1st tz125 full engine rebuild. Help appreciated

yes, try an atv shop. it is a common puller.

 

Since I'm stuck on the rotor, can I go ahead and pull the transmission out and pull the water pump off? I'm going page by page in the manual...those are next

 

should be fine.

 

You can pull everything off the right side: clutch, case cover, primary gears, and transmission. Also, I would strongly suggest the case splitter / crank remover and clutch basket holder along with the rotor puller. Actually, I would suggest every tool in the front of the manual.

Also, you can't remove the water pump impellar until you split the case.

Don't rush things. Take your time and you won't be fixing things later.
Good luck,
Matt

 

the rotor puller tool looks suspiciously similar to a bicycle crank puller tool. I have no idea if the threads are compatible, but might be worth calling a few local bicycle shops...

also, the fellow who helped me tear down my tz engine used a home-brewed crankcase splitter to split the cases. I think he modified a tool he got at pep boys and it worked fine. I'll check with him and see what he used.

 

They're not left-hand threaded.

That I remember...

 

Plenty of pics and questions on the way.:up:
Motor is completely apart. I've seen on here that there is a bearing tool to help remove the bearings easier and with less damage. Info on tool is appreciated.

OK.
1. pics of the crank. I think it's f#cked. It's ground down to where one side of the groove for the (not sure of correct name) 1/2 circle piece that holds the rotor on is gone. It's also got a small amount of rust on it. The rust pics are crappy iphone pics, sorry.
2. is the crank useful anymore? What would cause the wear on the crank like that?
3. Purpose of this teardown was because I found a pretty good amount of rust on the wrist pin, and after further inspection, found rust on the crank. What is a common cause for water? Also, just so I have a better basic understanding of how water travels through this motor:

The lowest point of travel for water is the pump. Flow of water is: radiator ->pump->up to jug? Since there was very little rust on the crank and it looked to be in a small enough spot that it was possibly the spot on the crank that's exposed to the inside of the cylinder while the motor is at rest....is it possible that all of this was just condensation from sitting or something? Bike sat for about 3-4 months and has been moved from Atlanta area to South Florida (different temps, humidity, etc...?)
4. Should all bearings be replaced?
5. Water related: pump housing gasket, head gasket, and o-ring where crank case connects. Are there any others that need to be replaced?

6. pic 4 shows two "brass?" philips screws. They're getting worn and I would like to replace them. I buy all of this stuff at Home depot, and doubt I'll find them easily. Anybody know where I can order bolts/nuts in somewhat bulk?

7. If I wanted to put the case covers, etc. in a parts cleaner, do I need to pull the bearings out first? Do I need to pull the bearings out anyway? Again, is there a tool to make it easier? Anything that I shouldn't put in a parts cleaner?

Pics of anything on request
Thanks

 

I'll answer the questions for which I know (or think I know... ) the answers.

The "1/2" circle piece is a woodruff key. Did key fall out when you were pulling out the rotor, or was it missing?

I suppose you could get the crank repaired and rebuilt, but it may not be worth it.

I'm in the process of rebuilding a motor that I bought and did not know the history of it. So, I'm replacing all the seals and bearings since the engine is apart anyway. Might be overkill, but I'd rather have the engine in a "known" state than chance a seal or bearing failing.

Take a look at the water pump itself - if the blades/fins on it are looking worn or damaged, replace it.

For regular, stainless steel metric bolts, I've found McMaster-Carr to be a useful source (www.mcmaster.com). they've also got a pretty good selection of brass screws.

 

Thanks for the link on the bolts:up:
OK, the woodruff key was still in there, and looks to be in good shape. I'm sure it's cheap, so I'll buy another one. I've got the seals in the spare parts bin, so I think I should order the bearings that I need. Where do you guys order them, just form the dealer? Crappy thing is the local dealer here just closed last month. I'll also check on a new water pump.
Truthfully, I'll replace anything someone suggests, because it would be discouraging to build this motor and then have it fail. That would not be confidence inspiring.:tut:

Edit: better pic of the crank damage. Also the only partial pic of the water pump, but I'll take more of the pump tomorrow.

 

1) If there was any sign of rust inside the engine, I would change all the bearings. The bearings and cranks should always have a oil film and should not be rusted, even if it's been sitting for a few years. There was most likely a leak, or water got in when pulling the head, then was left without running.

