Top end damaged, need help!

[TimSr]

The dings in the piston are from good old fashioned debris smacking into it. Nothing more. My first guess is chunks of carbon coming loose from the head. The marks on the crank are from something major coming apart at one time, but who knows when. If it just happened there would be shrapnal inside, and something wouldnt be moving right.

There are absolutely no signs whatsoever this was running lean or hot. Just the opposite. You dont get excessive black carbon buildup from a machine running lean. You dont get black carbon on the top of the piston. When a piston melts, it looks like its been sandblasted away, you dont get dings in it. It typically starts at the exhaust side of the piston.

What this looks like to me is somebody ran a 20:1 mix for a long time, and never got it hot enough to burn off, and never set it lean enough to burn off. I agree the piston is probably okay to use, but my guess is youre going to need a bore job, because those carbon chunks rubbing the clylinder walls have probably formed some grooves too deep to hone. It wont hurt to try a mild hone job first, but Id be surprised if that takes care of it. Youve got plenty of room to bore as I think that goes up to 3.0mm oversize (.120") if I remember right. Then get a good high performance 2 cycle oil, and mix it up at 50:1, and adjust carb accordingly.

[jason 32]

i wouldnt go 50 i use klotz at 40 - burns clean and smells good 2 lol
depends if you use racing fuel too

[MathGSR98]

The dings in the piston are from good old fashioned debris smacking into it. Nothing more. My first guess is chunks of carbon coming loose from the head. The marks on the crank are from something major coming apart at one time, but who knows when. If it just happened there would be shrapnal inside, and something wouldnt be moving right.

There are absolutely no signs whatsoever this was running lean or hot. Just the opposite. You dont get excessive black carbon buildup from a machine running lean. You dont get black carbon on the top of the piston. When a piston melts, it looks like its been sandblasted away, you dont get dings in it. It typically starts at the exhaust side of the piston.

What this looks like to me is somebody ran a 20:1 mix for a long time, and never got it hot enough to burn off, and never set it lean enough to burn off. I agree the piston is probably okay to use, but my guess is youre going to need a bore job, because those carbon chunks rubbing the clylinder walls have probably formed some grooves too deep to hone. It wont hurt to try a mild hone job first, but Id be surprised if that takes care of it. Youve got plenty of room to bore as I think that goes up to 3.0mm oversize (.120") if I remember right. Then get a good high performance 2 cycle oil, and mix it up at 50:1, and adjust carb accordingly.

Wow dude, you rock big time! The previous owner did run it 20:1 with probably barely cheap oil. I used klotz super techniplate at 45:1 and at the end Sinto Racing performa (40:1) which is semi synthetic (http://www.sinto.ca/). I liked more the klotz but it's harder to get it in Quebec, Canada...

I don't think I would be able to hone it because the scratch that you can see on one pic is really deep. What tool you use to hone it and clean the carbon deposit?

Now for a 66.75mm piston, what bore size I have to ask to a mecanic. I mean, he will have to do it larger than 66.75mm because of the rings?

Some other guys in this thread told me that my pin is blued. Does it means that the pin is more fragile?

[jason 32]

a 3 blade, flex hone - i used a soft wire wheel on a dremel to remove the carbon
it will kinda polish the head , did it to the piston too
check the piston to cylinder clearance and the ring clearance after honeing it lightly
if you use a ball type hone- it is supposed to be ? like 10 % smaller than the cylinder- so it will not catch the ports
i dont like them!! if they catch they can do damage / and break your wrists ouch!!
use warm soapy water and i like dawn dish soap its 1 of the best soaps out there
rince throughly and lightly oil

[MathGSR98]

Thanks man and thank everybody. This forum is very helpful and I'm very proud riding a TRIKE! even if it's not running now
hehe

[MTS]

a 3 blade, flex hone - i used a soft wire wheel on a dremel to remove the carbon
it will kinda polish the head , did it to the piston too
check the piston to cylinder clearance and the ring clearance after honeing it lightly
if you use a ball type hone- it is supposed to be ? like 10 % smaller than the cylinder- so it will not catch the ports
i dont like them!! if they catch they can do damage / and break your wrists ouch!!
use warm soapy water and i like dawn dish soap its 1 of the best soaps out there
rince throughly and lightly oil

Are you nuts, 3 blade flex hone WILL catch ports and do dammage, Ball hone all the way...

[TimSr]

Are you nuts, 3 blade flex hone WILL catch ports and do dammage, Ball hone all the way...

I agree, but if you dont already have a hone, Id just send it out for a bore and save the expense of buying something thats not going to fix it anyways.

[Bryan Raffa]

Are you nuts, 3 blade flex hone WILL catch ports and do dammage, Ball hone all the way...

I agree also,,,, ball hone all the way..3 blade flex hones are a thing of past and suck.. I would bore the next size up,,and take that plastic right out of the reed cage! more air = faster..

[MathGSR98]

Now what bore size I need for a wiseco 66.75mm (.75 over)? I assume I have to tell the size I want to the machine shop dude?
Thanks

[MTS]

Now what bore size I need for a wiseco 66.75mm (.75 over)? I assume I have to tell the size I want to the machine shop dude?
Thanks

Bring the Piston and cylinder to the machine shop....make sure its a reputble one that Know's how to bore a 2 stroke cylinder properly, Heck i would Shove it in the mail and Send it Right to Wiseco....do belive they do boring, and its For Damn Sure proper.....

[Bryan Raffa]

yes thats what you need.. check ebay you might find one cheeper that what a shop will carge you. and dont for get the top rod bearing they dont come with a kit.

[hrc85250r]

um, it looks like you need a whole rebuild, the dings on the crank are from someone using a metal to true it, you're supposed to use a lead , and the pitting is a peice of metal bouncing around, and wiseco pistons dont need extra clearance because they are "heavy duty" they expand slightly more because they are forged, not cast like the ghetto pistons like pro-x. and you can take the reed stuffer right out of that cage, it just snaps in, it will give you a little better top end, i dont know if you would be able to feel it on a stock bike though.....i say bore it with a new piston and do a new rod kit and main bearings/seals, if not a brand new crank and mains/seals...