disepyon Posted May 13, 2012 Share Posted May 13, 2012 (edited) I just replaced my slave and master clutch cylinders. My problem is that when cruising through the neighborhood at around 30mph in 4 gear the car hesitates, when i try to give it some gas it doesnt feel smooth, it has a hard time accelerating. This can be in 2nd or 3rd gear at low speeds. like if i am cruising at 20 to 25mph in 2nd or 3rd and then give it some gas to get up to higher speeds it will hesitate. But the car feels fine when i accelerate through all the gears getting up to high speeds as if im racing it or just want to drive fast off the line. The engine revs fine, running a bit rich though. Does any of this make sense? do i need to explain it better? I have a stock 240z with the adjustable slave cylinder. does this sound like a clutch problem or a carb problem? I spent hours trying out different adjustments with the slave and master cylinder and as it is now feels the best. Im also certain that the clutch system is bled good. Edited May 13, 2012 by disepyon Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted May 13, 2012 Share Posted May 13, 2012 Have you checked ignition timing? Checking over carb adjustment and function will also be a good idea. Quote Link to comment Share on other sites More sharing options...
Miles Posted May 13, 2012 Share Posted May 13, 2012 By chance did you pull the vacuum line off of the vacuum advance? Did the car run ok before you worked on it? Replacing the clutch slave and master should not cause the symptoms you described. Quote Link to comment Share on other sites More sharing options...
at-jefft Posted May 13, 2012 Share Posted May 13, 2012 Check to see if one of your jets is stuck in the down position. IE the choke is stuck on Quote Link to comment Share on other sites More sharing options...
beermanpete Posted May 13, 2012 Share Posted May 13, 2012 Check the oil in the damper (in the carburetor). It might be low. Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 13, 2012 Author Share Posted May 13, 2012 Have you checked ignition timing? Checking over carb adjustment and function will also be a good idea. I just checked the timing and carb adjustment, i also played with it too. It seems like it doesnt matter if i lean it out or richin it, still have the symptom. By chance did you pull the vacuum line off of the vacuum advance? Did the car run ok before you worked on it? Replacing the clutch slave and master should not cause the symptoms you described. About a month and half ago it ran fine until i had to readjust the floats. Instead i just replaced the fuel needle and seat and readjusted the floats again just yesterday. Check to see if one of your jets is stuck in the down position. IE the choke is stuck on I took the chokes off and readjusted it. About a month and half ago i took everything apart to readjust and clean things up. It ran fine for a week and then i didnt drive it for about half a week and thats when it acted up on me and i decided that the floats needed to be readjusted and thats when i replaced the fuel needle and seats yesterday. Check the oil in the damper (in the carburetor). It might be low. Should be good but ill check again. However when i readjusted the jet needle i did slightly bend them, i straighten them out as best i could. That was when i worked on it a month and half ago and it ran fine for the week before i let it set a half a week. I now just advanced the timing a bit and it seem to run a little better but not much. Could there be something wrong with my distributor? It does look really old. i noticed that every now and then the timing light would go blank for for like half a second as if something is skipping. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted May 13, 2012 Share Posted May 13, 2012 It sounds like it might be running rich and loading up when cruising at low RPM. Do the suction pistons move freely? If you bent the one of the jet needles it could be rubbing on the jet and binding. Lift the suctions pistons and make sure they both drop freely, drop at the same rate, hitting the bottom firmly at the same time. Make sure the nozzles both move freely when you operate the choke and return to the fully seated position when you turn the choke off. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 13, 2012 Share Posted May 13, 2012 (edited) 30 mph in 4th? 20 in third? You're lugging the engine, of course it is going to be boggy-soggy as hell when driven like that! I don't know your rear gearing, and it's been so long since I drove a stock over-geared US Spec cari don't remember the shift points any more, but generally you want to be cruising at a MINIMUM of 2500-3000 RPMs to get smooth proper acceleration. That being said, depending on how much throttle you lay into it, it can "pull smoothly" from 1000 RPMs intop gear if the throttle opening change isn't that big, you just don't go anywhere fast. More throttle opening gets you into the bucking response of a lugging engine which diminishes as RPMs rise. Edited May 13, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
