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new bike won't start after backfire

Discussion in 'Technical and Troubleshooting Torque' started by TheForgotten, May 16, 2012.

  1. so i got this bike (99 zx-6r) and i've had it running many times

    i was pulling the swingarm spool off today with the engine running, and noticed a hole in the can, figured it'd need to be blocked for RWC so shut the engine off, plugged it with exhaust gasket putty, then tried to restart and it wouldn't.
    after a while of on/off starting it backfired, but wouldn't actually start. and yes i wiped away the putty, thinking maybe the hole WAS supposed to be there.
    tried bump starting too, exhausting and fruitless effort

    while pulling the spark leads off to check spark i *think* i may have torn a plug lead. well, it's torn. the cap and cable are separated. but from what i can gather that's how they're designed, so i might not have stuffed anything. the other 3 leads are fine.

    it's getting fuel, it's getting spark. but it's not getting running.

    have i missed soemthing??
  2. ... have you missed anything? Hell, I don't know. As a mate on the mcnews forum says, "The Hammer: originally designed as an implement of war, but now employed as divining rod to identify the most expensive part near the thing you were trying to hit."

    I don't quite see how blocking a hole in the muffler could produce that result. I'm leaning toward the hole and the breakdown being unrelated. But I also lean toward the idea that if it's got fuel and it's got spark, it should go.

    Stick your finger in the plug hole and crank, see if it's got normal compression. It might be that the camchain has fallen off.


    Backfired, you say? As in 'Pop' in the muffler, or 'Pop' through the airbox? Have a look at the air filter. If that's torn or blown loose or something, it can result in a completely off (lean) mixture ... Also look for any vacuum lines that got blown off when it backfired. Give the whole carby set a wriggle and make sure it hasn't blown them back off the rubber boots...

    Bikes I've known to backfire had ignition problems, usually related to breaker points, so that was a while ago. Cars I've known to backfire tended to be taxis, and the usual cause was plug leads that were old and stuffed, and the spark was jumping between the leads and firing the wrong pot at the wrong time. I have several times been suspicious of plug leads and or coils on a bike, but I've been wrong every time.

    How old are the spark plugs? How old is the fuel in it?

    You say you've had it running many times. Do you mean you've ridden it for an hour, or that you started it and gave it a few revs to piss off the neighbour?

    Doesn't help much, I know. Sorry - I don't what's going on there.
  3. It wasn't the big hole in the end was it, I'm pretty sure that one's meant to be there :p

    Don't think I can help much but, while I doubt plugging the exhaust would have done anything, is it still pushing air out the back of the pipe when you turn it over?

    It sounds like it's getting spark, but are you certain its getting fuel, ie wet plugs, wont start with areostart?

    Best of luck
  4. Kick the kunt til it works...good luck...wear steel caps otherwise it hurts...alot.
  5. kneebreaker - pop was in the muffler
    can't get plugs out, didn't get a factory plug spanner and it's too deep/awkward for regular tools
    ridden round the block yes
    fuel is half unknown (but was usable) plus half fresh yesterday.
    Airbox/filter etc is fine

    MOS - nah i skipped the big hole, too much putty.
    Guys on zx6r.com said that is a drain hole so the can doesn't fill with water.
    I've tested as far as the fuel pump working. Haven't tried aerostart
    will drain carb bowls tonight and test if they refill

    crisis - joys of electric start brother
  6. How long was the engine running for?
    What type of fuel? (unleaded or premium)?

    Story time - I had a 1996 GSXR750 (carb'd). One very cold Canberra morning, I started her up no issues at all, went inside to grab helmet/gear and the bike stalled. No worries, put my gear on, go back outside to bike and she would NOT start! All I got were some very nasty (loud) backfires.....Hmmm, that's odd, she JUST started perfectly 3 mins ago and now this?! WTF...

    A quick call to the local mechanic and he advised fouled plugs without doubt. At $40/plug I didn't want to believe him as the damned thing had JUST started fine but he came around, swapped em out and she was perfect from there on in.

