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FZX250 Zeal not starting

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by alex90gt, Feb 24, 2014.

  1. First post here, go easy haha.

    TL;DR is the bike isn't firing. It has spark and (some) compression but won't run even with start ya bastard. Valve clearances are all in spec and the timing is spot on. I'm by no means an expert with this though so I might have missed something.

    The bike is a 1998 yamaha fzx250 zeal with 42,000 k's on it.

    I had the bike die on me shortly after an oil change. Clutched in and it stalled, wouldn't crank over, turned out the battery had lost charge. Tried bump starting the bike and got nothing. Same with a jump from a car battery. Pulled the bike apart roadside to check the spark. The plugs were firing but were fouled, gave them a clean and still nothing. Wouldn't get any ignition even with start ya bastard. I had half a tank of fuel and had recently serviced the carbs. The temp light didn't come on and she didn't seem noticeably hotter than normal.

    Holding a finger over the spark plug hole for pistons 3 and 4 I noticed there was next to no compression. I also found coolant residue backed up in the carbs. Assumed a blown HG as I hadn't noticed any horrible mechanical-sounding noises, and the motor would still crank freely with a jump.

    I might mention I assumed the battery charge issue was due to a rec/regulator issue so I got a replacement. I trailered the bike back home after having no success getting her running again.

    Assuming I had a blown HG I dropped the motor from the bike and got the head off. Didn't notice anything odd about the oil and coolant when I drained it. Removed valve train and head bolts in proper sequence. I found some muck in pistons 3 and 4, but nothing excessive. The HG didn't seem obviously damaged either. I had a look at the head and couldn't see any obvious damage. The valves show no signs of damage and appeared to be seating fine. The pistons themselves looked fine, with no visible scoring to the bore either.

    I've since installed a new HG, torqued the head back to spec. I checked the valve clearances and they are all within spec. Timing chain went back in fine, all marks matching up perfectly, chain guides went back in and the tensioner is doing it's job.

    I've reassembled everything and chucked some oil and coolant in her. She still won't fire but managed a little cough with some start ya bastard. I've checked the compression and got about 90 across all cylinders, although these are cold readings. I still get spark, but it may be weak, or mistimed. Haven't changed the spark plugs yet but probably will. I'd also like to do a leakdown test but I don't have a tester.

    I've tried to include every detail I think is relevant, but there's a fair chance I've missed something important.

    Hopefully there is just something simple I've missed or forgotten to check, but I'm at the limit of my mechanical knowledge here. Ultimately it should probably go to a shop but I'm a poor student just trying to fix things himself.
  2. Well ill be damned, good to know some one else is still floging around a mighty zeal. Well sorry i cant be of much help but your on the right track. The big four, compression ignition fuel and air. If youve got all four it has to run, not well nessisarily, but run in a burping sputter kind of way.
    Compression: you say is there at even if its abit out theres enough for running.
    Fuel: if youve spayed a bit of your hydrcarbon of choice down the plugs theres enough for a good bit of spluttering along. Not going over board remembering thoughs little cylinders the size of a shot glass.
    Air: well thats gotta be coming in even on idle circuit.
    Sprk: could be intresting make sure its nice n bright (just google some images of a good looking plug) and throw a multimeter over the battery make sure its still giving good juice whilst cranking and resting.
    Only other thing to make sure theres not a horrible amount of friction but if you can crank it it cant be that bad.

    You sound spot on about the reg rec. Had the same thing on mine but if you want to double check this flow chart will solve any problem in the charging sys https://www.electrosport.com/media/pdf/fault-finding-diagram.pdf . good luck yeah i dont want to be the last zeal left :p
  3. Hi Alex, No bright idea for you but it sounds like fuel starvation.
    Choke position?
    After you crank do you get fuel smell as if it is flooding?
    Fuel tap, does fuel come out when you pull the pipe off and open the tap?
    Fuel pump, these are electric (I think) in this model. Is it running?
  4. Hey guys, thanks for the replies.

    So a bit of an update; I got it running the other day. I hadn't done anything differently, it just decided it wanted to fire up. I let it idle for a while to warm up. The idle seemed nice and steady. I took it for a little ride around the block and everything seemed fine, was quite happy to rev out to around 10k (I didn't want to take it beyond that). It's definitely getting fuel, and everything seemed to be working fine at this point.


    The next day I tried to get her started again and have had absolutely no success. I've managed to narrow it down to a weak spark. There is spark there, it's just tiny. I've checked the battery is fully charged; it's reading around 13V and I had supercheap check it with a battery tester and it's all good. I've also tried jump starting it with a car battery, so that doesn't seem to be the problem.

    I've replaced the regulator/rectifier previously, but I'm not sure that was actually a problem. I've tested the stator coil and I'm only getting about 4.8VAC between two of the coils, and nothing from the 3rd one. I'm thinking the stator was the reason I had the battery die on me when all this trouble started. That being said, by my understanding the bike should still run even with a dead stator if the battery is ok (it'll obviously run flat though).

    At this point I'm thinking it might be the ignition coils that are the issue. I've measured the primary side which comes out at 3.2 ohms (spec is 2.8 +/- 15%) for both coils. Measuring the secondary side (which I think is between one of the primary inputs and the lead?) I get an open circuit.

    There's a few people wrecking FZR250's on ebay which I might get second hand parts from. My current research suggests new parts from Yamaha are gonna cost and arm and a leg.

    I'm just wondering if anyone else thinks these are logical conclusions, or whether there's anything else I should be checking? I'm going to check power to the coils, and have a bit of a dig around just to check there isn't just a connection issue somewhere.

    Thanks guys
  5. Ok you are just outside spec on the Primary coil resistance but measuring low resistance is a bit hit and miss. Put your multimeter leads together to read what resistance the leads are adding in your measurement. That figure you can subtract from your coil measurement.

    Measuring the secondaries, (the high voltage side) is between a spark plug lead and the metal where it bolts on to the bike. If your multimeter doesn't have autoranging you will need to change the range in to the kiloohm range.

    If the battery voltage is low then you may not get enough power to produce a good HT spark. Measure the DC volts across the battery to see what it is. Those alternator stator figures don't sound good.
    • Agree Agree x 1

  6. I'm also at this stage.
    Bike is not running. I keep trying to start her every hour or so.
    This is all after doing a radiator flush..
    I need help figuring this out.