at-jefft Posted May 13, 2012 Share Posted May 13, 2012 Last summer I was having hesitation issues. Turned out to be the float level. Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 14, 2012 Author Share Posted May 14, 2012 (edited) 30 mph in 4th? 20 in third? You're lugging the engine, of course it is going to be boggy-soggy as hell when driven like that! I don't know your rear gearing, and it's been so long since I drove a stock over-geared US Spec cari don't remember the shift points any more, but generally you want to be cruising at a MINIMUM of 2500-3000 RPMs to get smooth proper acceleration. That being said, depending on how much throttle you lay into it, it can "pull smoothly" from 1000 RPMs intop gear if the throttle opening change isn't that big, you just don't go anywhere fast. More throttle opening gets you into the bucking response of a lugging engine which diminishes as RPMs rise. Makes sense but ive never had this issue in the past. I notice that while im turning, lets say im in second gear, the car will hesitate a bit. Last summer I was having hesitation issues. Turned out to be the float level. Could be. I forgot to mention that who ever had this car before me mix matched the float bowl lids. So the front float bowl lid has the longer ears where as the second float bowl lid has the shorter ears. I have tried to get the two floats matched as best i can but its hard because the lids are different. This could be my problem. I guess ill try and find a lid with the shorter ears like the second lid i have. Just seems like it doesnt matter how lean i make the carbs, it still smells really rich. But there is no fuel spewing out from the jet needle, just feels a little damp/wet when i stick my finger in there while the car is on. Edited May 14, 2012 by disepyon Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 14, 2012 Author Share Posted May 14, 2012 (edited) It sounds like it might be running rich and loading up when cruising at low RPM. Do the suction pistons move freely? If you bent the one of the jet needles it could be rubbing on the jet and binding. Lift the suctions pistons and make sure they both drop freely, drop at the same rate, hitting the bottom firmly at the same time. Make sure the nozzles both move freely when you operate the choke and return to the fully seated position when you turn the choke off. Yes the pistons move freely and smooth and both have the same return rate. Choke feels good and isnt getting caught up on anything. Edited May 14, 2012 by disepyon Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 14, 2012 Author Share Posted May 14, 2012 Took off the sparks and took a picture for you guys to view. Im no master mechanic, so what does this mean that all of them are black? to rich? The order is 1 on the very left and 6 on the very right. Quote Link to comment Share on other sites More sharing options...
madkaw Posted May 14, 2012 Share Posted May 14, 2012 You need to check all aspects of your ignition. Heaving loading at low rpm will put a large load on your ignition and will show a weak coil or bad wires. Have you checked your charging voltage? Weak spark will exhibit your symptoms. Quote Link to comment Share on other sites More sharing options...
Miles Posted May 14, 2012 Share Posted May 14, 2012 (edited) Yes, too rich. Go to Z Therapy and buy the Video "Just SUs" it will teach you everything you need to know about tuning SU carbs. http://www.ztherapy.com/ They also sell quality rebuild kits and rebuilt SU carbs. Look at this: http://www.mudinmybl...?pg=sprkplgchrt Edited May 14, 2012 by Miles Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 14, 2012 Author Share Posted May 14, 2012 thanks guys, looks like ill be inspecting my ignition system. That spark plug chart helped a lot and listed the symptoms i am having. I have the su carb video from z therapy, I guess ill just mess with the floats a bit more and check the ignition components. Quote Link to comment Share on other sites More sharing options...
