Main Bearing Repacement

[BDI]

this is my high tech case splitting tools. steering wheel pullers work just fine but you need to source up the correct bolts. On the pullers I have the slots had to be lengthened by 1/8" with a round file but thats no big deal. I like useing two pullers when ever possible, on yamaha 450 engines if you let the cases get out of parallel to each other just a little bit it will crack the case where the shift fork slides in. On any engine if you let the cases get out of parallel you run a chance of screwing something up.

[bigbellybob]

nice when we going to split my cases?

[mustangfury]

Cool, I have a steering wheel puller and i was wondering if it would work.  The only problem i have is i dont have bolts long enough.

I was looking over my parts and the piston has some wear patterns on it. I was wondering what they could be signs of.  This could be from the goofy mixture that was being run due to the leaking crank seal. I know the black crown is from all the crank oil getting in to the cylinder. I was just wondering about the marks on the skirt. Let me know what you guys think.  My camera takes good pictures up close. If you need a zoomed in shot click on the image.

I will post pictures of the inside parts once i split it.

Thanks.
Stang.

[jonny500]

i would renew that piston. you need to have your bore measured too. i have not see marks like that on  a piston before.
take the ring off the piston and put it in the bore as if it was on the piston about 1/4 inch down the bore and post a pic

[kaw rider]

check your piston clearance

[mustangfury]

The piston clearance was almost perfect when i rebuilt the top end. It only has about 5 hours on it.

I was running a really lean fuel mixture because I was getting a lot of oil out the silencer.  That solved the problem for a short time, then it started spitting oil out the back again and that is when i decided to break down the bottom end. The excess oil was not from a rich mixture but rather from the crank case. I had the bike jetted pretty lean with a 150 main and a 50 pilot. The manual calls for a 168 main and 52 pilot.  I kept seeing oil so I kept going leaner, one size at a time. I have never seen a piston like this either, that is why i am wondering if it is due to the lean mixture I was running.

The piston currently in it is a standard size.  Fortunately if the walls are worn I will be able to get a B, C, or D size.

Stang.

[BDI]

I would say it was trying to seize up.

[jonny500]

bdi, do you think the funny marks (the spirally curved marks) on the piston are due to vibration from the bottom end. the bore looks ok but should be measured i think

[mustangfury]

oh sorry, I know what you are referring to now.  The curling marks are an optical illusion from the way the camera picked up the lighting and the way the software compressed the full size picture.  Click on the top picture of the three i posted earlier and zoom in to full resolution and you will see the ribs are running the way they should.

The marks i was wondering about were the two vertical lines on the intake side and the top wear on the exhaust side.  the ribs are worn down a bit. BDI, do you think that the reason it was trying to sieze was from the lean(hot) mixture?

Here are two more pictures.  They are a little darker but they don't show the ribs zoomed out.

sorry for the confusion.  I guess you definitely haven't seen that before.

Stang

[BDI]

oh sorry, I know what you are referring to now.  The curling marks are an optical illusion from the way the camera picked up the lighting and the way the software compressed the full size picture.  Click on the top picture of the three i posted earlier and zoom in to full resolution and you will see the ribs are running the way they should.

The marks i was wondering about were the two vertical lines on the intake side and the top wear on the exhaust side.  the ribs are worn down a bit. BDI, do you think that the reason it was trying to sieze was from the lean(hot) mixture?

Here are two more pictures.  They are a little darker but they don't show the ribs zoomed out.

sorry for the confusion.  I guess you definitely haven't seen that before.

Stang

I would say yes.

[jonny500]

i though my eyes were playing tricks but its the camera, cool thats sorted.

[Motorrad]

 Drinking tranny fluid is exactly how my bike stuck 2 years ago... crank seal let go, without warning, in a sand wash, started going slurp, and stuck, boiled the radiator also....

[mustangfury]

That's comforting to know that might be my only problem.

what were you using for trani fluid, ATF? Does it seize from simply too much oil?

The back of your piston looks like my last piston when i last did the top end. It had that little melted lip on the exhaust side. Mine was even more melted. It didn't seize or mess up the cylinder though. Those previous pics are of the same cylinder wall, no changes. I put in a plug one step hotter because I though that might help with the oil problem I was having. I went down the trail and it just quit. Being fairly new to dirt bikes, I thought it was from riding it hard and hotter. Once I rebuilt the top end, I realized that wasn't my problem, went to jetting, and now i am here. Learned a lot since then.

[mustangfury]

I got the cases apart. The left main bearing did not come off the crank shaft. It came out of the case still on the crank. 

How do you remove the shift drum?

Is there a way of removing the crank shaft from the right case half without the special tool?

Any suggestions are appreciated.

Stang.

[jonny500]

that sometimes happens. look at this vid http://www.youtube.com/watch?v=q38HUzr043c
those tool are expensive. but you can see what you need to do. if you made a case spliting tool like mine or bdi's steering wheel puller, you can use that. if you weld 2 or 3 bolts even in length to the outer bearing case and then use nuts on the end. if you do weld on the bearing be sure to sheld the crank from splatter. i have not done this before i have used the proper tool but see no reason why it wont work, its an idea anyway