covered, and the oil type is of correct specification.
    Any advise to build my experience would be great, but the new electronic ignition and regulator have improved the bike immensely.
    Thanks,
    Nick,
     
  2. In the original 1980/81 500SL Pantah, the clutch was marginal even when new, and not really up to hard use. It was soon replaced with a different, slightly larger clutch which is adequate.

    Apart from that, depending how the clutch is assembled it is possible for the lifting mechanism to be touching all the time, causing clutch slip. I suggest you check that it doesn't.

    Another option is to fit harder springs. May cause your left hand to ache, but at least it doesn't slip ...
     
  3. Thanks for the reply, by larger am i to assume that I need to source a 600 clutch pack or was this a bespoke 500 upgrade?
    as for heavier springs again is this after market purpose built or just ones that fit but with a heavier spring rate.

    Thanks for the help.

    Nick.
     
  4. Avoid oils with 'friction modifiers" avoid additives, as said elsewhere, ensure lifting mechanisim has mechanical clearance when the lever is released,
    check the plates if aftermarket provide good clutch performance, and increase spring seated pressure over standard, as measured at the lever is the easy way to do it, if it is harder to pull lever then the clamping pressure is higher?? make sure the stack height of plates is great enough, to not allow, the pressure plate to contact the end of the inner drum if it does then the springs dont matter
    Riding a bike with a slipping clutch; loads the oil with rubbish, and converts the horsepower used for moving the bike into heat in the clutch? I rebuilt a honda CB 750 engine during my apprenticeship and decided to load the new engine against a locked front wheel by slipping the clutch the clutch lasted a few seconds the disintegrated; never used the clutch as a engine dyno since.
    depends only on clamping pressure? not spring constant (unless springs same unloaded length to start with); long spring with lower constant might provide higher pressure at the working length?
    I have many springs out of ducati race bikes, if you are stuck , tell me the; unconstrained length, wire diameter, coil diameter ?and number of complete coils, and i will look for some and post them to you? for cost of post if I have some?
    I used a product called MIL-Tech in my Pantahs F1s and it DIDN'T affect clutch operation, but slicked the gear changes up.
     
    #4 breakout998, Aug 21, 2017
    Last edited: Aug 21, 2017
  5. Thank you, sorry for the late response away with work. I will proberly fit new plates (any suggestions of make ) and when apart relace the oil and filter, measure the springs and increase the spring rate. Perhaps mix springs 3 and 3. The new oil is of the correct spec but the old oil which was fitted at the same time was not so possibly a degree of contamination. Hopefully that will address the issue as once sorted I would not expect a clutch tlo be a regular service issue?
    if you have spare springs I will do as you suggested and see whats fitted I intend to pull the clutch in a few weeks so will be in touch,
    thanks in advance

    Nick.
     
  6. n
    Nick I need;unconstrained length, wire diameter, coil diameter ?and number of complete coils, and i will look for some and post them to you? for cost of post if I have some?
     
  7. By larger I mean a larger overall diameter, so the plates are different and not compatible. You need to establish whether you have the earlier (smaller) clutch or the later (larger 600-type) one. In the smaller one, the plain steel plates have an overall diameter of 125 mm. Can't remember the diameter of the larger ones, but must be approx 135 mm.
    Back in the day I had some springs made up which were just like the standard springs but 3 mm longer, so more preload when installed. Bit of a struggle getting the three pressure plate screws started!
     
  8. Do you know what the spring sizes are are, i have offered to send springs out of my 998parts? coil diameter lenght (free), wire diameter number of whole turns (pitch)?
    thinking the springs would be smaller as the clutch sounds inadaquate, In my F1, i can only remember problem with a seized lift mechanism fixed that and the clutch stopped slipping
     
  9. I have just looked through a boxful of assorted springs in the garage and refreshed my memory about Pantah clutch springs, 6 per set. Pantah clutch springs have an overall diameter of 16 mm. The internal diameter is not critical, but is about 13 mm. The standard free length as originally supplied in 1980 500SL Pantahs was 35 mm. The installed length is fixed as the three screws must be fully tightened.

