piston question

staj hickman

New Member
May 10, 2014
8
0
1
35
So I bought a 2000 blaster, for 500 "guy" told me it needed a carburetor clean which I did and it started right up. He said it had oil (BIG LIE) got all excited fired up and took off ten minutes after doing so it shut off. No compression took it home took the head and jug off (BIG PROBLEM) the piston skirt has broken off but the motor is bone dry . Which is the reason it broke right? so I've gotten all the pieces out ran some diesel through it and ordered a standard 65.92 nameradu piston my question is if I just hone it and don't bore it what will happen will it ride? Theres a few tiny scratches on the jug but that's it.
 
You will never get all the bits of broken piston out by flushing, they just love to hide in bearings.

A case split, clean, preferably replace bearings is absolutely needed!

If the engine has been run with no lubrication for a while, I fear you are stuffed as bearings do not like to be run dry!
 
You will never get all the bits of broken piston out by flushing, they just love to hide in bearings.

A case split, clean, preferably replace bearings is absolutely needed!


But if I split the case I need pullers and gaskets right? Im broke thats why I ask
 
Cases can be split without special tools and no gasket needed.

My main concern is that you will be wasting what money you have only for it to blow up as soon as you fire it up, a pointless exercise.

Take my tip and split, clean and or replace bearings, you will be better off in the long run.
 
Main crankshaft, crank pin and wrist pin bearings, all need attention and measuring for specs.

Replace the crank seals while you are in there.
 
A little bit of debris smaller than the head of a pin lurking in a bearing is enough to destroy an engine completely.

Check for case damage as crankshafts have a habit of slamming piston skirts through cases.
 
Main crankshaft, crank pin and wrist pin bearings, all need attention and measuring for specs.


So basically I should by a new motor your talking 300 in parts when just the piston broke 2 pieces broke off it only ran 4 10 min and everything else looks great its had 16 hrs of ride time total its basically brand new did the piston possibly just get hot and brake or did everything bust I don't make a lot of money so if I have to do all that Ill just sell it
 
He is referring to the crankshaft main bearings, you can buy a All Balls crank main bearing kit which comes with the main seals for like 50 on eBay. How are you sure that the piston is stock 66mm bore, an if run with no oil an broken piston how does cylinder walls look, usually the broken pis
 
the piston has the size on the top of it the crank spins freely after runnig fuel to get the 2 or 3 pieces that broke off and i bought it from the original owner with only 16 hours on it i just needed to no if i can just hone it or do i have to bore it first like is it 100 percent needed its not scored up real bad
 
You may have seen only two parts of the piston that broke off, but where they break a myriad of little bits of silicone particles are expelled into the crankcase and will lodge in bearings sometimes rendering them useless.

Some folks have jagged it by just replacing a piston, but the majority of times when they do not get all, and I mean ALL of the debris out the engine lasts less than minutes.

If you are confident that you have all the bits out and the bearings are serviceable after extreme punishment without lubrication, just chuck in another piston and go for it.

I would rather have you doing the job properly than wasting your hard to find money.
 
  • Like
Reactions: staj hickman
^^^x2 there is never enough time or money to do it right but you always find the time an money to do it again, an the second time around is usually double what it would have been to do it right first time
 
  • Like
Reactions: staj hickman
well how do open it up to remove the pieces without having to buy more parts or is that not possible? do I need a puller?
 
I have seldom heard of a piston dropping a skirt from a lack of lubrication, the piston usually freezes in the bore.

I would tend not to believe the PO about the low hours of run time, piston skirts usually drop off of in a bore in an engine with excessive piston/cylinder wear.
 
There is a description on BF which explained case splitting/replacing without special tools, I am not in the position at present to search for it, you may try.
 
so I can crack the case without spending money I thought I had to buy gaskets and a seal?
$_57.JPG



so I can crack the case without spending money I thought I had to buy gaskets and a seal? this is what bought and I will crack the case if I can do it without having to have more stuff so let me
 
Your gonna need yamabond or 3bond for sealing the cases, an i would highly recommend buying the crank bearing kit on eBay its 50 bucks, dont buy junk parts though, buy the All Balls kit
 
You need to get yourself a leak tester too. There is a downloadable manual on here somewhere as well. If PO was truthful than it is barely broke in and obviously not properly. Is it mixed gas or oil injection. You'll need a couple other minor parts as well, ktm filled me in on another thread:
You'll definately need New oil seals,gaskets, 2 lockwashers , one on both the clutch basket and counterbalancer,and 2 snaprings for the idler gear. And I would definatly take the time to inspect the clutch all the transmission bearings and both main crankshaft bearings. As far a mods go theres a thread on here that shows you how to modify the shift star for smoother shfting, and i think ken o conners got a youtube vid on how to drill small holes in the clutch basket for better lubrication on the clutch disks.
 
so I can crack the case without spending money I thought I had to buy gaskets and a seal?
$_57.JPG



so I can crack the case without spending money I thought I had to buy gaskets and a seal? this is what bought and I will crack the case if I can do it without having to have more stuff so let me
Throw away the green paper base gasket, they leak, and buy an OEM or cometic gasket.

Also buy both crank oil seals.

I am not going to allow you to put a new piston on a crankcase full of crap, If you cannot afford to wait to buy it when your money is available, buy them and send me the bill for bearings and seals.