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Discussion Starter #1
First I want to thank everybody that has helped people on this forum over the years.

Bike is a 1998 EX500, has some light cosmetic mods but everything that would effect drivability is stock. Bike has 33k miles on it, I’m not the first owner but most of those miles are mine. I noticed that the Nike was surging so I pulled the carb and cleared the jets, since it was off I cleaned the entire carb. Not the first time I’ve cleaned the carb but I soak everything minus the diaphragms in cleaner and rinse repeat until satisfied. Diaphragms are in perfect condition, ran wire through the pilot jets and set the air/fuel screws too 2.5 turns out since that’s what it usually runs the best. Fresh gas, new spark plugs, new air filter, cleaned the entire air box out and cleaned the petcock inside and out with full disassembly.

Problem, bike ran for about 1 mile and bogged down and then cut off. Started for a min and cut off, would not start again. I pulled the carb again and jets were clean (could see light out of all four easily) and floats were not stuck. Gas was in both floats, I charged the battery completely and had it tested, even tried jumping it and using starter fluid......nothing. Both spark plugs are producing spark, both are wet after pulling. Engine has good compression with and without oil, checked the woodruff key and its fine. I have a started solinoid in order since just for PM.

When I try to start the bike it turns over and eventually will backfire. It has almost started a few times but it’s seldom. Noticed fuel is coming out the side of the Petcock where the vacuum hole is in the white wafer, does this in on and reserve. Pulled the carb again and checked the diaphragms, still good, checked the jets again and they are clear. Took the petcock apart and the diaphragm in it looks perfect. Im going to check the timing tomorrow, after that I am at a loss.
 

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Did you replace the float needles and check fuel level in the bowls? It sounds like it's flooding.
 

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Discussion Starter #3
Replaced them before last summer, I even tried the old ones and no change. Did not notice any fuel in the air box, but I’m getting some clear tubing to check the levels tomorrow anyway.
 

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sounds like the flywheel key has sheared, pull the flywheel and check

FOG
 

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quoted from post #1 .... "checked the woodruff key and its fine"
 

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OK now check for gaps in the high voltage, renew all the high voltage connections and clean the insides of the plug caps.

FOG
 

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Discussion Starter #8
Cleaned the plug caps, both have rusted clips so I’m going to replace both of those. Looked at the wiring and didn’t see any breaks or gaps, cleaned any connections I can see. I will have to pickup batteries for my multimeter to trace the high voltage wires. Starter relay is going out but the part should be here Friday to replace that. I got the bike running once I cleaned the plug terminals but it was a hard start and the Petcock is shooting gas out of the wafer hole still. Once the bike cools down I will pull it off and check the diaphragmand put some diametric grease on the rims of the Carb diaphragms. I appreciate the assistance from everybody, this was my first bike and I want to keep it running for as long as possible.
 

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cleaned the petcock inside and out with full disassembly.
QUOTE="Screwofdriver, post: 934231, member: 79775"]
Petcock is shooting gas out of the wafer hole still.
surging so I pulled the carb and cleared the jets, since it was off I cleaned the entire carb.
bogged down and then cut off. Started for a min and cut off, would not start again
Obvious multiple fuel related issues. I'll submit your carbs may not be adequately metering fuel through all circuits. Additionally, the petcock requires immediate rebuild or replace.
 

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renew means cut off a 1/4" clean and re connect each joint, clean the porcelain of the plugs as well

FOG
 

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Discussion Starter #11
Engine was flooded, starter solenoid is shot and works intermittently. Also have new plug wires on order since one of the boots is cracked under the rubber and both feel loose. I just trimmed both (how I found the crack), probably keep them as a spare since I have a old set of boots somewhere in my shed. Pulled the plugs and cleaned both, checked gap at .025. Timing is spot on by the way, I am looking into a new tensioner since the one I pulled off the bike is 22 years old. I think the flooding was my fault, kept trying to start it for so long with a bad solenoid. But, the bowl levels seem higher than normal, I’m clearing the flat part of my shed out so I can check accurately.
 

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Discussion Starter #12
To sum this up, I checked the bowl levels (bendy straws work great for this by the way) and both were spot on. Starter solenoid was replaced, one of the screws just came out of it. Figured out that the pilot screw on the right hand side was backing out while riding flooding the engine. Thread locker and new washer fixed that. Also I noticed both boots from the air box were not being held by the springs around them so I just replaced with zip ties. Rides great now, I do have to replace the rear sprocket, going with a 45 tooth, if I like the feeling of it I will by a complete set new. Thanks for the help.
 

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pilot screw backing out? Spring and oring are present and accounted for? as well as washer which you replaced? Ps, the retaining spring should exert stability and prevent the screw from floatation. You no mention the presence of the spring.
 

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Discussion Starter #14
Springs were there but I do forget they exist. One of them was a PITA to get out when I did the cleaning. It does nothing to keep the pilot screw from backing out like it should, almost like it’s not there. I do have a replacement set of pilot screws washers and springs arriving Tuesday and I will do a full switch. I thought I had lost a pilot screw in the grass so I ordered a spare set just to find it in the cuff of my jeans. It could be binding or lost its spring tension, I will have to compare it with a new one on Tuesday. I should have looked at both when I had them soaking but lesson learned.
 

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hi. people forget sometimes that the carbs are precision engineered pieces equipment. anything amiss can put them out of whack. yes anything. they have to meter the exact amount of fuel at exactly at the right time for all riding conditions have the right amount of air to fuel ratio. have no loose or sticky bits and with the bike having two of them perfectly balanced so each cylinder is fed the same. it can be hard for the novice (or even the die hard enthusiast) to remember this sometimes. small differences and adjustments can make a big difference to how they preform.

if anything is wrong with either carb it's game over.
 

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Discussion Starter #16
So the pilot screw replacements came early so I went and replaced both with new washers and springs. One spring was visibly compressed and shorter than the other when I removed it, broke in half when I tried to decompress it. Petcock still leaks from vacume hole in the white wafer (Petcock is new)so I’m guessing somehow someway the diaphragms are buggered or floats are over filling (measured these so I don’t know how that could be a thing.) Also found that coolant leaked into the clutch area, white milkshake all inside oil fill area. Guessing water pump gasket and a bad thermostat, will be checking tomorrow.
 
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