A bit of a rattle in a DT250a, could ya'll have a listen?

Discussion in '2 smokers' started by OffBeat, Mar 6, 2013.

  1. OffBeat

    OffBeat Pissing in the wind!

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    A friend dropped a Yamaha DT250a off to me. It runs really, really well other than a bit of a rattle. This video/audio makes it sound a little worse than it really is. My son was putting some miles on it in the dirt at our house (we have a few acres) and have trailer-ed it to some woods. Not sure if the oil injector is working as it should so we put pre mixed oil / gas in it. Couldn't ask for a better running bike. Just has this rattle. Any ideas??? Thanks!

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    #1
  2. stainlesscycle

    stainlesscycle Long timer

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    sounds like a small or big end bearing to me. pull the top off of it and have a look see.
    #2
  3. OffBeat

    OffBeat Pissing in the wind!

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    Thanks for the suggestion. Getting some ideas ready and when the snow melts some and the temps get above freezing I want to investigate. I was checking on a battery tender on my KLR today and couldn't help but fire up the little bugger and make some noise. Crikey, the thing has been setting since last fall and it only took two kicks and it was off and running! Thanks again, Bill
    #3
  4. YZEtc

    YZEtc Feel lucky?

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    Sounds like large-ish piston/cylinder clearance (wear).
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  5. lrutt

    lrutt SILENCE.....i kill you

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    yup, piston slap, no doubt. They are worse when cold. Easy to check your injector, pull the line from the side of the cylinder when it's running and see if the oil is pumping out. A brief disconnect won't hurt. Get a manual and set it proper would not hurt although unless someone has been mucking about they won't go out of adjustment.

    If you are tasked with making the bike proper, use an OEM Yamaha piston and rings. A forged Wiseco will require even larger piston / bore clearances and make the rattle worse than it needs to be.

    My RT1 I'm redoing was that bad or worse so I picked up a NOS piston and rings for $50, plus a gasket set (complete) for $20, and bored the cylinder for $50. Motor is good to go for a long time now.

    that is a mighty clean 74 you got there.
    #5
  6. OffBeat

    OffBeat Pissing in the wind!

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    Thanks for the replies! Looks like I will have plenty of fun things to look for when I get the time.

    I will give the injector a try with the hose off and see what I can see, thank you. I have a Clinton manual for the bike. I will take a look and see if any of what they have to say makes any sense.

    My friend gave me the bike as I had one back in the 70's and he had a 360 that we road all over the place. We will locate the 360 for him and see if we can get out in the dirt again.

    Here are a couple more pics of the bike I took last summer before putting it away for the winter. Thanks again, Bill




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  7. anonny

    anonny What could go wrong?

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  8. buls4evr

    buls4evr No Marks....

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    It is not the oil injection so leave it alone and run straight gasoline in the tank. It will not help shot rings, piston and small end bearings to throw extra pre-mix on them. Fix the top end problems. The DT series were quite susceptable to worn small end cages/needles. Before buying a piston chk the fit. May only need rings and a fresh needle cage.
    #8
  9. OffBeat

    OffBeat Pissing in the wind!

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    Will do! The reason I add oil to gas is that oil level hasn't gone down any after several tanks of gas, and I do mean "not a drop" down.
    Had to mount the plow back on the truck to deal with snow and driveway issues. Will be looking forward to getting the bike into the shop and checking all above when the weather breaks. Tired of snow and cold!!


    #9
  10. RideFreak

    RideFreak Torque Junkie

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    Piston slap, also sounds like the rubber fin dampeners are missing, they ring allot when those get removed. Might have a forged wiesco in it too, noisey bastards.
    #10
  11. joexr

    joexr Banned

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    Ditto. If it still runs good its nothing to worry about. Unless of course you can start it with your arm.:rofl
    #11
  12. OffBeat

    OffBeat Pissing in the wind!

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    Well, you got me to thinking. Put my snowshoes on and made my way out to the pole barn. Took a peek, 7 dampeners on each side of the jug. Not very springy, I'm sure, but they were there.

    Figured, what the hell. Gave it 3 kicks and it started up. I don't notice the rattle under load. Though, to be honest, I don't have much hearing left in these old ears. Only when you you let off on the throttle. Got it all warmed up nice, did a few circles raising some dust in the barn and then backed it back into it's sleeping spot till I have time/warmth to dig a little deeper.

    Thanks again for all the great suggestions.
    Bill
    #12