Why did the Bashee Blow-Up?

[dbkid13]

So yeah I added a big landing to my jump today and was out just breaking it in and the shee started knockin. The machine is 6 years old (99) and was on its originall set of pistons and rings however last time I did a compression check it was 110 PSI so it should of still been fine. I always run klotz R50. Now my questions are how do I get the pieces of metal out of the low end?? I dont feel like splitting the case because I am not very knowledable and I think that I got most of the pieces out because they were still on top of the piston. I was thinking about just flushing it out with some ATF or some kind of cheaper oil. My second question is why do you think it blew up. Plugs looked rich (I like to be on the safe side) and the compression seemed fine. THis is my first Banshee rebuild so any advice and words of wisdom would be thankful (problems that you might of ran into on your rebuild or anything like that). Here is a link to the tear down pics. http://community.webshots.com/user/dbkid13

 

THanks for your help.

[MonkeyBoy]

Kinda hard to see but it looks like a ring broke. It's common when you run the motor long past rebuild time.

 

Could be wrong, but that's what I saw.

[tOj]

For starters, 110 psi is not that great of a compression, I think I've heard it wont even start if it is under a hundred, you should be upwards of 130-150 on stock pistons/cylinders. Depending on how big the chunks of metal are in the bottom end, I would suggest a magnetic drain plug, will grab metal particals.

[wayfst]

if any metal went down you need to pull the crank for a rebuild, a magnet won't work.

[Redlined]

Removing piston pieces from the lower end:

Dump some solvent (Or even some fuel) into the lower end and then flip the bike upside down. Keep doing it until you get it clean.

 

How did it happen?:

Did you, by any chance, over rev the motor for longer than usual?

[dbkid13]

Yeah I know that 110 isnt great but I heard that you didnt really need to reduild them till 100, anyways next time I know to rebuild it at like 115 and play it safe, it actually blew up when I was just letting it warm up. Kinda werid but I figured that it had prolly already started to come a part a little or crack or somethign and then just let go. I will be using MOTO-MAN in canton to do the jug work and wiesco pistons. ANYONE heard of these peopl (motoman in Canton, MI) and know how good of work they do??????????????

[IRONDOG]

More than likely you had excessive piston to cylinder clearance- the piston rocks back and forth until the skirt breaks off. Scheduling a rebuild via compression readings can get you into trouble. Skirt clearance is far more important than compression readings but of course is much harder to check than compression.

 

Connecting rod big end bearing failure is a possibility also, but that usually pecks up the combustion chamber more than yours appears to be.

In any event, if you want the job done right you will have to split the cases- no ifs, ands or buts about it. Don't even think about flushing it out, you won't get it all.

Good luck with it.

[sweetshee4312]

i just rebuilt my engine, and right after break it my compression tester was reading 110....??? it was colder out then does this mean i did somethng wrong, i mean the pistons and bore job was dont by passionre so i think everything is right, and i followed a clymers all the way through, if ne one reads this and knows can u pm me? casue i know it is alittle tricky to start, the engine is also ported

[chris642]

i just rebuilt my engine, and right after break it my compression tester was reading 110....??? it was colder out then does this mean i did somethng wrong, i mean the pistons and bore job was dont by passionre so i think everything is right, and i followed a clymers all the way through, if ne one reads this and knows can u pm me? casue i know it is alittle tricky to start, the engine is also ported

409345[/snapback]

you have the stock head? no milling? that sounds right for a ported bike with a totally stock head, that is what jim said. you need to either mill the head or get a noss head, i got the noss head because i had the cash and wanted some bling, i have 19cc domes and it brought me to 150PSI.

[sheefreak]

For starters, 110 psi is not that great of a compression, I think I've heard it wont even start if it is under a hundred, you should be upwards of 130-150 on stock pistons/cylinders.  Depending on how big the chunks of metal are in the bottom end, I would suggest a magnetic drain plug, will grab metal particals.

409242[/snapback]

 

Magnetic drain plug is not going to do shit for the crankcase. Don't forget the crank compartment and transmission are separate, so unless it was your tranny gears you are worried about, drain plug isn't going to help you. To me it looks like detonation, or a head gasket leak. The piston is awfully eaten up.

[pimpeinkc]

when i shot a piston i just rebuilt it, drained my oil a few times, the crank is sealed and the piston crap shoots out on top of the piston, f's up the piston and head then goes out the exhaust port... i know may people who have done it this way

[dbkid13]

Is there any good tutorials on how to split the case?? and is there anything else I should do while I am in there?? Thanks. ------------------Sam

[Holyman]

Where in the world are you people coming from???

First and foremost, you engine oil has NOTHING to do the piston chunks. There is NO WAY for piston debris to get into the engine oil unless the case is SEVERELY damaged.

Second, the crank is not "sealed". The oil/ gas blend surrounds the balls in the bearing and provides ALL lubrication for the crank. If the crank bearings were sealed from the inside, they would fail almost immediately ecause there would be NO lubrication!

Third, all the crap that was bouncing around on top of the piston is almost guaranteed to have become embedded in your crank bearings, which again are NOT sealed, and no matter how many gallons of stuff you flush it with, the little fragments could always come back to haunt you later. And if one of the rods break {caused by a pin-head sized bit of piston you didn't flush out getting lodged in the bearing of the crank}, it usually goes straight out the top of the case or the bottom of the case or BOTH {like mine did}.

The best thing for you to do is check your intake boots for fine cracks and the back of the boost bottle for a pin hole from rubbing cables. And when you get done with the rebuild, stomp the boost bottle to a pancake and get new intake boots and make sure you get a new crank or at least have your bearings and seals replaced. Yes it will be a little more hassle to do it now BUT it's cheap compared to new cases, double the work and money and pushing your blown banshee back home from the trail.

[wayfst]

Where in the world are you people coming from???

First and foremost, you engine oil has NOTHING to do the piston chunks. There is NO WAY for piston debris to get into the engine oil unless the case is SEVERELY damaged.

Second, the crank is not "sealed". The oil/ gas blend surrounds the balls in the bearing and provides ALL lubrication for the crank. If the crank bearings were sealed from the inside, they would fail almost immediately ecause there would be NO lubrication!

Third, all the crap that was bouncing around on top of the piston is almost guaranteed to have become embedded in your crank bearings, which again are NOT sealed, and no matter how many gallons of stuff you flush it with, the little fragments could always come back to haunt you later. And if one of the rods break {caused by a pin-head sized bit of piston you didn't flush out getting lodged in the bearing of the crank}, it usually goes straight out the top of the case or the bottom of the case or BOTH {like mine did}.

The best thing for you to do is check your intake boots for fine cracks and the back of the boost bottle for a pin hole from rubbing cables. And when you get done with the rebuild, stomp the boost bottle to a pancake and get new intake boots and make sure you get a new crank or at least have your bearings and seals replaced. Yes it will be a little more hassle to do it now BUT it's cheap compared to new cases, double the work and money and pushing your blown banshee back home from the trail.

409522[/snapback]

this is what I'm say'n. you frick'n go Holy! flush the crank, MY GOD!

[Redlined]

You

Edited August 31, 2005 by Redlined