Why did this part of my motor break?

[WaveDemon]

I've finally bought and recieved everything I needed to re-assmble my motor that I broke in January. I was under the assumption that I broke a ring because of an assembly error. I even found a 2" piece of a ring in the head pipe. It turns out that the broken piece was part of the crank(a retainer or locator on the outside of the rear bearing? not sure what it's name is). at first I couldn't figure out how that peice could break and enter the motor since it's traped in a groove in the case. I put the crank back in the upper case and noticed that it rocks up and down. It seems the the crank is bent or the case is warped. It doesn't seem that the crank was installed wrong because it ran fine when I recieved the motor and I never split the cases until last night.

Any thoughts?

I showed pics of the upper and lower case to show that it didn't shear through there.


Looks like the attachements arn't working. I'll get the pics up soon.

[PAIR-A-DICE]

I've finally bought and recieved everything I needed to re-assmble my motor that I broke in January. I was under the assumption that I broke a ring because of an assembly error. I even found a 2" piece of a ring in the head pipe. It turns out that the broken piece was part of the crank(a retainer or locator on the outside of the rear bearing? not sure what it's name is). at first I couldn't figure out how that peice could break and enter the motor since it's traped in a groove in the case. I put the crank back in the upper case and noticed that it rocks up and down. It seems the the crank is bent or the case is warped. It doesn't seem that the crank was installed wrong because it ran fine when I recieved the motor and I never split the cases until last night.

Any thoughts?

I showed pics of the upper and lower case to show that it didn't shear through there.


Looks like the attachements arn't working. I'll get the pics up soon.

Tim---that sucks. Especially after all you've been through to get your Blaster going.

Did you get your employee manual?

[WaveDemon]

pics were to big to attach before.

here we go

[WaveDemon]

Tim---that sucks. Especially after all you've been through to get your Blaster going.

Did you get your employee manual?it does suck. We'll just add this to the list of sucky blaster problems.

I got the manual, thanks.

[Ollie Rastabean]

Bro,
Something aint adding up here. That locator ring is trapped once the cases are together. that thing aint migrating into the flow path without the case apart. The halves would not go together if that aint exactly where it needs to be.

I also dont see how your motor ran as long as it did if that thing was hanging out in the bottom of the case.

Did you split the case the last time you put cyls in it??????

This is bizarro.

"Dykstra the Destroyer"

Guess this puts the chill on riding at your place on sat.

-O

[WaveDemon]

bizaro is right. I didn't split the case until last night.


the curse started with the purchase of the ski. It's been non stop ever since.

how the :-):-):-) does that part end up sitting in my head pipe? Some how it breaks, escapes the grove in the bearing and case, bounces around the case, travels up a port bounces around the chamber and lands in the head pipe?

[WaveDemon]

Guess this puts the chill on riding at your place on sat.

-O

Come on by Sat. I think the SJ will be running by then.

[Ollie Rastabean]

I need to take a look at this in person.

Hold off throwing the whole thing in the lake just yet (I know you are close).

-O

[yamaslut]

Holy freaking jesus!!!!!

Tim.... that is strange.. I want to look at that bitch too

[WaveDemon]

you guy just come on by on sat like we were talking about before. We'll scratch our heads about the latest weird thing, ride some sj's and have a good time. :beerchug:

I'm not thinking about tossing it in the lake Ollie. I have accepted that things like this happen to my ski on a regular basis.

[Idok]

you guy just come on by on sat like we were talking about before. We'll scratch our heads about the latest weird thing, ride some sj's and have a good time. :beerchug:

I'm not thinking about tossing it in the lake Ollie. I have accepted that things like this happen to my ski on a regular basis.




part it out dude, you caught my blaster curse.......you are destined to ride a SJ!

[WaveDemon]

I think your buddy bill needs to trade me for his h20 SJ.

[PAIR-A-DICE]

I think your buddy bill needs to trade me for his h20 SJ.

:haha: :arms: :Banane01:

[Idok]

I think your buddy bill needs to trade me for his h20 SJ.



i think bill will be cremated, then his ashes will be tossed in with the premix for that ski...



although he did say he'd sell it complete for 6500

[Big Kahuna]

as far as the rocking motion, does it do that if you rotate the crank around......... are you sure you had all the small keeper pins in the guide holes???

this could kick up the crank.........

[WaveDemon]

as far as the rocking motion, does it do that if you rotate the crank around......... are you sure you had all the small keeper pins in the guide holes???

this could kick up the crank.........I checked many times. the holes line up.

[WaveDemon]

that was my first thought. the pins/holes are easy to find but sometimes the last ones to go in are deceiving. makes sense.
I know, I thought the same thing. I checked many times.

