Fresh Rebuild - Black Grit in oil



  • Greetings all,

    I've just competed the first startup on my freshly (full) rebuilt engine (DT125R '02). A major oil leak was noted by the sprocket drive so I drained the oil and replaced the seal. When the oil was drained I noticed a pretty substantial amount of fine black grit. The oil used was castrol and is pink/red in colour (definitely 4T oil) so these flecks of black stand out quite clearly.

    I've inspected some of the larger pieces which are still quite fine, they are hard and some a little sharp. Its almost like paint flecks? Sorry its difficult to describe. Certainly nothing that looks like metal so far or at least nothing silver in colour has appeared. I will try and get a photo for this.

    I very much hope this wont be cause for another teardown, here's some additional detail about this engine:

    2003 unit, supposedly 16k on it. Total rebuild top and bottom. Bike was run with no filter on the carb and no coolant. Engine started on 2nd kick and stayed running on full choke for approx 2 mins



  • @liquid-snake how thoroughly did you clean the inside of the cases



  • definitely 4T oil?
    Do you mean 2 stroke oil?



  • @declan I'd like to think pretty good, but you've cast doubt in mind! I think and hope you're onto something there. Fingers crossed with a few flushes we'll be clear

    @oldman 750mls of 4T 10/30 for transmission. I picked up castrol for 2T also which is the usual crimson red but I was surprised to see this 10/300 stuff as pinkish-red too. First time I've seen anything besides the usual golden brown (texture like sun...) engine oil



  • @liquid-snake just saying because ive had simmilar things come out of the inside of engines



  • What sort of castrol? It could be messing with the clutch plates breaking them down. Could be clutch you are seeing.



  • What sealant did you use on the cases?
    Also how well were they cleaned, the gears, clutch, bearings, ect, ect...
    Could of been some old crud washed out by the new oil...



  • Isn’t 4T 4stroke ‘racing’ oil? Just cause it sez 10w/30 doesn’t mean that it’s gear oil. Engine oil is different.
    Gear oil used to be EP90 in my day, it’s so fekin confusing now...



  • @SpookDog I have only ever ran 4T engine oil in my DTR.



  • @Calum same I've always had 4 strokes so I just have one oil for all



  • I should clarify, 4T oil in the transmission fluid.

    Gear oil in the Aprilia though 😃


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