firstgear Posted February 20, 2008 Report Share Posted February 20, 2008 Below are some test ran by my Father in the efforts to reduce clutch pull efforts. This is in ref to a 2007 Rev 3 250 however I suppose it would apply to all Rev models. On a post several months back I saw a topic on removing two of the 6 clutch springs to reduce the clutch pull effort. I have been told since then that this may cause the clutch to slip under extreme conditions. I have a Dad with to much time on his hands and he has been playing with his clutch effort and came up with this. I am wondering if anyone has tried this and what the results were. Here in Michigan it is difficult to test with the cold and deep snow. Clutch pull measurements taken using a RCBS Premium digital trigger pull scale (8oz - 8lb) placed at the end of the lever next to ball. 8 pull test were taken at each stage than an avg was taken from that. 1.Stock Clutch pull = avg 6.9lbs lbs. 2.Clutch plates & pressure plates cleaned up to remove burrs. = avg 6.6lbs 3.Next test was removing 2 springs using 4 springs total = avg 5.2lbs (Like on previous TC post) 4.Next test back to 6 springs (stock) with a .060" shim placed on top of each spring to lesson spring preload. = avg 5.9lbs 5.Next test was same 6 springs with a .118" shim placed on top of spring = avg 5.2lbs. (this is the largest shim that can be used without hitting the side cvr. a button head bolt was used to gain additional clearance) 6.Clutch put back to stock same as test #2. (shims removed & 6 springs) but removing lever & lubing with grease = avg 6.1lbs 7.With the big gain in a well lubed lever he re-ran test #5 with the .118" shim and lubed lever = avg 5.0 (better than running 4 springs) Ok with that said has anyone tried to lesson the preload on the clutch springs and if so what were the results? Quote Link to comment Share on other sites More sharing options...
paul w Posted February 20, 2008 Report Share Posted February 20, 2008 use these................. http://www.powerhouse-fitness.co.uk/store/...mp;dept%5Fid=11 leave springs/clutch alone...........improve grip................ride bike...............job done. Quote Link to comment Share on other sites More sharing options...
firstgear Posted February 20, 2008 Author Report Share Posted February 20, 2008 I agree 100% but try teling that to a retired 64 year old powertrain Engineer. He has to mess with everything. He did spike my interest with the reduction in clutch effort though. Nothing is a replacement for quality time on the bike but if a 25% reduction can be had in clutch pull effort without any negatives it is worth it. Now that he is in the Senior class his arms give out sooner than his younger years, this is why he is play around with his clutch. Quote Link to comment Share on other sites More sharing options...
sectionone Posted February 20, 2008 Report Share Posted February 20, 2008 What I did on both levers is used a hammer to straighten them out and reduced the travel with the adjusting screws. Then I use one finger near the ball ends. More leverage=less effort. Quote Link to comment Share on other sites More sharing options...
neil king Posted February 20, 2008 Report Share Posted February 20, 2008 Firstgear, I ran min with 2 springs removed, not to decrease lever pull but to increase friction length. I found that it was too wide and I couldn't snap the front tire up sometimes when I needed to. I'm sure you dad will know the things I'm about to tell you. When you decrease spring pressure you increase the possibility of slippage it doesn't matter if you do it by decreasing the number of springs or by shimming the springs. Shimming is the better of the two as this distributes the load evenly and keeps the clutch in balance. I tried running with 1 spring removed but the uneven load made it difficult to disengage the clutch fully but the friction area seemed about perfect. Another way to decrease lever pull and increase friction length is to change the possition where the pressure is applied on the lever. At the ball end where ya'll have been measuring the pressure applied to the lever is the location where the least amount of pressure is needed to be applied and has the longest arc from stop to stop. As you move closer to the fulcrum the more pressure is needed and the shorter the arc or friction length will be. Sectionone gave you the short version. I moved my master cylinder as far to the middle as I could, it doesn't put my finger at the ball but it was enough to solve my problem. Maybe a combination of the thin shims and moving the lever will do the trick? Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 21, 2008 Report Share Posted February 21, 2008 Why not use a smaller bore master cylinder or a larger bore slave cylinder? Quote Link to comment Share on other sites More sharing options...