[WaveDemon]

the crank not fitting in the case helps explain why that retaining ring broke and fell into the motor.

[Big Kahuna]

yeah, but how was it running, if crank not seated, the cases wont seal.........

[WaveDemon]

do u have another crank or case to mock up that you can use for process of elimination?
I do but it's in an assmbled short block. I might pull it appart this weekend. Ollie may also take the crank and mesure it on his lathe.

[Ollie Rastabean]

I have a spare set of cases I will bring too so you dont have to break that shortblock.

-O

[Rockstar]

OMG that sucks big time dude. Im sorry. You can ride my SJ over the weekend all you want.

[WaveDemon]

OMG that sucks big time dude. Im sorry. You can ride my SJ over the weekend all you want.thanks bro, I was planning on it. :wink:

[WaveDemon]

this is what that little peice of crank ring did to my motor in about 10-15 seconds of total run time.

[Mouthfulloflake]

hold on....

is this the same motor that you posted on pwcnowhere.com?

the one that according to everyone had a 'great' crank in it?

hmmm

you might want to put that on some V blocks and check it.

something is WAY wrong there.

[keefer]

I agree, if the cases were not tight, there would be a major air leak not to mention massive failure because of the crank rattling around. It just dont work like that. Are you sure that is not a piece of one of the thrust bearings on the big end of the rods? Truly bizarro. Hope you figure it out.

[douglee25]

Just throwing out some things that came to mind:

1. Could the wrong bearing be pressed on the crank?
2. Could a wrong retainer ring been used?
3. Could the retainer ring have been pinched in the cases when assembly took place? Are there any marks on the case indicating that?
4. Is the bearing bad? Noisy? Rocks in the race?
5. Have you tried a new retainer ring on the bearing and mock up the engine again to see if the slop still exists?

Doug

[MADMAT]

This thread is depressing:banghead:

I'm about to reassemble my first motor ever. I'm nervous.

Very sorry to see what happened to your motor demon.:frown:

[ski4]

me too matt, my finsihed motor is starring me in the face and i am having nite mares about something like this happening

[WaveDemon]

It may be time for a little history on this motor. It was built by a reputable builder for JetRock. JetRock used it for only a few hours (he claimed 1 or 2 hours all on one outing) then got the bug for MX and sold it to me. I ran it for a few more hours (less than 10 total) and put in higher compression domes. It turned out to be to much compression for pump gas and I destroyed the pistons and rings. I replaced the pistons and rings and cleaned the case without dis-assmbling it (probably a mistake). I put new pistons and rings in. I did a pressure check, it had a slow leak at the carb gasket. I figured I would throw a little 1211 on the gasket and run it anyway the next morning. On the initial start up it free reved, twice. I figured I didn't seal the carb gasket well enough. I pulled the head for damage control and found what the pictures show on the first page, one busted piston (rings are intact) one busted dome and a 2" long crank ring in the head pipe.

[Mouthfulloflake]

ahhhh...

and now, we know...

the REST of the story.

:biggrin:

[Flash-FX]

Wild guess...The 2" piece is left over from the piston/ring failure. The bearing locating circlip could never jump out of that machined groove in the crankcase....unless it was split/broken.

It's a piece of ring? I never saw anything that BIG survive thru a motor...WOW!!
Good scavenging..

:frown: Just a guess..

Hope you get it back together soon.

[keefer]

I agree with what Flash said, I think that you had a piece of piston ring instead of the retainer ring. I bet that retainer ring was broken all along or broke when you took it apart. It is tempting to not split the cases with a top end failure but sometimes you can get all the metal out and sometimes something is hiding and bites you in the butt. Check that crank with a set of V blocks and guages and pay special attention to the big end bearings. You dont want to be right back in there again because of a crank failure. I went through that last fall on my wife's SJ Good luck.

[WaveDemon]

I found the crank ring in the head pipe while the motor was still assemled

[WaveDemon]

could it have been a piece of piston ring from the first failure that you didnt know was in there?it could have been but why is there a big chunk missing from the crank ring? Does that ring not close? is it supposed to be that open?

[WaveDemon]

thanks for checking, it's going to be tested very soon.

[WaveDemon]

after closer inspection this was a false alarm. I apprecieate everyones input and willingness to help. You guys rock.

The crank and cases are fine. I must have been to sleepy to notice a mis-aligned crank pin (I tried to assemble it after a 15 hr work day) . The ring chunk must have come from the previous melt down. as you were.

[WaveDemon]

then why does the ring on the bearing have that big gap? does one end look broken?
nope, both ends look perfect.