Bike will start but not Tick over ?

  • Hi
    The other day I took my DT out to start putting some miles on the clock after re-bore, bike went well for 5 miles ,then died on me, would not restart.
    Have stripped carb and cleaned twice second time fitted petrol filter, but bike still not ticking over will start after 10 or so kicks go to 4000 rpm then starts bogging and then dies out.
    Any clues anyone.

  • Is the choke on?

    Sounds silly but I remember doing that back in the day. Had me scratching my head for ages lol. Well a few hours but still.

  • Well had me scratching my head as well so ,thinking its ever air fuel or spark ,i new air was good fuel was good, so changed brand new iridium Denso spark plug for new normal NGK and the old girl started first kick and all is good.
    Bike seems to self adjust still on tick over one minute tick over perfect next minute its at 4000 rpm or cutting out any clues on that one would be helpful..
    Oh I never use choke out here as so hot all the time.

  • Not sure why it would konck out. Sounds like your Pilot jetting is off perhaps, how does it respond to adjusting the idle?, does it make a difference winding out? Try a smaller Pilot if you cannot obtain a lower idle speed.

  • Sounds like an air leak to me. Under Idle it's drawing in way too much air to fuel, this is exacerbating under throttle.

    The way to test air leaks is by spray wd40 on areas where this could be possible. Inlet manifold, generator crank seals are the most common areas.

    It will be areas PAST the carb. The spark plug may give you an indication of running lean, but I doubt it will show much after a rebuild

  • Right will start by looking for air leaks past Carburetor ,as I fitted a new Mikuni carb and in-let and out-let slightly smaller on new one so could be that, cheers.

  • could find no leaks and fitted rubber shim to screw clips that go either side of carb on rubber conections,,but bike starts of idling OK ,but as it warms it increases and can not get it to go below 2500 rpm, still scratching head lol

  • @Leftyno1 If the air screw is screwed all the way in,

    then there can only be two options, carb is leaking air into the tract.

    Or the engine is.

    Air - Fuel - Fire

    Is what is required for combustion.

    The problem isn't Ignition or fuel related, it is Air related.

    A common error can be the throttle cable slightly ajar! This then takes the control off from the idle mixture. So no matter what you do to the idle screw it has no effect because the throttle is open slightly.

    Go and make sure the carb is completely closed!

  • Cheers will check Calum,,will report on progress

  • Well so far found no air leaks but air snorkle was not seated properly (it is now) going to have a good set to tomorrow as have some time bike is running rich smokey as hell ) and screw is only 3/4 of a turn out,but will hopefully set it up properly tomorrow.

  • @Leftyno1 throttle cable ajar?

  • Well I have got the bike ticking over at a lovely 1500 rpm nice and steady,how i got there was by starting with main Jet funnily enough the bike from cold or warm would tick over about 1800 rpm cold to 2100 warm (not good),, I also realized if I revved bike over 5000 rpm it would bog and stop warm and cold, so I thought I would take out 230 Main Jet and replace it with original 180 Main Jet, I also made sure everthing was clean ( though I have fitted a filter) and that throttle cable was not ajar. put everthing back together and she started first time and then I had to adjust tickover to correct rpm and set mixture screw out 1.5 turns, bike now revs past 5000 rpm and settles back to 1500 rpm .

  • So I know Jet is small but I have a standard exhaust, does the Jet need to be bigger like 210 or so ,because at moment I am just bloody happy that bike is running properly lol.

  • @Leftyno1 Definitely would not recommend 180 main jet.

    Have yoy read the guide on tuning carbs on here?

    The main jet has nothing to do with idle!

    Very odd why that has sorted itself out.

    Is the needle correct?

    180 main jet will cause it to lean out on wide open throttle.

    Of course every engine is different and no two jettings will work the same. But Yamaha set it to 240 for a reason.

    Definitely seems like an underlying problem.

  • @Calum Yes agree it does seem small took it out and engine is smoking when revved hard but also clutch slipping at 5500 rpm I changed oil Castrol GTX 10w 30 oil ,so something new to investigate changed oil because it was slipping a bit before .
    Going to try 230 Jet back in tomorrow and see how it goes but bike is definitely not running lean as I leave a trail of smoke every where like a good un.,but it is ticking over well and not cutting out like before.

  • @Leftyno1 Just because it smokes doesn't mean its not running lean.

    Sounds like if it's smoking excessively that the oil is too rich. However the fuel, which remember is critical in keeping yhe engine cool, can still run lean!

    The oil is controlled via a separate pump and bares no relation to the fuel.

    If the clutch is slipping then it could be assembled incorrectly. I have described how to balance the clutch amd install it on this forum.

  • Do not despair, five minute job worth doing right to avoid catastrophic failure!

  • @Calum Just remembered when engine seized I sprayed some WD (moment of madness) in Barrel so Transmission oil probably contaminated which in turn probably contaminated clutch plates so even though I've changed the oil it is still on the plates themselves .
    will fit the 240 jet in morning and see how it runs, this bike is like a show jumping horse always another fence to clear it is now the most worked on Bike I have ever owned not feeling the love at this moment lol.

  • @Leftyno1 Doubt the wd will cause the plates to slip.

    I appreciate how you feel but these bikes take such a battering it's amazing there are still so many left.

  • Well thats good news about the WD and clutch, after rebuild Clutch was way out and took a lot of adjustment ,will check tutorial link and also have a haynes so maybe he says with fingers crossed it might just need adjusting. But with cars i have found once there slipping you have to change them ,is it the same with the DT.