slapshot 3 Posted February 21, 2008 Report Share Posted February 21, 2008 guys, I'm intrigued by this thread, I've never noticed my clutch ever being anything other than lightness itself. It's well maintained, oil changed every 6 to 8 hours riding, mechanical parts burr free and always well lubed, I'm not sure what force is needed at the lever for actuation but I've never seen the need to try and lighten the action D Quote Link to comment Share on other sites More sharing options...
dan williams Posted February 21, 2008 Report Share Posted February 21, 2008 You guys aren't paying attention. Smoothing the rough edges of the fiber plate tabs, matching them to the clutch basket slots and then polishing the tabs MUST be done before reduction of the clutch spring pressure. The reason for the heavy clutch springs is the rough edges from the forging process on the tabs dig into the sides of the clutch basket slots causing the plates to not engage or disengage properly under load. Just removing the springs will make for a slippimg clutch but not due to insufficient spring pressure to hold the plates together but insufficient pressure to slide the plates together completely before they bind on the side of the clutch basket slots. Take a look at any of the really good accessory clutches and you'll see they use steel inserts in the clutch basket slots and polished ends on the fiber plates for just this reason. Either do it right or don't do it. 1 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 21, 2008 Report Share Posted February 21, 2008 You guys aren't paying attention. Smoothing the rough edges of the fiber plate tabs, matching them to the clutch basket slots and then polishing the tabs MUST be done before reduction of the clutch spring pressure. The reason for the heavy clutch springs is the rough edges from the forging process on the tabs dig into the sides of the clutch basket slots causing the plates to not engage or disengage properly under load. Just removing the springs will make for a slippimg clutch but not due to insufficient spring pressure to hold the plates together but insufficient pressure to slide the plates together completely before they bind on the side of the clutch basket slots.Take a look at any of the really good accessory clutches and you'll see they use steel inserts in the clutch basket slots and polished ends on the fiber plates for just this reason. Either do it right or don't do it. Dan Yes the lower co-efficient of friction of the steel inserts is one reason for the special treatment for the basket finger/fibre plate interface, but it also greatly reduces the rate of formation of grooves in the basket finger slots ie because steel is more wear resistant than aluminium. David Quote Link to comment Share on other sites More sharing options...
neil king Posted February 21, 2008 Report Share Posted February 21, 2008 You guys aren't paying attention. Smoothing the rough edges of the fiber plate tabs, matching them to the clutch basket slots and then polishing the tabs MUST be done before reduction of the clutch spring pressure. The reason for the heavy clutch springs is the rough edges from the forging process on the tabs dig into the sides of the clutch basket slots causing the plates to not engage or disengage properly under load. Just removing the springs will make for a slippimg clutch but not due to insufficient spring pressure to hold the plates together but insufficient pressure to slide the plates together completely before they bind on the side of the clutch basket slots.Take a look at any of the really good accessory clutches and you'll see they use steel inserts in the clutch basket slots and polished ends on the fiber plates for just this reason. Either do it right or don't do it. Oh yeah, I forgot to mention the 3 hours I spent working on clutch plates before I did anything else. Quote Link to comment Share on other sites More sharing options...
firstgear Posted February 21, 2008 Author Report Share Posted February 21, 2008 Dan As mentioned in my first post (step #2) the clutch clean up was performed. He has over 6 hours in fileing,sanding and polishing of the clutch assembly. I believe he is working on "doing it right" Thats why he is looking at reducing efforts by keeping all 6 springs! I think some are getting a little side tracked from the topic. Neil, your reply is what I was looking for. Thank You. There is not a problem with the factory clutch efforts he is just trying to reduce the effort as much as possiable. All should expect to see gains after file work, sanding and polishing has been done, he is just curious if he can shim without clutch slipping. Since it is difficult to test at this time in our state I was looking for others that have tried this. We understand shims will eventually cause the clutch to slip but like Neil King said it seems to be the better of the 2 options between removing springs and shimming. His efforts to ruduce clutch efforts are driven by age and a wrist that gives him trouble on that last loop at every event. Every little bit may help and could benefit many with similar concerns. Quote Link to comment Share on other sites More sharing options...
