brucey Posted October 17, 2011 Report Share Posted October 17, 2011 Hi, I know this is a common problem and I have to get it past tdc before trying to kick start. I have a standard crank shaft duplex gear (19t?), low compression piston, 'R' Cam, strong clutch springs, ally billet pressure plate, primary chain tensioner and fill the case with about 100cc of ATF to keep the primary chain wet. I also have the Alan Whitton Modified (longer) Clutch Operating Arm Assy. The clutch slip when kick starting seems to be getting worse. This may be because the rings have bedded in and raised the compression. Should I just tighten the 3 clutch spring adjusters by a turn each and see what happens? Any advice appreciated. Bruce. Quote Link to comment Share on other sites More sharing options...
totalshell Posted October 17, 2011 Report Share Posted October 17, 2011 yes.. Quote Link to comment Share on other sites More sharing options...
gii Posted October 17, 2011 Report Share Posted October 17, 2011 Just a thought: Have you got a little bit of free play at the clutch operating arm? If you haven't it doesn't matter much how tight you wind the springs up. I set my clutch up this way: Release the cable at the handlebar lever Turn the central adjuster in the pressure plate clockwise gently until I feel the clutch arm touch the outer cover. Turn the central adjuster 1/2 turn anti clockwise then tighten the lock nut. This gives around 1/2mm free play. Re fit the cable at the handlebar lever and adjust to suit - again a little bit of slack. I then only tighten the 3 clutch springs enough for their heads to clear the inside of the primary cover, but I check that the lift is even using a dial test indicator ('engineers clock')I aim to get the variation at full lift within 0.25mm My Cub is 250cc and I only have to think about clutch slip kicking it over cold, once it's warm I have no problems at all. I haven't seen a Whitton clutch arm, does the increase in length reduce the weight of the clutch significantly? Quote Link to comment Share on other sites More sharing options...
brucey Posted October 17, 2011 Author Report Share Posted October 17, 2011 Totalshell, Thanks for you nice and simple reply. Gordon, thanks for your slightly more detailed reply. I have a couple of questions: Are you using a billet ally clutch cover and stronger springs? I presume you pull (and hold) the clutch lever in and then run the DTI on the top face of the clutch cover somewhere near the edge of the clutch basket. Finding a place to locate the mag base should be fun! By adjusting the spring adjusters so they only just clear the cover, you imply you use minimum spring pressure. Is that right? What oil and how much oil do you put in your clutch? I don't have anything to compare Alans Clutch Mod with as I haven't ridden another Cub. However, I can pull the clutch lever in easily with 1 finger. I guess the arm is about 25% longer so the clutch should be 25% lighter! I modified the arm myself, Alan just modified the case for me. Alan was also working on a mod that allowed you to fit an extra friction plate in the clutch basket to prevent slippage especially when using a 16T primary gear. Bruce. Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted October 18, 2011 Report Share Posted October 18, 2011 Hi Guy's Hi Bruce. Just reading your problems. And I will say that I have had problems with the alloy billet preasure plates on two of my C15's and they are both of diferent manufacture. By fitting the old steel BSA plates back after surface grinding them solved the clutch slip problems. I might add that another C15 with a different billet alloy plate is just fine, no problems. But it may be worth you just trying the old steel plate back. I am also working on a Cub clutch, trying to fit another plate, I will let you know if it works or not later. Regards Charlie. Quote Link to comment Share on other sites More sharing options...
windlestone Posted October 18, 2011 Report Share Posted October 18, 2011 (edited) Totalshell, Thanks for you nice and simple reply. Gordon, thanks for your slightly more detailed reply. I have a couple of questions: Are you using a billet ally clutch cover and stronger springs? I presume you pull (and hold) the clutch lever in and then run the DTI on the top face of the clutch cover somewhere near the edge of the clutch basket. Finding a place to locate the mag base should be fun! By adjusting the spring adjusters so they only just clear the cover, you imply you use minimum spring pressure. Is that right? What oil and how much oil do you put in your clutch? I don't have anything to compare Alans Clutch Mod with as I haven't ridden another Cub. However, I can pull the clutch lever in easily with 1 finger. I guess the arm is about 25% longer so the clutch should be 25% lighter! I modified the arm myself, Alan just modified the case for me. Alan was also working on a mod that allowed you to fit an extra friction plate in the clutch basket to prevent slippage especially when using a 16T primary gear. Bruce. Gordon was kind enough to set up my clutch. Billet ally clutch cover, springs were already in so i don't know if they are standard or stronger. DTI on top face of clutch cover near basket, magnetic base stuck to frame. Pull and hold in clutch while kicking over using kickstart The less adjustment on the springs, means less pressure, making a lighter clutch Mark the pressure plate 1,2 and 3 to help identify springs to tension Use 100mm of oil in clutch, just enough to keep the chain wet. Some folk use ATF Appologies for butting in but Gordon may be on holiday now Edited October 18, 2011 by windlestone Quote Link to comment Share on other sites More sharing options...
