Main Bearing Repacement

[jonny500]

sorry stang, the shift drum, try and leave it in you should be able to work round it if you use blocks of wood. i use an electric of air powered impact wrench to remove the bolt, thay are normaly very tight with thread lock on

[mustangfury]

Here are pics of the guts.

How about getting the crank out of the right case half?

Stang

[mustangfury]

more pics

[jonny500]

if you put it on blocks of wood with the clutch side up. you should be able to tap it out, put a peice of wood over the crank shaft end so you dont bruse it and knock it with a hammer. if the wood splits get another piece. an extra pair of hands would be use full

[Motorrad]

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.

That is my 500 motor of course...

I was running Bel Ray Gearsaver....

The reason my main seal went...
was the Crank journal was actually sized small and no one caught it.. Odd as it looked perfect (no sign of wear or tampering...... (I bought it with a fresh motor).. so the main bearings  actually were loose on the crank (didnt spin on the shaft) but could be installed and removed way too easy.... also guess what... the crank seal didnt seal properly because of thsi,,, bike got warm and started drinking oil...

[mustangfury]

I tried running bel ray gear saver but the clutch was sticking really bad with it. When I would go to put the bike in first it would not go in easy. It would slam in and try to take off if I did not hold in the front brake. I don't know why. I was told you could use 10W-40 motor oil and that is what I have been running. When I put the motor oil in, I did not have the clutch problem anymore. It works fine?  From experience, has anyone found motor oil to be a bad idea? If you have found it causes problems, what is the best to use to avoid wear?

Thanks.

[alward25]

10w40 oil is fine as long as it meets the standard for motorcycles.  Friction inhibitors are bad for clutches,  it makes them slip.  I ran ATF based on a after reading some chatter on this site.  In 5th gear pinned I had the oil build up enough pressure it pushed out the countershaft sprocket seal.  Going back to motor oil never had the problem.  Stewart runs 30 weight non synthetic in his engines for what that is worth.  Gear oil like a Bel-ray gear saver or Amsoil type stuff I would think would be good.  I like most have run about every oil out there over the years and have my preferences like most people.  Run what works for you. I run Amsoil 10w40 motorcycle in my K5.
Good luck!!!

[mustangfury]

What designates oil meets the standard for motorcycle Transmissions? I am assuming it is one of the two letter codes/standards on the bottle? If so, which one(s) should I look for? Would synthetic be worse or better? I ran walmarts supertech non-synthetic.

[alward25]

Usually API Service SG, SL/CF/CG-4, Jaso MA/MA2, ISO-L-EMA2 are all ratings that will work. Rotella 15w40 is a great all round oil. I have used it in 2 and 4 strokes and it is a great inexpensive oil that you can get at Wal-mart for less than $13 a gallon. It is made for diesel engines and holds up awesome.

What designates oil meets the standard for motorcycle Transmissions? I am assuming it is one of the two letter codes/standards on the bottle? If so, which one(s) should I look for? Would synthetic be worse or better? I ran walmarts supertech non-synthetic.

[mustangfury]

(1) when you heat up the cases to put the bearing in, do you have to get all the bearings in with one heating or can you reheat it one bearing at a time? 

(2) Will heating up the case with other bearings in it cause the case to crack because of different expansion rates of steel and aluminum? 

(3)When you say the bearings will drop right in, do you literally mean you can just set them in or will you have to tap them in with a hammer and socket?

(4) how quick do you usually need to get them in before it cools too much: seconds, minutes, 10 minutes?

[mustangfury]

I am looking to get the bearings in this weekend.  Anyone have answers to any of my questions?  any help is appreciated.

Thanks.

[BDI]

They need to come strait from the freezer to the cases. I get my wife to get the bearings out while I get the cases out and then drop them in right on the range top. if the bearings are not cold enough the cases are not hot enough the bearings will only go in part way and stick. you also have to have the bearings real strait with the hole or they will not drop. I recomend 225 to 250 surface temp on the cases. any hotter you run the risk of ruining the bearings.I use the spit test, when it sizzles spit its' hot enough. put the bearings in the freezer atleast an hour in advance inside a zip lock back.

[mustangfury]

Bearings are in! Piece of cake, thanks to all the help. Dropped right in. I am going to try and get the crank in and the motor back together tomorrow.  I'll let you know how things go. If all goes well, I may be giving it a test run by the end of the weekend.

Thanks again for all the help everyone,

Stang

[alward25]

Hmmmmmm, after that kind of confession I am not I want to come over for dinner on Sunday

They need to come strait from the freezer to the cases. I get my wife to get the bearings out while I get the cases out and then drop them in right on the range top. if the bearings are not cold enough the cases are not hot enough the bearings will only go in part way and stick. you also have to have the bearings real strait with the hole or they will not drop. I recomend 225 to 250 surface temp on the cases. any hotter you run the risk of ruining the bearings.I use the spit test, when it sizzles spit its' hot enough. put the bearings in the freezer atleast an hour in advance inside a zip lock back.

[kwakman]

Stang, if you go to youtube and search "2 stroke bottom end rebuild " you will find a few good videos in 3 parts which help a lot when your doing it for the 1st time.hth, K.