My Carb Vacuum Cylinders are floppy. And they work better than the replacements that aren't floppy??? My 83 Honda Shadow VT-500C is driving me nuts. I've already pulled out all my hair...help!!!! Bike has 83,000 miles on it. Over the last year or so it's been developing a problem. Runs excellent at low speed. Starts great when it's cold, but when warm, seems like it's just not turning over quite fast enough to start...don't think that's related, but you never know. If I take it out on the freeway, it runs fine for a while, then starts sputtering like it's out of gas. If I open the throttle a lot more, it sputters back to life. Runs fine for engine RPM over 5,000 or so. Problem is less when the air is cold. I've squirted water around the carb boots to look for air leaks. Boots look ok. I've popped the gas cap to see if the vent might be plugged. I've hooked up tubes to the carb drains to see if I could see the fuel level dropping at speed, but this test was inconclusive. Level seemed to drop when it didn't sputter and sputtered when the level didn't drop. Need to do this with better tubing clamps...and not at midnight. I've blown out all the fuel lines. I've drained the carbs with the valve open. Seems to be sufficient flow to run at full speed. Out of frustration, I replaced everything from the carbs up thru the petcock and filter that's inside the gas tank from a (used to be)running donor bike, 1986 VT-500C. I did blow out the jets and as many of the twisty little as passages I could find. I did use the choke cables and parts from the 83 bike on the 86 carb. If those parts aren't compatible, I could be causing major problems??? That didn't fix the high speed problem, but it added another one. Now, I also have severe hesitation when I increase the throttle. Worse at low speed, but exists at all speeds. Now for the confusing part. When I apply the choke a little, the RPM goes down. With a LOT of choke, the RPM comes back up. The hesitation problem is much better with the choke on, but can't tell if that's just because of the much higher idle RPM. I've messed with the pilot jets, but couldn't make it any better so set them back at 2-1/4 turns. I can't think of anything else to do except try raising the fuel level. I started another thread on the subject of measuring level from outside. The hesitation problem is better at high temperatures. The bike has always run cold, like the thermostat is stuck open. Has to get over 90 degrees outside before the temperature comes up high enough for the fan to come on. Don't know if this is related to anything. If that wasn't weird enough... If you poke the vacuum cylinder in the new carbs, there are two forces. There's a spring force plus a pneumatic force accompanied by the sound of air rushing thru some orifice. At idle, the cylinder is all the way down. At about 2500 rpm, it starts to rise. The stall/hesitation happens just when the piston starts to rise. As the piston rises, it's position is steady. The pistons were a little stiffer than I thought they should be. I recognized this when I first started the bike, but decided I should give it a chance to loosen up before I started messing with the carbs. It didn't loosen up ;-) so much for wishful thinking. I don't have an easy/safe way to check this under load. If you poke the vacuum cylinder in the old carbs, you feel the spring force, but there's no pneumatic force for the first half of the travel. During the last half, I do feel the pneumatic force and hear the air rushing. At idle, the piston is flopping up and down violently on each stroke...I guess it's every fourth stroke, but I digress... Since the piston is never sitting on the stop, there is no hesitation as the throttle increases. As the piston moves up, the movement is less violent, but not sure if that's not just the low pass filter action of the piston mass and air flow. It's been this way for as long as I can remember, just didn't have any comparative data to set off an alarm. Both carbs behave the same. I would expect failures one at a time. Suggestions??? I've been treating this as a fuel problem. Should I be barking up another tree? Thanks, mike -- Return address is VALID. Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. HP200LX 10MB + MODEM + LEATHER CASE Sony Digital Camera Compaq Aero floppy,ram,battery. FT-212RH 2-meter 45W transceiver. Toshiba & Compaq LiIon Batteries, Test Equipment 30pS pulser, Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/
It sounds very much like tight valve clearances but I don't remember if that year and model had manual -adjust valves. Check your service manual - if there is a spec and procedure to adjust valves, you need to do it. After you adjust the valves, you should run the engine, let it cool down, then recheck the adjustment. The CV slide thing is probably a red herring - vacuum slides always act in a bizarre fashion.
I never would have believed it. One of my intake valve clearances was ..002". I upped it to .004" and the mdirange "running out of gas" problem seems to have disappeared. Cleaning the air filter seems to have helped the low end hesitation somewhat...yeah, I know that should have been the first thing to do...got blindsided by all the confusing symptoms that appeared when I changed the carbs. The pilot screws don't seem to have any effect on the hesitation. I can kill the engine by screwing them all the way in, but they don't seem to do much otherwise. Still not quite right, but at least it's drivable. I've got myself convinced that I could solve the hesitation problem if I could reduce the friction/stiffness in the vacuum slides. Is there anything I can spray on 'em to clean them up and loosen up the friction? I'm afraid to spray WD40 or Chemtool B-12 in there cause of all the rubber diaphragm parts. Don't have any idea what the slides are made of. Just had a bad experience spraying control cleaner into the volume control of an FM radio and melting the plastic case. Wouldn't want that happening to my carb slides. mike -- Return address is VALID. Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. Compaq Aero floppy,ram,battery. FT-212RH 2-meter 45W transceiver. 2-meter linear Toshiba & Compaq LiIon Batteries, Test Equipment 30pS pulser, Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/
I don't think WD40 is considered a strong solvent... http://www.wd40.com/Brands/wd40_faqs.html suggests that it is safe for rubber and plastics. Considering how much fuel vapors any rubberized parts of a carb would be exposed to, WD40 should be safe. They do advise against polycarbonates and clear styrene plastics (so don't spray it on your Lexan R/C car body, impact resistant sunglasses or model cars <G>) The name derives from the original development -- the chemist obtained "water displacement" with the "40"th formula tried. (Though the company bought out the makers of 3-in-1 oil some years ago) Strangely, while I own a few shares in the company, I do not have a supply of WD40... One jar of 3-in-1, a bar of Lava soap... But I have an old can of RemOil, and some half dozen forms of BreakFree (they seem to have dropped the "CLP" tag). BreakFree is a teflon suspension. --
Hooray and kudos to Brady T! The pilot air screws usually help off-idle hesitation, when you pull away in first gear from an idling stop. The adjustment can be very finicky to get right (and temperature/humidity can affect it). Try starting from the manual-recommended setting, and then move it either way in 1/8th turn increments, testing after each adjustment. The carbs need to be synched, too. If you ride in very dusty areas, maybe the slides could be worn, but I think that would cause an erratic idle more than hesitation. Look at the synching. A smarter part of your brain connected to your eyes and memory is trying to get through to the less-smart part of your brain that is connected to your fingers
