MonkeyJim Posted June 14, 2010 Report Share Posted June 14, 2010 hi guys, hoping you might be able to help with a weird issue a mate is having. He's got a Aprilia RSV Factory which he's owned from new, but recently a strnage clutch issue has reared its ugly head, and won't go away. A few weeks ago, on a ride out [i wasn't there] the centre of the clutch cover just blew off. This happened at a standstill, while the bike was ticking over in a petrol station. They managed to get the cover back on but it happened again later that same day, again while the bike was ticking over. He suspected a faulty clutch cover - it's a weird set-up with a centre plate held in place with a big rubber gasket - and got one from Southern Cross, where he has the bike serviced. It's been fine since. Then on Saturday I was lined up behind him in the pit lane at Bedford Autodrome, all of a sudden BOOM! there's a loud bang, and the centre of the clutch cover goes flying off. I mean like a discus it flew for about 25 feet, right across the paddock. Now this was at the start of the 3rd session, so the bike had been thrapped around for 40mins previously, without issue. In all instances the engine has been running 100% fine, and there has been absolutely no warning or any indication there's anything wrong, until the cover literally flies off. The bike is fitted with an 'evolutione' [sp?] mechanical slipper clutch, which has replaced the original aprilia item. The mechanical slipper clutch has been in the bike for the last 5 years, without any problems, and is still operating as it should be. All the various breathers etc have been checked. he's had it checked with Southern Cross and they were unable to find anything wrong, but of course it didn't blow the cover while it was there. He's checked online like rsvr.net but nobody seems to know anything about it. Anyone got any suggestions as to possible causes / solutions? The clock is ticking as we're going to Germany in 3 weeks time, he's obviously concerned about it happening again while abroad. Cheers Link to comment Share on other sites More sharing options...
jollygiant Posted June 14, 2010 Report Share Posted June 14, 2010 Gaffer tape?? Sorry!!! I'm off to Germany/ The Ring in 3 weeks too!! Link to comment Share on other sites More sharing options...
MonkeyJim Posted June 14, 2010 Author Report Share Posted June 14, 2010 When you fit an STM clutch you need to block off the vacuum lines from the throttle body to the clutch housing. Sounds to me like something has been done wrong here and your mate's bike is getting +ve pressure into the clutch housing. Thanks. Yes having witnessed it first hand, there is clearly quite a bit of +ve pressure in there. It really did properly fire it out luckily no-one was stood beside him at the time. The vacuum lines from the throttle body to the clutch housing have alredy been blocked off. This was done by southern cross when they fitted the mechanical slipper clutch, approx 5 years ago. Yet this problem first occured about a month ago. What we can't fathom is, what is causing the problem now? And why does it now occur randomly at tickover, and not when the engine is being worked, and worked hard? Link to comment Share on other sites More sharing options...
Taqman Posted June 14, 2010 Report Share Posted June 14, 2010 I've got an older model Aprillia Falco, I remember reading somewhere (probably to do with the Renegade airbox conversion) - There's a large breather pipe that leads from the rear cylinder cam cover up to the base of the airbox. If this gets blocked then the pumping forces in the engine will blow the clutch cover off. - Might just be popular myth but worth a check. Taq Link to comment Share on other sites More sharing options...
MonkeyJim Posted June 14, 2010 Author Report Share Posted June 14, 2010 But have they blocked off both ends? There's a one way valve in the lines and it is possible that every time clutch is operated the diaphragm gets compressed and it acts like a pump and draws air past the one way valve and as the air heats up and the pressure expands the diaphragm. Why not take the diaphragm out and replace it with a gasket made from gasket paper (or just puncture the diaphragm so that it cannot build up pressure)? I don't know if it has been blocked at both ends, but will suggest he checks this. what is strange that it has been fine for the last 5 years or so. Which suggests to me that either a breather has become blocked, or maybe one that was blocked has become unblocked or is allowing air in somewhere. Don't think a paper gasket would work, the rubber one is pretty heavy duty to hold the centre of the cover in place. We did ponder puncturing it but he was concerned about possible oil leakage. I've got an older model Aprillia Falco, I remember reading somewhere (probably to do with the Renegade airbox conversion) - There's a large breather pipe that leads from the rear cylinder cam cover up to the base of the airbox. If this gets blocked then the pumping forces in the engine will blow the clutch cover off. - Might just be popular myth but worth a check. Taq Yep, although if this is blocked it normally blows the rear cam cover rubber gasket before it does the clutch cover. Still worth knowing, I'll pass this on to him and suggests he checks this also Link to comment Share on other sites More sharing options...
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