    What he advised me (and I'm no rocket scientist) was that the additives oil companies put in their fuels, particularly premium, will 'oxidise' (or basically fcuk the plugs) if the bike isn't properly warmed up.

    Apparently my start/stall (without restarting IMMEDIATELY) meant the fuel that had made its way to the plugs and won't burn off unless she's warm. Throw the plugs away, install fresh ones and:

    A) If you own a CBR250, ZZR250, GS500 etc etc - DON'T bother with premium. Your engine is not tuned for it and
    8) if your bike does like premium, never ever ever just start and stop it, always let it run for a while before switching off....

    I've also seen this syndrome at the track many times now. Bike starts at pits, makes it to pit lane, stalls, is left the 3-5mins while they wait to start their session - BAM backfires and fouled plugs all round DOH!

    That's my guess...sucks that on so many bikes the plugs are so hard to get at....I really do miss the dirt bikes and their ease of access/single plug to replace! :)

    Good Luck with it.
  7. I've also had a case of a bike (CB900 Bol d'or) that would start and idle but break down under any load. Plugs looked brand new. Mechanic told me to change them. So after waffling around and trying other things, I bought 4 new plugs. Problem solved.
  8. yep that's basically what happened jrad, maybe 3 mins between stop and start, but i don't think the fuel is premium.
    I'll chase down some new plugs and see how i go
  9. Do that. You should be able to pick up a cheapy tube spanner from supercheap in the right size for 5 bucks.

    Drain the floatbowls, too. Confirm that the vacuum line (if it has one?) to the fuel-tap is still on and hasn't split at one end or the other. I saw that kill a very tasty RVF400 with lots of bling and go-fast stuff a couple of weeks ago. Easy fix once we figured out what it was...
  10. Thats what happened to my strumpy when i first got it. Sat at the dealers for a little while that a brief kick in the guts to make sure she would fire up gummed up the plugs.
    New plugs and a charge of the battery to be sure of her cranking amps, and pow off it went.
  11. Hmmm...well premium fuel or even old fuel could give you grief....but sounds like if you've had it running a fair bit then the fuel wouldn't be all that old.
    Since you've accidently busted a lead, may as well replace the leads/plugs - drain ALL the fuel as Kneedragan said and go from there - post up your experience for others...I'd be interested in hearing if it was something different so I can add that to MY knowledge base ;)

    I hate hate hate changing plugs LOL I'd almost be tempted to take it into the shop and get them to go over it....? Hadn't thought of the vacum line but that's another good idea, older bikes do suffer from rubber breaking down etc.
    My (now ex) wifes CBR250 was a shocker...full carb rebuild eventually...!

    Sucks don't it...!! "But I just started the sucker and it was running fine..." it's hard to believe that fuel can foul the plugs so easily but there you go! :)

    Other than that, sell the Kwaka and buy a Suzuki :) :) :)
  12. wash your mouth out boy!
    i've wanted this bike for YEARS, now i've finally got one. for less than half what it's worth.
    even after putting new pirellis on it this week i still haven't quite got to half-value

    plus zookis suck :bannanabutt:
  13. Dark Angel fan, perhaps?

    I have a daughter who now has 3 kids and weighs about 100kg, who had the biggest adolescent crush on Jessica Alba. Mind you, I could see why it worked for her...
  14. Being a tight ass I would try and clean the plugs before shelling out on new ones. Well if the electrode still looked ok.
    Was told only this week that Premium has a couple of year shelf life with it's octane levels. Was by a fuel track driver.
  15. you're a strange man michael
  16. [MENTION=24838]j-rad[/MENTION] seriously dude, i love you!
    it was fukt plugs.
    fresh cr9's and she's roaring again
  17. hahaha good stuff glad to be of assistance! :) Even if you do ride a Kawasaki hehehehe 8-[
  18. Glad to hear it's running again.

    There's a pleasure, sure, in being strange,
    Which none but strange men know ....