Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: eprovenzano on December 06, 2016, 08:15:48 AM
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A friend of my son asked is I could repair his cylinder (2001 KTM 250SX).. Someone forgot to install the 2nd circ clip and the piston pin did a great job of machining a groove into the cylinder wall.
(http://i18.photobucket.com/albums/b125/eprovenzano/ktm%20cylinder.jpg) (http://s18.photobucket.com/user/eprovenzano/media/ktm%20cylinder.jpg.html)
He's purchased a new sleeve from LA sleeve and new wiesco piston. This repair is way beyond my backyard garage expertise so I've contacted a local machinist I trust and he will handle the repairs... I can't believe just how perfectly the grove was machined without destroying a port... It looks like its supposed to be there... :D
I'll post pics of the repaired cylinder when after its fixed .
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wow! thats unreal. seeing how I have suffered two crank failures, I can feel for this guy lol.
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i had an engine rebuilt , they didn't torque the front barrel bolts down 2nd ride it sucked air leaned out and seized :-{{ i was not impressed, lucky i caught it fast got away with only and new piston and rings
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If the circlips are lined up wrong they may vibrate out, not that this is the case here though there is no apparent circuit gouging.
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The cylinder has been repaired... (Sorry forgot to take pics) but it's perfect... The owner of the bike went over the cylinder and couldn't find one issue to complain about.. ;) He decided to polish the ports... I asked why??? you don't ever use the full power now... to which he asked me why I ride a 380?? Simple... I like to dig ditches and roost you and everyone behind me with boulders, trees etc... The 380 is not a high strung beast... It's a very docile animal, until you unleash the beast... An 01 KTM 250SX is a high horse power high strung beast, and you need more... OK... have at it... :o
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Polishing the intake ports will actually reduce the power. The roughness creates turbulence in the charge which helps keep the fuel in suspension.
Polishing them allows the fuel to drop out before it gets to the combustion chamber resulting in a lean mixture, high combustion temps, reduced engine live and loss of power.
If he, really wants to polish something, polishing the exhaust port is worthwhile, it improves flow and reduces carbon buildup.
Or you can just let him detune his engine to make roosting him even easier.
--Ron.
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Or you can just let him detune his engine to make roosting him even easier.
--Ron.
At this point, I'm done dealing with stupid people who think they know everything... If he were getting the head milled and or the ports adjusted to gain power is a certain area... OK, I could understand that.. but no... he's just a backyard mechanic that's read on the internet to get better power you need to do X... Well it's your bike, have at it son... :-\ I'll let my mighty 380 do the talking err roosting... I'll see ya back at the finish line... ;D
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A little knowledge is a dangerous thing!
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A little knowledge is a dangerous thing!
The internet can be great, except it made a lot of people feel like they could fix anything because they watched a youtube video :) .