    I had a series of sets of springs made up, in a range of free lengths: 40, 41, 42, 45, and 49 mm. Then I could try different options and select the most suitable ones, ideally enough pre-load to avoid slippage without being impossibly hard at the hand lever.

    So I still have these sets, which have not deteriorated from sitting in a box for decades. If you would like to try a set @Breakout998 , feel free to start a private conversation.
     
  10. Looks like you are ahead of the game? Wire gauge and number of complete coils also effect the spring constant your way keeps a standard constant but adds more preload, totally good idea.
    Clarify: I am trying to assist the member who originally posted about his bike, I havent yet been able to go down to my shed because of a bad, ongoing case of gout, which is making me scream all night (almost), soon as I can stand on my ankle,i will go and look for clutch springs from 916 racing or 998RS got heaps and send pictures and measurements
    Pantah Nick; would be good if you had part of the solution for him, above is the guy with the problem
     
  11. Nick look to Pete 1950, seems he has a full or part solution with his graded spring kits, allowing a re balancing of the torque the clutch will transmit, and the size of your mitt, would be worth talking to him?
     
  12. Sorry, I should have addressed this comment to @Pantah Nick .
     
    • Like Like x 1
  13. Okay I will pull the case and see what diameter plate is fitted assuming it's standard, also reviewing the history the bike had a new clutch in 2016 and again before I picked it up. If both invoices are correct it's cover very few miles and gone through two clutches, the oil was replaced only 500 K ago when the bike had the electronic ignition fitted by DTS. And looks quite black so indicative of the clutch overheating?
    As I stated I have no problem replacing the clutch but would want a more robust solution, ordered the correct grade oil and gasket so will investigate this week.
    I might try up rated springs before a new clutch but as it's been slipping it may be fried already.
    Will update blog once I know what I'm looking at and may try stiffer springs I assume you can intermix springs to get the correct preload on the pressure plate, with a moderate to stiff clutch action.
    Thanks.
    Nick.
     
    • Agree Agree x 1
  14. https://netrider.net.au/threads/project-pantah.111287/page-5
    Just a word on clutch slip if I may. The clutches slipped even when the bikes were new. There are 125cc UJMs with bigger clutch baskets than these bikes had. I've tried just about every known cure down the years with mine, and the only one that ever worked (and still does) is changing the primary drive ratio to reduce the torque the clutch transmits. You can try other solutions, but I've done most of them along the way and for what it's worth, this is my recommendation.
    new plates, and non friction mod oil, and heavier springs? bigger clutch conversion?
     
  15. When I bored and stroked my 500 Pantah to make it a 750, in 1981, I needed to find a way of making the clutch indestructible - other than fitting impossibly strong springs. So I replaced the feeble alloy lined plates with a set of sintered bronze steel plates. These were made by taking a set of Norton Commando clutch plates (which are immensely tough) and machining them to fit the Pantah dimensions. This was effective, but I do not recommend it as a practical solution nowadays.
     
  16. Hello chaps, I have the new clutch (supaflex) but yet to fit, also got Silkolene classic oil EP3 so with correct grade oil and a new clutch hopefully that will be the end of the issues.; At the first sign of slip I will go down the stiffer spring route rather than ruining the new clutch.
    The only comment on the clutch is the retaining clip or large retaining ring needs caution in fitting? is it problematic or prone to popping out once installed.
    Quote from Mick Walker Restoring Ducati V twins.
    On another issue when I had the bike serviced and race ignition as the Bosch pickups crumbled in my hand, it came back with NGK BP8HS, the book by Mick Walker states BP7HS. The only reason I ask it that both plugs failed simultaneously whilst parked up?
    This threw me a curve ball, as it,s never happened to me before, thinking of fitting Bosch but have you had any bad experiences with either?
    The 7's are a higher heat range so may be more robust but now riding with a pair in the seat hump.
    Bikes going great by the way, sourced a AG Strada manual online and a seal kit so rear shocks next, any body know if replacement springs are available or the spring rate of the originals before I consign them to being replaced.
    All advice as always brilliant bit needy at the moment but learning exponentially'
     
Do Not Sell My Personal Information