dan williams Posted February 22, 2008 Report Share Posted February 22, 2008 (edited) OK so I'm a bit touchy. Since I figured out this clutch improvement method my main concern was that people would take shortcuts and not only not see the benefits but make their clutches worse. Blame it on the engineer's paranoia that the exhilaration of the "Ah HA!" moment gets ruined by poor execution. It happens often. Dilbert cartoons are too real for many of us. If it makes you feel any better I get to do it again myself. I'm picking up my '08 Saturday. I'm psyched! Can't wait for that new bike smell. Oh yeah one other thing to note is that the pull is just the pull. In a static environment (engine off) the effect of the unfinished clutch plates is going to be extremely small. I'm actually surprised you measured any difference in clutch pull from dressing the plates. The question that is raised by the smoothing of the plates is how much force is required to move a fiber plate under side torque as is the case when the engine is running and the clutch is partially engaged. For that you would need to know the rotational torque pushing the fiber plates into the basket. Remember the heavier springs don't do their mojo until the clutch is starting to engage and the plates are wedged into the side of the basket. If they are jamming against the side of the basket and the springs are not heavy enough to overcome the drag then the plates will never sit flat to make full contact so all the friction material comes into play. On the flip side when the clutch is disengaged the plates are still jammed into the clutch basket sides and can't release until the side torque is reduced to less then required to slide the plates apart. That leads to another question. If the plates are not making even contact around the basket are they disengaging cocked in the basket grooves. This would cause the plates to skew in the stack and possibly warp. This may not be a bad thing though as the main mechanism for the plates disengaging may require this to some extent. Basket wear is definitely a consideration. One of the reasons I'll be fixing the clutch on the '08 before I even ride it so any unpolished edges on the plates don't wear themselves a groove. All this is academic though and the simple truth for me is I've never had a better clutch on a Beta then the one in the '05 with two springs out and the plates polished. The pull doesn't fatigue my clutch hand anymore, which used to be a major problem, and aside from the initial stickyness of the clutch from a cold start the clutch doesn't drag or stick all day and hasn't shown any signs of slipping. Even with my fat A** on the bike. Edited February 22, 2008 by Dan Williams Quote Link to comment Share on other sites More sharing options...
ikb Posted August 29, 2008 Report Share Posted August 29, 2008 Having read the above, I have made some new spring caps that act as 3mm (0.120 inch) shims on the springs. I now have a lighter cluch that even looks better!!! (only when in bits though!!). Is there a market for these? so i can make my fortune!! Quote Link to comment Share on other sites More sharing options...
steve Posted August 29, 2008 Report Share Posted August 29, 2008 IKB - Those spring caps look good. But....... what do the standard one look like? Surely by making them 3mm thicker you have inreased pre tension on the springs making the clutch heavier? Talking of spring pressure, by adding shims you are not actually making the spring any weaker, just shortening it. The best way to achive what you want would be to fit lighter springs. If these aren't available, how about grinding a litttle from the side of the springs? Make the spring thinner you make it weaker. Quote Link to comment Share on other sites More sharing options...
ikb Posted August 29, 2008 Report Share Posted August 29, 2008 The standard spring cap is just a flat washer so the top of the spring is level with the top of the posts in the clutch centre basket, my caps are stepped so the springs are compressed 3mm less so they have less pre load making the clutch lighter. I think this makes sense at this late hour!!! Simpley the springs arent squashed as mutch!!! IKB Quote Link to comment Share on other sites More sharing options...
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