shattered piston skirt advice

[pportera]

Second topend rebuild obviously "honed" it to much with three blade spring honer. Shoulda gone larger on piston bc it showed signs of blow by. Any way I put a standered size piston back in it. Had great high rpm power but not much low end off the pipe power. Lot of clutch slipin to get in power band. After about three rides it would make a marble rattle kinda sound. I tried to make it home but did not. So I tear into it and the intake side piston skirt was gone. Can't find anylarge pieces but lots of gritty sandy chunks.

I'm almost for sure the cylinder was honed way to much and was causing the piston to rattle around and shatter. Now the head has cuts gouges and looked like shroud metal was buckshot into it. The rod has zero up down movement but does kinda giggle side to side. The crank will rotate freely and had no sighns of shroud metal damage. But it does have the gritty sandy aluminum oil all in the crank. Obviously I need a larger pistonand rings. Obviously I should take the head and cylinder and a new piston to a machine shop to clean this up and bore it to corect tolerance. Should I get. 20 over or go with.30? Also what the hell do I need to do to the crankcase to get it ready for a new machined topend?

 

[duneracerweston]

the 3 sided spring hones wont keep in true for one and there should only be about 2-3 thou cleance in there

 

[pportera]

BTW. The old piston before this one had a few little jagged edge on the bottom if intake side. Like if it were hitting on something? Does thus mean the cylinder needs chaferd??

 

[xjma]

Take your cylinder to a shop, they will be able to tell you if it's salvageable or not.

Clean crank out with diesel or kerosene, tip upside down, repeat, pray. If the noise goes away and you can feel the crank rotate all smooth and don't think anything is in the bearings, you could try to run it.

I would venture to guess you may have also been running lean, what's your jetting like?? Are you pre mixing or running the injection system?

If the bottom end is OK, take the cylinder to a shop and have them tell you what it needs. I always have a shop do a hone job, they generally charge like 10-15 bucks and they do a 100% perfect job. A good hone job = good ring sealing, and the better your rings seal to the cylinder walls, the more power you get!! Not that honing can't be done at home, but leave that to those that really know what they're doing (no offense, not trying to be a dick, just saying). Any halfway decent shop will be able to tell you what size new piston to get. They may tell you your jug is junk, in which case go to the for sale section, people always have good ones for sale!

Good luck on the rebuild. Go with either a wiseco oversized or even a stock oversized piston and ring set. Nothing wrong with stock pistons, they're good stuff and if you're one that doesn't like to properly warm up the bike before riding, they're your best chance against a 4corner seizure!

 

[Awk08]

i tried the "flush it out" bottom end cleaning method, after 6 months the crank finally let go and took another brand new top end with it, and another $200 down the drain, the crank spec'd out after the flushing,
apparently i didn't get everything out, which i believe to be next to impossible
it's full rebuilds for me from now on..
rebuilt crank, (rod/big end bearing)
new mains and seals, and the topend ...
all professionally done < way cheaper in the long run

 

[joeak47]

To clean out the botton end,try this >>>
Get a can of engine gunk (engine spray cleaner),and spray the can down into the case. The engine gunk will keep the bearings and seals lubricated while you rotate the crank. Put a bunch down in the case until it comes to the top,and rotate ALOT.
Next... Flush out the case by tipping the bike on its side. Now take a pan of VERY HOT WATER and DAWN DISHWASHING LIQUID,and pour this into the case (I know what everybody is thinking),spin the crank a bunch more,then tip the the bike on its side once again to get all the water out.

Next flush the cast with VERY HOT WATER,and then tip to flush. Now finish up by blowing out the water with an air compressor.

Last thing to do is spray with an oil,and pour some oil on the bearing holes and rod bearing.

The hot water evaporates very,very fast and leaves the metal parts bone dry and rust free long enough to spray with some oil.

Believe it or not,WATER is the best solvent on earth!

 

[pportera]

Does anyone know of a good machine shop that specializes in two strokes
around the Birmingham Alabama area?

 

[pportera]

Is splitting the cases necesery to replace the crankseals? Sometimes it blows oil out the breather tube on the crank. Plus I have never replaced either seals.

 

[blasterBruce]

You Do Not need to split cases to do crank seals , But you do have to take a good amount of parts off the bottom end , Best bet is to buy a Yamaha Manual Or Download the one on here- http://www.blasterforum.com/general-support-17/downloadable-yamaha-blaster-manual-17325/

 

[JBRoc01blaster]

I agree with what Awk said ( no offense to anyone else ) you should just rebuild/replace the bottom end along with a new top end kit. My piston shattered last November/December and I bought a top and bottom end kit from Wiseco, thats the only way to guarantee your motor will be in tip top shape and last ! It's worth every penny just for the peace of mind knowing your motor is good to go and you won't have to worry about your bottom end for some time

 

[Blaaster]

I too agree with what Awk said ( and if anyone is offended so be it.)

Take a tip from an old timer, split the cases and do the job properly, one grain of shrapnel lurking inside a bearing cage can cause a catastrophic failure down the track.

No amount of flushing can be enough to be sure that the crancase is free from the gritty residue that a dropped piston skirt provides.

Best thing to do is to replace the bearings and seals.

 

[sporty982000]

When I first started rebuilding the top end on the blue blaster.

I was new to blasters and more or less still am.


I did not remove the bottom from the frame. Well you cant easily see into the cases, at the crank shaft area.

So, I rebuilt the top end and out put it back together. And leak down test, notta.

Turns out when the piston skirt broke on mine, it got pieces betwee the crank and the case walls and broke / cracked the case walls.

And I am actually glad it did not run and ect.

Upon taking it apart, I found the broken pieces of the case and one had went into the tranny area. There was also a ton of small pieces all over by the bearings.

So, I pretty much have to say what mostly every one else is saying. Its far better to spend the time , splitting the cases.

Clean it out and check for cracks and damage. It will likely save you allot of time later, if there is andyou didnt get it or cracks or damage to the cases.

Split the Cases..

Sporty