brucey Posted October 18, 2011 Author Report Share Posted October 18, 2011 Charlie, I did wonder what the coefficient of friction was on the ally pressure plate compared with the standard steel one. I'm still a little unclear on how to 'clock' the pressure plate. I have done the following: Adjusted push rod clearance as Gordons instructions. Adjusted pressure spring nuts until the top of the head is approx 10mm (3/8") above pressure plate face (as Haynes Cub Manual instructions) Refit Clutch Cable to lever and adjust to allow 2mm clearance. Pull and hold clutch lever fully in against handlebars with rubber band. Put DTI on outer circumferance of pressure plate at 3 o'clock position (Mag Base on footrest) Rotate clutch plate using Kick Start Lever and adjust springs until within 0.2mm deflection on pressure plate face. There are a couple of things I noted: The pressure plate can be moved over 1mm by just pressing it. This makes it difficult to adjust the spring nuts without disturbing the settings. Upon releasing the clutch lever, there is now more than 1mm difference in height from the top of the spring nut to the top of the pressure plate. I'm just off to try and start it with the cover off to see if it still slips. Bruce. Quote Link to comment Share on other sites More sharing options...
gii Posted October 18, 2011 Report Share Posted October 18, 2011 I don't know if my clutch springs are standard or stronger either. I run the springs as light as possible to reduce effort at the clutch lever Both Windlestone and myself have suffered the central adjuster stripping out of the alloy pressure plate - another reason for keeping the springs light. Plates are branded surflex Quote Link to comment Share on other sites More sharing options...
brucey Posted October 18, 2011 Author Report Share Posted October 18, 2011 Windlestone, I really must type faster. Thanks for that, it seems like I've done it right! Bruce. Quote Link to comment Share on other sites More sharing options...
gii Posted October 18, 2011 Report Share Posted October 18, 2011 (edited) Yep, sounds right. Of course you can deflect the pressure plate with your finger, when the clutch lever is pulled in the plate's only supported in the centre, effectively on a needle point. There are only 3 stabilising springs. A modern engine would have twice as many, or a lovely diaphragm. You've done 2 important things: You've set it so that there is a little clearance in the clutch operating mechanism so that when the clutch lever is released the full force of the springs is applied to the clutch plates, and you've set it so that the clutch pressure plate lifts evenly giving the cleanest clutch action with the least drag. Particularly important for you as your extended clutch arm gives less lift than a standard one Another question, when you extended the clutch arm, did you just cut and extend by welding in a new piece or did you reinforce the arm too? Edited October 18, 2011 by GII Quote Link to comment Share on other sites More sharing options...
brucey Posted October 18, 2011 Author Report Share Posted October 18, 2011 Gordon, Thanks for your vote of confidence. I tested the bike with the cover off and there was no slip when starting cold and hot! Things are looking up so I've replaced the cover and put 100cc of ATF in. I stengthened the arm when I extended it by adding a small web on both sides. This seems to work well. Thanks to everyone for taking the time to help me. I now plan to enter my first pre67 trial in Horsmonden this Sunday! Bruce. Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted October 19, 2011 Report Share Posted October 19, 2011 Hi Guy's. Hi Bruce. Yesterday after getting involved with this thread. I set to and redesigned and made a new clutch arm, longer, wider, and stronger, and with better leaverage. I just hope it will work as well as it looks. The only down side is that the cable end protrudes through the outer case hole. I am today going to weld on a new cap and screw cover over this. Fingers crossed it will work. The build of the old one was crude was'nt it. and not a thing you would put into production today, or should have then. PS I fitted steel insert into one alloy presure plate to stop threads stripping, very common on these alloy plates to strip the thread, not good engineering practice. A better solution would be to make the area stronger(thicker) and modify the primary chain case. Regards Charlie. Quote Link to comment Share on other sites More sharing options...
brucey Posted October 19, 2011 Author Report Share Posted October 19, 2011 (edited) Hi Charlie, I remembered what I did to lengthen my clutch arm. The standard Cub arm is twisted so it goes from vertical at the pivot end to horizontal at the cable end. I cut mine at the twist, flattened and slotted it out. I then made another (longer) cable end of the arm and slotted that too. I pushed the slotted pieces together and silver soldered them. Hey presto, an extended, webbed clutch arm. Alans mod effectively moves the cable entry point further towards the back of the engine case. I won't say how as that's his IPR, but it isn't difficult to work out! Hope this helps, Bruce. Edited October 19, 2011 by brucey Quote Link to comment Share on other sites More sharing options...
jack_the_lad Posted October 19, 2011 Report Share Posted October 19, 2011 The best way I have found to stop the clutch slipping is to use 4 friction plated and 4 metal plates as to Charlie re inventing the wheel i've had know problems with the adjusting nut. With the extra plates you do not have to adjust the screws as tight and the clutch becomes lighter. PS my bike is ridden most weekends? Quote Link to comment Share on other sites More sharing options...
charlie prescott Posted October 20, 2011 Report Share Posted October 20, 2011 Hi Guy's. Hi Bruce. Yes longer arm New hole!! I yesterday made the new alloy cover hole and bung and welded it in place. Then I set too and made a new longer bronze pushrod bush for the mainshaft. then a new bearing carrying plunger, that now works in the mouth of the main shaft. this seems to be a lot better (if it works OK), and I think it will. I would put a picture on of the conversion, but then I would be reinventing the wheel so there is no point is there Bill. PS do you have an Armac fitted to your bike? My modification is going onto a bike that is going to be ridden every week end in the IOM OK. PS and in the week as well. PPS, I will put the photo's onto my web site. :banana2: Regards Charlie. Quote Link to comment Share on other sites More sharing options...
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