piston fail2, new crank breather, questions
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Thread: piston fail2, new crank breather, questions

  1. #1
    Senior Member slowmod's Avatar
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    piston fail2, new crank breather, questions

    my bikes been down since october 2017. i had noticed a bit of an oil leak. topped it up. did a 40mile round trip. got home, oil was down (barely showing in window), and had oiled the right side of the rear tire - the return trip had taken me off straight highway at speed onto a very twisty side road - luckily i don't have the chops to rail the bike in turns so i survived. located the leak, at the rear of the right side cover. ~500ml oil recovered. cut a new gasket, with a less-likely-to-distort corner, and reassembled.

    tw rigtside leak.JPG

    ran the bike for a few minutes, rechecked the oil level. then headed out on the road a few days later, noticed a few hickups, like an occasional electrical drop out. whatever. about 14 miles out there was a big bog out, clatter, and a blue smoke cloud behind me filling both lanes. goaded the bike another 1/2 mile to my buddy's.

    tw_pfail2_2.JPGtw_pfail2_3.JPG

    as the cyl wall relies on splash for lube, my initial thinking was that oil barely showing in the window (at the end of the first trip) doesn't cut it and damage had been done then.
    xavsolo likes this.

  2. #2
    Senior Member slowmod's Avatar
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    so there's the piston, there's the cylinder, and here's the top of the connecting rod after i got the wrist pin out - which took a puller made of washers, and a 3/8" #8 bolt with the head ground down to the same dia as the wrist pin. barely got it out without snapping the bolt, it was that tight. still in the engine, so couldn't whack at it.

    tw wrist repair.JPG

    cleaned off any proud ridges till the new wrist pin was happy but w/o slop. it's a hardened steel on hardened steel situation, so i'm not overly worried about it, despite the uglyness of my repair. time will tell, and should some warning if there is an issue...

    that was the used (but all good) piston and cyl i had got from elime after my first piston fail. i still had a new wiseco from elime for my stock cyl, so in aug 2018 (bike down for a year at this point, ugh) bought a hone and set out to tidy up the stock cyl (i'll admit, despit having rebuild a few auto engines, i hadn't understood the whole cross-hatching, riding on the ridges, oil in the grooves thang). anyway, cleaned off the piston residue with the scouring-pad-in-a-drill trick, and muratic acid. years ago i had a buddy who floated out speed from diet pills or something with muratic acid, not that i went near it. but i digress.

    did the initial hone with #240, and then plateued it with #300. in hindsight the crosshatch angle is a little steep. and yes there's still a score, but it's shallow and smooth.

    tw piston2 hone.JPG

    cleaned things up good, gapped the rings, fine. put it all back together. head seems fine.

  3. #3
    Senior Member slowmod's Avatar
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    as soon as the engine comes up to temp (but not before), major blow-by apparently. as in, half the crankcase ends up in the airbox right quick. rigged up an oil separator, which saves taking the airbox apart (again), but didn't keep the oil in the damn engine. parked the bike, no coin or time to throw at it.

    tw oil separate.JPG

    cut to march 2019, spring approaches. it occurs to me to change the vent point to middle of the timing cover - way high, and centrifical sends the oil off the chain away from the center.


    tw breather.JPG

    did about 5 road miles and 3 miles mild slogging off road through retreating snow, and sand. ~40deg f ambient, so that would've kept the temps down. some of the best break-in info i came across was on aviation forumns, and they talked of keeping temps low. their world seems an odd mix of mission-critical don't fk around and seat of one's pants in-air mechanical tweeking. a bit like bikes, come to think of it.

    anyways, the new oil point worked like a freakin' champ, a wee bit of oily condensation or ambient splash, but the oil stayed in the damn engine. which allowed me to actually run it for more than 10 minutes. engine power increased about 20% during today's activity, still maybe a little down from "before". bike is running lean, so i need to address that right away. the aviation guys said to run rich during break in, which would make sense.

    am using rotella 15w40. am generally near sea level. stock jets iirc.

    shimmed the needle up a bit (.04") with a couple aluminum washers made from the side of an old travel trailer, and also finished building a better engine-to-carb flange < link > to replace the failing sealant-repaired factory boot.

    bike starts much easier, and runs good, steady, no popping, idles well. haven't done a plug chop or compression test yet. put another ~12 miles on the bike, combo of secondary roads and spring mud road slogging.

    blocked the new breather point and swapped back to the stock point with my oil separator as soon as i got back, and didn't make it 1/4 mile before i had to turn around and limp back, 400ml in the can. so something is still amiss.

