Solved: Yamaha 701 WOT issue

Discussion in 'Tech Discussion' started by Johnny, October 28, 2014.

  1. Johnny

    Johnny New Member

    Hey Guys,

    Got a Waveraider 701 single carb. And just noticed over the long weekend when at wide open throttle I get a problem, not quite sure what it is.
    Feels like either cavitation, engine missing or lack of fuel.

    Only at WOT, as when you back it off a bit she's fine. Which sort of makes me think its fuel related.
    Also it only happens after ridding for a few mins.

    Ill do a compression test in the next couple of days.

    Its bone stock apart form a Solas 13/17 impeller. Impeller and wear ring only about 12hours old. Haven't checked for damage yet.

    Any ideas as to what I should check first?
    Blocked fuel filter?
    Varnish in the carbs?

    Last edited: October 28, 2014
  2. Flan

    Flan Well-Known Member

    Hi. It wont be cavitation as that normally happens on acceleration and you have a new pump etc. Definitely check you fuel lines and filter for water etc. Does it happen when when the engine is cold? Some coils have been knowing to break down when hot. If all else fails sell the couch and buy a superjet. You wont look back.
  3. Johnny

    Johnny New Member

    Yea didn't think it was cavitation (just had that sort of lagging feeling).
    Doesn't happen when cold. Only after say 15min or so of riding. After a bit of googling I'm leaning towards the coil at this stage. But cant hurt to give all the fuel lines a once over.

    Funny you should say that. I just bought myself an superjet. And loving it.

    However the raider can still pull my 95kg arse out of the water with ease wakeboarding etc. So Ill probably keep it just for that, and so the mrs can ride.

    I might swap the superjet coil in and see if I can rule that out.
  4. dickwebb

    dickwebb Active Member

    Definitely start with your carb and fuel lines. I would make sure you pull it completely to bits and give them a good clean out. When was the last time you did any maintenance on fuel system? If its been a while I'd suggest you take the opportunity to replace parts that haven't been done in a while - like external fuel filter etc. Maybe even give your carb a birthday with a new carb kit. Also, if you're tanks empty and easily removed, pull it and drain it.

    Could also be the coil too - not ruling that out. You may find by swapping out with another fixes the problem but in fact there is no issue with your coil. More likely the HT leads have frayed and you're getting weak spark. These can be replaced.

    But start with the fuel system, clean it out, then go and test. If it hasn't resolved the issue then move to the next item on the list.
  5. Johnny

    Johnny New Member

    Ok bit of an update.

    Checked compression. 150psi on both
    Replaced fuel filter
    Pulled carb and gave a good clean out (still waiting for rebuild kit to arrive)

    I noticed that the rear spark plug was a bit milky looking. Covered in condensation (any likely cause for that?)
    I cut that HT lead half an inch back and reattached the cap.

    Took her out and was fine for ages. Jumping waves fine. Straight line fine. But then I started doing some really tight turns left and right and that's when the problems starts. And doesn't sort itself out if you let it idle or go straight. Also if let to idle for a bit will bog (almost die) when you whack the throttle open.
    Wont rev past 4400rpm
    When its running fine I can get about 6240rpm out of it. Is that a bit low for a 13/17 Solas concord? Everything else stock.

    On my to do list is:
    Replace fuel lines
    Rebuild carb
    Check fuel pick up
    Swap coil out.
    Check reeds
  6. dax

    dax Member

    Could be heaps of things, but sounds similar to my ski when the crank seals were shot. Once the engine bay got a bit of water in it would get in through the crank seals and run real shitty.
  7. T Bear

    T Bear Active Member

    your original problem almost sounded like it was simply rich,if as you say it only happened at wide open throttle and if you backed off a little it would come right.
    asking for tunning solutions on forums opens you up to a whole lot of opinions that may have nothing to do with your original problem, (mine included )sounds like your problem is now worse than before.Where abouts are you as there are a few on here that can help you out depending on who is closest.
    dax likes this.
  8. Johnny

    Johnny New Member

    I'm in Auckland, halfway between Clevedon and Maraetai.

    Just want to make note that the problem is still the same.
    I've just discovered what seems to set it off. And have tried to get as much detail about the problem as I can.

    I appreciate the help people are providing. I know im going to get a heap of opinions. But that's oks. Ill work through the easier or more likely ones till I can solve the problem.

    Its hard to explain what's happening without feeling it. So if someone is willing to help me out then sweet.
  9. dickwebb

    dickwebb Active Member

    I can easily meet you down at the waikato river (say either the elbow or at tuakau bridge) and have a look. Problem is I'm working night shift so probably can't make it till next weekend (not this).

    p.s. milky looking spark plug is caused by water ingress. if its appearing after sitting in your shed for a few days then its condensation/water sitting in the bottom of your engine. If its milky directly after riding it then you have an issue - most likely a very small hole in your head gasket between the dome and water jacket allowing water back into the cylinder.
    Dazza likes this.
  10. Johnny

    Johnny New Member

    Could a leaking crank seal cause that? or more likely head gasket being that its only in the rear cylinder.
    Ill have to figure out if its there after a ride. Or after sitting.

    Ill see how im placed for the next weekend.

    On a side note. If I end up pulling the engine out to do gaskets n seals. Where's best place to get some Threebond 1211?

    And by best I mean cheapest.
  11. dickwebb

    dickwebb Active Member

    Seals are more likely to make the ski run rough and/or lean. However, if you have a lot of water sloshing around your hull and the two rear seals are partially gone then yes its possible.

    Haha... If you want a tube probably your best bet is Roger (Jetworks) on here. I usually have a spare unopened tube in stock but am out at the moment. If you want to do it on the cheap then bring your cases, seals, crank, and beer to me and I'll threebond them together whilst we have a beer. :)
  12. Johnny

    Johnny New Member

    Well fingers crossed I might have solved the problem. Pulled the coil out to run some tests. (and was curious to see what the inside of my ebox looked like)

    Tried to measure the primary winding. But my multimeter doesn't go that low.

    So then checked the secondary.
    Was getting absolutely no resistance across both plugs.

    Decided to pull off the caps, and then check the resistance. Still nothing....

    Started cutting the HT cable back further and further until I finally got some readings.
    Put the caps back on and the readings seem to be in spec.

    Hopefully report back after the weekend with good news.

    Also the HT lead doesn't appear to be replaceable at the coil end. Is that the same for anyone else?
  13. Johnny

    Johnny New Member

    Happy to report that the problem appears to be solved for now.
    And seemed to gain about 110rm at top end. Now pulls 6350rpm.

    Cheers all for the input.
  14. dickwebb

    dickwebb Active Member

    Good to hear. What was it in the end?
  15. Johnny

    Johnny New Member

    Seemed to just be corroded/frayed HT leads. They just reach now after trimming back. (without being too stretched)
    However if it happens again I think im in for a new coil.

    Is it possible to rip the leads out and replace them at the coil end? seem to be epoxyed in.
  16. tofa

    tofa Well-Known Member

    Yes you can change your leads out.
    Little tricky if you haven't seen it done before but if you want help ask Roger at Jetwerx
    He does mine for a very reasonable fee.

Share This Page