Miles Posted May 14, 2012 Share Posted May 14, 2012 thanks guys, looks like ill be inspecting my ignition system. That spark plug chart helped a lot and listed the symptoms i am having. I have the su carb video from z therapy, I guess ill just mess with the floats a bit more and check the ignition components. I had some of the same issues with my SU carbs. After a few years of constant tweaking I finally realized the carbs needed a complete rebuild. The throttle shafts were leaking air so I opted to buy a pair of ZTherapy rebuilt SU carbs. About $600 at the time, but I never had to mess with them once they were installed and tuned. Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 14, 2012 Author Share Posted May 14, 2012 I had some of the same issues with my SU carbs. After a few years of constant tweaking I finally realized the carbs needed a complete rebuild. The throttle shafts were leaking air so I opted to buy a pair of ZTherapy rebuilt SU carbs. About $600 at the time, but I never had to mess with them once they were installed and tuned. Thats nice to hear, im glad that worked out for you. I cant spend that kind of money right now, so i may just have to put up with it if my carbs are the problem. Well i took some pics of my ignition components for you guys to view. Are my distributor cap and rotor ok? The xr700 is what came with the car when i bought it so i figure i would go through the instruction manual as if i am installing this for the first time. Ill be checking the wiring for bad connections as i go. Also is that wire that plugs into the coil bad? could that be a cause of my problem or not? Just that one side is all messed up looking. Quote Link to comment Share on other sites More sharing options...
Miles Posted May 14, 2012 Share Posted May 14, 2012 You are on the right track. Your equipment looks worn. Go ahead and repalce the plugs, plug wires, coil wire, distributor cap, rotor etc. That pick up module in the distirbutor may be suspect as well. On mine I had to also replace the distibutor as the shaft was so worn that the timing and points were next to impossible to set. Also, clean all of the electrical contacts in your ignition system. Replacing the parts will eliminate them as a variable as you continue to research your problem. Motor Sports Auto (MSA) sells all of the tune up parts you need. I prefer the MSA plug wire set as I didn't have good luck with auto parts store replacements. If you don't want to replace your carbs Z Therapy does sell SU rebuild kits. They are suposed to be better than the kits sold elsewhere. Check to see if air is leaking around the throttle shafts. It is a common problem with old SU carbs. The air leaking around the throttle shafts creates a lean condition that makes it hard to get the mixture set right. You can check the throttle shafts for air leaks by spraying carb cleaner or propane where the shafts rotate in the carb body. Listen for RPM to increase as you spray the shafts indicating an air leak. Quote Link to comment Share on other sites More sharing options...
disepyon Posted May 15, 2012 Author Share Posted May 15, 2012 Good news fellows, my car is running like it should be now. I knew i tuned those carbs almost perfect, wasnt the problem all along. Like many have suggested it was my ignition system. Makes sense, if im not getting good spark, then all the fuel isnt being burned causing me to run rich. No more hesitation what so ever!! even during a regular rev, it is smooth. Before when i rev the motor, at first it would hesitate then run smooth. Car doesnt smeel rich anymore either, just a bit but not like it used too, a lot leaner. The things i did were replace the wires going to the optical trigger (which is used for xr700 ignition system) because the original wires had some exposed sections, readjust the optical trigger adjustment (I still need to adjust it a bit more for safety to give more clearance for the shutter), replace the female connectors for the wires hooking up to the coil and resistor because the original ones where loose and dirty looking, and lastly the spark plug and coil wires. New wires. Replaced the female connectors. The original wiring for the optical trigger. Rewired, covered with heat shrink wrap and e tape. Picture showing that i need more clearance for the shutter, way to close on the bottom side of the trigger. The reason why i cant get the trigger black box to move down to give more clearance for the shutter is because of this screw (red arrow pointing to it) closer view. Anyone know if i can get rid of it and how? Does not seem to serve an importance, just turns loosely. Well if i can get that clearance issue figured out then im set. Like Miles said, ill most likely replace the distributor cap and rotor for optimal performance. Thanks for the help everyone!! Quote Link to comment Share on other sites More sharing options...
Miles Posted May 15, 2012 Share Posted May 15, 2012 Good to see you worked it out. Quote Link to comment Share on other sites More sharing options...
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