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  5. #4
    Senior Member slowmod's Avatar
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    when i cut the new gasket, after carefull though potentially incomplete consideration, i cut it "wider" in a few places for more strength, to help avoid a repeat of the outward migration that caused the leak.

    i'm not one to take apart repairs on a guess, so here are my questions i am hoping someone can answer -

    did the covered area indicated by the arrow somehow cause the stock breather point to be overwelmed by oil?

    tw rightsidegasket1.jpg

    the blurry picture in the manual looks like it's not an enclosed space behind that area.

    tw_rightsideinside.jpg

    if covering that area did somehow arse things up, is it possible that the engine held on for 14 miles after the initial replacement (it would have taken a few miles to warm up and begin puking oil into the breather, which i wouldn't have noticed while riding), and then oil being drawn into the cumbustion chamber via the airbox could have provided some top-end cyl wall lube, until finally the whole thing just croaked?

    in other words, did i toast the piston due to cutting a gasket wrong?

    thanks in advance.

  6. #5
    Senior Member TW-Brian's Avatar
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    Hey Slowmod, so sorry to hear about these problems that you are having. I am not sure what the cause(s) might be, but I thought that a couple of inside pics of the right side engine and a side cover might be of some use to you. Sorry that the gasket on the side cover is kind of torn up. Side cover is also from a TTR225, but I believe that it is identical to a TW200 in the areas that you are asking about.

    I hope this helps.

    IMG_1773[1].jpg

    IMG_1772[2].jpg
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  7. #6
    Senior Member slowmod's Avatar
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    thank you tw-brian, nice clear photos. looks like that oblong section may very well be a drain port for the breather area. will pull the side cover and cut my gasket clear of that area.
    Dryden-Tdub, TW-Brian and grewen like this.

  8. #7
    Senior Member elime's Avatar
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    That oblong hole is where the blow-by exits the crankcase and it looks like your gasket blocked it.

    I took some pictures of a crankcase TWBrian gave me a long time ago so credit goes to him. I am only the photographer.

    Follow the white wire:
    PA130062.JPG

    Where the white wire comes out on the inside:
    PA130063.JPG

    The path of the blow-by. A little hard to see because I used a black zip tie:
    PA130069.JPG

    And as the gas goes up it looks like the oil dribbles down the channel along the back edge.
    PA130071.JPG

    And a view of the other half of the case -- the side without the vent tube but matching chambers:
    PA130070.JPG

    No doubt covering that vent hole did bad things. Thanks for sharing. We all learn from the experiences of others.
    Long live the internal combustion engine!

  9. #8
    Senior Member elime's Avatar
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    I brightened the picture with the black zip tie. A little easier to see.
    PA130069.JPG

    On the left half of the case there is a hole in the roof of the chamber the blow-by first comes into. That upper chamber leads to the vent tube. This half has the other half of the path to drain the oil back to the crankcase.
    PA130070A.jpg
    Last edited by elime; 04-22-2019 at 03:38 PM.
    admiral likes this.
    Long live the internal combustion engine!

  10. #9
    Senior Member slowmod's Avatar
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    Quote Originally Posted by elime View Post
    That oblong hole is where the blow-by exits the crankcase and it looks like your gasket blocked it.

    -

    No doubt covering that vent hole did bad things. Thanks for sharing. We all learn from the experiences of others.
    i ain't proud - i'll make dumb mistakes and post them online so others don't have to!

    great pictures and explaination elime. i'll pull the cover and fix that if it ever stops raining here (wrenching outside at the moment).

    here's a couple more photos of the destruction.

    tw_pfail2_5.JPGtw_pfail2_4.JPG
    elime, UncleRandy and Dryden-Tdub like this.

  11. #10
    Senior Member Sthrnromr's Avatar
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    Quote Originally Posted by slowmod View Post
    i ain't proud - i'll make dumb mistakes and post them online so others don't have to!
    LMAO! I do the same. Check out my ATV rear tire threads before I finally got it right. =) For others not to repeat!
    elime, UncleRandy and Dryden-Tdub like this.
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    Way too many past bikes and builds to list. I won't bore you. Questions? Just ask.
    =)

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