hey guys,

its been a long time coming but ive finally got hold of a digicam and snapped some pics of my piston and cylinder. The bike had new pistons put in it approx 100kms before this happened... the previous pistons were missing about 1 cm of ring, so im thinking there still some metal bouncing around in there Any remarks/comments/advice on fixing properly are welcome

http://www.bikepics.com/members/tvjoyce2002/91nsr250/

Cheers,
Tim [/url]

Paaaa! thats not a broken piston, plenty left on that, mear flesh wound, LOL you want one like this!!!

http://www.bikepics.com/pictures/650865/
http://www.bikepics.com/pictures/650866/
http://www.bikepics.com/pictures/650867/

On the serious side, when mine went i had the complete top end redone, at a great cost, but a week after it came back it went again!!!!!, It appears altough the crank cases where flushed there may still have ben a bit of ring still in there (not comfirmed yet but will soon) as the same barrel went and JAMMED solid this time. if you have the time dont rely on a flush take the crank OUT and have a good look. that way youll be 100% sure when you put it back!

hey rc46,

your piston is amazing~!! how do you flush the crankcases? i am probably going to completely disassemble the whole motor, get the crank out, measure clearances etc as a project since im a mech eng student and dont need this bike for transport anymore

do you think i need a new cylinder head since this one is pitted? also i think ill need to get the barrel replated a it is slightly burred at the exhaust port...

Cheers
Tim

Its hard to see the cylinder, but I think it may just need to be replated, and you'll need a new piston and head. You could proabably slap it all back together and it would run.
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Not entirley sure how the Flush is done, I have someone else do the work, someone techy could answer, but maybe compressed air, or fuel oil mix blasted through.. Id get the barrel replated and a new head, And yes if you have the time strip it down and rebuild it, that way you can be sure its done!
of course you also need to find out what casued it and fix that too, otherwise itll happen again i would think.

When I recently had my top end done he split the cases just to make sure everything was OK. Then found a rust nail in there! So the leason today is.......when spending 500quid on a new top end rebuild.......check the cases for small nails, kids toys and rodents poo.

It's pretty odd for debris to stay in the motor that long isn't it? I'd have thought that any bits of ring would have been well out of the ex' port by now. Hard to really tell from the pic's, but are you absolutely sure that isn't good old-fashioned detonation damage? I can't see any cylinder damage in the pic's, only head and piston crown pitting.

Only other thought is that the crank could be slowly coming apart and shooting a steady straem of debris up the cylinders. I've never heard of bits of piston ring stying inside a top end for that length of time though.

What colour was the plug?

Rgds

Wb


Last edited by wb on Tue Aug 08, 2006 11:37 am; edited 1 time in total

rc46 wrote:Paaaa! thats not a broken piston, plenty left on that, mear flesh wound, LOL you want one like this!!!

Are you kidding! There's nothing wrong with that.

THIS, is a knackered piston....

http://i7.photobucket.com/albums/y269/Barry_mc21/DSC00052.jpg

you win... Shouldnt keep mice in the engine, You know theyll eat anything, and a soft 4 stroke is easy peasy to munch for lunch...

LOL

Anyone else with a war wound?

That doesn't count Barry, that motor was already disadvantaged by being a bore-stroke!

4-stroke is the internal combustion engine version of being ginger!!
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Here are my war wounds. The locating pin for the ring failed and the ring spun. lucky for me it didn't seize hard (was traveling about 70-80 mph in a turn). I tried to bump start it before I came to a stop. Might have caused some more damage.

http://photos.yahoo.com/rothmansmc18
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rc46 wrote:It appears altough the crank cases where flushed there may still have ben a bit of ring still in there

timnsr250se wrote:how do you flush the crankcases?

Sane people don't, they split the cases, take the crank out and check for bits properly, Garry at Apex assured me it took quite a while to get my crank bearings spinning freely after riding 10 miles with half the chrome ripped off the bore.
Presumably they blasted the case through (from either the intake or the top barrel) with something hopeing in vain that any bits floating around would come out. Whatever, it didn't work.

And Mr Andy, I've been out with two ginger girls and they were both lovely
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timnsr250se wrote:hey guys,

its been a long time coming but ive finally got hold of a digicam and snapped some pics of my piston and cylinder. The bike had new pistons put in it approx 100kms before this happened... the previous pistons were missing about 1 cm of ring, so im thinking there still some metal bouncing around in there Any remarks/comments/advice on fixing properly are welcome

http://www.bikepics.com/members/tvjoyce2002/91nsr250/

Cheers,
Tim [/url]

Looks like it`s just detonation to me.
Running a bit too lean/ too much compression for the fuel grade/ ignition timing advanced too far, etc.

Can`t see but I`d have thought the barrel would be okay & you `d be able to clean up the head I`d have thought. Meaning just a new piston really.

What piston is that? Never knew NSRs had piston ports.
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That is a Wiseco, I believe.
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