First top end rebuild...

therealVB99
Profile picture for user therealVB99
Posts
106
Joined
5/9/2014
Location
Jacksonville, FL, USA
therealVB99
Edited Date/Time 5/7/2015 6:55pm
Let me just start off by saying this is probably the biggest squid question ever but it's my first time doing it myself, and I want to do it correct.

I have a 1998 cr 250 and I'm gonna pull the cylinder Tommorow. when I check the bore with a bore gauge and if it is all within spec according to my clymers service manual, putting a new piston and rings in it and a gasket kit, should be fine right?

If I pull it and it is not in spec, what should I do? Replate it or iron sleeve.. Which is better?

Any advice is greatly appreciated .
|
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 5/3/2015 2:01pm
5/3/2015 2:01pm
Re-plating is always the best route.

Paw Paw
project racer 5/3/2015 2:38pm
5/3/2015 2:38pm
Check to see what letter size is on the piston. It is on the top. Use some carb spray and light grit sand paper to clean the carbon off so you can see the letter. If the plating is not flaked / peeling, and is just a bit thin, you can put say, a C piston if you have a B in it now, and use the cylinder the rest of the way up.

Slapped a 97 CR250 together way back. It had a B in it. The plating was a bit worn. Put a C in it, and it ran good for the next owner for quite a while.
therealVB99
Profile picture for user therealVB99
Posts
106
Joined
5/9/2014
Location
Jacksonville, FL, USA
therealVB99 5/3/2015 3:50pm
5/3/2015 3:50pm
Paw Paw 271 wrote:
Re-plating is always the best route.

Paw Paw
Thanks paw , that what's Ive been reading but as I'm sure you know.. there's always mixed opinions.

therealVB99
Profile picture for user therealVB99
Posts
106
Joined
5/9/2014
Location
Jacksonville, FL, USA
therealVB99 5/3/2015 3:51pm
5/3/2015 3:51pm
project racer wrote:
Check to see what letter size is on the piston. It is on the top. Use some carb spray and light grit sand paper to clean...
Check to see what letter size is on the piston. It is on the top. Use some carb spray and light grit sand paper to clean the carbon off so you can see the letter. If the plating is not flaked / peeling, and is just a bit thin, you can put say, a C piston if you have a B in it now, and use the cylinder the rest of the way up.

Slapped a 97 CR250 together way back. It had a B in it. The plating was a bit worn. Put a C in it, and it ran good for the next owner for quite a while.
Thank you for the advice man! I'm gonna pull it Tommorow and see what I see. Is there a certain wrench I need for the base cylinder bolts? Looks a little tight for a box wrench.

The Shop

See All »
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 5/3/2015 5:35pm
5/3/2015 5:35pm
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will fit over the nut. If you use a cheep one it most likely will just break.

Paw Paw
therealVB99
Profile picture for user therealVB99
Posts
106
Joined
5/9/2014
Location
Jacksonville, FL, USA
therealVB99 5/6/2015 11:33pm
5/6/2015 11:33pm
Paw Paw 271 wrote:
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will...
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will fit over the nut. If you use a cheep one it most likely will just break.

Paw Paw
So I have taken everything apart and will have the head and jug off Friday, and I'm sure it will tell me a story.
Now I will send it off to get replated as you said paw paw but this leads me to a new set of questions. When I send it off and they replate it will that bring the cylinder back to oem spec so that I can buy a wiseco or pro x piston, at the oem size? Forged piston or cast? Like it says up top, first rebuild ever for me, so I'm a little confused as to what everything means, and what will work.
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 5/7/2015 8:11am
5/7/2015 8:11am
You will have to work with the re-plating company so they know what you desire. If OEM is the desired size and they do it correctly , then yes you can run any oem based piston as it is then your choice.
I prefer forged pistons, but it's like selecting an oil....Everyone has their own ideas on what to run.

Paw Paw
mxtech1
Profile picture for user mxtech1
Posts
1968
Joined
7/21/2011
Location
Galesburg, IL, USA
mxtech1 5/7/2015 10:05am
5/7/2015 10:05am
Paw Paw 271 wrote:
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will...
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will fit over the nut. If you use a cheep one it most likely will just break.

Paw Paw
therealVB99 wrote:
So I have taken everything apart and will have the head and jug off Friday, and I'm sure it will tell me a story. Now I...
So I have taken everything apart and will have the head and jug off Friday, and I'm sure it will tell me a story.
Now I will send it off to get replated as you said paw paw but this leads me to a new set of questions. When I send it off and they replate it will that bring the cylinder back to oem spec so that I can buy a wiseco or pro x piston, at the oem size? Forged piston or cast? Like it says up top, first rebuild ever for me, so I'm a little confused as to what everything means, and what will work.
If you have to replate the cylinder, I always prefer to buy the piston kit ahead of time and ship it with the cylinder. This lets them match the bore perfectly to your choice of piston without the guessing.
Paw Paw 271
Profile picture for user Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
Paw Paw 271 5/7/2015 1:38pm
5/7/2015 1:38pm
That is a very good point!

Paw Paw
therealVB99
Profile picture for user therealVB99
Posts
106
Joined
5/9/2014
Location
Jacksonville, FL, USA
therealVB99 5/7/2015 6:55pm
5/7/2015 6:55pm
Paw Paw 271 wrote:
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will...
You can buy a very high quality boxed (6 point preferred) wrench of the correct size (14mm?) and then grind the outside walls so it will fit over the nut. If you use a cheep one it most likely will just break.

Paw Paw
therealVB99 wrote:
So I have taken everything apart and will have the head and jug off Friday, and I'm sure it will tell me a story. Now I...
So I have taken everything apart and will have the head and jug off Friday, and I'm sure it will tell me a story.
Now I will send it off to get replated as you said paw paw but this leads me to a new set of questions. When I send it off and they replate it will that bring the cylinder back to oem spec so that I can buy a wiseco or pro x piston, at the oem size? Forged piston or cast? Like it says up top, first rebuild ever for me, so I'm a little confused as to what everything means, and what will work.
mxtech1 wrote:
If you have to replate the cylinder, I always prefer to buy the piston kit ahead of time and ship it with the cylinder. This lets...
If you have to replate the cylinder, I always prefer to buy the piston kit ahead of time and ship it with the cylinder. This lets them match the bore perfectly to your choice of piston without the guessing.
Thanks guys for all your advice, I will be ordering a forged piston and sending it with the cylinder as well. When I get some more news and/or finish this deal up, I will post the finished result and/or first startup.

Now to clean this intimidating carb while I wait for it to come back. So many pieces !

Post a reply to: First top end rebuild...