2) Crank. It's not good that the key way is worn that way. I guess you could have the key welded in place. There's usually no reason to remove them anyway.

3) Crank. Since it looked like some rust on the pin, you may want to have the crank rebuilt. (Reference) They may be able to fix keyway also. Getting expensive...

4) Parts. I highly suggest RSCycles. It's easy to find OEM parts. Small stuff like screws and seals shouldn't be much if you can find them in the parts catalog.

5) Parts Cleaner. As stated before, it would be highly suggested to replace the bearings. Parts cleaner will not hurt the bearings. You should be able to remove all but 2 or 3 bearings with a simple punch, or they should just fall out. There are 2 or 3 blind bearings that may require a standard bearing puller.

Good luck... Keep going,
Matt

 

Thanks doormatt.
$250 for the crank rebuild is cheaper (IIRC) than what the previous owner had stated. I have one new, and one that will need to be rebuilt. I may send both off and see what they can do.
I'll swing by HF tomorrow and pick up the bearing puller.:up:

 

Hey paul, about the keyway on the crank. when i sent that crank to be rebuilt, Kevin Murray at MCE racing magnafluxes and sprays liquid nitrogen (I may not be correct on this but does something similar) or something on the cranks when he rebuilds them to show cracks forming. That piece that is missing came off during this process but he rebuilt the crank, personally, I would have just junked it but he assured me it would be fine. I never had any issues with it, though I never put many miles on it. Just some info, I would be wierded out by that to but he cleaned up the edges which is why it is smooth.

 

Ahhh... So it was like that after the rebuild. You had 500 miles on it, and I put about 80 on it at the track day. I know this is dumb, but which is the new crank and which needs to be rebuilt? (pic at beginning of thread) I'm assuming the one with the x's need to be rebuilt? I'll contact Kevin and see what the cost on both will be.

 

The 4DP11 cylinder is a 56mm jug. It may be marked with a letter A, B, C, or D, to be matched with a piston having the same letter to give proper piston-cylinder clearance. (I think it has been shown you can use the biggest piston in the smallest cylinder and still make clearance. Or was that for the YZ250?) Anyway, I like the feeler gauge stock method of measuring clearance. If you are an expert machinist and you've got a bore gauge, go for it, but if you're just another schmuck like me, forget about trying to get accurate measurements from a telescoping inside gauge.

Be sure to match the cylinder with its proper head. When reassembling, check the squish clearance.

 

ok....
It's down to the bare bones, sort of

I'm having trouble getting these last two bearings out, both of which I believe are transmission bearings on the rider's left case: (pic below)
The philips screws are in too tight, and I'm going to strip the screws if I continue. Also, I bought a puller, but cannot get the other out.

Finally, I just spent $217 for bearings and oil seals:wow:
How often should the bearings be replaced?
The seals actually weren't that bad money-wise, so I'm guessing every time I do a bottom end rebuild, I need to replace the seals....

 

Impact driver with a #3 phillips bit. Hammer driven impact driver, that is. Those screws have loctite on them, so a little localized heat wouldn't hurt. Also, try putting the case halve in the freezer for a couple of hours to help loosen the "unsecured" bearing, on the right in the pic. The aluminum will come up to room temperature faster than the steel bearing, so you might have beeter luck pulling the bearing.

 

:up: you know, I had one of those impact drivers, but never had used it. I don't think I brought it with me in the move
I'll try the freezer tonight.
So do you change bearings and seals every time you rebuild the bottom end?
Thanks

 

Also, does that mean I should put all the bearings in the freezer for a few hours before installing?

 

No. Seals yes, bearings should last until the crank needs to be rebuilt, possibly longer.

Yes. Leave the cases in the sunshine for a couple of hours as well, just to help. Some recommend 170* F in the oven for the cases for 20-25 minutes, but a good soak in the warm afternoon sun will help. Of course, that usually means a heat gun and a big mallet up here in Seattle. Another trick that I discovered recently was the dishwasher set for hot rinse. That will get the cases nice and clean and toasty warm.

 

Bearings are in the freezer.
Hopefully starting the rebuild tomorrow night.

Big thanks to RS Cycles for the bearings and seals:up: